Do ordinary temperature display instruments connected to thermocouples require temperature compensation?

If the connector is connected directly, there’s no problem; but if it’s connected after the wires are attached, that won’t work

Reply to 2# zzzi: Thank you. Isn’t it the case that the temperature values shown on the temperature display instrument are all based on the values from the scale? And the values on the dial indicator are all obtained at a cold-end temperature of 0 degrees. Isn’t compensation not needed when the operating environment is not at 0 degrees?

There must be some error; the cold end must be placed in a location with stable temperature

The connection from the thermocouple to the display gauge should use a compensation wire, right?

Temperature compensation is necessary, as the thermoelectric potential of a thermocouple is determined when its cold end is at 0°C. In actual measurement situations, however, the cold end of the thermocouple cannot be at 0°C. If the measuring instrument has automatic temperature compensation, the thermocouple can be connected directly to it (make sure that the calibration settings of the instrument match those of the thermocouple; a compensation wire should also be used). If the instrument does not have such automatic compensation, then a temperature compensator must be added, or the cold end of the thermocouple must be placed in an ice bath, or the compensation temperature must be calculated manually.

Reply to 6# jlszhoujidai: The compensation wire you mentioned is usually included with regular thermocouples, right? The thermocouple I purchased has a thermal electrode connected to a wire, which is further divided into red and blue wires; can I simply connect these two ends directly to the back of the temperature controller? Is a compensation wire included in this case? Is it necessary to connect an additional compensation wire?

Reply to 7# kai_ma1984: From what you’ve described, the thermocouple you purchased already comes with a compensation wire~~~~

OP, there are already many theories mentioned above, so I won’t go into further detail. In practical applications, if the display instrument and the thermocouple are in the same environment and at a short distance apart, it is not necessary to use a compensation wire ； If the display instrument and the thermocouple are not in the same environment (for example, the display instrument is indoors while the thermocouple is outdoors), or if the distance between them is large, a compensation wire must be used.

What the original poster is referring to is probably not the compensation wire, but rather the leads of the thermocouple itself, which only reach the terminals of the thermocouple; generally, thermocouples do not come with compensation wires.

The function of a compensation wire is to extend the thermocouple and bring its cold end to a location with a more stable temperature (usually the control room). The cold-end temperature can then be adjusted manually, by setting the instrument’s zero point at room temperature, or through automatic compensation by the circuit within the instrument. It is also impossible to extend precious metal thermocouples, as the high cost makes it unfeasible; instead, base metals with similar thermoelectric properties are used as extension wires. The intermediate temperature rule forms the theoretical basis for the use of compensation wires. Compensation wires cannot automatically compensate for changes in the temperature at the cold end of the thermocouple; they merely move the cold end of the thermocouple to a location with a more stable temperature. Compensation still needs to be carried out manually using instruments. Therefore, the compensation wire should be called a thermocouple extension wire, so as to avoid misleading people. Additionally: When selecting thermocouple compensation wires, it is necessary to ensure that the models are compatible and that the polarity is correct; moreover, the temperature at the connection point between the compensation wire and the thermocouple should not exceed 100°C. If you don’t require high temperature measurement accuracy and the temperature difference between the thermocouple terminals and the instrument terminal is not significant, ordinary copper wire can be used.