Temperature transducers resistance thermometers

Whereas it is no longer an iaterpolation standard of the scale, the thermoelectric principle is one of the most common ways to transduce temperature, although it is challenged ia some disciplines by small iadustrial platinum resistance thermometers (PRTs) and thermistors. Thermocouple junctions can be made very small and ia almost infinite variety, and for base metal thermocouples the component materials are very cheap. Properties of various types of working thermocouple are shown in Table 3 additional properties are given in Reference 5. 

A bolometer is a type of resistance thermometer constructed of strips of metals, such as platinum or nickel, or of a semiconductor. Semiconductor bolometers are often called thermistors. These materials exhibit a relatively large change in resistance as a function of temperature, The responsive element is kept small and blackened to absorb radiant heat. Bolometers are not so extensively used as other infrared transducers for the mid-infrared region, Flowever, a germanium bolometer. operated at 1..3 K, is nearly an ideal transducer for radiation in the. 5 to 400 cm (2000 to 2.3 pm) range. 

Vapor pressure and gas thermometry offer sensitive methods of temperature measurement with the advantage that no calibration is necessary. Further advantages are that these transducers are not sensitive to magnetic fields or electric fields. In the case of vapor pressure thermometers, the time response may be made comparable to the resistance thermometers. 

---