Operating Mode C, D - Frequency Measurement - Festo CPX-P-8DE-N Series Description

3. Input module CPX-P-8DE-N-...

3.3.6 Operating mode C, D - frequency measurement

Festo P.BE-CPX-P-EA-EN en 1209NH English
In the frequency measurement procedure rising edges of the
digitised signal are counted within a parameterised gate time
and the frequency subsequently calculated (f = n/t). If the
value exceeds or falls below the specified limit values, the bit
assigned to the relevant channel is set in byte 0 of the PII
( Tab. 3/9).
Certain parameter alterations cause an initialisation of the
respective channel. This stops the current frequency meas-
urement ( section 3.3.8).
Channel Frequency measurement
0 ... 3 Control possibilities
– Start and stop via byte 0 of the PIO
– Current frequency in byte 2 ... 9 of the PII
– Alarm signal in byte 0 of the PII
Parameterisable properties:
– Gate time
– Lower and upper limit value
– Input debounce times
(signal extension times are ignored)
– Diagnostic response upon reaching limit values
Maximum values of operating mode C:
– max. signal frequency (f
– min. pulse length: 400 µs
– min. signal pause: 400 µs
– Range of values for lower limit value: 0 ... 999
– Range of values for upper limit value: 1 ... 1000
Maximum values of operating mode D – channel 0 only:
– max. signal frequency (f
– min. pulse length: 40 µs
– min. signal pause: 40 µs
– Range of values for lower limit value: 0 ... 9999
– Range of values for upper limit value: 1 ... 10000
1)
Only applicable for extended process image (
2)
Only effective in operating mode C: The edges of the debounced
signal are counted. The debounce time limits the max. measur-
able frequency. At a debounce time of 3 ms, for example, this is
approx. 166 Hz.
Tab. 3/15: Frequency measurement (operating mode C
and D)
1)
2)
): 1250 Hz
max
): 12500 Hz
max
Tab. 3/10)
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