Re: Ultrasonic

[Norman Lohstreter <petel@TENET.EDU>]

If the oscillator frequency is 40 kHz and you are pulsing at 120 Hz with
a 50% duty cycle, then the transducer is listening for 4.1 msec each
cycle. that allows about 166 ultrasonic pulses to be sent and reflected
each cycle. On the slow end, a 5 Hz sample rate allows about 4000 of the
reflected pulses to enter the system.  Higher sample rates (if the
signal is strong) will provide higher position resolution than lower
rates.  High sample rates require the signal to arrive during a smaller
window, that means the maximum range is reduced. Of course there are
ailiasing problems inherent with all sampled signals.  But that's
another story...


paul o johnson wrote:

> Pete,  Since we can set the pulse rate (at least in the Pasco sonic ranger)
> anywhere between 5 and 120 Hz, what is the pulse length? It's got to be
> short enough to leave a suitable echo  reception window even at the highest
> pulse rate.

 poj

--
Pete Lohstreter                              "Reality is merely an
illusion,
The Hockaday School                           albeit a very persistent
one."
Dallas, TX 75229                                               A.
Einstein
petel@tenet.edu
plohstreter@mail.hockaday.org
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