The basic law of thermocouples:
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1. Law of homogeneous conductors. A closed loop composed of a homogeneous conductor (or semiconductor) cannot generate a thermoelectric potential, regardless of the cross-sectional area of the conductor (or semiconductor) or of the temperature distribution throughout it. To generate a thermoelectric potential, a thermocouple must be made of two materials with different properties. 2. Law of the intermediate conductor. By inserting third and fourth conductors into the thermocouple circuit, as long as the temperatures at both ends of the inserted conductors are equal and the inserted conductors are homogeneous, the temperature distribution within those conductors will not affect the value of the original thermoelectric potential. 3. Law of intermediate temperature. The thermoelectromotive force of a thermocouple at junction temperatures t and t0 is equal to the algebraic sum of its corresponding thermoelectromotive forces at junction temperatures t and tn, and tn and t0; that is, EAB(t, t0) = EAB(t, tn) + EAB(tn, t0). Those who are familiar with measuring instruments should know this – it’s something from old textbooks, brought back here to be reviewed once again!
I need help: What are the differences between thermocouples and thermal resistors in terms of their areas of application?
In terms of application scenarios, there isn’t much difference; thermocouples are generally used to measure relatively high temperatures, while thermal resistors are used to measure relatively low temperatures
Reply to floor 2: There are various types of thermocouples, which are generally used for measuring temperatures above 500°C. There are two common types of thermal resistors: Pt100 and Cu50. The platinum thermal resistor Pt100 is used for measuring temperatures below 500°C, with a measurement range of 500°C to –200°C℃； The copper thermoresistor Cu50 is used for temperature measurement below 150°C, with a measurement range of 150°C to –50°C. This post was last edited by mlxx2008 on 2008-11-14 16:51.]
Learn the knowledge on Floor 1; agree with the view on Floor 4
I’d like to add regarding the fourth floor: in certain situations, the precision may vary, with grades A and B.
First, the selection is based on the range; since PT100 thermistors are made by winding very thin platinum wires, their lifespan is relatively short in high-temperature environments above 300 degrees. And nowadays, standard resistors are generally made of platinum resistors. It has high precision, which is why thermal resistors are basically used at low temperatures.
What are the consequences if a thermocouple is not insulated?