1. RTD platinum resistance element: This is the actual temperature sensing portion of the RTD. Elements range in length from 1/8" to 3". There are many options. The standard temperature coefficient is an alpha of .00385 and the standard resistance is 100 Ω at 0° C.
2. RTD Outside diameter: The most common outside diameter is ¼" in the US or 6mm (.236") for non-US applications. However, outside diameters range from .063" to .500"
RTD Tubing Material: 316 Stainless steel is commonly used for assemblies up to 500° F. Above 500° F it is advisable to use Inconel 600.
3. RTD Process Connection: Process connection fittings include all standard fittings used with thermocouples (i.e. compression, welded, spring-loaded, etc.).
4. RTD Wire Configuration: RTDs are available in 2, 3 and 4 wire configuration. 3 wire configurations are the most common for industrial applications. Teflon and fiberglass are the standard wire insulation materials. Teflon is moisture resistant and can be used up to 400° F. Fiberglass can be used up to 1000° F.
5. RTD cold end termination: RTDs can terminate on the cold end with plugs, bare wires, terminal heads and any of the reference junctions common to thermocouples