Damping is a smoothing function to make process measurement with point-to-point variability a stable measurement that reflects the moving average or the product measurement for adjustment and control.
If you are measuring hog fuel for a boiler or ore for mining or even paper moisture for label stock, you want the measurement quickly and also representative of what is being measured over time so that the control scheme doesn’t “chase itself” and instead optimizes operation. Instead of reacting to point-to-point measurement variation that causes over compensation, a moving average allows control based on a more representative continuous measured value.
The moving average “smoothes” the measurement to allow for real time process control of application dependent unit operations. Damping is the expression of the “Time Constant”. The Time Constant is the time it takes for 2/3 of a step change to be reflected in the measured value. The Time Constant or Damping is necessary to make the measurements more useful to optimize process control.
Example: System is operating at 2%, an upset causes the constituent (moisture, organic, active ingredient or other) to 8%. The system upset is 6% in this example. The damping time constant is the time for the digital display an analog output to reflect 2/3rds of this change. If the time constant is set for 1 second, the display and outputs will display 6% at one second. If the trend continues, it will continue to increase value. If trend stops or “lines out” (stabilizes), it will also reflect that in the moving average.
The damping is used from 1 to 10 seconds depending on application to smooth the real time measurement into a useful process control measurement. There are also other integration and average measurements available.