Ultrasonic Spiral Strip Waveguide Sensor for Temperature Measurement of Solid Surface

Temperature measurement of a solid surface is critical in the process industries like reactor pipes, steel and glass melters, and hot plates. These high-temperature regions often need to be monitored using appropriate sensors. Ultrasonic waveguide sensor is a suitable sensor with no junction to fail compared to conventional temperature sensors (Thermocouple and Resistance Temperature Detector-RTD). Ultrasonic thin spiral strip waveguide sensor provides a better surface contact on the measurement region of interest, as it has a flattened surface compared to a cylindrical waveguide sensor. This work uses a conventional shear wave transducer (0.5 MHz) at the 0-degree orientation to the waveguide axis for transmitting and receiving the S0 wave mode in the spiral strip waveguide sensor. We intentionally made notches on the waveguide surface to get reflected signals to find the time of flight (ToF) for that sensor region. The reflected signal’s time of flight from the waveguide reflectors (notches) is used to measure the surface temperature of the hot plate at multiple locations. The change in time of flight (δToF) has been used to calibrate the spiral strip waveguide sensor with co-located conventional thermocouples. After calibration, the waveguide sensor measured the solid surface’s temperature at multiple locations (25–350 °C). This spiral strip sensor concept significantly improved the sensor’s sensitivity while measuring the solid surface temperature. The presented technique can monitor the temperatures continuously on sold plane surfaces.