Re: ultrasonic distance measurement using 89c51

On Sun, 04 Feb 2007 19:55:51 +0100, Stef Mientki
<S.Mientki-nospam@xxxxxxxxxxxxxx> wrote:


If you wanted an accuracy of +/- 0.001" out of 2 inches, that's
+/- 0.05%, which I think is highly unlikely to be attainable since
the air temperature, pressure, and humidity would have to be known
to , say, twice that accuracy in order for the reading to be
believed.

I think something like +/- 5% is achievable, so that comes out to
0.1" for a 2 inch path, which is 7.6µs.

don't forget that the accuracy in this practical case is mainly limited
by the bandwidth of the ultrasonic transducer,

---
I hadn't even thought of that, thanks!
---

which isn't much at 40 kHz (and can't go much higher than a few hundred kHz).
Or you can use special tricks to create US,
like electronic generated sparks (works great)
and use high frequency US receivers.

---
OK. :-)


--
JF
.

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