Posted 26 Jul 2019 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. Share this post Link to post Share on other sites
Posted 26 Jul 2019 Download 1769-UM002B-EN-P and read it. Page 2-11 clearly states that the IF4 and IF8 do not supply loop power. Share this post Link to post Share on other sites
Posted 26 Jul 2019 Thank you for your response, If I try to use a 4-20 mA signal can I get away with two wire control? Share this post Link to post Share on other sites
Posted 26 Jul 2019 Look at the pages that follow for the differences Share this post Link to post Share on other sites
Posted 27 Jul 2019 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. Share this post Link to post Share on other sites
Posted 7 Sep 2019 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. Share this post Link to post Share on other sites
Posted 7 Sep 2019 1 hour ago, Anthony07 said: Yes because current flows positive to negative, Oh my Anthony07 those a fighting words. You must be an engineer. 1 person likes this Share this post Link to post Share on other sites
Posted 7 Sep 2019 The rockwell manual actually shows how to wire this. Ah, I see engineers must think positrons leave their atoms. Share this post Link to post Share on other sites
Posted 7 Sep 2019 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. Share this post Link to post Share on other sites