Re: Reduce ringing of ultrasonic with some special housing


Joerg wrote:
Hello Sara,


I have found many topics related to ringing of ultrasonic sensors and a
way to damp this ringing.
I have a expirience of designing an ultrasonic range meter and some
ways to damp ringing:
1.first of all you can reduce the number of pulses which is sent toward
the target for example 4 cycles
2.This is my own experience and I haven't seen it any where and also it
answers practically
that is keeping the transmitter sensor in a compliant mount and that
damps the ringing very much.
3.if using two sensors one for transmitting and the other for receiving
surely use horns to reduce the effect of transmitting pulse on
receiver.
also I have found some way in the pages of group one of them was
using a inductor ,I will thank you if anybody explains it more for me.


While the transmitter stage does influence ringing there are two other
technical areas that have a much larger impact:

a. The backing material behind the transducer. I am sure you can find
some good literature on that in papers from, for example, the IEEE-UFFC
society. The actual "recipe" for backing material is a closely guarded
trade secret. Therefore, I cannot disclose much here. The only
suggestion I can give here is to think about methods of sound proofing
in acoustics. The principles are, by nature, very similar.

What we used at EMI in 1977 was tungsten-loaded epoxy - the tungsten
powder was appreciably finer than the wavelegth of the 2MHz and 4MHz
ultrasound we were using, and we took care to de-air the mix while the
expoxy resin was still liquid.

We used a couple of millimetres of this brew behind our (IIRR) lead
zirconate titanate piezo-electric transducers, and a quarter-waveplate
on the front as an impedance transformer.

It got the Q down to around two, at a guess.

b. Look at what happens after the transmit pulse. Here you would have to
tell us more about your system. Is there a T/R switch and a receiver?
Basically you need to make sure that the transducer isn't left open
after a transmit burst.

Sounds like a good idea. In principle you could kill the residual
energy in the transducer with a carefully tailored de-excitation pulse,
but I've never heard of anybody getting anywhere with the idea.

--
Bill Sloman, Nijmegen

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