Mitsubishi Electric WS0-CPU0 - Frequency Monitor

Chapter 9
178
Logic programming – Function blocks
9.8.13 Frequency monitor
Function block diagram
General description
Using the frequency monitor function block the frequency or the period duration of
up to two signals can be monitored separately. Optionally it is also possible to
monitor the pulse duration (thigh). This feature can be used, for instance, to evaluate
signal sources that output a pulsed signal at a specific frequency as an enable
signal.
Function block parameters
Parameters Possible values, each for frequency 1 and frequency 2
Min. period duration 20 ms to 2.54 s in 10 ms increments.
The value must be greater than the logic execution time.
Max. period duration 30 ms to 2.55 s in 10 ms increments.
The value must be greater than the min. period duration +
the logic execution time.
Average value of the
pulse duration (t
high
)
0 = inactive, 10 ms to 2.53 s in 10 ms increments.
With 0 = inactive the pulse duration is not evaluated. The
pulse duration is then always valid for the evaluation.
If the value is not 0, it must meet the following conditions:
 > 2 x Logic execution time
and
 < (Min. period duration – Tolerance of the pulse duration)
Tolerance of the pulse
duration (t
high
)
10 ms to 310 ms in 10 ms increments.
The value must be greater than the logic execution time.
Error message if period
duration too short
 With
 Without
Use Fault present  With
 Without
This parameter applies to the function block and therefore
to both Frequency 1 and Frequency 2.
Figure 165:
Logic connections for the
frequency monitor function
block
Table 78:
Parameters for the
frequency monitor function
block