VTI Instruments EMX-4016B, User Manual

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APPENDIX B 55
A
RMING
Arm is the gating condition to acquire data. In order to trigger data acquisition, the measurement
must be armed first. There are several ways to arm a measurement. The default condition is to arm
automatically (or
Immediate arming).
Self-arming
When the Immediate arm source is enabled, the EMX-4250/4350/4380 arms by itself.
Arming by User’s Command
The EMX-4250/4350/4380 arms by the SendSoftwareArm method when a Software arm source is
enabled.
Arming at a Certain Time Interval
The EMX-2500 controller can be configured to assert a PXI trigger line (PXI0-7) at a specified time
interval using the platform driver’s
Alarm interface. The EMX-4250/4350/4380 can be armed with
these events.
Arming from Backplane Trigger Line by Other Instruments
The EMX-4250/4350/4380 can receive an arm event from the other instruments in the same PXI
chassis by configuring one a PXI trigger line (PXI0-7) as an arm source.
Arming from LAN Events by Other Instruments
The user, or another LXI device, can send LAN events to arm the EMX-4250/4350/4380s using the
digitizer/DSA driver. Alternatively, a LAN event can be sent to the EMX-2500 controller using the
platform driver. Upon receiving a LAN arm event, the EMX-2500 can assert one of the PXI trigger
lines to arm the EMX-4250/4350/4380 (or any other devices within a same chassis). The former
method is more flexible, and is the recommended approach when using all SentinelEX plugins. It is
only recommended to use the Platform method when synchronizing with non-SentinelEX cards in
the same chassis.
T
RIGGERING
When the measurement is armed and when there are enough digitized samples already collected in
the FIFO for pre-trigger delay, the measurement becomes ready to receive an trigger event.
Self-triggering
When the Immediate trigger source is enabled, the EMX-4250/4350/4380 triggers automatically and
acquires data records as soon as it is ready to receive a new trigger event.
Triggering by User’s Command
The EMX-4250/4350/4380 triggers by the SendSoftwareTrigger method when a software trigger
source is enabled.
Triggering by Analog Signal
The EMX-4250/4350/4380 is triggered when an analog signal at an input channel crosses the trigger
threshold level. In order to trigger from the analog signal, the channel must be enabled as a trigger.