Recorder/Time base groups
Note
Perception V6.20 and earlier version use recorder settings for the next setting.
In later version of Perception, these recorder settings have been replaced by
Time base group settings. The basic behavior of the “External Clock Divider” is
identical.
External Clock Divider
This setting can be found in the Recorder Memory & Time base settings. The
default value for this setting is 1, which means that samples are stored at each
external clock pulse. If it is required that GEN DAQ only samples every third
external clock pulse, setting the “External Clock Divider” to 3 will create the
required sampling rate.
Note
GEN DAQ systems cannot sample at higher speeds than the external clock
signal supplied.
H.1.3
Calculating sample limits for external time base use
External sample rates are limited per card type. See the individual specification
sheets of the different acquisition cards for details. Make sure and check that
the maximum external sample rate is not exceeded. Exceeding the sample rate
will results in missing samples at one or more external clock signal events.
Calculation example
Engine runs at 10 000 RPM maximum.
6 000 RPM equals 100 rotations per second.
For example, with a maximum external clock speed of 500 kS/s (all acquisition
cards having a maximum sample rate of 1 MS/s), the maximum pulses per
rotation are:
500 000 / 100 = 5 000 pulses per rotation maximum
However, it is not advaisable to exceed 10% of the maximum sample rate of
the acquisition card used. When in external clock mode, GEN DAQ systems
internally operate on the maximum sample rate, storing the next sample after
an external clock has been detected.
Using a 1 MS/s acquisition card, an external clock at 500 kS/s would appear to
contain jitter of up to 1 us. The jitter is then 50% of the external clock time period
(1/500 kS/s = 2 µs).
GEN3i
932
I3763-3.1 en HBM: public
