Sensor Question

I am currently in the planning/purchasing stage of my new brew rig build.
I am thinking about doing a rims mash system, and was wondering if anyone else out there is using a FLOW sensor to detect flow rates on the pump, and protect wort from scorching and element dry firing.

Flow meters are expensive. I want one real bad for our 2bbl system but cannot talk the guys out of $700 to get a cheap one.

My sugestion would be to use a ball valve on the output of the pump. All you have to do is choke it down a bit and never really adjust it. Thats what I do on my HERMS, we start out with it nearly closed and slowly open it up just a bit at a time to increase the flowrate as the grainbed starts to channel wort.

As far as dry firing. You could just watch it manually(the cheap old fashioned way) or add a liquid contact switch if you really wanted to.

I haven't built my RIMS yet, but I am planning on installing a flow switch on the outlet of the RIMS. I bought one one ebay for $25 similar to this:

http://cgi.ebay.com/GEMS-FS-380-FLO...ltDomain_0&hash=item5d2e7deb2c#ht_1928wt_1141

The flow switch contact will be in series with the control signal to the SSR.

I was looking at a similar set up with a gem flow switch, but using the flow switch to trigger a digital input on my controller, so the controller could not only shut the element off, but also trigger an alarm.