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Reply-To: "Kevin Aylward"
From: "Kevin Aylward"
Subject: Re: Ultrasonics basics
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Date: Thu, 21 Nov 2002 17:29:09 -0000
NNTP-Posting-Date: Thu, 21 Nov 2002 17:29:14 GMT
> Hello all,
> I want to measure short distances (1 to 2 inches) using reflected
> ultrasonics (i.e. a Tx bouncing back to an Rx). Using 40KHz
> transducers the minimum achievable seems to be about 6 inches.
> Looking at existing circuits the transmitter usually sends a burst of
> 6 to 10 pulses? What is the reason for this i.e. why not one pulse?
> The reflected pulse the receiver looks for is surely the reflection
> of the last pulse transmitted?
More pulses mean that if you can average them to get better noise
rejection. You need to know when the pulse is not there as well as
> Is the reason for the 6 inch minimum distance because the transducers
> "ring" and so swamp any reflected pulses?
This is one reason.
>If so would a higher
> frequency be the answer?
There resolution certainly gets better as you go up in frequency. The
minium distance being of the order of one wavelength. i.e. v=fl, v is
330M/S in air.
> If this is the case are any standard transducers available other than
Don't know on that one.
SuperSpice, a very affordable Mixed-Mode
Windows Simulator with Schematic Capture,
Waveform Display, FFT's and Filter Design.
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