Minimum Pulse Width For Quadrature Mode - Siemens SIMATIC TI505 User Manual

Minimum Pulse
Width for
Quadrature Mode
High Speed Counter Encoder Module User Manual
The input filter has a clock that synchronizes the input pulse train. The
clock periods for each filter are listed below.
Filter Frequency 1/2 Filter Period
100 kHz filter: 2 microseconds
25 kHz filter: 8 microseconds
6.25 kHz filter: 32 microseconds
1.5 kHz filter: 128 microseconds
400 Hz filter: 512 microseconds
100 Hz filter: 2048 microseconds
To properly register the counting edges, the edges must be separated by at
least these times. This is demonstrated in Figure C-4 with a 100 kHz
Quadrature signal.
Input Signal A
Input Signal B
Figure C-4 Pulse Width Requirements for Quadrature Filtering at 100 kHz
The period of a 100 kHz signal is 10 microseconds ( s). A 90 degree phase
shift between two 100 kHz signals is 2.5 s, edge to edge. The filter period is
2 s. Therefore, the signals can be 0.5 s off of a 90 degree phase shift, and
still count properly.
To calculate phase shift, use the following formula:
Signal Pulse Width
4
In the example above, the phase shift is calculated as follows:
10 s
– 2 s
4
0.5 s 36 / s
Therefore, an offset of 0.5 s produces a phase shift of 18 degrees.
2 s 2 s 2 s
18
( 0.5 s)
5 s
– 1/2 filter period
360 degrees
10 s
18 degrees
2 s
5 s
360 degrees
Signal Pulse Width
Specifications C-5