TCAV-L Averaging Soil Thermocouple Probe


The TCAV-L typically provides the average temperature of the top 6 to 8 cm of soil for energy-balance in flux systems. It parallels four thermocouples together into one 24 AWG wire. Each member of a thermocouple pair can then be buried at a different depth. The two pairs are separated at a distance of up to 1 m.

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Benefits and Features

  • Used in conjunction with soil heat-flux plates and soil-moisture probes to compute total soil heat flux

The "-L" on a product model indicates that the cable length is specified at the time of order.


Detailed Description

The TCAV uses type E thermocouples, which 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 datalogger manual.
Weight 0.45 kg (1 lb) with 15.24-m (50-ft) cable


Datalogger Considerations

One differential analog input channel per probe is required.

Compatible Contemporary Dataloggers

CR200(X) Series CR800/CR850 CR1000 CR3000 CR9000X

Compatible Retired Dataloggers

CR500 CR510 CR10 CR10X 21X CR23X CR9000 CR5000 CR7X

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

Frequently Asked Questions

Number of FAQs related to TCAV-L: 4

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  1. Yes, as long as the TCAV-L is measured using a differential measurement instruction. Be sure to connect the shield wire to analog ground.

  2. The TCAV-L measurement range, accuracy, and resolution are a function of the datalogger used to measure the TCAV-L. Refer to the appropriate datalogger manual measurement section for more information.

  3. The TCAV-L is constructed using a Type E thermocouple wire. The high-order NIST polynomials were fit over the temperature range of -270° to 1000°C. The temperature range of a TCAV-L on a datalogger depends on the measurement range selected in the thermocouple measurement instruction. For example, using a CR3000 and the ±20 mV input range and a reference temperature at 20°C, the TCAV-L temperature range is -270° to 300°C. Refer to the measurement section in the appropriate datalogger manual for a detailed discussion on thermocouple measurements.

  4. The TCAV-L is a Type E thermocouple. Use a Type E (chromel –constantan) Thermocouple found in the Sensor | Temperature group.

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