Measuring - Siemens Simatic S7-1500 CPU 1512C-1 PN User Manual

Technology functions
3.1 High-speed counters
Hysteresis
You can specify hysteresis for the comparison values, within which a digital output is
prevented from switching again. An encoder may stop at a certain position, and slight
movements may make the count value fluctuate around this position. If a comparison value
or a counting limit lies within this fluctuation range, the corresponding digital output will be
switched on and off often if hysteresis is not used. The hysteresis prevents these unwanted
switching operations.
Reference
For more information on the counter, refer to the S7-1500, ET 200MP, ET 200SP Counting,
measurement and position detection function manual
(http://support.automation.siemens.com/WW/view/en/59709820).
3.1.1.2

Measuring

Measuring functions
The following measuring functions are available:
Table 3- 1 Overview of available measuring functions
Measurement type
Frequency measure-
ment
Period measurement
Velocity measurement
The measured value and count value are both available in the feedback interface.
Update time
You can configure the interval at which the compact CPU updates the measured values
cyclically as the update time. Larger update times smooth uneven measured variables and
increase the measuring accuracy.
Gate control
Opening and closing the hardware gate and software gate defines the period of time during
which the count signals are acquired. The update time is asynchronous to the opening of the
gate, which means that the update time is not started when the gate is opened. After the
gate is closed, the last measured value calculated is still returned.
44
Description
A measuring interval calculates the average frequency based on the time sequence of the count
pulses, and returns this frequency as a floating-point number in units of hertz.
A measuring interval calculates the average period duration based on the time sequence of the
count pulses, and returns this period duration as a floating-point number in units of seconds.
A measuring interval calculates the average velocity based on the time sequence of the count
pulses, and returns this velocity in the configured unit.
CPU 1512C-1 PN (6ES7512-1CK01-0AB0)
Manual, 12/2017, A5E40898741-AA