FW05 Type E Fine-Wire Thermocouple
Research Grade
High accuracy for eddy-covariance applications
weather applications water applications energy applications gas flux and turbulence applications infrastructure applications soil applications


The FW05 is a Type E thermocouple with a 0.0005 in. diameter. It measures atmospheric temperature gradients or fluctuations with research-grade accuracy. The FW05 is compatible with most Campbell Scientific dataloggers, and it is often used in eddy-covariance systems.

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Benefits and Features

  • High frequency response suitable for eddy-covariance applications
  • Extremely small diameter virtually eliminates solar loading
  • Well-suited for measuring atmospheric temperature flux


FW05 fine-wire thermocouple
FW05 fine-wire thermocouple
FW05 fine-wire thermocouple
FW05 attached to an IRGASON
Exploded view of FW05 attachment to an IRGASON
FW05 attached to a CSAT3B
Exploded view of FW05 attachment to a CSAT3B

Detailed Description

The FW05 has the smallest diameter of our fine wire thermocouples. Because of this, it experiences the least amount of solar loading, but is also the most fragile. The thermocouple's small mass eliminates the need for a solar radiation shield.

The FW05 consists of a type E thermocouple with a connector. The connector attaches the thermocouple to a datalogger via the FWC-L cable.

Type E thermocouples are comprised of a chromel wire and a constantan wire joined at a measurement junction. A voltage potential is generated when the measurement end of the thermocouple is at a different temperature than the reference end of the thermocouple. The magnitude of the voltage potential is related to the temperature difference. Therefore, temperature can be determined by measuring the differences in potential created at the junction of the two wires.

A reference temperature measurement is required for thermocouple measurements. The temperature sensor built into many of our dataloggers' wiring panel typically provides this measurement.


Type Chromel-Constantan
Typical Output 60 μV/°C
Accuracy Refer to the Thermocouple Measurement section in the data logger manual.
Diameter 0.0127 mm (0.0005 in.)
Length 36.8 cm (14.5 in.)
Plug Dimensions 1.8 x 3.3 x 1.0 cm (0.7 x 1.3 x 0.4 in.)
Weight 45 g (2 oz)


Please note: The following shows notable compatibility information. It is not a comprehensive list of all compatible products.


Product Compatible Note
21X (retired)
CR10 (retired)
CR1000 (retired)
CR1000X The CR1000X is compatible when used with the CDM-A108 or CDM-A116.
CR10X (retired)
CR200X (retired)
CR211X (retired)
CR216X (retired)
CR23X (retired)
CR500 (retired)
CR5000 (retired)
CR6 The CR6 is compatible when used with the CDM-A108 or CDM-A116.
CR9000 (retired)

Additional Compatibility Information

Data Logger Considerations

The thermocouple connects to the data logger via the FWC cable. One differential analog input per sensor is required.

Reference Temperature Measurement

A reference temperature measurement is required. Options for measuring the reference temperature include:

  • Thermistor built into the CR800, CR850, CR1000, CR3000, or CR5000 wiring panel
  • PRT built into the wiring panel of the CR9050 or
  • CR9051E input module for the CR9000X Measurement and Control Datalogger
  • PRT built into the wiring panel of the CR723T input card for the CR7 Measurement and Control Datalogger
  • CR10XTCR thermistor that connects to the CR10X wiring panel

Carrying Case

The FW/ENC Carrying Case is required to ship our FW05 thermocouples. It holds up to four thermocouples. Thermocouples returned to Campbell Scientific for repair without this case will be shipped to the customer in a new case and the account charged accordingly.

Frequently Asked Questions

Number of FAQs related to FW05: 7

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  1. Measuring the thermocouple with an accuracy of 0.01°C is difficult, if not impossible, because of polynomial errors, voltage errors, and potential temperature gradients across the data logger terminal strips.

  2. Sensible heat flux is defined as the covariance of vertical wind and temperature fluctuations, measured with fast-response sensors. For more information, refer to a micrometeorology textbook.

  3. Most Campbell Scientific data loggers can measure a thermocouple without any external signal conditioning. Therefore, a dedicated module is not required.

  4. No. The fine-wire thermocouples were designed to measure ambient air temperature.

  5. The FW05 has a frequency response that is adequate for the eddy-covariance flux application.

  6. No. If the fan is off during the day, the shield will suffer from radiation loading, and the thermocouple will measure a higher ambient air temperature. If the fan is off during the night, under clear sky conditions, the ASPTC-L shield will emit long-wave radiation and cool to a temperature lower than ambient air temperature. Consequently, the thermocouple will measure a lower ambient air temperature. Running the fan and aspirating the thermocouple ensures that it is measuring ambient air temperature.

    If the site temperature is expected to fall below -10°C, consider using a naturally aspirated fine-wire thermocouple, such as the FW3, FW1, or FW05, in combination with the FWTM Fine-Wire-Thermocouple Mount and the FWC-L Connector Cable for Fine Wire Thermocouples.

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