An Ultrasonic Time of Flight Sensing System Based on Custom Hardware of Time to Digital Converter (TDC) for Measurement of Glucose Concentration

• Published in: IEEE sensors journal Vol. 24; no. 7; p. 1
• Main Authors: Zalke, Jitendra B., Pandey, Sandeepkumar R., Narkhede, Nitin P.
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-04-2024; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analog to digital converters; Anniversaries; Correlation coefficients; Digital to analog converters; Field Programmable Gate Array (FPGA); Field programmable gate arrays; Glucose; Hardware; Pulse Interpolation Technique (PIT); Pulse Shrinking Time to Digital Converter (PSTDC); Room temperature; Standard deviation; Time measurement; Time-of-flight (ToF); Ultrasonic wave; Velocity measurement; Wave propagation
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2024.3363763

The proposed work presents a custom hardware implementation of Pulse Shrinking Time to Digital Convertor (PSTDC) on a Field Programmable Gate Array (FPGA) for the measurement of Time-of-Flight (ToF) of an ultrasonic wave. The PSTDC is used here to measure a time interval between two events (START and STOP) and convert it into a corresponding digital output value. It improves the measurement accuracy by estimating the width of pulse between the time intervals, which is dependent on the ToF of the signal. The proposed system was successfully implemented on FPGA to measure the ToF of an ultrasonic wave when propagated through the glucose (aqueous) solution. The experiments were conducted, and around 50 readings were taken for approximately 8 hours at various concentrations of glucose (aq.) solution at room temperature (27°C). The experimental results show the correlation factor (R 2 ) equal to 0.99997 between glucose concentration and corresponding velocity measurement. A Relative Standard Deviation (RSD) of 0.01395, a standard deviation of 0.203, and relative error within ±1.48%, was obtained between the measured and actual value of glucose concentration which provides us the accuracy of around 98.52%. The obtained result shows that the proposed system can be useful in the design of an ultrasound system for precise measurement of the ToF of the signal. The proposed implementation process the signal in the digital domain, thus avoiding signal conditioning front-end such as Analog-to- Digital Converter (ADC), Digital to Analog Converter (DAC), etc., offering the benefits of reliability, more comprehensive dynamic range of 192.6dB, and higher precision.