Calibration of thermocouple temperature measurement circuit
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I’m seeking help from experts: Regarding the calibration of the thermocouple temperature measurement circuit, the temperature at the field site is different from the cold-end compensation temperature in the control room. The millivolt signal is sent from the field site; should the millivolt value corresponding to the temperature be reduced by the millivolt value of the temperature at the field site, or by the millivolt value of the cold-end compensation temperature in the control room??
The thermoelectric potential of a thermocouple is the difference between the temperature functions at its working ends, rather than the difference between the temperature functions at its cold end and its working ends；
The compensation issue must be considered in the temperature loop verification. The millivolt signal of the circuit entered on-site using a calibrator is obtained from the thermocouple calibration table, which shows the potential values measured under standard conditions (0°C, 101.325 Kpa). Therefore, it is necessary to add the potential value corresponding to room temperature; this is the actual value displayed by the circuit. The potential value measured in the control room must be subtracted from the room temperature potential value to obtain the actual temperature inside the thermal container. Learn more about the principles behind thermocouple temperature measurement, and you’ll understand it.
Subtract the millivolt value of the cold-end compensation temperature in the control room
The answer to the question states \"subtract the millivolt value of the field-side temperature\", so is that wrong?
When using compensation wires, the millivolt value of the cold-end compensation temperature in the control room must be subtracted during calibration.
The thermocouple calibration table is measured at t0 = 0°C. When to is greater than 0, the central control MV value decreases; in this case, an additional MV value needs to be added as compensation. Conversely, when to is less than 0, the central control MV value is too high, and at this time a negative MV value needs to be added as compensation
Subtract the ambient temperature at that location from the MV value you measured there.
First, check the millivolt value corresponding to the control room temperature. When entering the millivolt value for the control room on-site, add the millivolt value of the point being calibrated to this value; then enter the resulting figure into the display instrument in the control room. In this way, the temperature shown on the instrument in the control room will be the actual temperature of the point being calibrated.
Correct answer: Subtract the millivolt value of the field terminal temperature； The control room’s millivolt value is automatically compensated by the safety barrier or card.