Jim ‘Slim’ Mimlitz, SCADAmetrics
When interfacing an open-collector pulse output signal from a flow meter to an EtherMeter, it can sometimes be necessary to provide an electronic isolation & amplification buffer between the flow meter and the EtherMeter.
For example — if the open-collector does not have sufficiently low impedance when it is in the closed state (or if the open-collector does not have sufficiently high impedance when it is in the open state), then the EtherMeter might not detect the pulses.
One solution is to add an interposing solid-state relay into the circuit to provide isolation and amplification.
The diagram below illustrates the details. Click on the image to zoom in.
Important Note: in the circuit illustrated below, 3.2 milliamps will pass through the meter’s open-collector circuit when closed. Please ensure that 3.2 milliamps does not exceed the specified maximum current capacity of your open-collector pulse circuit!
Pulse Isolation and Amplification Circuit.