How to determine the positive and negative poles of a thermocouple
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For various reasons, there are issues with the positive and negative wiring of the thermocouples (K-type) installed on site; some of them are connected reversely, and the “+” and “-” markings on the thermocouple terminals can no longer be used as a reference. Some simply don’t have “+” or “-” marked. How can one easily and simply identify the positive and negative poles of a thermocouple?
You can use the millivolt setting on a multimeter.
Reply to 2# cxhsdqd: Please be more specific
If it’s reversed! The temperature will be much lower! ! Look, the two cores have different colors! I feel that for nickel-chromium-nickel-silicon, the slightly green one is positive and the gray one is negative
1. It can be determined using the millivolt setting on a multimeter. 2. The positive and negative poles of a K-type thermocouple can be identified by checking whether the thermocouple wire is significantly magnetized; those that are significantly magnetized are nickel-silicon or nickel-aluminum types, and these serve as the negative poles
Reply to 5# dmsh444: :'( The gauge doesn’t have a magnet. Do you mean to use the millivolt function on a multimeter to measure voltage? Is the voltage reading obtained by connecting the positive and negative terminals of a multimeter to the positive and negative terminals of a thermocouple higher than that obtained by connecting the negative and positive terminals of the thermocouple?
Reply to 6# seven7: Connect the positive terminals together and the negative terminals together; it will display the positive millivolts, otherwise it will display the negative millivolts
Reply to 7# dmsh444: Sometimes, even when measuring directly with the correct settings, a negative millivolt value is obtained. We have encountered such situations; under normal operating conditions, the temperature reading always seems to be incorrect, being too low. It was only later that it was discovered that the positive and negative poles were reversed.