Thermocouple Reads Excessive Noise on USB DAQ Devices

Updated Dec 13, 2023

Reported In

Solution

Using a USB DAQ for thermocouple measurements may be noisy for a variety of reasons:

The instrumentation amplifier input bias currents can move the voltage level of the floating source out of a DAQ input's valid range.
- This can be mitigated by using bias resistors to connect the thermocouple terminals to ground. See Field Wiring and Noise Considerations for Analog Signals for more information.
The low resolution of some USB DAQ devices (such as USB-6002 and USB-6008) may provide undesirable results when measuring the small voltage output of a thermocouple. There are potential workarounds for this:
- Read the signal in as a voltage instead of as a temperature and convert it with the Convert Thermocouple Reading VI
- Amplify the thermocouple output before it reaches the DAQ device
- Obtain data with another, higher resolution device

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