Slightly off topic: parallel pulse from meter

Ken Moore

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May 2004
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North, West, South Carolina
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This slightly off topic, but I counldn't think of a better place to ask, so here goes:

I currently have a magnetic flow meter (Rosemount 8732C) that sends a pulse output to a PLC-5 via a 1771-CFM flow meter card. The flow meter doesn't really generate the pulse, it must have an external power source (5-24VDC) that it switches (solid state) on and off to generate the pulse. The meter is located about 1/4 mile from the PLC.

Now the question.
I now need to have the pulse output to the PLC and a local Red Lion Display unit. Has anyone tried this before?
I'm thinking that if I use the same 24 volt source and common, I might be able to have parallel outputs.

I've attached a zipped PDF file with a simple wiring diagram.


thanks,

Ken
 
The PDF looks reasonable.

Many counter displays don't require a voltage, just dry contacts.

One question. Why not have a separate PLC Output Pulse the Red Lion Counter?
 
That should work fine. We use CUB5XXXX on a daily basis to do this sort of "sharing." Very rarely when sharing with certain other totalizing devices we may need to add a pull-up/down resistor depending on loads and npn/pnp considerations.
 
It should work fine the way you have planned, but tying the Red Lion and PLC inputs together MIGHT have an effect. If this is a problem, isolate them using 2 diodes (go away, mrowen!).

One diode between the flowmeter and Red Lion, and one between the flowmeter and PLC.

| |
| Flowmeter DIODE |
+--------] [------+------|>|------> Red Lion <-----+
| |
| DIODE |
+------|>|---------> PLC <-------+


beerchug

-Eric
 
I don't think it to be a problem either as long as the signal strength is stable.
Eric has a good point.. electrical isolation between receivers is a precaution worth looking at. If one unit fails with input short, then the other should be able to still work.
(mrowan is not far from moron)

bitmore
 
Last edited:

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