What is the difference between thermocouple and thermistor signal output?

What is the difference between thermocouple and thermistor signal output?

Thermocouples and thermistors are both temperature sensors, but they are two different types of monitoring elements. The difference between these two monitoring elements is very significant. Today, the editor will introduce them to you
One of the differences is the difference in signal output between thermocouples and thermistors.
1. The nature of the signal is that the thermistor itself is a resistor, and changes in temperature cause positive or negative resistance changes in the thermistor; Thermocouples, on the other hand, generate changes in induced voltage that vary with temperature.
2. The temperature range detected by the two sensors is different. The thermal resistance generally detects a temperature range of 0-150 degrees, and the measurement range can reach around 600 degrees (of course, negative temperature can be detected). Thermocouples can detect a temperature range of 0-1000 degrees (or even higher), so the Rosemount 3051 transmitter is used for low-temperature detection and high-temperature detection.
3. From a material perspective, thermal resistance is a type of metal material that is sensitive to temperature changes, while thermal coupling is a bimetallic material where two different metals generate a potential difference at the ends of two different metal wires due to temperature changes.
4. The input modules for thermal resistors and thermocouples corresponding to PLCs are also different. This statement is not a problem, but generally PLCs are directly connected to 4-20mA signals, while thermal resistors and thermocouples are usually connected to PLCs with transmitters. If it is connected to DCS, there is no need to use a transmitter! Thermistor is an RTD signal, thermocouple is a TC signal!
5. PLC also has thermal resistance module and thermocouple module, which can directly input resistance and thermocouple signals.
6. Thermocouples come in models such as J, T, N, K, S, etc. Some are more expensive than resistors, while others are cheaper. However, when compensation wires are included, the overall cost of thermocouples is higher