Error in measuring the temperature of a B Type thermocouple below

[LAVA 1.0 Content]

In one of our applications,we are measuring temperature.We configured DAQ mx VI in AI Temperature,thermocouple.We are measuring temperature based on type and units as per the user configuration.For all thermocouple types except B Type,DAQ mx Read VI is giving correct values based on the range user configured.But,for B Type thermocouple,after 200 degrees to 300 degrees only,DAQ mx Read VI is giving correct values.If we source 0 degrees,DAQ mx Read VI is not giving any value.If we give 5 degrees to 90 degrees its showing temperature from 100 to 101 degrees.If we give 100 degrees,its showing 125 degrees.After 200 degrees only,DAQ mx Read VI is giving correct values.But range for a B Type thermocouple is -250 degrees to 1830 degrees.Is there any limitation in the measurement of temperature of a thermocouple of B Type?

Regards,

Naresh.N

[PaulG.]

A type B thermocouple is generally used for temps from 100 to 1800C and they are useless below 50C. A good overview to read is here. In the cases I was plotting data from type B's I just wrote the code to ignore temps below 100. I don't know if that is an option for you.

[Neville D]

Also make sure your DAQ can provide enough gain for TC measurement. The signal from a TC is in the uV, so you need a gain of minimum 1000 to get something meaningful.

Make sure your Cold Junction Compensation is correctly set as well.

N.