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Re: Ultrasonic

On Thu, 7 Oct 1999, Norman Lohstreter wrote:

Hi David;

As I understand the operation, The metal disk is a support and one
electrical lead for a piezoelectric ceramic material. When an
oscillatory potential is applied, the ceramic material distorts and
creates a longitudinal wave in the air. The frequency is about 40 kHz,
therefore ultrasonic. This frequency is pulsed at a rate that allows
the reflected wave to act on the ceramic in the reverse direction and
produce a potential between the two lead connected to the disk. The
rest is electronics wave shaping and amplification.

Thanks for this description. It helps me understand why the object must be
more than 40-50 cm away. If the object is too close the return and send
are
overlapping. Also the sampling rate controls the max distance. Am I right?

Ken Fox