Hi,

> The pressure sensor sealing the top of an air filled tube seems to me to
be the easiest and most >reliable solution. 15 PSI differential pressure
sensor  with one port to the (filtered) atmosphere would >be the sensor to
use (maybe more PSI advisable).

    You can even look at cheap pressostats made for washing machines ! Some
of them have 3 outputs and are incredibly reliable. I never could figure out
how that could work reliably but it does in fact. I have never seen one of
those fail and I always have the first look on the broken washing machines
of all my family :-) The pressure sensor will give you more details but if
you just need 3 or 4 levels of water just put together one or two of these
washing machines pressostats and you will have something that is more
reliable than a single sensor. I do not think vibration will be a problem
either. I had an old machine that kept "walking" around all the time during
the washing cycle. My fellow countrymen will probably remember the first
washing machines from "enxuta" ! It was a great piece of equipament but had
this terrible noise, shaking and "walking" problem. The level sensor never
gave me any trouble on that one either and it lasted many years.

Best regards,
Alexandre Guimaraes

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