Measurement Computing DaqScan 2000 Series - Manual (Page 57)

In regard to synchronization, the following applies:
• One of three signals can be used to drive the DaqScan/2000 Series acquisition scan
rate. These are:
− the internal acquisition pacer clock
− an external acquisition pacer clock (for DaqScan/2001 and /2005 only)
− the global sync (G-SYNC) input from the SYNC ports
• Both the SYNC connector input and the external clock input can be divided down.
• When a DaqScan is in the Master Mode, both the trigger condition and the scan timing
are output on the SYNC port. The global trigger (G-TRIG) is selected instead of the
TTL Trigger Input.
Whether the DaqScan is using its internal scan clock, or external clock input, it can be
programmed to output the clock on the SYNC connector. In either case, the unit is behaving
like a synchronization master. Other DaqScan units [that are connected to the master, via
a SYNC port] should be programmed as synchronization slaves.
When a DaqScan is programmed as a synchronization slave, it will derive its scan period from
the SYNC port. If the slave unit must be triggered at the same time as the master unit, then
the slave unit should use TTL Trigger as its trigger source.
Sync Notes:
•
When a DaqScan/2000 Series device is programmed as a synchronization slave, the TTL
trigger source is automatically derived from the SYNC port.
•
When a DaqScan/2000 Series device is programmed as a synchronization master, it will
output its trigger condition on the SYNC port.
•
When synchronizing two or more DaqScan/2000 Series devices, the slave units should have
at least 0.1 µs of dead time in the scan period. By “dead time,” we mean a duration in
which no channels are sampled. This accommodates fundamental differences in the clocks
[for each DaqScan].
•
All DaqScans that are connected via SYNC cables can be scan-synchronized to within
0.1 µs of each other.
•
A maximum of 4 units can be synchronized; scan-synchronous (post-trigger).
•
Sync cables are not to exceed a total combined length of 15 feet (4.57m).
Multi-unit synchronization via the SYNC ports does not support pre-trigger
data. Only post-trigger data can be collected and time correlated between
the units.
DaqScan/2000 Series 898195 Taking Measurements 8-7