Questions about thermocouples
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For a normal thermocouple, the positive and negative terminals should be connected, resulting in a very low resistance value. But with this multi-point thermocouple, the connection doesn’t work; the resistance is around 200–500 ohms. Could anyone please explain this? It’s a K-type thermocouple with a length of over 5 meters
A thermocouple generates a thermoelectromotive force due to the difference in temperature between its measuring end and the wiring terminal; measuring its resistance with a multimeter can result in certain errors, and it is normal for the resistance value to range from 200 to 500Ω.
1. If it’s a single-point thermocouple, its resistance is indeed a bit high! 2. It is suspected to be a temperature measurement cable, used to measure the temperature at the highest point of the entire thermocouple ； However, the resistance value is on the low side. It’s best to ask the manufacturer.
““Multi-point thermocouple”? 1. How many points are there? 2. What is the temperature measurement range? ... .
3. Take a photo of the label and take a look.
I’m interested in the multimeter UT71D you use. For its current in mA setting, how many decimal places can it display? Some time ago, I bought a few UT61E units. Once everyone started using them, it was discovered that the current measurement in mA could only be displayed up to 0.001mA – there was one digit missing, which made the reading seem quite inaccurate.
A thermoelectric potential is generated when the temperature at the measuring end of the thermocouple differs from that at the wiring terminal, and measuring its resistance can result in certain errors. A resistance value of 200–500Ω is considered normal; what matters most is the calibration rating.