Re: Low cost water flow switch?

If you are willing to screw around with a home brew, some version of a
differential thermistor flow sensor might do it:
One thermistor in the flow, a second shielded from the flow, but at
the same temperature. Both in series from a 12 volt source, and the
voltage across the lower one is proportional to flow rate.
This *could* be made to fire a solid state DC relay at a suitable set
point - but it could be fiddly to set up.
Cheap though....

Brian W


On Thu, 18 Sep 2003 00:13:49 GMT, "Bob" <[EMAIL PROTECTED]> wrote:

>Is anyone aware of any low cost flow switch for potable water service that
>could be used to trip a low power (nominal 12VDC at < 0.5 amp) relay at
>about 5-10% of typical max residential flow rate (ie about 0.5  litres per
>minute or 0.1 usgpm) but not unduly restrict max flow. Purpose is to trip an
>alarm or shutdown in the event of lost water flow on small lab condenser
>when water pressure and flowrate fluctuates all over the place (20 to 60
>psig). non hazardous location, could be plastic.
>