Jetter AG
Programming | 8
jxm-io-ew30_ba_2151_manual
46 / 56
8.7 Frequency measurement at the digital inputs
For the frequency measurement at the digital inputs 2 measuring methods are available:
■
Gating measurement
■
Pulse length measurement
Gating measurement
The gate time (GATE_TIME) is the time period during which pulses are counted. Measurements
of high-frequency signals can thus be easily recorded. The values I_FREQUENCY and I_PERI-
ODIC_TIME are determined using this method.
In order to achieve the resolution of 0.1 Hz for low frequency signals, the gate time must be ad-
justed accordingly. The maximum gate time is 10 seconds.
INFO
Gate time and update rate
A gate time of 10 s means that the update rate is also 10 s.
Pulse length measurement
This method is suitable for the resolution of low frequencies. It is based on the time between the
edge changes. To do this, it is necessary to calculate the values I_HPULSE_TIME and
I_LPULSE_TIME externally:
f
[mHz] = 10
9
/ (I_HPULS I_LPULSE_TIME)
INFO
Decrease of resolution
In pulse length measurement, the resolution decreases with increasing fre-
quency.