Thermocouple Measurement Uncertainty

Chance92

posted Aug 21 '23 at 9:56 pm

I am trying to calculate the measurement uncertainty of the system. I can't find any info in the manual. Does DT80 series 4 has any specified accuracy for thermocouple measurement or the internal cold junction compensation?

dataTaker Expert

posted Sep 5 '23 at 7:43 am

Hi Chance92,

dataTaker does not use the cold junction method since it is not applicable for portable loggers; however, we replace it by measuring the temperature on the board track using an RTD. The channel that is known as REFT is a temperature measurement coming from the RTD. If you can see the reading output from REFT, you should be able to read the thermocouple.

The accuracy for thermocouples in dataTaker is calculated through voltage measurement accuracy. You can find the formula in the DT8x user manual in the last section Q. That formula is only a guide on the worst-case situation, but you need to run the calculation based on the target temperature you want to read. At least for comparison.

The actual voltage reading accuracy can be seen from the calibration certificate, roughly 10 - 20% of the accuracy value from the calculation (5 to 10 times better than the calculation).

From the voltage reading accuracy, you can recalculate back to temperature using the thermocouple RvT table. And you will get the accuracy from the reading, please also consider the thermocouple accuracy as a sensor.

Best regards,
dataTaker Expert

Hi Chance92, dataTaker does not use the cold junction method since it is not applicable for portable loggers; however, we replace it by measuring the temperature on the board track using an RTD. The channel that is known as REFT is a temperature measurement coming from the RTD. If you can see the reading output from REFT, you should be able to read the thermocouple. The accuracy for thermocouples in dataTaker is calculated through voltage measurement accuracy. You can find the formula in the DT8x user manual in the last section Q. That formula is only a guide on the worst-case situation, but you need to run the calculation based on the target temperature you want to read. At least for comparison. The actual voltage reading accuracy can be seen from the calibration certificate, roughly 10 - 20% of the accuracy value from the calculation (5 to 10 times better than the calculation). From the voltage reading accuracy, you can recalculate back to temperature using the thermocouple RvT table. And you will get the accuracy from the reading, please also consider the thermocouple accuracy as a sensor. Best regards, dataTaker Expert

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