Ultrasonic frequency´s effect on the sensitivity and signal level in pressure measurement

This paper investigates the frequency effect on the pressure measurement using the critically refracted longitudinal (Lcr) wave. Based on the acoustoelastic effect and the thin-shell theory, the pressure measurement model is derived, which constructs the relationship between the change of time-of-flight (TOF) and the internal pressure in cylindrical pressure vessels. Meanwhile, the relationship between the TOF and the frequency of ultrasonic probes is developed. Experimental tests are conducted with probes of different frequencies (2MHz, 3MHz, 4MHz and 5MHz). And the change of TOF between the transmitting probe and receiving probe is calculated by the cross-correlation algorithm. The experimental results show good agreement with the theoretical analysis, with the sensitivity (TOF versus the pressure) in high frequency being better than that in low frequency. However, the signal level on the receiver probe is much lower when the frequency is increased.