How to quickly understand thermocouples and thermal resistors?

Looking at the terminal connections, those with positive and negative limits are thermocouples, while those without such limits are thermal resistors. Additionally, thermal resistors usually have three terminal connections, whereas thermocouples have only two.

For thermocouples, check the voltage; for thermal resistors, check the resistance

A thermoresistor has three wires for a resistance signal (RTD), while a thermocouple has two wires for an mV signal.

Thermal resistors are almost always 3-wire or 4-wire, while thermocouples are almost always 2-wire (though dual-element types exist as well)!

The main difference lies in their working principles: thermal resistors rely on the thermoresistive effect (where temperature changes are reflected through changes in resistance); they are usually three-wire systems, though two-wire versions also exist. Thermocouples, on the other hand, utilize the thermoelectric effect (where temperature changes are indicated by changes in voltage); they generally consist of two wires (along with a compensation wire). The original poster can search online and compare the features of the two

The simplest way is to check how many wires are connected to the terminal. . . Thermocouples usually have 2 wires, while thermal resistors typically have 3 wires. . . . Next is to check the temperature measurement range. . . . Thermal resistors are mostly used below 480°C, while thermocouples are commonly used for measuring high temperatures. . .

Hello, I understand your confusion. For example, when there are many thermistor elements or thermocouple elements placed on a temperature rack, it can be difficult to quickly find the temperature you’re looking for. Firstly, they look similar in appearance, and thermal resistors also come in two-wire versions. The PT100 material is platinum, which is relatively soft; the material of thermocouples is harder, so it’s easy to tell the difference. One can also observe the color of the outer coating of the odd filaments or barrier filaments; the colors of these barrier filaments are usually quite vivid (yellow, red, white, blue, green, etc.), while there are specific regulations regarding the color of the outer coating of the odd filaments. Third, if you have a toolkit with a multimeter, use it for a final check (it’s also possible to determine whether the temperature sensor is functioning properly). Set the thermistor to the resistance setting, and set the thermocouple to the MV setting (pay attention to the position of the test leads).

The PT100 material is indeed platinum, but many of those seen in use on site are armored; the leads of these armored versions are made of nickel, not platinum – otherwise they would be even more expensive than noble-metal thermocouples. The leads of platinum resistance elements are generally not pure platinum, and those that are plated with platinum are already considered to be of high quality.

According to what you said, with the multimeter set to the mV range, it should show zero, right?