We’re working on calibrations for a couple of your NI-9214 modules, running through a cDAQ-9185 chassis , and I have a few technical questions. We have everything wired to the unit, using: Omega Type PLTC TCHCPL 20AWG wire Omega K Type Thermocouples (similar gage) I have tried various thermocouples (still k type, but different sizes) on the same line, and are seeing similar results across the board. The issue that we’re running into is that we’re seeing fantastic response at temperatures near 100°C, but extreme deviations increasing as we approach 0°C. At 105° the reference probe is 104.98°C, and the thermocouple is reading 103.13°C. At 0°C, the reference probe is -0.16°C, and the thermocouple is reading 31.13°C. So my questions are: As the temperature decreases, the mV charge from the K type thermocouple also approaches 0, is this module sensitive enough to make sense of that voltage and provide accurate (±0.1 - 0.5°C) temperature readings near or below 0°C? The voltage/temperature reading from the probe seems to take an ridiculously long time to stabilize at lower temperatures, ~30min, is this possible interference at these temperatures? Given the simplicity of the K-type, the reading should be almost instant, just long enough for the temperature of the wire to reach equilibrium with the surrounding environment. When the thermocouple is placed into the ice bath the readings usually jump down/up and then slowly but steadily rise until they settle out after a while. Is this an expected behavior? (maybe related to the above question). Is there a maximum wire run length for the configuration we’re using? Thank you for your time and assistance in this matter.

Multifunction DAQ

Interference with K-type thermocouples and NI-9214 Sensitivity

We’re working on calibrations for a couple of your NI-9214 modules, running through a cDAQ-9185 chassis , and I have a few technical questions. We have everything wired to the unit, using:

Omega Type PLTC TCHCPL 20AWG wire

Omega K Type Thermocouples (similar gage)

I have tried various thermocouples (still k type, but different sizes) on the same line, and are seeing similar results across the board. The issue that we’re running into is that we’re seeing fantastic response at temperatures near 100°C, but extreme deviations increasing as we approach 0°C.

At 105° the reference probe is 104.98°C, and the thermocouple is reading 103.13°C.

At 0°C, the reference probe is -0.16°C, and the thermocouple is reading 31.13°C.

So my questions are:

As the temperature decreases, the mV charge from the K type thermocouple also approaches 0, is this module sensitive enough to make sense of that voltage and provide accurate (±0.1 - 0.5°C) temperature readings near or below 0°C?

The voltage/temperature reading from the probe seems to take an ridiculously long time to stabilize at lower temperatures, ~30min, is this possible interference at these temperatures? Given the simplicity of the K-type, the reading should be almost instant, just long enough for the temperature of the wire to reach equilibrium with the surrounding environment.

When the thermocouple is placed into the ice bath the readings usually jump down/up and then slowly but steadily rise until they settle out after a while. Is this an expected behavior? (maybe related to the above question).