Operating Modes, parameters and commands
7.3 Count modes
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
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7.3.9 Hysteresis
Function principle of the hysteresis
An encoder can come to rest at a particular position and then "oscillate" about this position.
This causes the count value to fluctuate around a certain value. If there is a comparison
value within this fluctuation range, for example, the associated output would be switched on
and off in time with these fluctuations. FM 350-1 features a programmable hysteresis in
order to prevent this switching in response to small fluctuations.
A value between 0 and 255 may be set for the hysteresis.
Table 7- 24 Effect of the hysteresis
Hysteresis Effect
Hysteresis value n = 0, 1 The hysteresis has no effect (switched off)
The output reacts to the slightest change in the counter value.
2 ≤ Hysteresis value n ≤ 255 The hysteresis takes effect.
The output does not react until the counter value is offset by n units to
the comparison value.
The hysteresis applies to both overflow and underflow.
Function principle of the hysteresis when "Active within the range between the comparison value and
overflow/underflow" is set
The following figure shows an example of the effect of hysteresis. The diagram shows the
differences in the output behavior when hysteresis values of 0 (= switched off) and 3 are
assigned. In the example, the comparison value = 5
Parameter settings in this example:
● Main count direction up
● Active within the range from comparison value to overflow
The hysteresis is set when the comparison condition (counter value = 5) is fulfilled. When the
hysteresis is active, the comparison result remains unchanged.
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