Siemens SIMATIC SM 335 Manual page 80

Interval Counter Input
Upper limiting value
The upper limiting value results from the condition that the interval between two
positive edges must be at least 2.5 ms. The critical frequency is thus 400 Hz
(equivalent to 24,000 revolutions per minute).
At least 1 ms must be available for the high levels and the low level.
These limiting values apply for sensors, which generate one pulse per revolution.
When sensors generating several pulses per revolution are used, you must re-
assess the critical frequencies. A number of examples are listed in Table 4-1.
Table 4-1
N
1
4
8
16
4-4
Limiting Values for Different Numbers of Pulses N
Lower limit
7.15 rev/min
1.79 rev/min
0.89 rev/min
0.45 rev/min
SM 335 – High-Speed Analog Input/Output Module for the SIMATIC S7-300
Upper limit
24000 rev/min
6000 rev/min
3000 rev/min
1500 rev/min
6ES7 335-7HG00-8BA1