Noncontact Temperature Measurements of Hot Steel Bodies Using an Electromagnetic Acoustic Transducer (EMAT)

A noncontacting sensor system for measuring the average internal temperature of hot steel objects has been developed. The system uses a pulsed ruby laser for the generation of the acoustic wave and a pulsed Electromagnetic Acoustic Transducer (EMAT) as the receiver in a through-transmission technique. The pulsed EMAT design has been successfully tested to 1300° Celsius on a nine-inch-long stainless steel sample. The system measures the time-of-flight of the acoustic wave, which is coupled with the part dimension to determine the average acoustic velocity. From a calibrated relationship between velocity and temperature, the average sample temperature is determined.</p