Design of a High-Resolution Ultrasonic Temperature Meter for Soft Tissue-Mimicking Phantoms based on a PSoC Module

The measurement of temperature using non-invasive ultrasonic methods is based on changes in the ultrasonic velocity due to the temperature variation in the medium. This article describes an electronic device for measuring temperature in soft tissue-mimicking phantoms using a PSoC-5LP module, PVDF ultrasonic transducers (LDT1-028K), and an External Circuit Module. Control signals, signal acquisition and display of the temperature value are programmed using a PSoC module. The External Circuit Module was implemented with a PVDF transducer driver, an RF amplifier and a pulse voltage converter. In the experimental implementation, a distance was set between the PVDF transducers and then an operating temperature interval was selected. Considering these specifications, the flight time of the ultrasonic wave at the initial temperature is detected, which is compared with the flight time of the temperature to be measured. The difference between flight times produces a narrow pulse being converted to DC voltage, which is proportional to the temperature change. The device for measuring temperature in soft tissue-mimicking phantoms was designed to work at an operating frequency of 1MHz and a temperature measurement interval from 350C to 400C with a 0.10C resolution. The experiment was carried out using a temperature controlled water tank (bath); the device has a sampling rate of 100 samples per second, calculates the average and display the result with a refresh rate of one second. The device developed was found to be useful to measure temperature in soft tissue-mimicking phantoms due to the selected temperature interval and the resolution obtained.