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From: "Bill Sloman"
Subject: Re: Ultrasonics basics
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
Date: Fri, 22 Nov 2002 00:23:36 GMT
NNTP-Posting-Date: Fri, 22 Nov 2002 11:23:36 EST
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"Dave" wrote in message
> 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
> 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
> pulse the receiver looks for is surely the reflection of the last pulse
> Is the reason for the 6 inch minimum distance because the transducers
> and so swamp any reflected pulses? If so would a higher frequency be the
> If this is the case are any standard transducers available other than
> So many questions! Does anyone know the answers please?
> Thanks in anticipation, Dave.
IIRR the ultrasonic transducers are fairly hi-Q parts, and driving them with
a shorter pulse still produces the same six to ten cyces of the resonant
frequency; driving them with more cycles gives you a better-shaped pulse in
the air and at the receiver.
Bill Sloman, Nijmegen
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