Why is the curve of the digital feedback signal a ramp?
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In WINCC, feedback signals for the open and closed positions of the valve were archived. When examining the historical data, it was found that the signal followed a diagonal curve between 1 and 0 (corresponding to the open and closed states), with the transition from 0 to 1 or from 1 to 0 lasting around 1 hour. As far as I understand, it should be a passive contact signal that is either 0 or 1; logically, it should rise linearly to 1 or fall linearly to 0. Why then is there a diagonal change in the signal? Is the actual moment when the valve is opened or closed really the instant when the value on the curve equals 0 or 1, which is when the valve moves? I need experts to help solve this.
I’m not sure what your system is; take a look at the time range displayed on the screen for historical trends, as well as the sampling frequency at which variable data are recorded – the cause is likely to lie in these two aspects.
Is a valve position transmitter being used?
It can be set within the trends; you just need to watch the movements of 0 and 1
For the reason of setting it, try as mentioned above!
WINCC is set to record changes, so what you see are actually two points; the line connecting those points is generated automatically, and you don’t need to worry about it. You can also view the data in the table; there are two sets of data shown: one for when 0 turns into 1, and the other for when 1 turns into 0.