Analog input module not reading a specific signal
Created by: abdoosh at: 9/6/2012 9:27 AM (18 Replies)
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| 9/6/2012 9:27 AM | |
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Posts: 12 Rating:
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Dear expert , I have PLC S7-300 with several I/O module , one of them in analog input moduleSM 331 - 6ES7331-1KF02-0AB0 , this module take one signal from we weighing system 4-20mA andevery thing was going perfectly until some one mess with weighing system box. NOW THE PROBLEM is: that specific signal (from weighing system) is not reconize by input module any more even than i can read it using amber meter and it read correct value (4-20mA) that represent weight, i also tried to use another channel and the same , I open Step7 to monitor input and its read 16#8000 (as there is no signal at channel terminal) the last thing to mention is that i test all channels and they work perfectly.
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Last edited by: abdoosh at: 9/6/2012 9:35 AM |
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| 9/6/2012 11:09 AM | |
Joined: 4/22/2010 Last visit: 3/31/2025 Posts: 5697 Rating:
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Hello, Hard to say without documentation off your scale. You have tested the card so the problem must be at the weighing equipment. can you attach documentation off this equipment. Regards, Marcjan |
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Problem solved? |
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| 9/6/2012 11:50 AM | |
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Posts: 12 Rating:
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I can't get any thing about the weighingsystem because its out of ourresponsibility its another contractorresponsibility and all we know about is the (4-20mA) signal . Theconfusing thing about the hole problem is that i can measure the signal using multimeter and its read correct value but the PLC module cant recognize it.
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| 9/6/2012 11:58 AM | |
Joined: 4/19/2008 Last visit: 11/21/2024 Posts: 1525 Rating:
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Hello abdoosh, Can you Tell me have checked the Same Channel With 4..20mA Simulator ? It is problem with only one Channel or other Channel also ? You can Put the Signal Isolator to avoid the such problem. |
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Ammy |
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| 9/6/2012 12:08 PM | |
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Posts: 12 Rating:
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Yes i test all channels with 4-20mA simulator , they are all OK. I tried to use another channel for the weghing signal and the same problem. Its veryconfusing but I'am sure that there is nothing with channels the problem is the signal but i dont know what is it and how to fix it. |
| 9/6/2012 2:37 PM | |
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Posts: 2348 Rating:
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1) Check polarity. 2) PLC has some diagnostics time - if you've made scheme correctly and you sure about it - wait 5-10 minutes and re-check values. 3) Can you place your testing scheme here? I mean electrical drawing |
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| 9/6/2012 2:58 PM | |
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Posts: 5 Rating:
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The 331-1KF01 has isolation to the S7 backplane but not between channels. I would bet the changesyou mention have created an offset or disconnect between grounds of the different inputs. All the inputs to the module must have a common ground, replace this and I think it will work again. |
| 9/6/2012 3:44 PM | |
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Joined: 4/19/2008 Last visit: 11/21/2024 Posts: 1525 Rating:
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Hello abdoosh, 6ES7 331-1KF0X-0AB0 Having the no. of Input Possiblity, 1. Checked the Wiring Part Also, As per 4..20mA 2. What you have Define in the Hardware Configuration, Should be "I" in Measuring type & Range 4..20mA or 3. Put the Isolator in between & then Connect the Signal to Module. |
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Ammy |
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| 9/9/2012 4:39 PM | |
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Posts: 12 Rating:
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Dear all Thanks for your concern , today I solved the problem by chance . I tried first to connect or make bridge between negative and shield (Earth) but nothing happened , Then i tried to connect the shield (Earth) instead of negative edge and its worked !!! the negative edge is now free !! Anyone have an explanation is welcomed. And thanks to all who replayed. |
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| 9/9/2012 7:53 PM | |
Joined: 5/28/2008 Last visit: 3/24/2025 Posts: 4520 Rating:
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Hello, Please send a scketch for your worked connection in order to found an explanation. I would like to know what was the reading before doing this connection? I believe that after telling us answers of above questions and seeing the following FAQs we will found an explanation.
Hope this helps. |
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Ayman Elotaify |
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