Main Content


Specify duration of acquisition


When working with the session-based interface, use the DurationInSeconds property to change the duration of an acquisition.

When the session contains analog, digital, or audio output channels, DurationInSeconds is a read-only property whose value is determined by

s.ScansQueued / s.Rate

If the session contains only counter output channels with PulseGeneration measurement type, then DurationInSeconds represents the duration of the pulse train signal generation.


In a session with only input channels or counter output channels, you can enter a value in seconds for the length of the acquisition. Changing the duration changes the number of scans accordingly. By default, DurationInSeconds is set to 1 second.


Create a session object, add an analog input channel, and change the duration:

s = daq.createSession('ni');
s.DurationInSeconds = 2
s = 

Data acquisition session using National Instruments hardware:
   Will run for 2 seconds (2000 scans) at 1000 scans/second.
   Operation starts immediately.
      Number of channels: 1
      index Type  Device   Channel  MeasurementType      Range        Name
      ----- ---- --------- ------- ----------------- ---------------- ----
      1     ai   cDAQ1Mod1 ai0       Voltage (Diff)  -10 to +10 Volts