Ultrasonic Measurement with Electrostatic Transducer

This is a Electrostatic transducer for ultrasonic measurement circuit. This circuit uses the LM1812 ultrasonic transceiver. Transducer x1 and LM1812 will transmit a burst of oscillations. Then  the return echo is listened by using X1. The LM1812 detector will generate a pulse of the same width as the original burst when the X1 receive an echo of sufficient amplitude. If the return echo is early, it’s mean the object is near. Here is the schematic diagram of the circuit:

If the parts and values shown are used, this circuit has a range of about 4 inches to 30 feet. The X1 has a 500-pF capacitance that resonate with the L6 at 50 to 60kHz. The L1 is tuned to this frequency by watching for maximum echo sensitivity with a scope at pin 1. [National Semiconductor Linear Application Handbook]