Analysis of the differences between thermocouples and RTDs

Thermocouples are made of two different metals connected together. The "hot contact" is in progress, and the "cold contact" is located at the controller. In theory, EMF (electromotive force) occurs at each junction, which is millivolt current and is related to the temperature at each junction. To measure a single temperature, one junction (usually a cold junction) is kept at a known reference temperature, while the other junction (a hot junction) is in the process of being detected. By combining artificial cold junction compensators (thermistors, such as thermistors or diodes), the controller subtracts the temperature of the cold junction from the signal of the thermocouple to eliminate errors in the cold junction, resulting in the actual temperature occurring at the hot junction. This is called cold end compensation.
Unlike thermocouples, RTDs (resistance temperature detectors) are generally made of platinum, nickel, or copper wires wound around ceramic or glass cores, which may be electroplated thin film components and sealed in ceramic or glass capsules. Due to changes in the working resistance of the RTD, the leads (from the RTD to the controller) have resistance and can add errors to the signal. If the lead wire is long, the error may be significant and must be corrected.
Industrial application of 3-wire RTD. Two wires are connected on both sides of the resistor. Measure the temperature of the resistor and the errors in the leads. One of these two wires has the other wire. When measuring these two wires on the controller, they only provide the resistance of these two wires. Then subtract the measurement value from the two wires of the resistor to eliminate the wire resistance. Now the controller only reads the temperature of the resistor.
Application differences:
According to the type of thermocouple (using different metals in production), thermocouples have a wide temperature range of -328 to 4800 degrees Fahrenheit. Thermocouples have fast response time, low initial cost, and durability, making them suitable for harsh industrial applications. The temperature range of RTD is -328 to 1202 degrees Fahrenheit. Due to its lower temperature scale, RTDs are more precise than thermocouples, resulting in a more stable output over time and easier calibration.