5/11/2022 6:33 PM | |
Joined: 9/21/2006 Last visit: 5/25/2023 Posts: 247 Rating: (62) |
I am not finding any information on the 6ES7 335-7GK02-0AB0, so I am assuming that this is a typo and that you are actually using the 6ES7 335-7HG02-0AB0. Many of our Analog Input modules have filtering modes, and you select a conversion time/filtering setting for the inputs. The longer the conversion time, the larger the integration time and therefore the more stable the input value. This module, however, is a high-speed input card that is optimized for very fast conversion times. It does not do ANY input filtering, regardless of the scan time set. According to SM 335 parameters which can be set up in HW Config, setting the cycle time to any value other than 0.5 ms does not cause more filtering: instead it switches the module from "free cycle" to Conditional cycle mode. In "Conditional cycle mode", the mode reads the analog input values once, then sits in a loop updating the outputs until the configured cycle time has elapsed. Therefore we are seeing exactly what would be expected: the values you are reading at a 16ms cycle are the same as those read at a 0.5 ms cycle, just not updated as frequently. Since the module does not do filtering in software, to get stable values we need to examine why it is seeing fluctuating values at its inputs. The most common cause of Analog Input value fluctuations is electrical noise from wiring problems and/or inductive coupling from other signal and power wiring. To minimize this, you should carefully follow the wiring recommendations in Wiring the analog inputs. Alternatively, you could implement the stability filtering in PLC software by doing something like:
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This contribution was helpful to1 thankful Users |
5/12/2022 8:40 AM | |
Joined: 4/7/2012 Last visit: 5/24/2024 Posts: 113 Rating: (4) |
Thank's for the very detailed answer! |
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