Oval Gear Flow Meter

It is recommended that all "signal" cables are screened and run separately to power lines and switched inductive loads and are located well away from inverters and other "noisy" apparatus. Always use sound wiring practice. Both Hall effect and optical detectors (NPN) require a 10K Ohm external pull-up resistor connected between the output and a suitable power supply to attain a pulse. Typically the flowmeter PSU may be used but sometimes a dc pulse, which is of a different voltage, may be required e.g. using a PLC with a 24V PSU and an internal 5V rail for the pul-up