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SM1231 4AI, current inputs two wire (or three) transmitter 4-20mA

Created by: Marko Bursic at: 5/6/2013 9:57 AM (3 Replies)

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5/6/2013 9:57 AM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	Hi, I have a problem because of poor documentation. I have two wires transmitters 4-20mA and I want to wire them on SM1231. I have wired them like in documentation, but they don't work. Measuring on analog modules further discovers that there no supply voltage (24vdc) comes out from module, so it is normal that can't be working. Now I would like if Siemens give a detailed scematics on wiring current transmitters 2 or 3 wires. I can try making on my own, but I don't like to burn anything. I also think that this is a must for Simens, to give exact wiring. Attachment Sm1231.JPG (592 Downloads)

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5/6/2013 10:06 AM	Rate (0)
Marko Bursic Platinum Member Joined: 9/8/2009 Last visit: 7/17/2023 Posts: 1410 Rating: (153)	Think, I got the solution: http://support.automation.siemens.com/CN/view/en/40914972

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7/27/2013 7:43 PM	Rate (0)
malkawi Posts: 35 Rating: (0)	i have the same problem, im confused why the SM1231 manual shows different wiring,.. so did this work ?
malkawi Posts: 35 Rating: (0)
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7/31/2013 9:08 AM	Rate (0)
BryanG2001 Posts: 113 Rating: (22)	You always have to have something providing a voltage to drive a 4-20mA loop. The manual shows a current or voltage source but doesn't show the source for the current or voltage, it ios assuming that the external device is powered. If the external device is 2 wire, loop powered then you need to include a voltage source in the loop. I tend to use the 24Vd.c. output available on the PLC as my voltage source for loops and use it for nothing else, it tends to avoid interference from switching devices.
BryanG2001 Posts: 113 Rating: (22)
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