Questions about K thermocouples
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Due to the heating-up process of the new furnace in the facility, a K-type thermocouple 3 meters long was selected for temperature measurement. A KC compensation wire was used; there is no digital display unit connected to it, and the operator uses a digital display to read the temperature by connecting the compensation wire. However, when using a multimeter to measure the resistance value of the thermocouple, only a resistance value of 3-4 ohms is obtained. What is the reason for this? The multimeter is fine. The wire connection is normal.
Reply to 1# 276295553: This resistance value is within the normal range! A thermocouple itself consists of two metal wires, so its resistance should not be very high. Additionally, for thermocouple outputs, a multimeter is generally used to measure their “millivolts (mV)” value ； As for the output of a thermal resistor, it is measured using the “resistance” setting.
Thank you for your help, big brother on the second floor. How do I convert the measured MV value to temperature? Is there a fixed formula? Checking the lookup table directly doesn’t seem to be very accurate.
Reply to 3# 276295553: Use the “measured millivolt value” plus the “millivolt value corresponding to the ambient temperature”, then consult a table to obtain the corresponding “temperature value”.
Digital meters usually have a direct conversion function; check the wiring diagram in the manual – it’s generally available there. Once it’s set up, that’s it. Alternatively, a temperature transmitter can be used to convert the signal to 4 to 20mA and send it to the display instrument.