2/23/2016 5:25 PM | |
Posts: 3 Rating: (0) |
Good Afternoon, I have this same issue at the moment, the AO card is 332-5HD01-0AB0. The control loop is 0-100% = 4-20mA = 3-15PSI to control a steam valve. However I am getting 20.71mA output at 50% it then goes upto 25.1mA and remains at this value from 60% upwards to 100%. This issue is causing the PID to constantly oscillate with a detrimental effect on the consistency of the temperature. I have changed the PSU, checked all cabling to each IP converter, and changed the AO card. The HW config is set up for 4-20mA. The wiring is as per the drawing for current output. Any help would be greatly appreciated. Regards Raymond O’Connell Control Systems Technician Devro (Scotland) Ltd Tel: 01236 878 257
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Last edited by: Min_Moderator at: 2/24/2016 12:52:05 PMNew subject after splitting |
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2/23/2016 6:08 PM | |
Joined: 9/27/2006 Last visit: 9/19/2024 Posts: 12282 Rating: (2684)
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Hello Raymond; What numerical value do you send to the analog output channel? Siemens analog modules (all models, all resolutions) use a single numerical scale for scale/unscale operations. Is is from 0-27648 for unipolar signals, and +/-27648 for bipolar signals. the theory is explained in the chapters on analog value representation of the S7-300 Module Data manual: https://support.industry.siemens.com/cs/ww/en/view/8859629 Step 7 has functions to manipulate analog values between engineering values (3-15 psi for example) and the input or output value oat the analog module: - FC105 SCALE reads a 4-20 mA or 0-10V signal as an input and transforms it to a specified engineering value in REAL (floating-point format). - FC106 UNSCALE takes as input (REAL) an engineering value and transforms it in an output in 4-20mA/0-10V for example. Look at this Siemens Support Download for an example program using FC 105 and FC 106: Ladder programming examples (LAD)
https://support.industry.siemens.com/cs/ww/en/view/23330722 Hope this helps, Daniel Chartier |
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