Swinging door deadband: rate and value

In the following diagram, a signal with some "noise" is shown. The effect of applying both a rate and value deadband to swinging door storage is illustrated. The value deadband is indicated by two horizontal dashed lines.

Assume that point 1 has been stored to disk. Point 3 passes the value deadband check, allowing points 2 and 3 to be evaluated for rate change. Assuming that the point exceeds the rate change requirement, then point 2 is stored. Until point 13 is received, all intermediate points are discarded by the value deadband filter. In this example, it is assumed that the change in slope between points 2 through 3 and points 12 through 13 is greater than the rate deadband, so point 12 is stored on disk. When point 14 is received, the normal operation begins.

If a rate deadband is applied without a value deadband, all of the "noisy" points (3 through 11) would have been stored, because the slope of the signal changes radically between successive points. The value deadband removes the noise, but also introduces some amount of distortion in the resultant signal.