Effect of changes in ambient temperature on the temperature measured by thermocouples
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Thermocouples measure temperature based on the thermoelectric effect; theoretically, the cold end of a thermocouple should be at 0 degrees for accurate measurements. Therefore, we apply cold-junction compensation when using thermocouples to take temperature readings. The temperature in the control room changes very little, but the temperature of the cold end of thermocouples in the field is subject to significant variations due to environmental factors. The temperature difference between winter and summer is large – what impact does this have on the measurement results? When the temperature at the measurement terminal is lower than that at the compensation terminal, the temperature at the compensation terminal is displayed (in Rohde & Schwarz systems); when the temperature at the measurement terminal is higher than that at the compensation terminal, the actual temperature on-site is shown. I wonder if anyone has encountered this situation?
“When the temperature at the measurement terminal is lower than that at the compensation terminal, the temperature at the compensation terminal is displayed (in Enphase’s systems). Do you mean that it displays the temperature between the cabinets?
In Honeywell’s systems, the thermocouples have compensation built into the modules inside the cabinet. When the temperature at the measurement end is lower than that at the compensation end, the temperature at the compensation end is displayed. That is, when the measured temperature is lower than the indoor temperature, the indoor temperature is displayed. Solution: Add LA=, LB=, LC= with a certain value during low-level configuration. It’s usually 10. I think someone asked this question before
Confirmation: When the system thermocouples of 1 and Rossi measure a temperature lower than the indoor temperature, the indoor temperature is displayed. 2. For the Yokogawa CS3000 system, this refers to the temperature at the site.
However, the temperature at the cold end of the thermocouple on-site varies greatly due to environmental influences; there is a large difference between winter and summer. What impact does this have on the measurements? There shouldn’t be any impact, I guess. . . . The electromotive force of a thermocouple depends only on the properties of the materials that make up the thermocouple and the temperatures at the cold and hot junctions, whereas it is independent of the diameter and length of the thermocouple wire as well as the temperature distribution along its length.
As long as the length differences of the wires are compensated for, the measurements are generally accurate.
I don’t seem to have encountered this problem; usually, I work with high temperatures. . . . Learned * here
Regardless of whether the temperature of the cold-end environment changes, the temperature measured by the DCS system is not affected by it. If there is a problem with the DCS in the factory where the poster works, they can turn to the manufacturer for assistance in resolving it