Problems with thermocouple temperature measurement
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As the title suggests, when the distance between the heating end and the cooling end of a thermocouple is small, is it possible to avoid using a compensation wire, and instead place one end of the thermocouple in an ice bottle to achieve zero-point compensation?； What is the difference between compensating wires of the compensatory type and the extended compensatory type? ? ? Which one can achieve more accurate measurements
It is possible to achieve zero-point compensation by placing one end of the thermocouple directly in an ice bottle, without the need for a compensation wire. Note that it is one end of the thermocouple, not the lead wire from that end; if a lead wire is used, it must be a compensation wire. The material of the compensating wire used for compensation is different from that of the thermocouple; it can only maintain the same (actually, approximately the same) T-E characteristics as the thermocouple at room temperature ； The material of the extended compensation wire is the same as that of the thermocouple; it can even be used directly to make a thermocouple. B, R, and S thermocouples do not have extended compensation wires (and even if they did, they couldn’t be used) ； E, J, and T thermocouples do not have compensated wires (they are too cheap to warrant development) ； Only K and N thermocouples come equipped with both compensated and extended compensation wires. Generally speaking, extended compensation wires truly extend the thermocouple, so they offer higher precision.
Extended compensation wires are more expensive than standard compensation wires; therefore, for accurate measurements, standard compensation wires are generally used. The material of the compensating wire in a compensating type is the same as that of the thermocouple.
Thank you for the reply; the explanation about compensation wires was very helpful. I still have some questions regarding setting the zero-point compensation point. You wrote in your reply: Note that it is one end of the thermocouple, not the lead wire coming from that end; if a lead wire is used, it must be a compensation wire. May I understand it this way: if no compensation wire is used, the zero-point compensation must be set at the end of the thermocouple (that is, the cold end)? ?
That’s exactly what I mean. Zero-point compensation must be set at the cold end of the thermocouple
Thank you for your advice:handshake:handshake. Are there any good instruments available on the market that can provide zero-point compensation? ? ? It seems that neither the Agilent data acquisition device nor the DC potentiometer can perform zero-point compensation; is it necessary to use an amplification circuit for this purpose?
Temperature indicators available on the market (single-point, multi-point, intelligent) can all meet the requirements for temperature compensation within their accuracy specifications. Neither data acquisition systems nor potentiometers are specialized thermocouple temperature measurement devices; temperature compensation for them must be carried out separately. If a dedicated thermocouple temperature compensator is used (this isn’t common; you might want to look it up on Baidu).
What is usually meant when talking about compensation wires is that they act as an extension of the thermocouple, moving the cold end from the connection point at the site of the thermocouple to the control room… In fact, this refers to the effect achieved after using compensation wires for temperature compensation. In other words, the function of a compensation wire is to generate a thermoelectric potential that is related to the temperature difference between the wiring terminals of the thermocouple at the field site and the temperature in the control room, thereby compensating for that temperature difference.
What is usually meant when talking about compensation wires is that they act as an extension of the thermocouple, moving the cold end from the connection point at the site of the thermocouple to the control room… In fact, this refers to the effect achieved after using compensation wires for temperature compensation. In other words, the function of a compensation wire is to generate a thermoelectric potential that is related to the temperature difference between the wiring terminals of the thermocouple at the field site and the temperature in the control room, thereby compensating for that temperature difference.
I’m from a thermocouple manufacturer; let’s communicate! Look at my profile picture; P