This is a
Proteus Industries 200 Series flow meter . The spinning impeller contains magnets at the tips, which generate a current in the coil that is located in the housing of the meter, separated from the chamber. The current, generated in the coil by the Hall effect, is directly proportional to the rotational speed of the impeller, thus being linearly indicative of the flow through the meter. The second half of the flow meter contains all the electronics that interpret the current and convert it to a 0-5VDC analog output. It also contains a relay with an adjustable trip point.
I connected the
Red Lion DC voltmeter to read the analog output from the flow meter. Also, this model of the meter can be set to scale the readout, and this is how I calibrated the meter to display 100 under normal circamstances. The buzzer is connected externally and is activated when the relay inside the flow meter senses flow that is below a set point.
The flow meter is able to output analog voltage signal that is proportional (very linearly) to the flow, and I have calibrated the panel meter to show 100, as in 100 percent, under normal conditions. I can adjust the voltage supplied to the pump through a pot, and the meter mirrors the reduced flow quite nicely, bottoming out at 36%, at which point the relay inside the flow meter trips off another relay that is connected to a loud buzzer, giving a nice warning signal.