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Thread: [PIC] How to measure level of liquids and sense relativeh umidity?
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face BY : Don Hyde email (remove spam text)



Some colleagues here took on a liquid-level sensor based on ultrasonic
ranging, and were suprised at what a major project it turned into.

For starters, cost was an important issue.  It turns out that, like with
many things, there are two kinds of ultrasonic transducers -- cheap ones
that aren't very good and very expensive ones that are still only pretty
good.

After spending a lot of time dealing with analog noise, they got down to
difficult problems with ringing in the transducer, multiple reflections, and
the fact that all the transducer's properties varied a whole lot with
temperature.  Then they got to work compensating for the fact that, while
the speed of sound in air and water vapor is fairly well-behaved, the speed
of sound in diesel fuel vapor is not.  It varies a lot, and in a highly
nonlinear fashion, with temperature (and to a lesser extent, from one batch
of fuel to another).

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Subject (change) [PIC] How to measure level of liquids and sense relativeh umidity?

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