USB-TEMP Readings

[RaymondFang]

There is a discrepancy of readings from USB-TEMP and a digital multi-meter when connecting USB-TEMP to NTC.

The discrepancy is about 10 to 20% between USB-TEMP & digital multi-meter (ohm readings). The discrepancy getting higher as the temperature increases.

We have keyed in the correct Steinhart-Hart Coefficients in the Instacal setup.

The setup is No Scale (as we want the measured value to be RESISTANCE.)

We are using 2-wire NTC, single-sensor configuration.

Can you please advise what is the possible cause of discrepancy in readings from InstaCal  and ohmmeter ?

Thank you.

 

 

[JRys]

Connecting anything to the input terminals while the device runs can alter the measurement, especially if it's an ohm meter. Can you share why you're doing this?

[RaymondFang]

The end user is doing this as he would like to confirm that the measurement from USB-TEMP is accurate.

 

[JRys]

Instead of probing the input terminals, they could use a resistor to simulate a temperature. Take, for instance, this thermistor profile. For this 10k thermistor, a 270 ohm resistance should return a temperature close to 134 degrees C. Use a 1% or 0.1% resistor for best results.