New temperature sensor sounds good

June 2, 2011, National Physical Laboratory
Acoustic thermometers could be used in hostile industrial environments (image courtesy of iStockphoto)

Temperature scientists at NPL are developing a thermometer that uses sound waves to measure temperature.

The thermometer works on the principle that the speed of sound changes with , travelling faster through warmer air. Such an instrument could potentially replace traditional thermometers in environments where cause a loss of accuracy.

NPL's Michael de Podesta, who leads Acoustic Thermometry research, said, in an interview with The Engineer magazine: "Potential uses include any hostile environment [for example] inside a furnace above 1,000 °C."

"Any contact thermometer used in this environment degrades as soon as it is used and is usually placed in the environment inside a protective tube. The practical acoustic thermometer consists just of the tube itself."

The acoustic works by transmitting along a gas-filled tube from a speaker at one end to a microphone at the other. By measuring the amount of time it takes the sound waves to travel along the tube, the temperature can be calculated.

"The principle is very simple but the application is pretty complicated," said Dr Rob Simpson from the Engineering Measurement team. "The difficult part is working out how to produce the sound and then how to listen to it."

Acoustic thermometry offers a cheap and robust alternative to current instruments, and could potentially reduce the need for equipment to be replaced and calibrated, providing cost and efficiency savings to industry.

Explore further: Scientists design bomb-proof thermometer to measure the heat of explosions

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not rated yet Jun 02, 2011
Thermocouples are going to work just as well if not far far better, not to mention they are very cheap. I do not see any application for this device as it cirtainly will not be replacing good old thermocouples and RTDs, unless.....

If you can make it a non-contacting temperature sensor, it would definitely have a few application. In otherwords, you would need to make a sound laser (which has been developed) and would need to be able to point it at the process. That being said, IR radiation is a more direct way of measuring temperature and has the same functionality.

Yeah, I don't see the need or any real world advantages or application.

I am an instrumentation & controls engineer.
not rated yet Jun 02, 2011

In my line of work I have a need to accurately measure temperature as high as 2000°C where the emissivity of the target is usually unknown or changing with both time and temperature and must be acquired through a quartz window. Tungsten-Rhenium thermocouples are extremely expensive and a prone to breakage. Assuming the gas in the tube was a good proxy for the process temperature this sort of technology would be very useful.

I know of others with more demanding and pressing needs than this... instrumentation development is certainly not complete.

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