4~20milliAmp loop situation

[TheSimo]

I need to connect 2 reading devices (loads) to the one loop.

(Load 1)is a 0~5volt load not sure maybe 250ohm external resistor across the analogue channel input of the ECO T paperless recorder.

(Load 2) The other is a 0~4volt load over an external 200ohm 1% resistor on the analogue input of the GSM device.

Analogue output is from The sensor an 'Endress & H Prosonic' ultrasonic level sensor with a 4~20mAmp output@5voltsDC.

On this loop i'm going to connect a paperless recorder (load 1) and some how I need to parallel/series or buffer the loop current into a GSM logger device (load 2)

So I have 2 analogue inputs (load 1&2) sharing the one analogue output 4 to 20mAmp loop Therefore what ever the output current is - both analogue inputs need that same reading. How do we do this?

thanking all in advance

 

[Skogsgurra]

The Prosonic devices are loop powered. So, you supply the necessary external voltage to the loop. That means that you can use any suitable PSU and connect transducer, recorder and logger in series and then feed the whole chain from your power supply. You need to check transducer's maximum voltage first. But I would be surprised if it is less than 15 or 20 volts. I would use a 15 V stabilised supply. No need to think about isolation. Supply, transducer, recorder and logger are usually all isolated devices.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[itsmoked]

Just to futher Skog's excellent summary:

5V + 4V + 5V = 14V
So any supply that supplies more than this but not more than the Prosonic can withstand will do the trick.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[TheSimo]

Well thanks it smokes and Skogs
I have done a few single loop in to out analogue but never added a second input channel make sense on the maths thanks to both of you.

John SImkin
Cyplex Communications Sdn bhd
Malaysia

(home in OZ on holiday)

 

[grahamlaming]

Hi TheSimo

There's a handy product on the market which splits a 4-20mA signal in to 2 or 3 separate channels - called a loop splitter. It means you can do what you want to one channel, the other won't be affected.

Take a look here for example ...

http://www.london-electronics.com/signal-transmitters.php#tim018

Hope that helps,

 

[bogeyman]

You could use a 200ohm and a 50 ohm in series, picking off 4v and 5v respectively, this will use less overhead but the loggers should/must have Hi z inputs to work correctly.