Type B high-temperature thermocouples do not have an mv value
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Under normal conditions, the resistance when measuring on and off should be in the range of a few ohms to several dozen ohms, but this resistance is almost 0 ohms! Could you explain why it’s connected?
Ohm – either the gauge is broken or the thermometer is broken. To measure MV in water, it is necessary to have
Do you have a multi-functional signal generator there? You can set it to the B-type thermocouple mode, connect the thermocouple directly, discard all the compensation wires, measure the temperature obtained, and then compare it with the actual temperature to see if there is a fault. Type B thermocouples are suitable for use at high and low temperatures; however, their accuracy is relatively low and they are not very stable. It is best to determine whether they are functioning properly at high temperatures (unless a open circuit indicates that the device is broken); testing them at low temperatures isn’t very useful.
I have already measured the lotus root threads directly
Well, if the actual temperature is 500 degrees (it can be measured using an infrared thermometer, or by removing the thermocouple and installing a bimetallic thermometer to read the temperature), then if the signal generator also shows a temperature of around 500 degrees when measuring the thermocouple wire, there’s no problem.
The resistance of the thermocouple is zero; after ruling out issues with the measuring instrument, there may be a short circuit. However, to check the condition of a thermocouple, it is best to measure its thermoelectric potential; measuring its resistance does not provide much insight. However, for thermocouples with grade B, measuring the thermoelectromotive force must be done at high temperatures; for example, at a room temperature of 20 degrees Celsius, if the temperature at the hot end is 1000 degrees Celsius, the thermoelectromotive force will only be 4.8 mV.
Ignore the length of the compensation wire and use a multimeter to check for continuity in order to determine whether the thermocouple wire is good or not. It’s best to use a signal transmitter to directly measure the temperature read by the high-temperature thermocouple, as well as the MV values at low and high temperatures. Using a multimeter results in too large an error; after all, the MV values are already low.
Why is it connected? The front end of the thermocouple wire is originally welded together.
A value of a few dozen ohms should be fine
Just measure the temperature; why worry about so much!