I have a flowmeter. The output is 80 Hz-5.3 Hz, represents that 30GPM to 2 GPM. the input of the sensor is 5V-18V. The user guide says, The sensor uses a paddlewheel-like rotor whose motion is converted into a high-level square wave pulse output by an open collector Hall Effect sensor. Pulse amplitudes from 5 to 18V are possible, depending on input power. When powered by the FPW-5, 5 Vdc wall socket converter, the sensor has a TTL level pulse output which can be used with a variety of pulse input flow indicators, signal conditioners and controllers. Also, For systems without an internal pull-up resistor (such as the DPF70 series panel meter), a nominal 10,000[ch937], 1[ch8260]4 watt resistor must be installed between the red and white wires. If 5 Vdc power is supplied, the output signal will be TTL level, which is compatible with a wide variety of computer interface equipment that accepts TTL level pulse input.
How could I wire the circuit to arduino and read the data ???