Resistance Temperature Detectors (RTDs) are more reliable and accurate than thermocouples. They have a sensing element which often contains a grid of conductive film or a coil of wire.
Materials to be used as sensing elements and wire materials for RTDs to select the suitable detector
The materials to be used as sensing elements for Resistance Temperature Detectors (RTDs) include platinum, nickel, copper, and iron. Platinum sensing elements can be exposed to temperatures of up to 1200 0F. Materials such as nickel/iron alloy, copper, and nickel can also be used. However, they cannot be exposed to higher temperatures like platinum. Their useful temperatures are often lower than platinum temperatures.
Materials such as tinned copper, nickel-plated copper, nickel alloys, and nickel can be used as wire materials. The maximum usage temperature for tinned copper is 221 0F, silver-plated copper 400 0F, nickel-plated copper 500 0F, and solid nickel wire 1200 0F (Desmarais et al., 2021).
How thermocouples types and temperature ranges are involved
Thermocouples have two electrical conductors made of different materials connected at one end. Various types of thermocouples include Types E, J, K, N, T, R, S, and B. Types E, J, K, N, and T are referred to as base metal thermocouples. They are made of silicon, iron, aluminum, nickel, and copper. Thermocouple types have their preferred usage conditions. For example, the temperature limit for Type J thermocouples is 1000 0F (Desmarais et al., 2021). Bare type T thermocouples have a limit of 700 0F. The temperature range for type S and R thermocouples is 1000 to 2700 0F, while the temperature range for type B thermocouples is 1000 to 3100 0F. Various types of thermocouples have different applications based on their temperature ranges.
References
Desmarais, R., & Breuer, J. (2021). How to select and use the right temperature sensor. SENSORS-PETERBOROUGH-, 18(1), 24-36.