Problems with S- and B-type thermocouple compensation wires
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If there are no matching S- and B-type thermocouple compensation wires, can ordinary copper-core wires be used as a substitute?
No. It can be heated on-site and transmitted as 4-20mA. Attached is the compensation wire chart:
No, it is necessary to specify whether the compensation wire is of K-type when ordering the cable for each type of thermocouple S-shaped, or others – they are not interchangeable with each other
What is the purpose of a thermocouple compensation wire? I have another question I don’t understand. Many control systems these days come equipped with thermocouple input cards, and the distance between these cards and the thermocouples in the field can be quite large, sometimes reaching hundreds of meters. How can we eliminate the voltage losses caused by the resistance of the connection wires, which in turn leads to measurement errors?
The voltage drop issue in long-distance transmission wires is minimal, as the input impedance of the temperature sensor is high; the thermoelectric potential generated by the thermocouple (on the order of millivolts) results in a very small transmission current (on the order of microamperes), leading to negligible voltage drop losses in the wires. Under normal circumstances, this is within the acceptable error range.
Type B thermocouples can use ordinary wires; double-shielded wires will suffice. The Type B thermocouples in our company use ordinary wires instead of compensation wires!
This post was last edited by broken01 on 2012-11-25 11:13. It is possible under certain conditions. It is sufficient to ensure that the ambient temperature of the thermocouple terminal box is the same as that of the secondary instrument, and this condition can be met—in my opinion.
No, it doesn’t meet the requirements for turtle testicles. . . . . . . . . . . . It’s still not allowed to say it again
It’s okay, but a compensation temperature needs to be added in DCS
It probably won’t work; I’ve never heard of it. A compensation wire is used to transmit the thermoelectrical potential to the DCS. Within 100 degrees, the thermoelectric properties of the compensation wire are identical to those of the thermocouple. If the temperature at the cold end of the thermocouple is the same as that at the DCS terminal, then a regular shielded wire can be used. However, if the distance is too great, there will be signal attenuation.
S-type wires are not suitable; compensation wires with an S rating must be used. For B-type wires, the thermoelectric potential is very small at low temperatures and can be ignored, so ordinary copper wires can be used as a substitute. As for the principle behind compensation wires, it is explained in many places; you can simply search for it on Baidu