Orcinus tiped us about this interesting app note on acoustic thermometry from Linear Technology:
People usually measure temperature in order to correct the distance determined using ultrasonic transducers. Acoustic thermometry takes the opposite approach – the distance is fixed and the time it takes for an acoustic pulse to make a round trip is used to calculate the deviation from a standard and, indirectly, the temperature.
Why would anyone want to do that? The app note lists a number of reasons, including:
– resistance to environmental extremes (temperature, radiation)
– very quick response
– does not require iso-thermal measurement path
– almost entirely insensitive to pressure and humidity
– makes for an interesting exercise in signal conditioning
Thanks Orcinus! Via the forum