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anlaog output offset caliberation possible or not?
Created by: hazem at: 6/20/2010 5:46 PM (9 Replies)
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| 6/22/2010 3:01 AM | |
Joined: 10/7/2005 Last visit: 11/11/2024 Posts: 3026 Rating:
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Hello hazem you didn't say what type of card (e.g. 6ES7 332 ...) nor what range (e.g. +/- 10V) you are using. Assuming you are using +/- 10V on a "stock standard" AQ card and assuming you logic is writing the same +/- valueto the AQ, your 50mV error could easily be explained by the operational limits of the AQand more about this can be found in the link below: What are the operational limits and the basic errors of analog inputs and outputs? Have a look too at the SIMATIC S7-300 S7-300 Module datawhich specifies the operational limits for each card, perhaps a different AQ card and/or different range setting may help solving your problem. I hope this helps |
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| 6/23/2010 3:39 AM | |
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Joined: 10/7/2005 Last visit: 11/11/2024 Posts: 3026 Rating:
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No need to apologise dear hazem, as I was the one whofailed to see that you posted in the Step 5 conference. Anyway, the suppliedinfo about te hoperatinal accuracy is generallyapplicable and you'll find that S5 AQ cards will NOT be better with their accuracy than S7 AQ's. Once you get a chance to get the part number of yoru AQ card, it still won't hurt to verify its technical spec and a good starting point for finding it is:https://www.automation.siemens.com P.S.: Are the sensor lines (S+ and S-) of the AQ connectedat the load? I hope this helps |
Last edited by: fritz at: 6/23/2010 6:38 AMAdded P.S: Cheers |
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| 6/24/2010 7:36 AM | |
Joined: 2/15/2010 Last visit: 1/20/2024 Posts: 329 Rating:
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Dear Fritz, The analog output number is 6ES 5470- 4VB12 Regards |
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Hazem |
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| 6/24/2010 9:05 AM | |
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Joined: 10/7/2005 Last visit: 11/11/2024 Posts: 3026 Rating:
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Hello again hazem the 6ES5470- 4UB12 is a +/-10V AQ cardand has an operational error of +/-0.6% and a linearity error of +/-0.2% which - as expected - isslightly worse thana simialrS7 AQ card. You can find its technical spec in the SIMATIC S5-135U/155U System Manualand while the previously supplied link about operational errors was written for S7 AI/Q modules, its calculations and ramifications are just as relevant for S5 cards. Bottom line, theerror you observe can be expected. Ihope this helps |
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Cheers |
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| 6/24/2010 11:34 AM | |
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Joined: 2/15/2010 Last visit: 1/20/2024 Posts: 329 Rating:
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Thanks alto Fritz Shall i consider that offeset is accepted finally? |
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Hazem |
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| 6/24/2010 11:52 AM | |
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Joined: 10/7/2005 Last visit: 11/11/2024 Posts: 3026 Rating:
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Only you can answer that dear hazem, itcan certainly be explained by "operational limits and basic inaccuracies" of the AQ card. The question is: Does the "offset" cause you any control releated issues? Also (as suggested before), can you verify the following: 1.) Have you checked that yourlogic iswriting the same +/- value 2.) Are the S+ and - lines connected to the load (the sensing lines compensate for voltage drop across longer lines and while not using them should affect - values as much as + values, they do help improving the accuracy. Have a look at the previosuly listed manual for more on them) |
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Cheers |
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