This glossary lists the terms that are commonly used in conjunction with Campbell Scientific products and related technology, solutions, and applications. The definitions provided are intentionally brief and serve to explain how we apply these terms.


-6999: This number is associated with mixed-array data loggers. It is the minimum value that can be stored as a low resolution data point in a mixed-array data logger. This number will be stored in the input location assigned to a measurement if the voltage input exceeds the programmed range.

-99999: This number is associated with mixed-array data loggers. It is the minimum value that can be stored as a high resolution data point in a mixed-array data logger. This number will be stored in the input location assigned to a measurement if the voltage input exceeds the programmed range.


- A -

Accuracy: A measure of the correctness of a measurement.

A/D Bits: The number of bits used to convert an analog signal to a digital value.

AE (Application Engineer): A Campbell Scientific employee whose job is to help customers configure data acquisition systems that fit their applications, provide quotes, assist ordering, answer technical questions about our equipment, and occasionally help program or install equipment. AEs who primarily focus on sales activities and system configuration are titled Sales Engineers. AEs who focus on technical support and troubleshooting are titled Customer Support Engineers.

Aeration: The production and entrainment of bubbles in water as it flows around rocks in a stream or a propeller. Bubbles cause a turbidity sensor to read higher than it would without bubbles.

ALERT (Automated Local Evaluation in Real Time): A data transmission protocol used in flood warning systems.

Aliasing: The erroneous interpretation of high-frequency signals as lower-frequency signals. Such misinterpretations are expected result of making discrete measurement with sampling devices such as analog-to-digital (A/D) converters. See also anti-aliasing filters.

Amperes (Amps): Base unit for electric current. Used to quantify the capacity of a power source or the requirements of a power consuming device.

Analog: Data presented as continuously variable electrical signals.

Analog Ground: Terminals on the data logger that provide a ground reference for a single-ended measurements or for excitation return.

Analog Inputs: Channels for measuring voltage levels. Each channel is programmed with software selectable voltage ranges allowing the best measurement range to be specified for a given sensor's output signal. Analog inputs can be configured to make single-ended or differential measurements. See single-ended and differential measurements.

Analog Voltage Resolution: The smallest change in an input voltage that our data loggers can detect.

Anemometer: A sensor that measures wind speed. Cup, propeller, and sonic anemometers are available.

Anti-Aliasing Filter: A device that attenuates signal content outside the desired bandwidth. It precedes the analog-to-digital converter (ADC) in instrumentation designs theoretically allowing only frequencies in the pass-band to be sampled by the ADC. See also aliasing.

Aquaculture: The cultivation of fish or shellfish, that is, fish farms. Campbell Scientific data loggers are compatible with equipment for monitoring water quality (especially dissolved oxygen) and other conditions that could affect the health of fish.

Argos System: A satellite telemetry system that uses two satellites with polar orbits. Full global coverage including the poles is provided. Transmissions are limited to 16 low resolution data points. To use the Argos system, you must pay a fee and the data that will be transmitted must be used for meteorological purposes.

ASCII (American Standard Code for Information Interchange): Pronounced "askee"; a specific binary code of 128 characters represented by a string of seven binary numbers and a parity bit.

ASCII, Comma Separated: A file format option available in Campbell Scientific data loggers that strips all IDs, leading and trailing zeroes, unnecessary decimal points, and plus signs. Data points are separated by commas; arrays are separated by Carriage Return Line Feeds. This format is typically the easiest to import to data reduction or spreadsheet software such as Excel, DaDisp, Access, or our SPLIT program.

ASCII Printable: A file format option available in Campbell Scientific data loggers that precedes each data point with a 2-digit ID and a + or - sign. The ID and fixed spacing of the data points make specific data easy to locate on a printed output. This format is difficult to import to data reduction or spreadsheet software. SPLIT can be used to convert this format to ASCII, Comma Separated.

Aspirated: To drain air through by suction. This usually refers to the radiation shields used with air temperature sensors. Naturally aspirated shields rely on ambient wind to keep air moving past the sensor. Mechanically aspirated shields draw air past the sensor using fans.

Asynchronous: The transmission of data between a transmitting and a receiving device that occurs as a series of zeros and ones. For the data to be "read" correctly, the receiving device must begin reading at the proper point in the series. In asynchronous communication, this coordination is accomplished by having each character surrounded by one or more start and stop bits which designate the beginning and ending points of the information (see Synchronous).

Automatic power control (APC): The regulation of light power such that the irradiance at the entrance window to a turbidity sample remains constant with time and temperature. In our turbidity sensors, APC is achieved with the output from a monitoring photodetector and an electronic feedback circuit.

AWG: A standardized system for sizing wires based on the wire's diameter. The smaller the AWG number the larger the diameter of wire.

AWS (Automated Weather Station): A weather station that accurately and automatically measures and records meteorological variables over extended periods.


- B -

Barometer: A sensor that measures barometric pressure.

Barometric Pressure: The pressure of the atmosphere expressed in units of mbars, psig, or Hg (inches of mercury).

Base Station: A focal point for data and communications. One base station can service one or more remote sites.

Batch Files: An ACSII text file that contains one or more DOS commands or executable file commands. When the batch file is run, the commands in the file are executed sequentially.

Battery-backed: A system or component with an auxiliary battery that allows information in volatile storage areas to be retained if the main power supply has been cut off.

Baud Rate: The speed of information being transmitted across a serial interface, expressed in units of bits per second (bps). For example, a baud rate of 9600 refers to bits being transmitted (or received) from one piece of equipment to another at a rate of 9600 bps. Thus, a seven bit ASCII character plus parity bit plus one stop bit (total nine bits) would be transmitted in 9/9600 sec. = 0.94 ms or about 1000 characters/sec. When communicating via a serial interface, the baud rate settings for two pieces of equipment must match.

Beacon: A signal broadcasted to other devices in a PakBus® network to identify the neighbor devices. A beacon in a PakBus network ensures that all devices in the network are aware of the other devices that are viable. If configured to do so, a clock set command may be transmitted with the beacon interval. This function can be used to synchronize the clocks of devices within the PakBus network. See also PakBus and Neighbor Device.

Binary: A file format option using patterns of 0s and 1s to represent each of the characters. This format is the most compact to store on the PC but must be converted before it can be imported, printed, or read. The binary format offers no advantage in data retrieval speeds because data is always transmitted using the binary format. This format option only refers to the format of the file stored on the computer. Programs such as SPLIT can be used to convert binary formats to ASCII, Comma Separated.

Binary File: A file based on software defined formatting. A binary file can only be interpreted by the software programmed to decode the formatting. This format is used for more efficient data storage than is provided by ASCII.

Bit: The smallest unit of computer information. Each bit is either a "1" or "0".

BMP (Block Mode Protocol): The communications protocol used by the server to communicate with table-based data loggers and RF modems.

BOOL8: A one byte data type that hold 8 bits (0 or 1) of information. BOOL8 uses less space than 32-bit BOOLEAN data type.

Boolean: Name given a function, the result of which is either true or false.

Boolean data type: Typically used for flags and to represent conditions or hardware that have only two states (true of false) such as flags and control ports.

Bowen Ration System: A system using air temperature, net radiation, soil heat flux, and dew point measurements to estimate evapotranspiration. The Bowen ratio technique increases accuracy by measuring air temperature at two heights. Campbell Scientific's system uses air samples from two heights that are forced through mixing volumes and routed to a cooled mirror dew point hygrometer.

Bridge Measurements: See full-bridge or half-bridge.

Broadcast: Part of the radio (RF) technique of polling remote radio modem data logger sites. A single modem sends a message (broadcast) that all affected remotes hear and respond to.

Burst Mode: An instruction available in the CR10(X), CR510, and CR23X that allows the data logger to measure sensors at a faster speed over short intervals.

Byte: A group of eight bits that a computer processes as a unit.


- C -

Calibration: Developing a mathematical relationship between signals from a sensor exposed to known values so the signals from unknown values can be converted to engineering units.

Callback, call back, or call-back: Telecommunications with a data logger where communications is initiated by the data logger, usually in response to a measured condition or set of conditions, generally for the purpose of sounding an alarm at a remote computer. With a voice-synthesizer phone modem, a data logger can call a telephone number and dictate an appropriate message. Callback is also used where it is impractical to call the data logger but the data logger can call out.

CANbus, CAN: A protocol developed by automobile manufacturers enabling a vehicle's on-board computer diagnostic system to output standardized data streams. Data loggers that include the CANbus instruction can store data output from the vehicle's computer, typically along side measurements taken directly by the data logger.

Carrier: An electrical signal used to convey data or other information.

CCT (Customer in Control TechnologyTM): A new concept for the RWIS industry. CCT permits customers to specify best-of-breed hardware and PC software, including products from other CCT vendors. The customer of a CCT-based system owns the data, which allows the customer to modify and redistribute the data without additional costs. See also RWIS.

Ceilometer: A device that uses a laser or other light source to determine the height of a cloud base.

Chill Hours: The number of hours the temperature stayed at or below a certain base (or reference) temperature.

Client: A software application designed to connect to a server. Usually provides some type of user interface or data acquisition. Email programs running on individual PCs are typically client applications that connect to an email server program running on a computer at an Internet Service Provider to receive and send email messages.

Coaxial cable: A cable with two conductors (center conductor and outer shield conductor). Classified by size, impedance, and loss characteristics. Used to connect MD9 modems and to connect radios to antennas.

Collimator: A device that narrows a beam of particles or waves. The CS725 may need a collimator to provide accurate measurements. The need for a collimator is determined by the characteristics of the measurement site.

Common Mode Range: The voltage range, relative to the data logger ground, within which both inputs of a differential measurement must lie for the differential measurement to be made. Refer to the data logger manual or Edlog help to determine the common mode range for specific data logger models. Also see differential measurements.

Communication Server: The software (typically packaged as a DLL) that provides the communications functions within other software such as PC200W, PC400, or LoggerNet.

CompactFlash (CF): Memory card technology used by some Campbell Scientific card storage modules. CompactFlash® is a registered trademark of the CompactFlash Association.

Compile: The software process of converting human readable program code to binary machine code. The data logger user programs are compiled internally by the data logger operating system.

Completion Resistor: A resistor, typically a precision resistor, that completes a bridge measurement system and across which a voltage drop is measured.

Compression Fitting: Individual cable entry fittings included in some of our enclosures. Each compression fitting accommodates a sensor cable and when the fitting's rotated, clamps tightly against the sensor cable providing a water-tight seal.

Constant: In CRBasic, this is a packet of data logger memory given an alpha-numeric name and assigned a fixed number.

Continuous Analog Outputs (CAO): Outputs providing programmable voltage levels (at low amperages) to strip chart recorders or proportional controllers.

Control Ports: Another name for digital I/O ports, although often applies to output only channels found in our older data loggers. These ports were typically used to control external devices.

CoraScript: A command line interpreter client to the server that allows the user access to many of the capabilities of the server using direct commands or programmed script files.

CPU: Central processing unit. The brains of the data logger.

CRBasic: A data logger program editor whose structure stems from the BASIC programming language. CRBasic supports keyword, algebraic expressions, and conditional expressions. Data loggers that use CRBasic include our CR200(X)-series, CR800, CR850, CR1000, CR3000, CR5000, and CR9000(X).

CRBasic Data Loggers: Data loggers that use the CRBasic program editor, which includes our CR200(X)-series, CR800, CR1000, CR3000, CR5000, and CR9000(X) dataloggers.

CRD: A flash memory card or the memory drive that resides on the flash card.

CSDC (Concurrent Synchronous Device for Communication): A packet-based protocol in many data logger operating systems that allow concurrent communication. CSDC products communicate synchronously the entire time a link is established.

CS I/O Port: A nine-pin "D" style port on Campbell Scientific data loggers for connecting data transfer and storage peripherals such as phone, RF, or short haul modems. Low state is 0 V; high state is 5 V. If the data logger does not have a port that's labeled RS-232, then this port is also used to connect the data logger to the computer's RS-232 port. However, an RS-232 interface such as the SC32A is required.

Current: Flow of electrons through a circuit.

Current Drain: The amount of current used by a device.

Current Shunt: A resistor that converts a current signal to voltage signal.

CVI (Communications Verification Interval): The interval at which a PakBus® device verifies the accessibility of neighbors in its neighbor list. If a neighbor does not communicate for a period of time equal to 2.5 times the CVI, the device will send up to four Hellos. If no response is received, the neighbor is removed from the neighbor list.


- D -

Data Acquisition: The process of acquiring data.

Data Acquisition System: One or more electronic devices whose primary purpose is to acquire data. It can be simple or complex, depending upon your needs. Typically a data acquisition system involves at least three main components. First, sensors respond to a physical stimulus and transmit signals or change electrical property such as resistance. Second, a data logger measures the electrical signal, converts it to a number and stores either that value or some statistics on that value (average, maximum, minimum, standard deviation, etc.). Third, a PC uses some communications link (serial port, phone modem, radio modem, etc.) to retrieve the data from the data logger. The resulting data is only as good as the sensors can measure and the data logger can resolve. Reliable communications and software on the PC are critical to retrieving an accurate copy of the data in a timely fashion.

Data Advise (Data Logger): A mutual agreement between the communication server and the data logger about which tables are to be collected every time the data logger is contacted. Based on the data logger table definitions.

Data Advise Notification: The packet of data sent by the data logger based on the Data Advise agreement.

Data Advise (Server): An agreement between a client application and the communication server to provide specified data as it is collected by the server.

Data Cache: The storage for data collected from the data logger by the communication server. This data is stored in binary files on the hard disk of the computer where the server is running.

Data Logger: Also known as Measurement and Control System or Micrologger. Data loggers are the brain of a data acquisition system. They make measurements at a specified scan rate, process data, and initiate telecommunications. Our data loggers also have control capabilities allowing them to automatically respond to a specified conditions by controlling external devices (for example, opening flood gates, turning fans off/on).

Data Point: A data value which is sent to Final Storage as the result of an output processing (data storage) instruction. Strings of data points output at the same time make up a record in a data table.

Data Retrieval: Retrieving data from a data logger, RTU, or field recording device. With the appropriate data retrieval peripherals, this can be done either locally or remotely.

Data Storage Table, Data Table: A portion of the data logger’s Final Storage allocated for a particular output. Each time output for a given data table occurs, a new record is written to the table.

DCE (data communications equipment): While the term has much wider meaning, in the limited context of practical use with our data loggers, it denotes the pin configuration, gender and function of an RS-232 port. The RS-232 port on our data loggers and on many third-party telecommunications devices, such as a digital cellular modems, are DCE. Interfacing a DCE device to a DCE device requires a null-modem cable.

DCP (Data Collection Platform): A term used in reference to transmitting data via the GOES satellite system. The data collection platform is the field site where the data logger makes the measurements and where the satellite transmitter transmits the data to the satellite.

DDE (Dynamic Data Exchange): A protocol for allowing different software applications or programs to share information.

Desiccant: Packets of drying agent used in our enclosures to extract water vapor from the enclosed environment thereby protecting the electronic equipment from condensing humidity.

DevConfig (Device Configuration Utility): A utility for setting up Campbell Scientific hardware. DevConfig allows you to send new operating systems to devices with flash memory, configure various PakBus settings in data loggers, and edit settings for Campbell Scientific devices such as the MD485, RF400, and SC105. DevConfig is bundled in PC400, LoggerNet, and RTDAQ, and is available at no charge from our website.

Dew Point: The temperature at which water vapor begins to condense.

DHCP (Dynamic Host Configuration Protocol): A TCP/IP application protocol.

Differential Measurements: Analog measurements in which the voltage is measured between two inputs. Both inputs must be within the data logger's common mode range. Differential measurements may eliminate errors due to a difference in ground potential between the data logger and sensors, such as when external signal conditioning circuitry is powered from the same source as the data logger. Differential measurements have better noise rejection than single-ended measurements. See common mode range and single-ended measurements.

Diffuse Horizontal Irradiance (DIF): Solar radiation that does not arrive on a direct path from the sun, but has been scattered by molecules and particles in the atmosphere and comes equally from all directions.

Digital: Numerically presented data.

Digital I/O Ports: Input/output ports that sense status, read SDM peripherals or SDI-12 sensors, and control external devices.

DIM: A CRBasic command for declaring and dimensioning variables. Variables declared with DIM remain hidden during data logger operation.

Direct Normal Irradiance (DNI): Solar radiation that comes in a straight line from the direction of the sun at its current position in the sky.

Disaggregation: The process of reducing sediment to a collection of dry particles with the smallest practical size. This process is used for calibrating turbidity sensors.

DNP3 (Distributed Network Protocol): An industry standard networking SCADA protocol that operates in our newer data loggers with minimal configuration by the user. This protocol is primarily used for communications between a master station and RTUs. DNP3 supports addressing, which allows several sensors to be multiplexed on a single communications port, providing more efficient use of resources.

DNS (Domain Name System): A TCP/IP application protocol.

Drift: An unpredictable change in sensor outputs caused by temperature and humidity fluctuations, deterioration of materials, and aging of electronic components.

DTE: While the term has much wider meaning, in the limited context of practical use with our data loggers, it denotes the pin configuration, gender and function of an RS-232 port. The RS-232 port on the data logger and on many third-party telecommunications devices, such as a digital cellular modems, are DCE. Attachment of a null-modem cable to a DCE device effectively converts it to a DTE device.

Duff: The fermentation and humus layers of organic material found on a forest floor. Our DMM600 measures the water content of duff material, which is critical to those conducting scheduled burns as well as those attempting to battle out-of-control fires.

Duty Cycle: The percentage of time a device is turned on. Duty cycle is an important factor in determining battery life.


- E -

E08: An error code indicating the watch dog timer has reset the processor and program execution. Frequent repetitions of E08 indicate a hardware or software problem which should be reported to Campbell Scientific and diagnosed with the help of an AE.

Earth Ground: 1) Using a grounding rod or another suitable device to tie a system or device to the earth at the data logger site. Such a connection is used as a sink for electrical transients and possibly damaging potentials, such as those produced by a nearby lightning strike. 2) A reference potential for analog voltage measurements. Note that most objects have "an electrical potential" and the potential at different places on the earth may be different. See ground loop.

Eddy Covariance: System that calculates atmospheric and vapor fluxes. Campbell Scientific's systems are based around a sonic anemometer and Krypton hygrometer and possibly a CO2/H2O open path analyzer.

Edlog: A data logger program editor that was designed for a 16-key keyboard (0-9, A-D, *, and #) and a 7-segment display. No computer is necessary, but computer-generated program files are often used. For many applications, our Short Cut software makes programming these data loggers extremely easy. Data loggers that use Edlog programming include our CR510, CR10(X), CR23X, and CR7.

Edlog Data Loggers: The data logger that are programmed using the Edlog program editor. Data loggers that use Edlog programming include our CR510, CR10(X), CR23X, and CR7.

EEPROM (Electronically Erasable Programmable Read Only Memory): The memory that stores the data logger operating system and user programs.

Emitter: A device (LED, tungsten lamp, laser diode, or IRED) that radiates energy when excited by an electrical current.

Engineering Units: Units that explicitly describe phenomena, as opposed to the data logger measurement units of millivolts or counts.

ESD (electrostatic discharge): Sudden flow of electricity between two objects caused by contact, an electrical short, or dielectric breakdown.

ESS (Environmental Sensor Station): A station used in road weather applications

Ethernet: A communication system that connects computers into a high-speed network. Often, the Ethernet is used for Local Area Networks (LANs) because it can network many types of computers and is not proprietary. To communicate in an Ethernet network, most Campbell Scientific data loggers use an interface (see Our CR9000X data loggers have an onboard 10baseT/100baseT Ethernet connector, and therefore an interface is not required.

ETo: Notation for potential evapotranspiration.

Evapotranspiration: The amount of water no longer available in the soil due to evaporation and transpiration. Transpiration is the movement of liquid through a plant then released through the stomata of the plant as water vapor. There are several methods for estimating evapotranspiration including the Penman Monteith equation and Bowen ratio technique.

Excitation: Programmable voltage provided for bridge measurements. See also switched excitation channels, full-bridge, and half-bridge.

Execution Interval: See scan, scan interval, or scan rate.

Execution Time: The time required to execute an instruction or group of instructions. The execution time should be shorter than the execution interval so that the data logger can complete the instruction set as written every time it's initiated. If the execution time of a Program Table exceeds the table's Execution Interval, the Program Table will be executed less frequently than programmed resulting in table overruns.

Expression: A series of words, operators, or numbers that produce a value or result.

External Signal Conditioning: Using peripheral devices to alter a sensor's signal so that an otherwise non-compatible device can read the signal. Signal conditioning circuits can be quite complex (e.g., temperature-compensated voltage output devices) or simple (e.g., a precision resistor used as a voltage divider).


- F -

FAO 56 Penman-Monteith or FAO 56 PM Equation: A version of the Penman- Monteith equation that is accepted by the Food and Agriculture Organization of the United Nations (FAO) as a method to estimate evapotranspiration from a turf grass surface, in all regions and climates. Campbell Scientific's Visual Weather software uses this equation. The equation was originally published in "Crop Evapotranspiration, Guidelines for Computing Crop Water Requirements, FAO Irrigation and Drainage Paper 56", Richard G. Allen, Luis S. Pereira, Dirk Raes, and Martin Smith, Food and Agriculture Organization of the United Nations, Rome, 1998. See also evapotranspiration and Penman Monteith equation. Penman Monteith Equation: An equation for estimating evapotranspiration using a turf grass reference. It requires wind speed, air temperature, relative humidity, and solar radiation measurements. See also evapotranspiration.

FFT (Fast Fourier Transform): A mathematical function describing the relative magnitudes and phases of frequencies in a time varying signal.

Fiber Optic: A data retrieval hardware link using a bundle of thin transparent fibers of glass or plastic that transmit light throughout their length by internal reflections.

FIELDbus: A communications protocol sometimes used in SCADA systems.

File Control: A feature of our data logger support software (for example, PC400, LoggerNet) used in management of files that reside in the data logger's memory.

Fill and Stop Memory: A memory option for external data storage devices. Data will be written to the memory until it is filled. Once full, the device won't allow any more data points to be written until the memory has been erased.

Final Storage: That portion of the data logger SRAM Memory allocated for storing data tables with output arrays. Final Storage is a ring memory, with new data overwriting the oldest data.

Final Storage Area 1 or Area 2: These terms are used in connection with Edlog programming and our legacy data loggers. The two independent Final Storage areas provided in the CR10(X), CR510, and CR23X; only one Final Storage area is available in the CR500, 21X, or CR7. Use of Final Storage Area 2 is determined by the data logger program. Data can be directed to, and collected from, one or both of the areas.

Finger-wave test: A procedure for testing OBS sensors whereby one waves a finger in front of the sensor and notes the output signal. Signal fluctuations indicate an OBS sensor is working.

Firmware: Programs or instructions stored in a PROM or EEPROM.

Flash Memory: Non-volatile memory used in our data loggers and other devices. Flash memory is used for data storage.

Flocs: A glob of particles that settles faster and scatters or absorbs more or less light than the individual would; see photomicrographs of flocs.

FP2: 2 byte floating point data type. Default data type for stored data for our CRBasic data loggers. While IEEE 4 byte floating point is used for variables and internal calculations, FP2 is adequate for most stored data. FP2 provides 3 or 4 significant digits of resolution, and requires half the memory as IEEE4.

FTP (File Transfer Protocol): A TCP/IP application protocol.

Full-bridge: System of four resistors that change resistance based upon some type of physical property (e.g., pressure, temperature). Full bridge circuits are usually more sensitive to change and are useful for sensors that produce a small change in resistance. Also known as Wheatstone bridge.

Full Duplex: Operational mode of a communication circuit in which each end can simultaneously transmit and receive data.

Full Scale Range (FSR): The full measurement range of a measurement channel or sensor.


- G -

G: Data logger terminals directly connected to the Earth Ground or Ground Lug terminal.

Garbage: The refuse of the data communication world. When data are sent or received incorrectly (and there are numerous reasons this happens), a string of invalid, meaningless characters (garbage) results. Two common causes are: 1) a baud rate mismatch and 2) synchronous data being sent to an asynchronous device or vice versa.

Geostationary Satellite Systems: Satellite systems whose satellites have orbits that coincide with the earth's rotation allowing each satellite to remain above a specific region. GOES and Inmarsat are geostationary systems.

Gill Radiation Shield: A naturally aspirated shield that houses temperature probes in order to reduce the effects of solar loading on the temperature measurement.

Global Horizontal Radiation (GH): The total amount of shortwave radiation received from above by a surface horizontal to the ground.

Global Variable: A variable available for use throughout a CRBasic program. The term is usually used in connection with subroutines, differentiating global variables (those declared using Public or Dim) from local variables, which are declared in the Sub () and Function () instructions.

GOES (Geostationary Operation Environmental Satellites) System: A geostationary satellite system available to only U.S. Federal, State, or local government agencies or users sponsored by one of those agencies. Potential GOES users must receive formal permission from NESDIS (the agency that coordinates GOES). See also Geostationary Satellite Systems.

GPS (Global Positioning System): A satellite system used to determine geographic position and deviation. Campbell Scientific data loggers can interrogate some GPS receivers then store the GPS position data.

Ground Loop: An alternative path in which voltage can travel. Ground loops can produce measurement errors. Refer to the sensor's manual for tips on avoiding ground loops.

Ground Lug: A lug used for connecting our data loggers to earth ground. Our data loggers must be connected to earth ground to protect them from transient potentials such as nearby lightning strikes.

Growing Degree Days (GDD): A measure of temperature condition that is favorable to plant growth.

GUI (Graphical User Interface): Pronounced "gooey"; the programming code defining the operation and graphics displayed on a computer monitor. It's the code that drives the "look and feel" of a computer program.

Guy: Cables attached to a tripod or tower to increase stability. Our 30 foot towers must be guyed. Other towers and tripods may be guyed if increased stability is required.


- H -

Half Bridge: System of two or more resistors wired in a series that change resistance based upon some change in of physical property (for example, pressure, temperature). Refer to the measurements chapter in the data logger manuals.

Half Duplex: Operational mode of a communication circuit in which each end can transmit and receive data, but not simultaneously.

Handshake, Handshaking: The exchange of predetermined information between two devices to assure each that it is connected to the other. When not used as a clock line, the CLK/HS (pin 7) line in the data logger CS I/O port is primarily used to detect the presence oabsence of peripherals such as a storage module. Phone modems also handshake when they connect (sounds like screeching).

Heat Index: The perceived temperature as influenced by relative humidity.

Hello Exchange: The process of verifying a node as a neighbor.

Hertz (Hz): Unit of frequency described as cycles or pulses per second.

High Resolution Data Value: For mixed-array data loggers, the data value having five significant digits and ranging in magnitude from ± 0.00001 to 99999. A high resolution data value requires two final storage locations (4 bytes) and must be specified by Instruction 78.

HTML (Hypertext Markup Language): A programming language used for the creation of web pages.

HTTP (Hypertext Transfer Protocol): A TCP/IP application protocol.

Hygrometer: A sensor that measures dew point.


- I -

IEEE4: 4 byte floating point data type. IEEE Standard 754. Same format as FLOAT. FLOAT is the name used when declaring data type for Public or Dim variables.

Indexed Input Location: This is used in Edlog. Commonly used with multiplexers or when repeating a series of identical measurement/processing instructions. Indexing an input location within a loop (Instruction 87) will cause the location address to be incremented by one with each pass through the loop. Indexing is also used with Instruction 75 to cause an input location, which normally remains constant, to be incremented with each repetition. See also indexing parameters.

Indexing Parameters: Altering the function of a parameter by pressing the F4 function key or C key. Not all parameters can be indexed, and the effect of indexing varies according to the parameter. To determine what parameters can be indexed, refer to the data logger's prompt sheet, individual instruction descriptions in the data logger manual, or Edlog help for individual instructions. In Edlog, a parameter is indexed by pressing the F4 function key while in the numeric or label field of the parameter, or the C key while in the numeric field of the parameter. If using the keyboard display, press the C key then the A key. Two dashes will be displayed after the entry indicating the parameter has been indexed. Pressing the respective key when a parameter is already indexed will toggle the index off.

INF: Infinite or undefined. A data word indicating the result of a function is infinite or undefined.

Inherent optical properties (IOPs): The physical properties, including absorption, scattering, attenuation, and the volume scattering function that affect the transfer of light through a water sample but are unaffected by ambient illumination.

Inmarsat System: A commercial Geostationary satellite system. The Inmarsat system maintains a satellite in each of four ocean regions: Atlantic Ocean East, Atlantic Ocean West, Pacific Ocean, and Indian Ocean. These satellites provide coverage throughout most of the world. To use this system, you must pay a fee and your site must be located where an Inmarsat satellite provides coverage. See also Geostationary Satellite Systems.

Input Bias Current: The average input current of two input terminals.

Input Impedance: The shunt resistance and capacitance (or inductance) measured at the input terminals, without including the effects of input bias or offset currents.

Input Locations: Used in Edlog. These are addresses in the data logger memory where measurement results are temporarily stored. Old data are overwritten by new measurement results with each new execution interval. The values stored in input locations are displayed in the Monitor or Graph Mode. When using the data logger's keyboard display, the input location values are displayed in the *6 mode. Input location values are not the values retrieved when data are collected.

Input/Output Instructions: Instructions that initiate measurements and store the results in Input Storage, or set or read Control/Logic Ports.

Input Storage: In Edlog, this is the area of the data logger memory that stores input location data. Default is 28 locations for most data loggers. The number of allocated locations can be changed using Edlog or the keyboard display's *A mode. See input locations.

Instruction Location Number: In Edlog, this number gives the sequential location of the instruction in the program sequence. When programming a table, the instruction location number and a P (e.g., 04: P00) prompts the user when it is time to enter an instruction.

Integer: A number written without a fractional or decimal component. 15 and 7956 are integers. 1.5 and 79.56 are not integers.

Interfaces: Devices allowing one piece of equipment to "talk" to another one.

Intermediate Disable Flag (Flag 9): This flag suspends intermediate processing when it is set high. This Flag is used to restrict the sampling of averages, totals, maximums, minimums, etc. to times when certain criteria are met. The Intermediate Disable flag is set as a command code option in a program control instruction. The flag is automatically set low at the beginning of each execution of the program table.

Intermediate Storage: That portion of memory allocated for the storage of results of intermediate calculations necessary for operations such as averages or standard deviations. Intermediate storage is not accessible to the user.

IP Address: A unique address for a device on the Internet.

IP (Internet Protocol): A TCP/IP Internet protocol.


- J -

J-bolt: A J-shaped bolt that is threaded on the long straight portion of the J. J-bolts are part of the CM320 pedestal kit for securing a mounting pole (CM300 series or user supplied) to a concrete base.


- K -

Keep: Memory preserved through reset due to power up and program start up.

Keyboard Display: A sixteen-button keypad and LCD that allows you to manually initiate data transfer and display sensor readings, stored values, or flag/port status. The CR850, CR3000, CR5000, CR7, CR23X, and 21X have integrated keyboard displays. The CR800 and CR1000 use the portable CR1000KD. The CR10(X), CR510, and CR500 use the CR10KD. The CR200(X)-series dataloggers and CR9000X dataloggers do not have a keyboard display.


- L -

Lidar (light detection and ranging) technology: An optical sensing technology that measures the distance to a target by illuminating it with light, using pulses from a laser. Our ZephIR300 uses this technology to measure wind speed and direction at multiple heights. The CS135 uses this technology to measure cloud height and vertical visibility for meteorological and aviation applications.

Light Absorption: The conversion of light to heat or some other energy form as it passes through a water sample. Unlike scattering, absorption does not alter the direction of light transfer. In a turbid sample, light is absorbed by water, dissolved material, and by suspended particles. The absorption coefficient, a, defined as the fraction of energy absorbed from a light beam per unit of distance traveled in the sample, is the measure of this IOP.

Light Attenuation: The combined effects of absorption and scattering that reduce (attenuate or extinguish) the intensity of light as it passes through a water sample. The attenuation coefficient, c, defined as the fraction of energy scattered and absorbed from a light beam per unit of distance traveled in a sample, expressed in cm-1, is the measure of this IOP. The formula, a + b = c expresses the concept (links to a and b). For example, a 40-NTU formazin standard has an absorption coefficient of 0.01 cm-1 and a scattering coefficient of 0.15 cm-1 at 650 nm (red) light. The attenuation coefficient is therefore 0.16 cm-1 and light intensity will decline by 63% for every 6.3 cm traveled in the formazin standard.

Light Scattering: The interaction of light with suspended particles and small-scale variations in the refractive index and density of the matrix that alters the direction of light transport in a sample without changing its wavelength. The scattering coefficient (b) is an IOP, defined as the fraction of energy scattered from a light beam per unit of distance traveled in a sample expressed in cm-1. For example, the scattering coefficient for 650-mn (red) light in filtered drinking water is 0.00012 cm-1. So, about 63% of the energy will be scattered out of a beam per 83,000 cm traveled in drinking water.

Linear Response, Linearity: The degree to which the output of a sensor is a linear function of the detected parameter.

Line-of-Sight: A straight path between a transmitting and receiving antenna that's unobstructed by intermediate topography. RF telemetry systems require line-of-sight transmissions. The use of repeater stations can overcome line-of-sight interruptions.

Local Variable: A variable available for use only by the subroutine wherein it was declared. The term differentiates local variables, which are declared in the Sub () and Function () instructions, from global variables, which are declared using Public or Dim.

Loop: In a program, a series of instructions that are repeated a prescribed number of times, followed by an "end" instruction to terminate the series.

Loop Counter: A counter that increments by one with each pass through a loop.

Low Resolution Data Value: For our mixed-array data loggers, this is the default output resolution from Final Storage. A low resolution data value requires one Final Storage location (2 bytes) and has four significant decimal digits that may range in magnitude from ±0.001 to ±6999.

LVDT (Linear Variable Differential Transformer): An inductance element that produces an electrical output proportional to the displacement of a separate movable core; used to measure position.


- M -

mA (milliampere): Unit of current that's one thousandth of an ampere.

Manually Initiated: Initiated by the user, usually with a keyboard, as opposed to occurring under program control.

Maximum Input Voltage: The largest input voltage value that the data logger can read. An input voltage greater than this value will cause errors and possible overranging on the other analog inputs. Voltages significantly larger than the maximum input voltage may permanently damage the data logger.

Mean Time Between Failures (MTBF): A quality assurance index describing the expected reliability of our data loggers.

Measurement and Control Systems: A more descriptive name for Campbell Scientific data loggers. Historically, data loggers were relatively "dumb devices" that had limited programming and no control capabilities. Campbell Scientific uses the name measurement and control system to inform the users that our data loggers have measurement and control capabilities and are not the "dumb devices" historically associated with the name data logger.

Measurement Current Drain: The amount of current our data loggers use to make measurements.

Meteor Burst: A telecommunication technique which uses meteor activity in the ionosphere as a mechanism for reflecting short data transmissions from field sites to a base station. Transmissions are "bounced" from a ground station, reflected off the ionosphere and received at another ground station.

Meteorological: Of or pertaining to atmospheric phenomena, especially weather and weather conditions.

Micrologger: The trademarked name for our CR3000, CR23X, 21X and CR21 dataloggers. Our Microloggers traditionally are compact, self-contained (that is, keyboard display, power supply are part of unit), and have a set number of I/O terminals (not card or module based like the CR9000X).

Micrometeorology: The detailed study of the weather at a specific location.

Mixed Array Memory Structure: A memory structure used by many of our retired data loggers. This type of memory stores arrays of data at specified intervals or when some other set condition has been met. As data is stored, each array of new data is added sequentially to a common storage area (Final Storage). After the data has been collected, it can be separated into files based on various criteria by using Split (part of LoggerNet and PC208W) or some other software program. The mixed array memory structure is used by our CR10, 21X, and CR7 dataloggers. Our CR510, CR10X, and CR23X dataloggers may also use this memory structure (the memory structure of these data loggers is determined by the selected operating system). Terms associated with mixed array memory structure include Final Storage, Output Array, Output Array ID, Output Flag, and Output Interval.

Modbus: Communication protocol developed by Modicon; widely used in SCADA and process control applications. Many of our data loggers support the Modbus protocol.

Modem: A device whose name combines the term "modulate" with "demodulate," which refers to its ability to transmit and receive data superimposed on a carrier frequency. In our usage, a modem also: 1) has the ability to raise the data logger's ring line or be used with the SC32A to raise the ring line and put the data logger in the Telecommunications Command State and 2) has an asynchronous serial communication port that can be configured to communicate with the data logger.

Modulo Divide: Mathematical operation wherein the result of interest is the remainder after a division.

MSB (Most Significant Bit): The leading bit.

MSHA (Mining Safety and Health Administration): Pronounced "em shaw"; an organization that sets safety requirements for mines. Historically, Campbell Scientific manufactured MSHA-approved equipment for use in methane environments, but a lack of available approved parts has resulted in the discontinuation of this line.

Multidrop Modem or Interface: Devices linking one computer to many data loggers on a common cable or wire. Multidrop modems have addresses which allow one data logger to communicate with the computer while the other data loggers remain in a quiescent state.

multi-meter or multimeter: An inexpensive and readily available device useful in troubleshooting data acquisition system faults.

Multiplexer: Peripherals that increase the number of sensors that can be measured by the data logger. Multiplexers essentially allow multiple sensors to share the same data logger channel. Several multiplexers can be controlled by a single data logger. The CR510, CR500, and CR200-series dataloggers do not support multiplexers.

Mux: Slang for multiplexer.

mV (millivolt): A unit of electrical potential equal to one thousandth of a volt. This is a typical output for sensors. In many sensors, the mV signal level varies to indicate change is occurring in the parameter measured.


- N -

NAN (not a number): A data word indicating a measurement or processing error. Voltage over range, SDI-12 sensor error, and undefined mathematical results can produce NAN.

Narrowband UHF/VHF: A type of RF telemetry that transmits data over a UHF or VHF frequency. An assigned frequency and an FCC license are required. See also RF telemetry, UHF, VHF, and Spread Spectrum.

Near Infrared Radiation: Light having wavelengths between 760 nm and 2,000 nm.

Neighbor Device: Devices in a PakBus® network that can communicate directly with an individual device without being routed through an intermediate device. See also PakBus and Beacon Interval.

Net Radiometer: A sensor that measures net flux of downward and upward total solar and terrestrial radiation through a horizontal surface.

NIST (National Institute of Standards and Technology): An organization in the United States that sets measurement standards. The organization was once called NBS (National Bureau of Standards).

Node: Part of the description of a data logger network when using LoggerNet. Each node represents a device that the communications server will dial through or communicate with individually. Nodes are organized as a hierarchy with all nodes accessed by the same device (parent node) entered as child nodes. A node can be both a parent and a child.

Noise: Undesirable electrical energy that interferes with accurate measurements.

NTCIP (National Transportation Communications for ITS Protocol): A protocol used for RWIS applications that allows roadside devices from different manufacturers to communicate.

NTU: Nephelometric turbidity units. A numerical scale for the cloudiness of water determined with a turbidimeter calibrated with a turbidity standard such as formazin or AMCO Clear.

Null Modem: A device, usually a multi-conductor cable, which converts an RS-232 port from DCE to DTE or from DTE to DCE.


- O -

Ohms Law: The relationship of current and resistance to voltage. Voltage equals the product of current and resistance (V = I*R).

Ohm (Ω): The unit of resistance. 1.0 Ω equals the ratio of 1.0 Volt divided by 1.0 Amp.

Omnidirectional Antenna: An antenna that can pick up signals from all directions (i.e., it doesn't have to be pointed directly at the source of the signal to pick it up). Typically this type of antenna is used when the specific direction of the signal is not known, when one antenna is receiving and transmitting in several directions (as in a repeater station in an RF network), or for mobile applications.

On-line Data Transfer: Routine transfer of data to a peripheral left on-site. Transfer is controlled by the program entered in the data logger.

On-Site Data Transfer: Routine transfer of data to a peripheral that remains on-site. Transfer is controlled by the program entered in the data logger.

Operating spectrum: The spectrum resulting from the wavelength-by-wavelength products of source intensity, filter transmittance, and detector responsivity. The operating spectrum represents the relative contributions of individuals wavelengths to a measurement.

Optional Data Memory: Extra data memory that is available if an additional memory option for the data logger has been ordered.

OS (Operating System): The portion of the memory of a data logger or other device containing the instruction set. The OS of these devices can be changed without opening the device and changing a hardware PROM. The new operating system can be downloaded from a computer connected directly to the device.

Output Array: A string of data points output to Final Storage. Output occurs when the data interval and data trigger are true. The data points which complete the Array are the result of the Output Processing Instructions which are executed while the Output Flag is set.

Output Array ID: The first data points of an Output Array when using Edlog. By default, the Output Array ID consists of the Program Table Number and the Instruction Location Number of the program instruction that set the Output Flag. For example, if the 40th instruction in the data logger's Program Table 2 is an Instruction 92 that designated data to be output at three hour intervals, the default Output Array ID for that output data will be 0240. The output array ID can also be specified using Instruction 80 in the data logger program.

Output Flag (Flag 0): A flag telling the data logger to send data to Final Storage. The output flag is set by entering option 10 for the command code parameter in a program control instruction. Data must be in Final Storage to transfer it to a storage module or printer, or to retrieve the data via a telecommunication link.

Output Interval: The time interval between initiations of a particular Output Array. Output occurs only when the Output Flag is set. The flag may be set at fixed intervals or in response to certain conditions.

Output Processing Instructions: Process data values and generate Output Arrays. Examples of Output Processing Instructions include Totalize, Maximize, Minimize, Average, etc. The data sources for these Instructions are values in Input Storage. The results of intermediate calculations are stored in Intermediate Storage. The ultimate destination of data generated by Output Processing Instructions is usually Final Storage but may be Input Storage for further processing. The transfer of processed summaries to Final Storage takes place when the Output Flag has been set by a Program Control Instruction.

Overrange: A voltage input exceeding the programmed range. When this occurs, the value stored in the variable is NAN (not a number). For our retired data loggers that use Edlog, the value stored in the input location is -6999 and -99999 for low and high resolution, respectively. Any output processing for that interval will also store an overrange value, even if only one overrange event occurred.


- P -

PakBus: A packet-based communications protocol developed by Campbell Scientific. The PakBus communication protocol improves upon traditional communications for data logger networks. PakBus networks have the distributed routing intelligence to continually evaluate links. Continually evaluating links optimizes delivery times and, in the case of delivery failure, allows automatic switch over to a configured backup route. The PakBus communications protocol is standard in our CR200(X)-series, CR800, CR1000, and CR3000 dataloggers; it's optional in our CR510, CR10X, and CR23X dataloggers.

PakBus Node: A device in the PakBus network that has a unique PakBus ID. The device can be a data logger, computer, or Ethernet Interface.

Parameter: Number or code entered to specify exactly what a given instruction is to do. Parameters are an integral part of the data logger's program instructions. Common parameter entries include reps, measurement channels, measurement ranges, input locations, etc. Once the instruction number has been entered in a Program Table, the data logger will prompt for the parameters by displaying the parameter number in the ID Field of the display.

Particle size distribution (PSD): This term is used in connection with water turbidity measurements. The weight of particles in each of the various size ranges determined by sieve sizes or settling speeds given as a percentage of the total solids of all sizes in the sample.

Particle Size Factor: This factor is associated with turbidity measurements.

PDA (Personal Digital Assistant): A hand-held computing device. Some communications are supported between a PDA and our data loggers; PConnect software is required for PDAs with a Palm OS and PConnectCE software is required for PDAs with a Windows Pocket PC/Windows Mobile OS. For more information, see the PConnect or PConnectCE product literature.

Penman Monteith Equation: An equation for estimating evapotranspiration using a turf grass reference. The equation is sanctioned by the Food and Agricultural Organization of the United Nations. It requires wind speed, air temperature, relative humidity, and solar radiation measurements. Campbell Scientific's ET106 station uses the Penman-Monteith equation. See also evapotranspiration.

PE (Pin Enable): The line on which print devices or peripherals receive output.

Period Average: A measurement technique using a high-frequency digital clock to measure time differences between signal transitions. Sensors commonly measured with period average include vibrating wire transducers and water content reflectometers.

Peripheral: Auxiliary or supplementary equipment. Typical Campbell Scientific peripheral equipment includes power supplies, measurement and control electronics (e.g., SDMs, multiplexers), and data retrieval hardware.

Ping: A software utility that attempts to contact another specific device in a network.

Poisson Ratio: A ratio used in strain measurements equal to transverse strain divided by extension strain
v = –(εtrans / εaxial).

Potential Evapotranspiration (ETo): The amount of water that evapotranspiration would remove from a specific site if an ample supply of water was available. See evapotranspiration.

Potentiometer: A variable resistor with three terminals—one on each end of the resistor and one "wiper" which contacts the resistor midpoint to indicate a variable position. Often used in wind vanes.

Power Supplies: An energy source for an electrical device. These can be ac powered through a standard wall socket, or dc powered through batteries and a solar panel. Many data acquisition systems work from a 12 to 24 Vdc power supply that can be kept fully charged by a solar panel or ac power.

Precision: A measure of the repeatability of a measurement.

PreserveVariables: A CRBasic instruction that protects Public variables from being erased when a program is recompiled. The PreserveVariables instruction enables the *4 table functionality of mixed-array data loggers, such as the CR10X.

Print Device: Any device capable of receiving output over pin 6 (the PE line) in a receive-only mode. Printers, "dumb" terminals, and computers in a terminal mode fall in this category.

Probe: A device used to send back information. Campbell Scientific uses the words probe, sensor, and transducer interchangeably.

Processing Instructions: These instructions allow the user to further process input data values and return the result to Input Storage where it can be accessed for output processing. Arithmetic and transcendental functions are included in these Instructions.

Program Control Instructions: Used to modify the sequence of execution of instructions contained in program tables; also used to set or clear flags.

Programmable Excitation Ports: Another name for Switched Excitation Channels.

Program Memory: The amount of data logger memory available for storing user-created programs.

Program Table: That portion of data logger memory allocated for storing user-created programs. The programs consist of a sequence of user-selected instructions which control data acquisition, processing, and output to Final Storage. Programming can be separated into two tables, each having its own user-defined execution interval. A third table is available for programming subroutines, which may be called by instructions in Tables 1 or 2, or triggered by a voltage on a control port. When using the keyboard display, the *1 and *2 Modes access Tables 1 and 2, respectively, and the *3 Mode accesses Subroutine Table 3. The length of the tables is constrained only by the total memory available for programming. Tables 1 and 2 have independent execution intervals. Table 1's execution has the higher priority; it may interrupt Table 2.

PROM (Programmable Read Only Memory): The portion of the CR10, 21X, or CR7's memory containing the data logger instruction set. To change the instruction set, the data logger is opened; the old PROM removed, then a new PROM inserted. PROMs are also used in other devices such as MD9 and RF modems.

Prompt Sheet: A short document that was provided with our retired data loggers. It contained an abbreviated description of the data logger instructions and parameters. One prompt sheet was supplied with the manual. It is primarily intended for use in the field by users who are familiar with data logger programming. Detailed descriptions of instructions and parameters are provided in the manual and Edlog help.

Protocol: Rules determining the format and transmission of data (computer science).

PRT (Platinum Resistance Thermometer): A sensor that uses a bridge measurement (a three- or four-wire half-bridge or a four-wire full-bridge) to measure temperatures. Just like any other resistive materials, platinum has a variable resistance depending on the temperature of the surrounding area and on the length of the platinum. The resistive variability measurement is expressed as "Temperature Coefficient of Resistivity". Platinum's low "temperature coefficient of resistivity" value means that its resistance variability does not swing as widely as many other metals, hence its use. Platinum's variability of resistance due to temperature is reproducible (most metals have this reproducibility), so the thermometer uses resistive measurements. A fifth order polynomial is used to increase the accuracy of the correlation between the temperature change and the corresponding resistance change on platinum because the variability of resistance is reproducible but it is not linear with temperature change.

psi (pounds per square inch): A common unit for expressing pressure measurements.

Public: A CRBasic command for declaring and dimensioning variables. Variables declared with PUBLIC can be monitored during data logger operation.

Pulse: An electrical signal characterized by a sudden increase in voltage follow by a short plateau and a sudden voltage decrease.

Pulse Measurements: Measurement type that counts switch closures, low level ac, or high frequency square wave signals. Sensors that use pulse measurements include tipping bucket rain gages, anemometers, and flow meters.

Pyranometers: A sensor that measures solar radiation.

Pyrgeometer: Sensor that measures the atmospherically far infrared radiation.

Pyrheliometer: An instrument that measures the direct beam solar irradiance with a field of view limited to 5 degrees.


- Q -

Quiescent: Not in active mode, "asleep". Typically this word is used in our specifications in conjunction with current drain in order for the customer to develop a power budget.


- R -

Rain Bucket: Device for measuring rainfall. Tipping bucket rain gages are the most typical sensor offered by Campbell Scientific in this category.

RAM (Random Access Memory): The portion of data logger memory used for data and running the data logger program. In newer data logger models, RAM is battery-backed so that data logger programs are maintained if the system loses power.

Real-time Monitoring: Observing measured results as they are happening.

Regulator: A device for conditioning an electrical power source. Campbell Scientific regulators typically condition ac or dc voltages greater than 16 V to about 14 Vdc.

Remote Site: Typically where a data logger is located at the other end of a communications link. Also can refer to the site where a radio (RF) repeater is located.

Repeater Station: A station used to increase line-of-sight coverage area or transmission quality for an RF Telemetry system. A measurement station can be used as a repeater, or a central location that does not make measurements can be set up.

REP (Repetition): A parameter used in many input/output and output processing instructions that allows one programming instruction to measure several identical sensors or to process data from several input locations. The sensors must be wired in consecutive channels. When REPs are greater than 1, the input locations are assigned consecutive numbers (e.g., with REPs of 2 and the first input location number is 5, the assigned input location numbers are 5 and 6). The input location's label for each repetition is the original label with an underscore and the next consecutive number appended to the end.

Resistance: A feature of an electronic circuit that impedes or redirects the flow of electrons through the circuit.

Resistive Tape: A linear sensor in which the electrical resistance changes as water level rises and falls.

Resistor: A device that provides a known quantity of resistance.

Resolution: A measure of the fineness of a measurement.

RF (Radio Frequency) Telemetry: A telemetry system that transmits data over a radio frequency. Our RF systems are compatible with UHF and VHF frequencies. In the US, an FCC (Federal Communication Commission) license is required to use an RF system.

RH (Relative Humidity): Ratio of the amount of water vapor in the air to the maximum amount of water vapor that could be held at the current temperature.

Ringing: Oscillation of sensor output (voltage or current) that occurs when sensor excitation causes parasitic capacitances and inductances to resonate.

Ring Line (pin 3): Line pulled high by an external device to "awaken" the data logger.

Ring Memory: A memory configuration in which data writes to the memory and when the entire memory has been filled, the new data writes over the oldest data.

RMA (Returned Material Authorization) Number: A number indicating that the user has contacted an Application Engineer, and the Application Engineer has confirmed that the product needs repair or recalibration. Before a product will be accepted for repairs or recalibration, the user must contact Campbell Scientific and acquire an RMA number.

RMS: Root mean square or quadratic mean. A measure of the magnitude of wave or other varying quantities around zero.

ROM (Read Only Memory): The portion of memory that cannot be altered and is used for storing permanent information.

RS-232 Port: A nine-pin DCE port on most of our data loggers (CR800, CR1000, CR3000, CR5000) used to connect the data logger to the computer's RS-232 port. If the data logger doesn't include a port with this label, an RS-232 interface such as an SC32B is required to connect the data logger to the computer's RS-232 port.

RS-232 (Recommended Standard 232): A loose standard defining how two computing devices can communicate with each other. The implementation of RS-232 in CSI data loggers to PC communications is quite rigid, but transparent to most users. Implementation of RS-232 in data-logger-to-RS-232 smart sensor communications is quite flexible.

RTD (Resistance Temperature Device): A sensor that measures temperatures with a bridge measurement (a three- or four-wire half-bridge or a four-wire full-bridge). The sensor uses materials that have a variable resistance depending on the temperature of the surrounding area and on the length of the material.

RTMC (Real Time Monitoring and Control) software: A client application to the communications server that displays data from the server’s data cache (only) and updates as new data is collected. RTMC is relatively easy to set up, and ships with LoggerNet, PC400, and RTDAQ.

RTU (Remote Terminal Unit): Device used to control/monitor/record sensor results especially in SCADA applications (that is, our data loggers can easily serve as RTUs).

RWIS (Road Weather Information System): Weather stations located along the highway that provide local pavement and meteorological data that may affect driving conditions. Individual weather stations in this system are typically called ESS. See ESS for more information.


- S -

Sample Rate: The rate at which measurements are made. The measurement sample rate is primarily of interest when considering the effect of time skew (i.e., how close in time are a series of measurements). The fastest sample rates are when measurements are made that are initiated by a single instruction with multiple repetitions.

Saturation Light Level: The irradiance in W cm2 required to cause the photodetector amplifier in an OBS sensor to clip and not respond to changes in backscatter from particles. This is caused by mounting an OBS sensor in direct sunlight or near underwater objects that reflect direct sunlight onto a sensor, typically about 180 µW cm2 or 0.2% of the sunlight in the visible-NIR band.

SCADA (Supervisory Control and Data Acquisition): Systems that integrate measurements control and redundant data storage. For example, water treatment plants often run SCADA systems.

Scan, Scan Interval, or Scan Rate: Interval between executions of a data logger program. Dependent on data logger model, scan may be entered as milliseconds, seconds, minutes, hours, or days. A data logger program is a timed infinite loop, each loop scheduled to begin at the top of each scan interval. Interchangeable with "execution interval."

Scattering angle: The angle between a light beam incident upon a scattering volume and light beam scattered from that volume is called scattering angle. Forward-scattered light fills the hemisphere surrounding the source beam and oriented away from the source (0 < θ < 90°) and backscattered light fills the opposite hemisphere (90° < θ< 180°).

SDC: Synchronous Device for Communication

SDI-12 (Serial Data Interface at 1200 baud): Communication protocol for transferring data between battery-powered data recorders and sensors. Sensors can measure one or more parameters, then transmit the data back to the data logger following the SDI-12 protocol. Both the sensor and the data logger must follow the protocol specifications. To read more about SDI-12, or obtain a copy of the specification, visit the SDI-12 Support Group Web Site.

SDK (Software Development Kit): Tools that allow software developers to add custom capabilities or interfaces to our data logger support software. SDKs currently available from Campbell Scientific include BMP5, LoggerNet-SDK, and LoggerNet Server-SDK. See our product literature for more information about the individual products.

Sealed Rechargeable Battery: A battery that can be recharged using solar panels, ac power, or vehicle power.

Security Code: A code entered into the data logger either directly with a keypad or via the data logger’s program to prevent unauthorized access to data logger settings, programs, and data.

Seebeck Effect: Induces microvolt level thermal electromotive forces (EMF) across junctions of dissimilar metals in the presence of temperature gradients. This is the principle behind thermocouple temperature measurement. It also causes small correctable voltage offsets in data logger measurement circuitry.

Seimens (S): Unit of conductivity where 1 S = 1/ohm. SI based unit is S/m.

Semaphore (Measurement Semaphore): In CRBasic's sequential mode, when the main scan executes it locks the resources associated with measurements (i.e., it acquires the measurement semaphore). This is at the scan level, so all subscans within the scan (whether they make measurements or not), will lock out measurements from slow sequences (including the system background calibration). Locking measurement resources at the scan level gives non-interrupted measurement execution of the main scan.

Send Text Messages (SMS): A service that is available when a newer data logger is used with a network link device that has the PPP/IP key enabled. The data logger sends text messages by leveraging email to SMS gateways (for example, [number] and by issuing serial commands to the network link device.

Sensitivity: The rate of change of a sensor output per unit of input change.

Sensor: A device that responds to a physical stimulus and transmits a signal or changes electrical property such as resistance. Campbell Scientific uses the words probe, sensor, and transducer interchangeably.

Serial: A loose term denoting output or a device that outputs an electronic series of alphanumeric characters.

Serial Server: A device that allows serial communication over a TCP/IP communications link.

Shaft Encoder: A device typically used to measure water level. This sensor is based upon the clockwise/counterclockwise rotation of a pulley. As water level rises and falls, a float sitting on the water surface moves with the water. A wire or metal tape connects the float around a pulley and is held taut by a counterweight on the other end.

Short Haul Modems: Asynchronous devices using two unconditioned twisted cables for communications between a data logger and computer.

Signature: A number which is a function of the data and the sequence of data in memory. It is derived using an algorithm which assures a 99.998% probability that if either the data or its sequence changes, the signature changes. It's primarily used to verify that a data logger's program has not changed or during the transmission of data via telecommunications. Data "packets" in which the data logger and computer signatures do not match are retransmitted.

Single-ended Measurements: Analog measurements in which the input's voltage is measured with respect to ground. Twice as many channels are available for single-ended measurements than for differential measurements. See also differential measurements.

SI (Systéme Internationale): The International System of Units.

Skipped Scan: Occurs when the data logger program is too long for the scan interval. Skipped scans can cause errors in pulse measurements.

Slow Sequence: A usually slower secondary scan in the CRBasic program. The main scan has priority over a slow sequence.

SMTP (Simple Mail Transfer Protocol): A TCP/IP application protocol.

SNMP (Simple Network Management Protocol): A standard internet protocol for managing devices on IP networks.

Snow Water Equivalent (SWE): Measurement of the amount of water contained in snow pack.

Soil Bulk Electrical Conductivity: Conductivity of electricity through soil.

Soil Heat Flux: The amount of heat flowing into a cross-sectional area of soil per unit time.

Soil Volumetric Water Content: The proportion of a volume of soil that is water.

Soil Water Potential: The energy status of water in soil.

Solar Radiation: Radiation originating from the sun.

Split: A report creation and data processing software tool provided in our data loggger support software.

Spread Spectrum: A sequential signal structure that spreads the normally narrowband information signal over a relatively wide band of frequencies. Spread spectrum radios correlate the signals to retrieve the original signal. Spread spectrum radios are more immune to noise and interference.

SRAM (Static Random Access Memory): The memory that stores the Final Storage data and runs the data logger program.

State: Whether a device is on or off.

Station Number: The LoggerNet server assigns and uses station numbers for routing packets to the data loggers. These numbers can be modified using CoraScript. Not to be confused with data logger serial numbers, PakBus addresses, or addresses set in communications peripherals such as RF modems.

Stilling Well: A cylinder installed near a body of water is used to hold and protect hydrological sensors. The stilling well allows water to move in and out freely but dampens wave and current action so as to provide a reasonable representation of the level of the water body.

Storage Module: A device used to transport data logger data and programs between a field site and an office. It also increases the data logger's storage capacity by storing data and programs in a solid state module or a memory card.

Storage Module Software (SMS): A legacy program for programming and retrieving data from storage modules. In PC208W, SMS is accessed by clicking Stg Module on the tool bar.

Strain Gage Pressure Transducer: A device measuring changes in electrical resistance in response to pressure changes on a diaphragm with an embedded or engraved strain gage.

String: A datum consisting of alphanumeric characters.

Surface Mount Technology: The technology used when components are mounted to the surface of circuit boards. Surface mount technology allows smaller component size, improves signal speed, increases reliability and automation in manufacturing, and requires less handling of parts.

Surge Protector: A device for protecting electronic equipment from damaging voltage levels sometimes occurring in electrical transients.

Suspended Solids Concentration (SSC): The mass of solid matter filtered from a water sample divide by the sample volume.

Switched 12 Volt: An output on the data logger used to power sensors or devices requiring unregulated 12 volts. This can be done under program control to save power.

Switched Excitation Channels: Channels that provide precision excitation voltages for resistive bridge measurements. Excitation is programmable. The range that the excitation is programmable varies with data logger model.

Synchronous: The transmission of data between a transmitting and receiving device occurs as a series of zeros and ones. For the data to be "read" correctly, the receiving device must begin reading at the proper point in the series. In synchronous communication, this coordination is accomplished by synchronizing the transmitting and receiving devices to a common clock signal (see Asynchronous).

Synchronous Device for Measurement (SDM): Addressable peripherals that expand digital control ports, analog output ports, or data logger measurement capabilities. Up to 16 SDMs may be connected to three control ports on the data logger. The CR510, CR500, and CR200(X)-series dataloggers do not support SDMs.


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Table-based Data Logger Memory: A data logger memory structure in which multiple storage areas (tables) are configured within your data logger. Each table can be individually sized and collected. This allows like data to be grouped and stored in separate tables. This memory structure is used by our CR200(X)-series, CR800, CR1000, CR3000, CR5000 and CR9000X dataloggers. Our CR510, CR10X, and CR23X dataloggers may also use this memory structure. (The memory structure of these data loggers is determined by the selected operating system.)

Table Definitions: List of data available from a table-based data logger. The data logger supplies this list on request. The tables are determined by the data logger program. The LoggerNet server must have a current version of the table definitions to collect data from the data logger.

Table Overruns: Skipped scans occurring when the actual data logger program run-time is longer than the execution interval. Table overruns may affect the number of samples included in processed analog measurements and can cause errors in pulse measurements.

Tables: An entry in the status table that shows the number of user-created data tables. (See also Data Table.)

Tab Windows: Some screens depict a series of related windows in a multitabbed notebook format. When you click the file folder tab, the information on the tab you chose will be displayed.

Task: An entry in our data logger support software on the Device Map representing a program scheduled for execution or a subsequent data logger to be called for data retrieval. Scheduling of execution can be done on a regular interval or following a call to a data logger.

TCP/IP (Transmission Control Protocol / Internet Protocol): Set of communications protocols used for the Internet and similar networks. It is generally the most popular protocol stack for wide area networks.

TD-RF: Time division polling used in some RF networks that quickly and efficiently move data through the network. It provides collision free communications as the base RF modem controls when and how all data moves. An area wide poll releases station-originated data, with each station having its own dynamically allocated slot in which to transmit. The data is then collected and moved through the network back to the base.

TDR (Time Domain Reflectometry): A system that uses a reflectometer to generate an electromagnetic pulse that is applied to a coaxial system. The resulting reflection waveform is analyzed and stored. The elapsed travel time and pulse reflection amplitude contain information that can be used to determine soil volumetric water content, soil bulk electrical conductivity, rock mass deformation, or other time-domain measurements.

Telnet: A software utility that attempts to contact and interrogate another specific device in a network.

Temperature Coefficient: The percent change in a sensor output per unit change in temperature.

Terminal Input Modules (TIMs): A family of small specialized terminal blocks that connect to a data logger terminal strip. Individual models provide completion resistance for bridge measurements, voltage division, and current shunts.

Thermistor: A temperature sensor consisting of a semiconductor that provides rapid and large changes in resistance for relatively small changes in temperature.The output of a thermistor is usually nonlinear, so measurement requires linearization, usually be means of the Steinhart-Hart or another polynomial equation.

Thermocouples: A temperature sensor consisting of a pair of wires of dissimilar metals. Temperature is determined by measuring the differences in potential created at the junction of the two wires. You must also have a thermocouple reference temperature sensor to measure the thermocouple. For a thorough discussion, see the Measurements chapter in the data logger manual.

Throughput: The rate at which a measurement can be made, scaled to engineering units, and stored. The data logger can scan sensors at rates exceeding the throughput rate (see Sample Rate). The primary factor affecting throughput rate is the amount of processing specified by the user. In the sequential mode, all processing called for by an instruction must be completed before moving on to the next instruction.

Time Stamp: The date and time when data are stored in the data logger.

TLS (Transport Layer Security): An Internet communications security protocol.

Toggle: To reverse the current power state.

Transaction: The exchange of data or information between two devices or programs. For example, setting the clock in a data logger requires a transaction between the server and the data logger.

Transceiver: A device that both transmits and receives data.

Transducer: A device that converts one form of energy into another, usually into an electrical signal that can be measured and recorded by our data loggers. Campbell Scientific uses the words probe, sensor, and transducer interchangeably.

Transient: A temporary change occurring in a circuit due to a sudden change of voltage or load.

Transmitter: A device that sends but does not receive data. Most of our satellite peripherals are transmitters.

TTL (Transistor - Transistor Logic): A serial protocol using 0 V and 5 V as logic signal levels.

Turbidity: The cloudy appearance of water produced by light scattered from suspended particles and light absorption by dissolved matter and particles.


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UDP (User Datagram Protocol) : A communication protocol that allows computer applications to send messages to other hosts on an Internet Protocol (IP) network. It does not require prior communications to set up special transmission channels or data paths. UDP is suitable for purposes where error checking and correction is either not necessary or performed in the application, avoiding the overhead of such processing at the network interface level.

UHF (Ultra High Frequency): Radio frequencies that are between 300 to 3000 MHz.

Ultrasonic: Sound frequencies above audible sound. Ultrasonic water and snow level sensors are available that do not make contact with the media of measurement. They send out a signal, track the amount of time it takes for the reflected signal to return then use the elapsed time to calculate the distance the signal traveled. Air temperature is also measured since the calculation needs to compensate for temperature-related fluctuations in the speed of sound.

Uncollectable Hole: Occurs when a hole in the data cache cannot be collected from the data logger before the data table wraps around and the records are overwritten.

UPS (Uninterruptible Power Supply): A UPS can be constructed for most data logger applications using ac line power, an ac/ac or ac/dc wall adapter, a charge controller, and a rechargeable battery.

User Program: The CRBasic program written by the user in the CRBasic Editor or the Short Cut program generator.


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Vac or VAC (Volts Alternating Current): Mains or grid power is high-level Vac, usually 110 Vac or 220 Vac at a fixed frequency of 50 Hz or 60 Hz. High-level Vac is used as a primary power source for Campbell Scientific power supplies. Do not connect high-level Vac directly to our data loggers. The data logger measures varying frequencies of low-level Vac.

Vapor Pressure Deficit of the Air: The difference between the value of saturated vapor pressure (maximum vapor it can accommodate at a given temperature without condensation) and the actual vapor pressure (the amount of vapor it holds at the time).

Variable: A packet of the data logger's memory given an alphanumeric name, which holds a potentially changing number or string.

Vdc or VDC (Volts Direct Current): Campbell Scientific data loggers operate with a nominal 12 Vdc power supply.

VHF (Very High Frequency): Radio frequencies that are between 30 to 300 MHz.

Vibrating Wire: A sensor that monitors pressure by measuring the change in resonant frequency of a tensioned wire in response to pressure or force changes.

Visible Light: Light with wave lengths between 380 and 760 nm.

Volt: A unit of measure for electrical potential.

Voltage: The energy potential from a source that can produce a flow of electricity in a circuit; expressed in volts.

Voltage Divider: A precision resistor network that reduces the output voltage of a device. Campbell Scientific's VDIV10:1 and VDIV2:1 are voltage divider modules that bring sensors with high output voltages into the data logger's common mode range.

Voltmeter: An inexpensive and readily available device useful in troubleshooting data acquisition systems.

Volume Scattering Function: The volume scattering function, VSF, is the angular distribution and relative intensity of light scattered from a sample. In water, VSFs depend mainly on the size factor. Suspended particles with D > λ scatter nearly all light in a small, forward cone. About half of the scattered light is contained in a 10-degree cone oriented in the forward direction whereas less than 2.5 percent of it is backscattered.


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Watchdog Timer: An error checking system that examines the processor state, software timers, and program related counters when the data logger is running its program. If the processor has bombed or is neglecting standard system updates or if the counters are outside the limits, the watchdog timer resets the processor and program execution. Voltage surges and transients can cause the watchdog timer to reset the processor and program execution. When the watchdog timer resets the processor and program execution, an E08 error code will be displayed while the data logger program is running. Frequent repetitions of E08 indicate a hardware or software problem which should be reported to Campbell Scientific.

Weather Station: An application-specific data acquisition system that monitors meteorological conditions. Typical weather stations include meteorological sensors (for example, rain gage, temperature and RH probe, wind vane, anemometer, and pyranometer), data logger, power supply, tripod or tower, data retrieval peripheral, and environmental enclosure.

Weather Tight: Describes an instrumentation enclosure impenetrable by common environmental conditions. During extraordinary weather events, however, seals on the enclosure may be breached.

Wet Bulb Temperature: The lowest temperature that can be obtained by evaporating water into the air at a constant pressure. The term comes from the technique of wrapping a wet cloth around a mercury bulb thermometer and blowing air over the cloth until the water evaporates. The wet bulb temperature is always lower than the dry bulb temperature (temperature measured without a wet cloth) in the same surroundings. The wet bulb and dry bulb temperatures can be used to calculate dew point or relative humidity.

Wheatstone Bridge: Another name for full bridge.

Wi-Fi: Technology that allows an electronic device to exchange data wirelessly over a computer network, including high-speed Internet connections.

Wind Chill: The still-air temperature that has the same cooling effect on a person's skin as a given combination of temperature and wind speed. Application Note 2T-M provides the wind chill equation that is used by the National Weather Service.

Wiring Diagram or Table: A diagram showing the way sensors, multiplexers, or SDMs wires are connected to the data logger. Short Cut's program generator automatically creates a wiring diagram after the sensors have been chosen and saved. Wiring diagrams are also found in manuals.

Wiring Panel: The set of terminals and underlying circuits that enable connections of sensors, power supply, and other wiring to the data logger. Some data loggers such as the CR3000 and CR5000 have built-in wiring panels. Others, such as the CR1000, have removable wiring panels.

WQ (Water Quality): Measurements such as conductivity, dissolved oxygen (DO), pH, oxygen reduction potential (ORP), turbididty, and water temperature.


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XML (Extensible Markup Language): A set of rules for encoding documents in a format that is both human-readable and machine-readable.


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Yagi Antenna: A directional antenna consisting of a rod pointed in the direction of the transmission/reception and several cross bars oriented at a 90° angle to the main rod and whose length and spacing is optimized to transmit and receive transmission in the desired frequency band.