Hysteresis With Ssi Absolute Encoder - Siemens SIMATIC ST-1500 Function Manual

The basics of counting, measurement and position detection
2.2 Basics of counting, measuring and position input (TM Count, TM PosInput, Compact CPU)
2.2.10.2

Hysteresis with SSI absolute encoder

Description
Hysteresis allows you to specify a range around the comparison values within which the
digital outputs are not to be switched again until the position value has gone outside this
range.
Slight movements by the encoder can result in the position value fluctuating around a certain
value. If a comparison value, "0", or the respective maximum position value lies within this
fluctuation range, the associated digital output is switched on and off with corresponding
frequency if a hysteresis is not used. Hysteresis prevents this unwanted switching, and
configured hardware interrupts when a compare event occurs.
Regardless of the hysteresis value, the hysteresis range ends at "0" and at the respective
maximum position value.
Function principle
The figure below shows an example for the hysteresis with the following parameter
assignment:
● Setting of a digital output between comparison value and high limit
● Comparison value = 10
● Hysteresis = 0 or 2 (gray background)
Hysteresis is enabled when the position value 10 is reached. When the hysteresis is active,
the comparison result remains unchanged. Hysteresis is disabled when the position values 7
or 13 are reached.
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Counting, measurement and position detection
Function Manual, 12/2017, A5E32009889-AG