What is the difference between thermal resistor and thermocouple signal output?

1. The nature of the signal. The thermal resistor itself is a resistor. The change in temperature causes the thermal resistor to produce a positive or negative resistance change; while the thermocouple produces a change in induced voltage, which changes with the change in temperature.
2. The temperature ranges detected by the two sensors are different. The thermal resistor generally detects a temperature range of 0-150 degrees, and the maximum measurement range can reach about 600 degrees (of course, negative temperatures can be detected). Thermocouples can detect a temperature range of 0-1000 degrees (or even higher).
3. From the material point of view, the thermal resistor is a metal material with temperature-sensitive changes, and the thermocouple is a bimetallic material, that is, two different metals. Due to the change in temperature, an electric potential difference is generated at both ends of two different metal wires.
4. The input modules of the thermal resistor and thermocouple corresponding to the plc are also different. This sentence is fine, but generally plcs are directly connected to 4~20ma signals, while thermal resistors and thermocouples are generally connected to plcs with transmitters. If you connect to DCS, you don't need to use a transmitter! Thermocouples are RTD signals, and thermocouples are TC signals!
5. PLC also has thermal resistor modules and thermocouple modules, which can directly input resistance and thermocouple signals.
6. Thermocouples have models such as J, T, N, K, S, etc. Some are more expensive than resistors, and some are cheaper than resistors, but including compensation wires, the comprehensive cost of thermocouples is high.
Thermocouple output
If it is a K-type thermocouple, that is, the temperature is below 1250 degrees, you can use the thermocouple conversion chip max6675, which can convert the thermocouple signal into a 12-bit digital signal, eliminating the AD conversion, and there is compensation, which is very good.
K-type thermocouples can also use AD597, which can output voltage according to 10mV/c, and then AD sampling conversion!
But for higher temperatures, that is, about 1500 degrees, S-type thermocouples are needed. This amplification circuit is difficult. I plan to use the conversion chip AD693, which converts the voltage input of the thermocouple into a current of 4-20mA, and then converts it into voltage with a resistor.
1. Nature of the signal: Thermistors are divided into platinum resistors and copper resistors. The change in temperature causes the thermal resistors to produce positive or negative resistance changes; while thermocouples produce changes in induced voltage, which changes with temperature changes.
2. The temperature ranges detected by the two sensors are different. Thermistors generally detect a temperature range of -200-450 degrees, and the maximum measurement range can reach about 600 degrees (of course, negative temperatures can be detected). Thermocouples can detect a temperature range of 0-1800 degrees.
3. The input modules of thermal resistors and thermocouples corresponding to PLC are also different. This sentence is fine, but generally PLCs are directly connected to 4-20ma signals, while thermal resistors and thermocouples are generally connected to PLCs with transmitters. If you connect to DCS, you don't need to use a transmitter! Thermal resistors are RTD signals, and thermocouples are TC signals!
4. PLC also has thermal resistor modules and thermocouple modules, which can directly input resistance and thermocouple signals. In fact, for industrial components, it is the best way to understand their differences and choose according to your actual situation. After reading, you should pay attention to accumulation and you will make a good choice.