Siemens SIMATIC S7-1500 System Manual page 186

Configuring
9.9 Configuration of digital inputs/outputs (X142)
Example 1: "Single period" measurement method
For an injection molding machine, the rotational speed of the extruder screw is to be
determined using a simple encoder based on a rotating slotted disk.
The pulses are to be acquired on the SIMATIC Drive Controller using a digital input/output
(X142) in the event/period duration measurement operating mode.
The rotational speed of the screw is determined from the time interval between 2 pulses.
Figure 9-25
In the "Single period" measurement method, the period duration is determined by counting
the number of 41.67 ns increments between the last two incoming rising edges in the
measuring cycle. The number of rising edges is additionally counted (circular counter).
Period duration t
If you know the number of pulses that the encoder generates per revolution of the extruder
screw, you can calculate the speed at which the extruder screw turns.
Calculation example
N = 16 pulses are emitted per revolution of the extruder screw (N
S
number of pulses per revolution of the encoder).
The distance between 2 pulses is N
Thus, the rotational speed of the extruder screw is calculated as follows:
Period duration t
184
Simple encoder on a shaft, single period measurement method
= 41.67 ns • N
P Inc
Inc
= 41.67 ns • N
P Inc
= 500,000 counted 41.67 ns increments.
System Manual, 11/2023, A5E46600094-AD
is also referred to as the
S
SIMATIC Drive Controller