I bought a flow sensor for my irrigation project and I'm having some trouble with it.
I connected it to ground and +5V and used a 10k pullup resistor for the signal output. When I blow into the flow sensor, the signal output drops in voltage (as it should) and sometimes it returns to +5V after that. But other times, it goes to about +50mV and stays there. The only way to get it back up to +5V is to shake or hit it.
The internal wiring is pretty simple, there's just a three-legged hall effect sensor that has "W130 3345" written on it. The three legs are connected to +5V, ground and signal output. Also, there's a 10k resistor between +5V and the signal output.
I checked all the solder joints and connections, but they seem to be fine.
This type of sensor will generally generate a series of pulses, with the pulse rate a function of the flow rate. There is a little rotor with a magnet on it and hall-effect magnetic sensor. With no flow at all, the sensor might wind up stopping in either the on or off state. Shaking it around or blowing again will turn it, possibly moving to, or winding in the other state.
I think that, to evaluate how its working, you need to watch the pulse train on the output while blowing or while liquid flows.
gardner:
This type of sensor will generally generate a series of pulses, with the pulse rate a function of the flow rate.
This is exactly what I'd expect. If you stop it at the right point then it'll be high, at other parts of it's rotation, it will be low.
The best thing you can do is just write a simple sketch to count the rising edges, as you push liquid through it. Chances are it's somewhere between 800 to 1200 pulses per litre.