160 Virtual Channels
imc CANSAS Users Manual - Doc. Version 1.9 - 05.12.2014© 2014 imc Meßsysteme GmbH
4.10.33 Hysteresis filter
Hysteresis width, for suppressing minor fluctuations
Description: The hysteresis filters minor oscillations up to the size of the hysteresis width out of the input
channel. The algorithm is as follows:
The 1st result value is set as the 1st sample value from the input channel. The trend is set as an upward
trend.
If the signal is currently in an upward trend, then one of the three procedures below is followed,
depending upon the status of the current signal value in the input channel:
If the current signal value from the input channel is greater than the last value in the result channel,
the current value in the input channel is adopted as the current value of the result channel.
If the current signal value from the input channel is less than or equal to the last value in the result
channel, but not less than: the last result channel value minus the hysteresis width (i.e., the negative
discrepancy to the last value is within a tolerance range stated as the hysteresis width), the last result
channel value is retained as the current result channel value.
If the current signal value from the input channel is less than the last result channel value minus the
hysteresis width (i.e., the negative discrepancy to the last value is outside the tolerance range stated as
the hysteresis width), the current signal value from the input channel becomes the current value of the
result channel, and the prevalent signal trend is now downward.
If the signal is currently in a downward trend, then one of the three procedures below is followed,
depending upon particulars of the current signal value in the input channel:
If the current signal value from the input channel is less than the last value in the input channel, the
current value in the input channel is adopted as the current value of the result channel.
If the current signal value from the input channel is greater than or equal to the last value in the result
channel, but not greater than: the last result channel value plus the hysteresis width (i.e., the positive
discrepancy to the last value is within a tolerance range stated as the hysteresis width), the last result
channel value is retained as the current result channel value.
If the current signal value from the input channel is greater than the last result channel value plus the
hysteresis width (i.e., the positive discrepancy to the last value is outside the tolerance range stated as
the hysteresis width), the current signal value from the input channel becomes the current value of
result channel, and the prevalent signal trend is now upward.
Notes: The hysteresis width is specified in the physical units of the input channel and must be 0. A
hysteresis width of 0 returns the input channel as the result.
Data types:
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