Identifying Changes in Signal Noise

[Allison Buenemann]

Background: 

I have a sensor that shows a step change in the amplitude of the signal noise a couple of days prior to instrument failure. It would be useful to be able to identify that step change in the amplitude of the noise so that preventative maintenance can be scheduled rather than running the instrument to failure and causing an unplanned shutdown or production loss event. 

Solution: 

Use a combination of Formula and the Value Search tool to identify when this increased signal noise is occurring. 

Starting signal: 

1. Use Seeq Formula and the runningDelta() and Abs() functions to calculate the absolute value of the running delta of the signal of interest. 

The formula code to achieve this is:

//calculates absolute value of running delta of signal
$signal
   .runningDelta()
   .abs()

2. Use the Value Search tool to identify the periods of time when this absolute value of running delta signal is above some threshold. In this example we use the remove short capsules/gaps functionality to remove capsules and gaps shorter than 1 hour to capture a single event each time the instrument noise increases.