I am relatively new to thermocouples. We are wanting to get the temperature of fire ball blast. We are using a Type-K thermocouple and a Phoenix Contact mini signal conditioner to amplify the signal. I am using a thermocouple DAQ to record the amplified voltage out from the signal conditioner (a 0-5V analog output) with a 150ms sampling period.

Questions I have:

  1. Do I require cold junction compensation? If so, is it best to just set it to 0°C? If not, how do I find out what it needs to be?
  2. What is the best way to calibrate it and how do I convert the amplified signal (V) back into a relative temperature (°C)?

Your signal conditioner contains linearization and automatic cold-junction compensation, as well as isolation. If there's an option to turn it off, don't do that. You'd only want to turn it off if you were doing some kind of strange differential measurement with two thermocouples.

All you have to do to get degrees C from the output voltage is to scale and offset the resulting value to represent the temperature range, which apparently is configured via a software interface with the signal conditioner.

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    \$\begingroup\$ The NIST ITS-90 database may also be useful, though the equipment may do it internally. \$\endgroup\$ Sep 20 '19 at 0:49
  • \$\begingroup\$ @CalebReister The datasheet says the output is linearized and compensated, so there is nothing to do in this case, but it's always good to have links to the tables and forward and inverse polynomial coefficients. \$\endgroup\$ Sep 20 '19 at 1:15
  • \$\begingroup\$ The thermocouple wires are welded, forming a 2mm bead. That bead will have a thermal timeconstant. I know a silicon cube of size 1mm has thermal timeconstant of 11.4 milliSeconds. Your thermocouple bead will have similar, or SLOW, thermal response. Does a 50 millisecond time constant provide good fireball measurement? \$\endgroup\$ Sep 20 '19 at 4:20

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