14.5
GEN series synchronization methods compared
GEN series systems support four different synchronization methods. Each
method has its own advantages and disadvantages. It is mostly the customer's
application use that determines the correct choice.
Synchronization overview
Master/Slave PTP
GPS
IRIG
Signal Phase
Very good
Very good
Good
Average/Good
Trigger(s) /
Sweep(s)
Very good
Average and
extra cabling
required
Average and
extra cabling
required
Average and
extra cabling
required
Absolute time
of day
When
combined with
PTP or GPS
When using a
synchronized
Grandmaster
Always
When using a
synchronized
IRIG source
Start of
recording
Very good
Average
Average
Average
Stop of
recording
Average
Average
Average
Average
As the GEN series systems support several recording modes, the impact of
each of these choices needs to be considered with respect to the recording
mode.
14.5.1
Signal phase shift synchronization
Since typical GEN series applications use sample rates ranging from 10 kS/s
to 100 MS/s, channel to channel phase match is the vital system characteristic.
Channel to channel phase shift is defined as the phase/time differences
measured between two channels recording the exact same signal. Phase shifts
should therefore not be measured by comparing the first or last samples of a
recording or sweep. Measuring phase shift should compare a single signal
recorded by mulitple mainframes and then establish the exact time difference
of the different signals when shown within Perception.
A quick and easy verification method uses a square wave and compares the
rising edge of the square wave. Make sure to use a square wave signal with a
time period that is longer than the expected phase match. This avoids larger
phase errors being missed, as the different subsequent rising edges cannot be
separated from each other. For example, a square wave of 100 kHz (10 μs
period time) and a phase shift of 10 μs would show a 100% synchronized trace.
Lowering the square wave frequency to 10 kHz would suddenly show the
10 μs phase error. When in doubt, lower the frequency and measure again.
GEN3t
370
I3995-3.1 en HBM: public