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Analog input issue

Created by: Mircea3M at: 9/25/2013 8:18 AM (3 Replies)

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9/25/2013 8:18 AM	Rate (0)
Mircea3M Bronze Member Joined: 1/3/2013 Last visit: 1/18/2025 Posts: 41 Rating: (3)	Dear friends, I just started my experience in Siemens world and I came into some problems already, so please have patience with me. I run uder Windows 7 with TIA portal V11 SP2 update 5 and I have the following setup: S7-1200 PLC CPU1215C ( 6ES7 215-1HG31-0XB0 ), one digital input/output module, two analog input modules SM1231AI8 ( 6ES7 231-4HF32-0XB0), and a VACON drive with a Profinet board. Even if the setup works pretty fine...I would like to solve or have an understanding about the following issues: The sensors from the process are 4...20 mA, so I have configured my analog input modules to measure current in the range of 4 to 20 mA. If there is no sensor connected to a specific analog input and I read the IW in software I got 0x7FFF. Accordingly to S7 programmable controller this would be an an overflow. Still, my question is: why the IW is 0x7FFF and not 0x0000. Please see the attached pdf with a picture.[schnippschnapp] I know that this is a long thread, but I wanted to provide you with all the requied info. Looking forward for your advices! Thanks, Mircea. Attachment ADC and Vacon issues.pdf (429 Downloads)
	Last edited by: O_Moderator at: 9/27/2013 11:50 AM new questions are splitted to /tf/WW/en/Posts/98456#top and /tf/WW/en/Posts/98457#top
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9/25/2013 10:05 AM	Rate (0)
BryanG2001 Posts: 113 Rating: (22)	You are not alone with the Analog Input weirdness. There is an option to switch off the Underflow and Overflow detection so that is the first thing I will try. Then I am wondering if the problem is to do with having a -1 coming out of the ADC, in digital 'zero - 1' = 1111111111111 plus some more ones. 7FFF in digital is 111111111111111. So I think it will be another work around to get over problems with the S7-1200 and TIA portal, so I will process and limit the analog inputs before passing the result to the rest of the program. The scary bit is that Siemens seem to think that the S7-1200 is now ready to use, they are putting the S7-200 prices up, removing discount and shortly will be discontinuing the S7-200 here in the UK. Can't help much with the Siemens PID, I gave up on it and wrote my own. It is posted here somewhere.
BryanG2001 Posts: 113 Rating: (22)
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9/25/2013 2:03 PM	Rate (0)
LarryAm Silver Member Joined: 9/19/2011 Last visit: 1/17/2025 Posts: 140 Rating: (33)	For the 4 to 20 mA range on S7-1200 analog input modules the following applies: Currents between 1.185 and 22.81 mA will result in an output of -4864 to 32511. Currents greater than 22.81 mA will result in an overflow output value of 32767. Currents of less than 1.185 mA will result in in an open wire detection output value of 32767. Larry

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4/1/2015 11:27 PM	Rate (0)
Rebornavt Posts: 2 Rating: (0)	Hi. Is there any solution for mentioned issue already? Theme was created more than a year ago =( Or, maybe, there is another way to get wirebreak/overflow (reading module diagnostics information in program cycle for example)?
Rebornavt Posts: 2 Rating: (0)	Last edited by: Rebornavt at: 4/1/2015 11:28:08 PM
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