4 - 20 MA 4 wire to 2 Wire Conversion

cbe.krishna

Member
Join Date
Apr 2010
Location
coimbatore
Posts
4
Dear all,

We using 2 wire 4-20 MA analog input module , (siemens ET2OOS Module)we have to connect these inputs channels to VFD and Field Analog sensors which is active device in a four wire connection.

We are in trouble to replace 2 wire module to 4 wire module so kindly anybody reply how to solve this case, any isolators are 4 wire to 2 wire converters is there, if possible Pls reply low cost converters make & mdl no.


Thanks & regards

kk
 
It's all abuot knowing electronics - passive and active analog output of devices...
If You are not familliar with this, then go to Weidmuller site and download catalog:
4.1 Electronics – Analogue Signal Conditioning.
You will find there many devices that gives you what you need, and schematics too.
 
Wire the analog output from the 4 wire device to the Siemens card as shown below:

24wf235.jpg


2lka2v9.jpg


p3uol.jpg


The other 2 wires on the 4 wire device are for power.
 
Last edited:
Thank you for reply,

I think that The wiring drawing shows the 2 wire loop powerd connection, in my application the field devices have the external 24 dc power supply will be in the 4 wire connection type.( VFD speed feedback,Ultrasonic sensor & resolver , 2 wire for power & 2 wire for current )

regards
kk
 
What leads you to believe that DC power (to drive a 2 wire loop powered transmitter) is provided on M0+?

Yeah, it says, "2 wire measuring transducer is supplied by means of measuring circuits", but that's some German translation of who knows what?

In the end, 4-20 is two wires; a plus and a minus.

The manual is not infallible. Note that both terminals 5 and 6 are labeled M1+, there's no M1-. It's typical crappy technical writing.

I'm not a Siemens guy, I just have the manual to look at. It sure looks to me like ANY 4-20mA signal gets wired to M0+ and M0(-).

You've got the hardware in front of you. If you put a voltmeter on M+ is there 24Vdc, or some DC voltage capable of driving a transmitter present?

If you think M0+ and M0- has power to drive a loop powered transmitter, hook a loop powered transmitter up and see if it turns on. I don't think it will. I suspect that DC power supplied to N.C. might be used to power a loop.
 
I find it invaluable to draw the loop and follow the current around the circuit, drawing arrows on the diagram as I do so.

Two wire has power and signal on the same circuit. Four wire has separate circuits for power and for signal. Three wire has a separate circuit for power and for signal, but they share the connection to the minus side of the power supply, closing both loops with a single wire.

The input doesn't care - it just sees signal current in and out.
 
I find it invaluable to draw the loop and follow the current around the circuit, drawing arrows on the diagram as I do so.

Two wire has power and signal on the same circuit. Four wire has separate circuits for power and for signal. Three wire has a separate circuit for power and for signal, but they share the connection to the minus side of the power supply, closing both loops with a single wire.

The input doesn't care - it just sees signal current in and out.

And here is a pretty picture to go along with the above.

analogWiring.jpg
 

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