Flomec-qs100 Open collector output

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Joined Nov 9, 2009
We are using multiple of these flowmeters (Flomec-qs 100, please see the link: https://fluidhandlingpro.com/great-...the-flomec-qs100-turf-irrigation-flow-sensor/). Now these have only two output wires and they are supposed to be connected as a open collector output. So connecting a pull-up resistor should work between the collector and the Vcc (power supply, 10-20 V). However, we are unable to display the output pulses on a oscilloscope even when we use a pullup resistor (we used 4.7k, 10 k, etc. see the connection diagram below). We have used a PLC before and it was able to count the pulses. But my question is how can I display the pulses in a scope or sample them with a National Instrument DAQ device. Thanks.

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