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Analogue log reference

5/11/2012 8:39 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hello Experts, In one of the application in 6RA70 Simoreg drive, analogue +/- 10V refernce is fed by 5K pot with 270 degree scale range. Application demand is, upto 75 % of pot scale range motor speed should vary upto 40 % of rated motor RPM & above 75% to 100 % balance 60% of rated speed should vary i.e. log pot. (Please see the attached graph) Now a days in market linear pots are available & log pots are not available. So how can linear reference be converted to log value. Can any one help in this matter? Thanks in advance. DEEP. Attachment ref pot skd.pdf (284 Downloads)
PISCEAN 2010 Posts: 8092 Rating: (884)
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5/11/2012 9:25 AM	Rate (0)
KSN Diamond Expert Joined: 8/25/2006 Last visit: 1/16/2026 Posts: 2221 Rating: (282)	For this use S00 and characteristic block on diagram B160.

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5/11/2012 10:25 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	Hello, But with this option only 10 points can be configured & shall not fulfill the application demand, precisely. Can PLC module help for this application.If yes, how linear analogue can convert to logarithmic out-put? Does anyone has come across such application? Regards, DEEP.
PISCEAN 2010 Posts: 8092 Rating: (884)
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5/11/2012 11:02 AM	Rate (0)
KSN Diamond Expert Joined: 8/25/2006 Last visit: 1/16/2026 Posts: 2221 Rating: (282)	If you have S00, you may build logic so, that all 9 characteristic blocks will be used for reference speed from potentiometer, and you will have more points. What PLC module do you mean?

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5/11/2012 11:33 AM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	KSN If you have S00, you may build logic so, that all 9 characteristic blocks will be used for reference speed from potentiometer, and you will have more points. What PLC module do you mean? No I don’t have any S00 option. We are first checking the application workability. The reply I received from Siemens RSC is, “With S00 option, the same characteristic cannot be guaranteed.” Regarding PLC module, I don’t have any specific module consideration. This is my thought, whether using analogue PLC module, is it possible to convert linear analogue value into logarithmic as per graph?
PISCEAN 2010 Posts: 8092 Rating: (884)
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5/11/2012 12:22 PM	Rate (0)
KSN Diamond Expert Joined: 8/25/2006 Last visit: 1/16/2026 Posts: 2221 Rating: (282)	You can temporary enable S00 option by entering in U977=1500 and test how characteristis block will work for your application.

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5/11/2012 12:27 PM	Rate (0)
PISCEAN 2010 Posts: 8092 Rating: (884)	I am informed that its an option & need to purchase. Apart from this, no one is sure about its functioning & suitability from application point of view.
PISCEAN 2010 Posts: 8092 Rating: (884)
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