Resistance Temperature Devices RTD Applications
Resistance Temperature Devices RTD Applications
Besides measuring temperature, RTDs are also used to construct other sensors, for example, bolometers and gas mass flow meters. A bolometer (Figure 1.a) consists of a miniature RTD and a resistor to measure electromagnetic radiation range from infrared to microwaves. When electromagnetic radiation presents, the resistor absorbs the radiation and converts it into heat.
Figure 1. (a) Internal structure of a bolometer; (b) an oxygen gas flow meter.
This temperature elevation is then measured by the RTD sensor, whose resistance change indicates the radiation level. Bolometers are broadly used in infrared temperature detection and imaging, high power measurement, microwave device testing, radiofrequency (RF) antenna beam profiling, and medical microwave heat monitoring. The oxygen flow meter shown in Figure 1.b is designed by FOX Thermal Instruments, Inc., Marina, California. It consists of two RTDs: a reference RTD and a heated RTD—both RTDs are constructed of reference-grade platinum wire wound around ceramic mandrels and then inserted into stainless-steel or Hastelloy tubes. The reference RTD measures the gas temperature. The other RTD is heated to a constant temperature differential (ΔT ) above the gas temperature and the cooling effect of the gas flow is measured. The electrical power required to maintain a constant temperature differential ΔT between the two RTDs is directly proportional to the gas mass flow rate.
