There used to be a company that made ultrasonic transducer / display units
for the marine industry. The transducer mounted on the bottom of the tank
and sensed the top surface of the water. I had one on a boat that I had
several years ago. It worked fine for awhile but as calcium builds up in the
tank the reading becomes unreliable. Also any debris floating in the tank
will cause errors. They fell out of favor for those reasons.
Automatic washing machines have a pressure switch with a tube running to the
bottom of the wash tub. As the water fills, the level forces water up the
tube and increases pressure on the diaphragm that opens a micro switch to
stop the tub fill.
My favorite for a simple and reliable water level indicator is a sight tube.
One connection at the bottom of the tank and another at the top or vented to
air. It accurately shows the tank level at all times. However don't connect
it to the same port at the bottom as the pump is connected to, or the pump
will pull the level down in the sight tube immediately and pull air into the
pump. Ben there done that!
73
Gary K4FMX
dan hearn wrote:
> Hi Phil: Have you looked into the ultrasonic gadgets used in
> construction for measuring distance in rooms, etc. A system of that
> type would give an idea of actual water level in the tank and could be a
> lot more useful than a single level detector. I believe I have also seen
> a similar detector used in parking a car in a garage to tell distance
> from a wall.
> The simplest thing might be to connect one or more pressure switches
> in the bottom pipe fitting on the tank. Plenty of pressure there to
> activate it.
>
> 73, Dan, N5AR
>
> Phil Clements wrote:
> >
> > Pardon the off-topic bandwidth, guys, but there are so
> > many resident parts-savvy folks here that might have a source
> > for me.
> >
> > I am in need of some switches that actuate when immersed
> > in water. I am building some quantity indicators for the water
> > tanks on the fire trucks @ my local fire dept. I want to rig
> > a light/alarm when the water level drops below a set value.
> >
> > Any ideas out there?
> >
> > Thanks,
> > Phil, K5PC
> >
> > Clements Communications and Fire Equipment
> > 410 VZ CR 4903
> > Ben Wheeler, TX 75754
> > (903)852-5211
> >
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