Step Response for Analog Input - Understanding Smoothing Selection

In the Siemens LGF (Library of General Functions) you can find a software filter block that may help you filter out that signal.

However, if you know when to ignore the step response, you can basically pause the input handling for 400-500ms, perhaps longer if you can maintain process control.

For example, let's say when a valve reaches some % of open or closed, or the tank fill level reaches a certain level during filling or consumption, the noisy and invalid response happens, and is repeatable, you can basically insert test logic for that exact situation.  When it happens, process the control system using the last analog input value just before the step response is about to happen.  Once the step response has passed and things are providing true data, start passing the current values on for process control.

For that type of thing to work, there is some amount of coordination between filtering (used to filter out local power grid frequency interference) and smoothing (for inherently noisy signals).

If during normal operation the 50 Hz interference filter does not seem to make much difference, do not enable it.  If during operation the signal is very stable, use minimal filtering.  Use just enough filtering to get a stable reading that is still responsive for normal process control without under and overshoot.

The step response problem should not be solved by those 2 analog input check boxes.

AutoGen_6738349

miami

It works in a internal FIFO configuration and samples the analog reading every 5ms, but the output is the average of the last 32 samples taken.

 thanks!