Signal Duplicators

Hi all,

I have a Watermaster with 4-20mA output and it needs to be hard wired to 3 different PLCs (due to client specific standards). The PLCs are controllogix & compactlogix. I ideally want these to go through a signal isolator/duplicator but I haven't come across a 1 in 3 out, only 1 in 2 out. Does anyone know of any? If not I assume the next best thing is to have the output of the watermaster going to multiple isolators/duplicators in a loop.

Thanks

Multiple loop isolators in series will work fine as long as the total input impedance doesn't exceed the maximum impedance the flowmeter can drive with its output (check the transmitter specs).

Most isolators will have a standard 250 ohm impedance, but i have come across some with 10 ohm and 100 ohm impedance.

Most 4-20ma outputs will drive at least 2 if not 3 in seties, I have done many systems where a 4-20ma transmitter is looped in series with a PLC & a chart recorder, I have even seen 3 but I'm a little wary of 3, so it would porobably be ok to loop the sensor to a PLC & a two output repeater so you have all 3, it will depend on the specs but never found a sensor that will not drive two, as it is 4-20ma there shuold not be any problem.

I thought it was us old folk that didn't know how to use the Internet

https://www.london-electronics.com/product/tim018-mk2-triple-output-4-20ma-loop-splitter/

https://www.measurementsystems.co.u...sg-3383--3-channel-dc-current-signal-splitter

http://www.loreme.fr/fichtech/CAL4-100ig_eng.pdf

You do have to watch out where the supply for the 4-20mA loops come from. If all devices are passive it won't work, if more than one device tries to be active it will cause problems.

I'm sure Phoenix Contact or Pepperl Fuchs will have something.

Other ideas:

If you have an AO card with three spares, you could use them to drive your other PLC's.

Another trick is to use Serial or Ethernet comms and reference the variable on the 'master' PLC that has the AI channel.

TimD said:

Other ideas:

If you have an AO card with three spares, you could use them to drive your other PLC's.

Another trick is to use Serial or Ethernet comms and reference the variable on the 'master' PLC that has the AI channel.

Click to expand...

Yeah, anymore when stuff like this comes up I suggest a cheap PLC like an Automation Direct Click and use that as the splitter. Quite likely cheaper than a traditional splitter.