Hydrogen Sensor Based on Peak-Delay Ultrasonic Time-of-Flight Measurement Using the Time-to-Digital Converter

A hydrogen gas sensor based on peak-delay measurement of ultrasonic time-of-flight (TOF) is reported. The sensor integrates a time-to-digital converter (TDC), a pair of 200 kHz ultrasonic transducers and an embedded microprocessor. An automatic identification delay measurement algorithm of ultrasonic signal characteristic peak is constructed innovatively to dynamically track the time domain feature of maximum amplitude. The time-to-digital converter has been used to measure the nanosecond time of flight accurately, which provides reliable time data for the hydrogen gas measurement. The experimental results show that the sensor presents a good linear response (R²=0.9989) in the hydrogen concentration (≤10%), and the detection sensitivity is up to 7.65 ppm/ns. At constant temperature, it showed rapid response (T90