Last night after ordering the Omega amplifier, I went to go put away all my electronics gear. Just for kicks, I thought I'd try to get the LM339 based circuit to work one more time. An Eddisonian inspiration led me to try grounding one of the magnetic pickup lines at the amplifier, and wouldn't you know it, the noise problems went away.
So, the circuit below seems to work perfectly in my application. To recap, I have the following
- A Cox AN8-4 turbine flow meter
- A magnetic pickup which outputs a 10 mV minimum peak to peak signal
- A Measurement Computing 1208FS
I'm sure that it never would have worked had I not bought the Omega unit.