The HFP01SC, manufactured by Hukseflux, measures soil heat flux—typically for energy-balance or Bowen-ratio flux systems. It is intended for applications requiring the highest possible degree of measurement accuracy. The HFP01SC outputs a voltage signal that is proportional to the heat flux of the surrounding medium. At least two sensors are required for each site to provide spatial averaging. Sites with heterogeneous media may require additional sensors.
The HFP01SC consists of a thermopile and a film heater. The thermopile measures temperature gradients across the plate. During the in-situ field calibration, the film heater is used to generate a heat flux through the plate. The amount of power used to generate the calibration heat flux is measured by the datalogger. Each plate is individually calibrated, at the factory, to output flux.
Self-calibration corrects for errors due to differences in thermal conductivity between the sensor and surrounding medium, temperature variations, and slight sensor instabilities.
Note: In an energy-balance installation, all sensors must be completely inserted into the soil face before the hole is backfilled.
|Sensor Type||Thermopile with film heater|
|Sensitivity||50 μV W-1 m-2 (nominal)|
|Nominal Resistance||2 Ω|
|Temperature Range||-30° to +70°C|
|Expected Accuracy||±3% of reading|
|Heater Resistance||100 Ω (nominal)|
|Heater Voltage Input||9 to 15 Vdc|
|Heater Voltage Output||0 to 2 Vdc|
|Duration of Calibration||±3 minutes @ 1.5 W (typically performed every 3 to 6 hours)|
|Average Power Consumption||0.02 to 0.04 W|
|Plate Diameter||80 mm (3.15 in.)|
|Plate Thickness||5 mm (0.20 in.)|
|Weight||200 g (7.05 oz) without cable|
Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.
|21X (retired)||An external relay (such as the A21REL-12) that supplies 12 Vdc to the heater is required when this probe is used with a 21X.|
|CR10 (retired)||An external relay (such as the A21REL-12) that supplies 12 Vdc to the heater is required when this probe is used with a CR10 with the silver wiring panel.|
|CR9000 (retired)||An external relay (such as the A21REL-12) that supplies 12 Vdc to the heater is required when this probe is used with a CR9000.|
Number of FAQs related to HFP01SC-L: 13
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The in-situ calibration is helpful for quality assurance/quality control. The multiplier determined from the in-situ calibration should be within ±10% of the factory-determined calibration. If it is not, the plate may be damaged, not wired correctly to the data logger, or not making full contact with the soil.
The example CRBasic program runs in either SequentialMode or PipeLineMode. To force the CRBasic program to run in PipeLineMode, add the instruction PipeLineMode to the beginning of the program.
No. The HFP01SC-L must be in full contact with the media. Railroad ballast is too coarse.
Rather than using a running average to find the millivolt output during a calibration, use a single sample with 50 or 60 Hz integration. See Example 1 in the 2014 or later version of the HFP01SC-L manual.
A calibration shift occurs if the HFP01SC-L is not making full contact with the soil during the calibration cycle. The following could cause the plate to lose contact with the soil: a soil freeze/thaw cycle, soil swelling/contracting because of extreme drying/wetting cycles, or rodents burrowing past the plate.
Add the appropriate code to the data logger program using a program example from the HFP01SC-L manual. Alternatively, contact Campbell Scientific for assistance.
This depends on the information contained in the calibration sheet:
Not every sensor has different cable termination options. The options available for a particular sensor can be checked by looking in two places in the Ordering information area of the sensor product page:
If a sensor is offered in an –ET, –ETM, –LC, –LQ, or –QD version, that option’s availability is reflected in the sensor model number. For example, the 034B is offered as the 034B-ET, 034B-ETM, 034B-LC, 034B-LQ, and 034B-QD.
All of the other cable termination options, if available, are listed on the Ordering information area of the sensor product page under “Cable Termination Options.” For example, the 034B-L Wind Set is offered with the –CWS, –PT, and –PW options, as shown in the Ordering information area of the 034B-L product page.
Note: As newer products are added to our inventory, typically, we will list multiple cable termination options under a single sensor model rather than creating multiple model numbers. For example, the HC2S3-L has a –C cable termination option for connecting it to a CS110 instead of offering an HC2S3-LC model.
The information included on a calibration sheet differs with each sensor. For some sensors, the sheet contains coefficients necessary to program a data logger. For other sensors, the calibration sheet is a pass/fail report.