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Andrew H.

1734-VHSC24 and E+H Promag Passive Pulse Output

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I'm looking for some further information regarding the proper wiring for the 1734-VHSC24 module and a Promag 50W electromagnetic flowmeter with the passive, positive pulse output. I currently have the signals +/- wiring to the A and Aret, respectively, sourcing 24VDC+ from the second module of the VHSC24 set. I cannot find any good documentation or information about these modules, and it's getting to be very frustrating. I'm looking for someone who may be able to shed some light on my problem. Any help is appreciated. Frequency output from the flowmeters is on pages 23-33. I also attached the terminal diagram for the VHSC24. 1734_wiring_diagram.pdf Promag_50.pdf

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A nice reference set of wiring diagrams for open collector, specifically for Signet, but really universal. http://www.icenta.co...ctor_output.pdf National Instruments has a 2 or 3 page document on frequency/quadrature input I/O, which is what your board is. http://www.ni.com/white-paper/7109/en But I suspect you already know that from what you've explained, since you're wired to A/Areturn and source 24Vdc from the card. This is E&H's minimalist documentation: If you put A and A return across the pull down resistor, then you should have the voltage drop across the input. I know 10K ohms is common for pull-up/down resistors, limiting current to 2.4mA. I'm guessing that this statement says 25mA is the maximum current rating (page 25) "For continuous currents up to 25 mA (Imax = 250 mA / 20 ms)" but it's not crystal clear to me. A 1200 ohm resistor in a 24V circuit would limit the current to 20mA. If it were me, I'd start high and work down. Better to limit too much current than too little. (R = E/I; 1200 = 24V/0.02A)

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