Influence of inclination angle of piezoelectric receiver of ultrasonic sensor on the error in measurement of the average fiber diameter

Abstract

During experimental studies, an ultrasonic device was used which in terms of design ensured maximum acoustic pressure on the receiving element, minimized the effect of external disturbances (environmental condition parameters) on the measurement result; decreased spatial variations of the source and receiver of ultrasonic waves during measurement, optimized the design and spatial positioning of ultrasonic vibration receiver. The measuring channel settings accepted during experimental studies are as following: ak -design constant of measuring channel; ak = 14, where a is half-width of the channel, a = 5 mm; k - wave number, k = 2.8. Experimental evaluation had confirmed theoretically substantiated effect of inclination angle of the receiving element of the ultrasonic sensor on the error in measurement of wool fineness in a disarrayed sample. At the inclination angle of the ultrasonic sensor receiver of fi = 48° relative to the longitudinal axis of the measuring channel, the error does not exceed ±1.5%, and at the angle offi = 0° it does not exceed ±5%. The reason for more accurate measurement of wool fineness at fi = 48° in accordance with the developed theoretical provisions is that the inclination of the receiving piezoelectric element of the sensor relative to the longitudinal axis of the measuring channel eliminates the need for receiver installation at the angle of fi = 0° strictly in so-called ultrasonic wave antinode, which poses a significant technical problem at ultrasonic wave frequency of 150 kHz. Besides, the receiver arrangement at inclination relative to the longitudinal axis of the measuring channel allows increasing the spots of contact of ultrasonic wave with the surface of the receiving element irrespective of wave phase, and increases the average acoustic pressure and decreases the measurement error.