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Why there is no COLD JUNCTION COMPENSATION BOXES are used for Thermocouples?

Please reply ASAP.....

Email-sarathbeece@gmail.com

Typically handheld electronic thermometers and electronic multi-purpose measuring instruments (such as multimeters) use ambient temperature compensation by an internal temperature measuring device as cold junction compensation is mostly impractical for portable instruments. CJC usually consists of inserting one portion of the TC circuit into a system (such as a CJC dry block or an water-ice bath) that is very close to 0 degrees C. However, this can be electronically compensated with pretty good precision by comparing the ambient temp to the TC probe temp.

Typically the compensation is done electronically. The temperature of the "cold" junction (the place where the thermocouple extension wire is connected to copper wire) is measured via an RTD (or possibly a thermistor if cost is more important than accuracy) and that temperature algebraically added to the measured process temperature.

I started in gas turbine controls back in 1968, and in that time the only place I have encountered an ice bath type cold junction is in laboratories.