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Absolute encoder value changes after power failure

Created by: sajit_345 at: 11/17/2014 5:51 PM (6 Replies)

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11/17/2014 5:51 PM	Rate (0)
sajit_345 Regular Member Joined: 11/3/2013 Last visit: 12/14/2021 Posts: 18 Rating: (0)	Hi, I am using a Absolute encoder with profibus interface connected to S7 315 2DP. Recently after a power shut down the value of this absolute encoder has changed. This happened thrice and not every time. Where could the fault be. Thanks in advance regards Sajit

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11/18/2014 4:30 AM	Rate (0)
ram123., Posts: 56 Rating: (2)	What is the application ? is this problem from commissioning or recently created ? is there any fixed positions?
ram123., Posts: 56 Rating: (2)
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11/18/2014 10:55 AM	Rate (0)
sajit_345 Regular Member Joined: 11/3/2013 Last visit: 12/14/2021 Posts: 18 Rating: (0)	Dear Ram, This is a running plant for last 2 years, never had this problem. for the same position if there is a power failure the encoder counts received at the PI input changes. regards Sajit.

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11/26/2014 11:05 AM	Rate (0)
allmächt! Posts: 215 Rating: (6)	Hi sajit_345, what was the value of absolute encoderbefore shutdown and after shutdown? Is the fault still present or is it gone? (This happened thrice and not every time.) Regards
allmächt! Posts: 215 Rating: (6)
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11/27/2014 8:01 AM	Rate (0)
sajit_345 Regular Member Joined: 11/3/2013 Last visit: 12/14/2021 Posts: 18 Rating: (0)	hi the counts changes every time there is a power failure. As we have a constant power supply this problem has not occured again. regards Sajit.

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11/28/2014 10:38 AM	Rate (0)
Henio Posts: 53 Rating: (2)	Hi, As far as i know, even absolute encoder can be preset by software. Is'nt there some subrutine (for example in OB 100/101) programed to set some fix value after restart ? Henio.
Henio Posts: 53 Rating: (2)
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11/28/2014 10:49 AM	Rate (0)
IBN-Service Posts: 8946 Rating: (995)	Is it an "endless" application? Remember: Even absolute Encoder may lost reference if maximum revolutions are reached! Some Encoders has a small battery inside to save number of revolutions after power failture. After some years this battery may be flat and reference is lost. What you can try: move the encoder some revolutions against major moving direction. What type encoder do you use?
IBN-Service Posts: 8946 Rating: (995)
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