SMC-Based Digitizers Multiple-Record Acquisition

SMC-based digitizers support multiple-record acquisition, which allows the capture of multiple triggered waveforms without software intervention. In this mode, the digitizer automatically begins a new acquisition in a new memory record soon after finishing the previous record. Multiple-record acquisitions can quickly acquire numerous triggered waveforms because they allow hardware rearming of the digitizer. Between each record, there is a dead time during which no triggers are accepted. During this time, the device sets up for the next record, as it transitions through the subsequent states of the SMC-Based Digitizers Acquisition Engine State Diagram. There is also a holdoff between the last trigger in a record and the trigger of a new record. This means that the minimum time between triggers is the greater of either:

• The between-record dead time plus the time per record, or
• The user-specified holdoff time (by default, the holdoff time = 0 s).

To increase the minimum time between triggers, use the trigger holdoff feature. For more information, refer to the SMC-Based Digitizers Acquisition Engine State Diagram.

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).

The number of records that can be acquired varies depending on the memory option of the device. Depending on the digitizer, NI-SCOPE limits to approximately 100,000 records that can be configured without fetching during the acquisition. However, if an application allows for fetching records while they are being acquired, NI-SCOPE allows more records to be configured. Refer to Acquiring More Records Than Fit in Digitizer Memory for more information.