Schematic for Saltwater Level Switch

Why not use a float switch?

Float switch has a tendancy to stick in high salinity brine. Conductivity has no moving parts.

Thanks anyway.

John

There are numerous devices available that will work with a brine solution (what concentration, a few % or saturated?) They range from a few dollars, a plastic pipe capped on both ends protruding through a short length of pipe mounted to the top of the tank or vessel (it floats higher as the level increases) to some of the more expensive and exotic. These include: electrical, AC, probes measuring the conductance; self cleaning floats; infra-red; sonar; capacitance; and even radar.

Suggest you first try McMaster-Carr, then do a google search if you need other sources.

We found that calibrating a float switch when it had accumulated a full load of salt on it was the best and most maintenance free solution. The float, if sized right, is always less dense than the brine solution but then we were only keeping the tank from overflowing and always charged it with saturated liquid.

Simplest is pierce 2 SS wires thruog a rubber bottle cork and suspend it from top of tank to the level needed. Use as a sitch to ON/OFF through an electronic cicuit.

Endress + Hauser Condumax W CLS21 <usual disclaimer>?

Mr. Johnbscot; To obtain long-term reliability, avoid physical contact with the saltwater, entirely. Use a low frequency RF source, say, around 500 KHz to 1 MHz, and then use a simple detector, fed into a comparitor that will change state when the RF level exceeeds a pre-determined threshold. The water should be allowed to raise and lower inside of a sealed glass or plastic tube, with either coils or simple metal plates on the exterior. The glass tube is recommended, as salt can eventually corrode plastic, but either one will work. Salt water conducts RF, so in essence, what you are doing is making a simple "capacitance" type detector. There are literally dozens of circuits that can be employed to do this, with, and usually at little or no great cost. A simple one transistor hartley oscillator should be the "source", and a simple, two-diode, one transistor detector, feeding an op-amp comparitor, will yield you a very reliable detector. J. Cullen, Phoenix, AZ.

Thousands upon thousands of boats are being kept afloat with plastic float switches detecting brine, of just about all concentrations.

Far worse for a plastic float body is any form of solvent in the fluid. Soap and oil has a likelyhood of damaging the insulation of the cable and making it brittle. Any crack soon results wire failure. Fecal tanks are a problem for float switches. Besides the solids which jam the hinge of a mech float switch, the chemicals used for cleaning the toilets damages the wires.

If you must have a conductivity switch then you you can just use a mosfet.

Thanks & a GA for promoting my idea in Post#4 above.

This post is put a number of times on CR & I have posted all the diagrams on CR4.

Look into CR4 posts.

I am not at home otherwise I would have posted it here