The difference between thermocouples and thermal resistors is one: the nature of the signal
The nature of the signal, the thermoelectric resistance itself is a resistance, and changes in temperature cause a positive or negative change in resistance value; And thermal coupling is the change in induced voltage that changes with temperature.
The difference between thermocouples and thermal resistors is that the temperature range detected is different
The temperature range detected by the two types of sensors is different, and the thermal resistance generally detects a temperature range of 0-150 degrees, with a maximum measurement range of around 600 degrees (of course, negative temperature can be detected). Thermal coupling can detect temperatures ranging from 0 to 1000 degrees (or even higher), so the former is for low temperature detection and the latter is for high temperature detection.
The difference between thermocouples and thermal resistors is three: different materials
From a material perspective, thermal resistance is a metal material with temperature sensitive changes, while thermal coupling is a bimetallic material that generates potential differences between two different metals due to temperature changes.
The difference between thermocouples and thermal resistors is four: input module
The input modules of the thermal resistor and thermocouple corresponding to the PLC 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 the PLC with transmitters. If connected to DCS, there is no need to use a transmitter! Thermistor is an RTD signal, thermoelectric ohm is a TC signal!
The difference between thermocouples and thermal resistors: PLC
PLC also has thermal resistance modules and thermocouple modules, which can directly input resistance and thermocouple signals.
The difference between thermocouples and thermal resistors six: price
There are models of thermocouples such as J, T, N, K, S, etc. Some are more expensive than resistors, while others are cheaper than resistors. However, when considering compensation wires, the overall cost of thermocouples is higher. Thermal resistance is a resistance signal, and thermocouple is a voltage signal
The difference between thermocouples and thermal resistors seven: Principles of temperature measurement
The principle of thermal resistance temperature measurement is based on the property of the resistance of a conductor (or semiconductor) changing with temperature, with a measurement range of -00-500 degrees. Commonly used include platinum resistance (Pt100, Pt10) and copper resistance Cu50 (-50-150 degrees).
The principle of thermocouple temperature measurement is based on the thermoelectric effect to measure temperature. Commonly used methods include platinum rhodium platinum (scale S, measurement range 0-1300 degrees), nickel chromium nickel silicon (scale K, measurement range 0-900 degrees), nickel chromium constantan (scale E, measurement range 0-600 degrees), and platinum rhodium 30 platinum rhodium 6 (scale B, measurement range 0-1600 degrees).
Ordinary thermocouples are generally composed of thermal electrodes, insulation pipes, protective sleeves, and junction boxes, while armored thermocouples are a solid combination of thermocouple wires, insulation materials, and metal protective sleeves that are assembled and stretched. But the electrical signal of the thermocouple requires a special wire