Combine an electrostatic transducer with an ultrasonic transceiver IC to build a ranging system that senses objects at distances from 4 inches to more than 30 feet. Transducer Yl `s broadband characteristic simplifies tuning. The secondary of T1 resonates with the 500-pF capacitor Cl at a frequency between 50 and 60 kHz.
You tune L1 to this frequency by using an oscilloscope to note the maximum echo sensitivity at pin 1. Step-up transformer T1 provjdes 150-V bias for the transducer.