Siemens SIMATIC S7-300 FM 350-1 Manual page 119

Function principle of the hysteresis with "Active on reaching the comparison value for pulse duration
(up/down)" setting
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:
● No main count direction
● Active on reaching the comparison value for pulse duration (up)
● Pulse duration > 0
The hysteresis is set when the comparison condition (counter value = 5) is fulfilled, and a
pulse of the assigned duration is output.
If the counter value leaves the hysteresis range, the hysteresis ceases to be active.
FM 350-1 saves the count direction when hysteresis is activated. A pulse is output if the
signal overshoots hysteresis range in opposite direction of the direction saved previously.
Figure 7-22 Example showing the effect of the hysteresis
FM 350-1 Counter module
Manual, 05/2011, A5E03648639-01
Operating Modes, parameters and commands
7.3 Count modes
119