2/16/2015 9:45 AM | |
Joined: 12/27/2006 Last visit: 7/7/2024 Posts: 1197 Rating: (113) |
Your LOGO! is very very very accutate. it Counts your rotations exact Notice: Its only accurate below the max frequentie of the inputs. Only with integers (hole numbers) to the max of 32767. (sometimes more) Only if the input pulses have the correct value If the precicion is not accutate, then your programm is made to make it not accutate. So tell us wat you realy want |
2/16/2015 10:15 AM | |
Joined: 12/18/2014 Last visit: 7/21/2024 Posts: 33382 Rating: (4143) |
The fault is not due to the pulse count, but at the time, which is applied for evaluation. So smaller the period, so greater the error. Because the actual period is extrapolated. You want the speed in the x / min. Then you choose a period of one minute. Only then will be updated only every minute. Best for the detection and evaluation take a threshold trigger (frequency). |
2/16/2015 2:57 PM | |
Posts: 11 Rating: (0) |
Thanks to all. My aplication just need to read the real rotation of one generator and compare with value. With 1530 turn ON Out, if less than 1505 then turn off. The refresh time is 5 to 10 second. I'm trying to read the time between pulses. |
2/16/2015 4:15 PM | |
Posts: 2930 Rating: (432)
|
Hi,
do you have a LOGO! with fast inputs? |
2/16/2015 6:15 PM | |
Posts: 11 Rating: (0) |
Yes, of course. I3 I see all option Thanks |
2/17/2015 8:42 AM | |
Joined: 12/27/2006 Last visit: 7/7/2024 Posts: 1197 Rating: (113) |
There ar always mistakes in such programms. Also with a cheap LOGO, or with and expensive S300. Thats the way it works. Take a time base p.e. 1 seconde, and count the pulses in that seconde, and multiply it by 60. Then you have the revolutions per minute. The mistake is always 1 puls more ore les in every timebase. Its by the LOGO! and by every other PLC system. After multipy the results fluctuate with 60. You can make it with less fluctuaties, then you must make the time longer. If you use 60 sec, then the fluctuations are + or - 1, but your sytem wil by very slow. It take 1 minute fort every calculation. If you can manage your system in revolutions / sec then you dont have to multiply by 60 and the fluctuations are less. You can als make more pulses per revolution, p.e. if you have 10 pulses per revolution, then you have to multiply by 6, and the fluctoations are less. (Notice not to exeed the max counts frequentie of the inputs) Its to you how to use it. So i have said, thats not only by the LOGO, but by evere PLC system. |
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