Heat Treatment Oven

[m_c]

Something I never knew until I covered Thermocouples as part of an HNC course last year, was that thermocouples are a precise loop, so if you change any wiring, you may need to re-calibrate them.
I'll admit it's something that I've never personally used, but always thought the wiring between the actual thermocouple and the interface wasn't that critical, but apparently it is

 

[daleyd]

lol Something I never knew until I covered Thermocouples as part of an HNC course last year, was that thermocouples are a precise loop, so if you change any wiring, you may need to re-calibrate them.
I'll admit it's something that I've never personally used, but always thought the wiring between the actual thermocouple and the interface wasn't that critical, but apparently it is

RTD are more picky, but depending what type you have they can self compensate (2 wire rtd don’t have any compensation, 3 and 4 wire do) for length of wires. As you add more length the resistance of the whole system changes, a 3 or 4 wire measures the resistance of the 3rd/4th wire and subtracts it from the actual “measured”resistance.

Thermocouples usually aren’t as susceptible using the correct compensating cable, but depending on the application you might be asked to calibrate the whole thing again - aerospace have particularly stringent requirements (as you’d expect I guess). For aerospace heat treatment the thermocouples also have a lifespan, depending on the number of uses and the temperature they are used at (hotter temps = less uses and vice versa), irrespective of if they are in cal or not.