Fluid Thermometry

The basic principles of fluid resistance thermometers are briefly stated, and the principles of the fluid oscillator types of temperature sensors are discussed in detail. The physical phenomena making an oscillator temperature-sensitive are covered including the edgetone effect and edgetone cavity coupling. It is pointed out that choked flow is required if the same modes of edgetone and cavity frequencies are to remain coupled over a large temperature range. Very fortunately this same condition (choked flow) makes the oscillator pressure insensitive.