How to connect 4-20 ma current loop

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spider
Phidgeteer!
Posts: 87
Joined: Sun Feb 03, 2008 2:23 pm

How to connect 4-20 ma current loop

Postby spider » Sun Feb 22, 2009 6:56 am

I would like to connect a pair of 4-20 ma current loop sensors to 8/8/8 analog inputs. I have 250 ohm precision resistors to convert the current to 1-5 volts. What is the exact wiring required vis-a-vis the reference voltage and should the inputs be ratiometric or non-ratiometric.

kiwi179

Re: How to connect 4-20 ma current loop

Postby kiwi179 » Tue May 05, 2009 7:00 am

I too have the same situation where I have a 40 bar (580psi) pressure sensor that works on a 4-20ma current loop.

I have tried 250 ohm resister across the +5V and analog input. But only get a 999 reading with varing pressure.

I know this is basic stuff - I must be doing something stupid, I'm a newbe!

Can anyone help??

Cheers,

Phil
(A kiwi under pressure)

fitchett
Site Admin
Posts: 263
Joined: Fri Dec 05, 2003 3:45 pm
Location: Canada
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Re: How to connect 4-20 ma current loop

Postby fitchett » Tue May 05, 2009 7:35 am

The 250 ohm resistor goes between Analog Input and Ground.

Chester


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