|NI-SCOPE (English | Japanese)|
Some NI digitizers support multiple-record acquisitions, also known as retriggerable acquisitions, which allow you to capture multiple, triggered waveforms without software intervention. NI-SCOPE stores each record in separate memory locations on the digitizer. Refer to Features Supported by Device for a listing of digitizers that support multiple-record acquisitions.
The main benefit of multiple-record acquisitions is that you can acquire numerous triggered waveforms quickly. Multiple-record acquisitions allow hardware rearming of the digitizer. The digitizer hardware must transition between several states (given by the digitizer's Acquisition Engine State Diagram) before it is ready to accept a subsequent trigger. If two triggers arrive, one shortly after the other, the digitizer may or may not detect the second trigger.
|Note The information above assumes that there are no holdoff values set (for example, trigger holdoff).|
The minimum time between triggers can be calculated with the dead time and the time per record as follows:
Minimum Time Between Triggers = Time Per Record + Dead Time
The maximum trigger rate can be calculated as follows:
Maximum Trigger Rate (Hz) = 1/(Minimum Time Between Triggers)
When the reference trigger type is set to immediate and all holdoff values = 0 seconds, the digitizer will trigger at the maximum trigger rate regardless of any external signal.
Some digitizers specify a minimum rearm time. Minimum rearm time is the minimum time between reference triggers as the record length approaches a minimum (for example, record length = 1 sample). Therefore, when the record length is 1 sample, Maximum Trigger Rate (Hz) = 1/(minimum rearm time).
For an introduction to multiple-record acquisitions, refer to the Multi Record example. Modify the niScope_ConfigureHorizontalTiming function in your application, setting the numRecords parameter to the number of records you want to acquire. The digitizer acquires an additional record each time a trigger is accepted until all the requested records have been acquired.