2 wire 1769-IF4II

[mws167 0]

Hello, I have a problem trying to convert an Allen-Bradley 1769-IF4I analog input card from three wire to two wire. The three wire used a seperate wire for the 24 vdc power supply. I have a Rosemount ultrasonic that requires 24vdc to power the display. I always thought that the analog cards supplied the 24 vdc along with the 4-20 Ma sign al. Right now I am wired to ch2 with a jumper on the channel, but I do not have any display to the ultrasonic. I am not sure what I am doing wrong. Any help would be greatly appreciated.

[pcmccartney1 141]

Download 1769-UM002B-EN-P and read it.

Page 2-11 clearly states that the IF4 and IF8 do not supply loop power.

[mws167 0]

Thank you for your response, If I try to use a 4-20 mA signal can I get away with two wire control?

[pcmccartney1 141]

Look at the pages that follow for the differences

[mws167 0]

Ok so 24 vdc as the first wire brought back to the plc as the second wire. The plc should be wired to the common. 

[Anthony07 0]

Yes because current flows positive to negative, which is what the plc is reading the returning current from the sensor in your case the ultrasonic.

[Mickey 71]

1 hour ago, Anthony07 said:

Yes because current flows positive to negative,

Oh my Anthony07 those a fighting words. You must be an engineer.

[NevergoldMel 38]

The rockwell manual actually shows how to wire this.

Ah, I see engineers must think positrons leave their atoms.

 

[Anthony07 0]

I’m sorry didn’t mean to offend you Mickey,  I’ll keep the electrical theory to myself from now on. Also to clarify, I meant to write that in DC circuits current flows positive to negative and the opposite in AC circuits from ungrounded-conductor to grounded-conductor.  And calling someone a engineer would be fighting words in my opinion.