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#173914 - 01/22/08 09:54 PM 4-20ma Pressure Transmitter  
Cinner  Offline
Member
Joined: Dec 2004
Posts: 78
Kelowna, B.C., Canada
Does anyone have any industrial experience with pressure transmitters. My question is this: If the voltage is 10 - 30 V DC and the output is 4-20ma, would this require 4 wires to connect( 2 for the voltage and 2 for the 4-20ma output). Can the transmitter run on only 2 wires?


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#173915 - 01/22/08 10:07 PM Re: 4-20ma Pressure Transmitter [Re: Cinner]  
bigrockk  Offline
Member
Joined: Jan 2003
Posts: 174
Middle of Canada
Yes it can work with only two wires. This is fairly common.

Positive transducer lead to positive of power supply. Negative of power supply to negative side of "load" . Positive side of load to negative lead on transducer.
So essentially it is just a loop.

The load could be many things such as a plc controller a meter or readout of some type etc.

Last edited by bigrockk; 01/22/08 10:15 PM. Reason: To add more info

#173952 - 01/23/08 02:44 PM Re: 4-20ma Pressure Transmitter [Re: bigrockk]  
NJwirenut  Offline
Member
Joined: Sep 2001
Posts: 806
Bergen County, NJ
4-20 mA control loops are very common in industrial control gear. In the 2-wire configuration, the transmitter is actually powered by the voltage drop across it.

A good introduction to current loop sensors here:

http://www.datel.com/data/meters/dms-an20.pdf



#173973 - 01/24/08 11:06 AM Re: 4-20ma Pressure Transmitter [Re: NJwirenut]  
JValdes  Offline
Member
Joined: Jun 2007
Posts: 301
South Carolina
How many terminals do you have on the transducer? And do you have the wiring diagram for it? Normally you will have an input 2 wires (10-30vdc) and an output 2 wires (4-20ma). Two in. Two out. No common. To test the output MA, put meter in series with one output conductor. Use the MA setting on the meter. Depending on how sensitive you need this, you may need to adjust the DC input or if provided the adjustment screw on the transducer.



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