water meter monitor
Just count the pulses from the water meter to one of the imp pins. Make sure the pulse voltage is less than 3.3 volts (you can use a simple voltage divider made by 2 resistors) You will have to calibrate the meter to find out the volume of liquid per pulse.
Basic use is described here or here.
It is designed for power rail of 5 to 24 vdc, so you cannot just use the 3v3 from the imp. The ouput seems to act as open collector, so you can use it with the imp by having a 10k pullup resistor to 3v3 which should give nice 3v3 pulses to read on an imp digital input.
Thank you so much. the 10k resistor worked 