Summary of Thermal Probes

On a relative scale thermal probe systems give reproducible and accurate measurements of ultrasonic power input provided that a few basic precautions are taken  

The preparation and nature of the coating should always be the same. 

The size of the probe should be small compared to the half wavelength of sound in the media. 

A reproducible size of the coating should be achieved, and when the size of the coating greatly exceeds the size of the thermocouple, the location of the tip of the probe inside the absorbing material should be carefully monitored. 

The coating should be periodically inspected and renewed because its sound absorbing properties change with time. This is especially true after prolonged exposure to cavitation which results in a different sensitivity of the probe. 

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