daq.Session Properties

Session object properties

Alphabetical listing of session object properties. Sessions for some vendors might not have all properties.

Session Properties

AutoSyncDSA — Automatically Synchronize DSA devices

false (default) | true

Automatically Synchronize DSA devices, specified as a logical true or false. Use this property to enable or disable automatic synchronization between DSA (PXI or PCI) devices in the same DataAcquisition. By default automatic synchronization capability is disabled.

To enable automatic synchronization, create a session and add channels from a DSA device:

s = daq.createSession('ni')
addAnalogInputChannel(s,'PXI1Slot2',0,'Voltage');
addAnalogInputChannel(s,'PXI1Slot3',1,'Voltage');

Enable automatic synchronization and acquire data.

s.AutoSyncDSA = true;
startForeground(s);

Example: true

Data Types: logical

BitsPerSample — Sampling resolution

Read-only: numeric

This property is read-only.

Sampling resolution indicating the maximum value of bits per sample of the device, based on the device specifications. By default this read-only value is 24.

Example: View BitsPerSample Property

Create an audio input session and display the session properties.

s = daq.createSession('directsound')

s = 

Data acquisition session using DirectSound hardware:
   Will run for 1 second (44100 scans) at 44100 scans/second.
   No channels have been added.
   
Properties, Methods, Events

Click on the Properties link.

              UseStandardSampleRates: true
                       BitsPerSample: 24
                 StandardSampleRates: [1x15 double]
                       NumberOfScans: 44100
                   DurationInSeconds: 1
                                Rate: 44100
                        IsContinuous: false
      NotifyWhenDataAvailableExceeds: 4410
IsNotifyWhenDataAvailableExceedsAuto: true
          NotifyWhenScansQueuedBelow: 22050
    IsNotifyWhenScansQueuedBelowAuto: true
              ExternalTriggerTimeout: 10
                      TriggersPerRun: 1
                              Vendor: DirectSound
                            Channels: ''
                         Connections: ''
                           IsRunning: false
                           IsLogging: false
                              IsDone: false
         IsWaitingForExternalTrigger: false
                   TriggersRemaining: 1
                           RateLimit: ''
                         ScansQueued: 0
               ScansOutputByHardware: 0
                       ScansAcquired: 0

Channels — Device channels

Read-only: array of channel objects

This property is read-only.

Device channels, returned as an array of channel objects.

Tip

You cannot directly add or remove channels using the Channels propert. Use addAnalogInputChannel and addAnalogOutputChannel to add channels. Use removeChannel to remove channels.

Connections — Device connections

Read-only: array of clock and trigger connection objects

This property is read-only.

Device clock and trigger connections, returned as an array of objects.

This session property contains and displays all connections added to the session.

Tip

You cannot directly add or remove connections using the Connections property. Use addTriggerConnection and addClockConnection to add connections. Use removeConnection to remove connections.

Example: Remove Synchronization Connection

This example shows you how to remove a synchronization connection.

Create a session and add analog input channels, and trigger and clock connections.

s = daq.createSession('ni')
addAnalogInputChannel(s,'Dev1', 0, 'voltage');
addAnalogInputChannel(s,'Dev2', 0, 'voltage');
addAnalogInputChannel(s,'Dev3', 0, 'voltage');
addTriggerConnection(s,'Dev1/PFI4','Dev2/PFI0','StartTrigger');
addTriggerConnection(s,'Dev1/PFI4','Dev3/PFI0','StartTrigger');
addClockConnection(s,'Dev1/PFI5','Dev2/PFI1','ScanClock');

Examine the session Connections property.

s.Connections

ans = 

Start Trigger is provided by 'Dev1' at 'PFI4' and will be received by:
         'Dev2' at terminal 'PFI0'
         'Dev3' at terminal 'PFI0'
Scan Clock is provided by 'Dev1' at 'PFI5' and will be received by:
         'Dev2' at terminal 'PFI1'
         'Dev3' at terminal 'PFI1'

   index     Type      Source   Destination
   ----- ------------ --------- -----------
   1     StartTrigger Dev1/PFI4 Dev2/PFI0
   2     StartTrigger Dev1/PFI4 Dev3/PFI0
   3     ScanClock    Dev1/PFI5 Dev2/PFI1
   4     ScanClock    Dev1/PFI5 Dev3/PFI1

Remove the last clock connection at index 4 and display the session connections.

removeConnection(s,4)
s.Connections

ans = 

Start Trigger is provided by 'Dev1' at 'PFI4' and will be received by:
         'Dev2' at terminal 'PFI0'
         'Dev3' at terminal 'PFI0'
Scan Clock is provided by 'Dev1' at 'PFI5' and will be received by 'Dev2' at terminal 'PFI1'.

   index     Type      Source   Destination
   ----- ------------ --------- -----------
   1     StartTrigger Dev1/PFI4 Dev2/PFI0
   2     StartTrigger Dev1/PFI4 Dev3/PFI0
   3     ScanClock    Dev1/PFI5 Dev2/PFI1

DurationInSeconds — Specify duration of acquisition

1 (default) | numeric

Duration of an acquisition, specified in seconds. 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.

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.

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

s = daq.createSession('ni');
addAnalogInputChannel(s,'cDAQ1Mod1','ai0','voltage');
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

Data Types: double

ExternalTriggerTimeout — Specify maximum wait time for external trigger

numeric

Maximum amount of time in seconds the session waits for an external trigger before timing out. To disable the timeout, set ExternalTriggerTimeout to a value of Inf.

Example: Specify External Trigger Timeout

Specify how long the session waits for an external trigger before timing out.

Create a session and click on the Properties link to display session properties.

s = daq.createSession('ni')

s = 

Data acquisition session using National Instruments hardware:
   Will run for 1 second (1000 scans) at 1000 scans/second.
   No channels have been added.
   
Properties, Methods, Events

                         AutoSyncDSA: false
                       NumberOfScans: 1000
                   DurationInSeconds: 1
                                Rate: 1000
                        IsContinuous: false
      NotifyWhenDataAvailableExceeds: 100
IsNotifyWhenDataAvailableExceedsAuto: true
          NotifyWhenScansQueuedBelow: 500
    IsNotifyWhenScansQueuedBelowAuto: true
              ExternalTriggerTimeout: 10
                      TriggersPerRun: 1
                              Vendor: National Instruments
                            Channels: ''
                         Connections: ''
                           IsRunning: false
                           IsLogging: false
                              IsDone: false
         IsWaitingForExternalTrigger: false
                   TriggersRemaining: 1
                           RateLimit: ''
                         ScansQueued: 0
               ScansOutputByHardware: 0
                       ScansAcquired: 0

Change the timeout to 15 seconds.

s.ExternalTriggerTimeout = 15;

Example: Specify External Trigger with Disabled Timeout

Set an external trigger on a session, without a timeout.

Create a session with an external trigger, then set its ExternalTriggerTimeout to Inf.

s = daq.createSession('ni');
addAnalogInputChannel(s,'Dev1','ai0','Voltage');
addTriggerConnection(s,'External','Dev1/PFI0','StartTrigger');
s.ExternalTriggerTimeout = Inf;

Data Types: double

IsContinuous — Specify operation to continue until manually stopped

false (default) | true

Use IsContinuous to specify that the session operation runs until you execute stop. When set to true, the session will run continuously, acquiring or generating data until stopped.

• Set IsContinuous to false to make the session operation stop automatically. This property is set to false by default.

• Set IsContinuous to true to make the session operation run until you execute stop.

Example: Create a session object, add an analog input channel, and set the session to run until manually stopped:

s = daq.createSession('ni');
addAnalogInputChannel(s,'cDAQ1Mod1','ai0','voltage');
s.IsContinuous = true

s = 

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

Data Types: logical

IsDone — Indicate if session operation is complete

Read-only: true | false

This property is read-only.

Indication that the session operation is complete, returned as true or false.

• Value is logical 1 (true) when the session operation is complete.

• Value is logical 0 (false) while the session operation is not complete.

Tip

• IsRunning indicates the session has started, but the hardware might not be acquiring or generating data. It is still true while the hardware is waiting for a trigger, and while transferring data in the process of stopping.

• IsLogging indicates the hardware is actively acquiring or generating data.

• IsDone indicates the session object has completed its operation, including all necessary transfer of data.

Example: Create an acquisition session and see if the operation is complete.

s = daq.createSession('ni');
addAnalogOutputChannel(s,'cDAQ1Mod2', 'ao1', 'vVoltage');
s.queueOutputData(linspace(-1, 1, 1000)');
s.startBackground();
s.IsDone

ans =

     0

Issue a wait and see if the operation is complete.

wait(s)
s.IsDone

ans =

     1

Data Types: logical

IsLogging — Indicate if hardware is acquiring or generating data

Read-only: true | false

This property is read-only.

Indication if the hardware is actively acquiring or generating data, returned as true or false.

• Value is logical 1 (true) if the device is acquiring or generating data.

• Value is logical 0 (false) if the device is not acquiring or generating data.

Tip

• IsRunning indicates the session has started, but the hardware might not be acquiring or generating data. It is still true while the hardware is waiting for a trigger, and while transferring data in the process of stopping.

• IsLogging indicates the hardware is actively acquiring or generating data.

• IsDone indicates the session object has completed its operation, including all necessary transfer of data.

Example: Check device logging.

Create and start a session.

ans =

     1

The session is running, so check for device logging.

s.IsLogging

ans =

     0

This result might indicate that the device is waiting for an external trigger. After triggering, wait until logging is complete.

wait(s)
s.IsDone

ans =

     1

Data Types: logical

IsNotifyWhenDataAvailableExceedsAuto — Control if NotifyWhenDataAvailableExceeds is set automatically

true (default) | false

Indication if the NotifyWhenDataAvailableExceeds property is set automatically, or you have set a specific value.

Tip

This property is typically used to set NotifyWhenDataAvailableExceeds back to its default behavior.

• When the value is true (default), then the NotifyWhenDataAvailableExceeds property is set automatically.

• When the value is false, you set the NotifyWhenDataAvailableExceeds property to a specific value.

Example: Enable Data Exceeds Notification

Change the IsNotifyWhenDataAvailableExceedsAuto to be able to set the NotifyWhenDataAvailableExceeds property to a specific value.

Create a session and display the properties by clicking the Properties link.

s = daq.createSession('ni')

s = 

Data acquisition session using National Instruments hardware:
   Will run for 1 second (1000 scans) at 1000 scans/second.
   No channels have been added.
   
Properties, Methods, Events

                         AutoSyncDSA: false
                       NumberOfScans: 1000
                   DurationInSeconds: 1
                                Rate: 1000
                        IsContinuous: false
      NotifyWhenDataAvailableExceeds: 100
IsNotifyWhenDataAvailableExceedsAuto: true
          NotifyWhenScansQueuedBelow: 500
    IsNotifyWhenScansQueuedBelowAuto: true
              ExternalTriggerTimeout: 10
                      TriggersPerRun: 1
                              Vendor: National Instruments
                            Channels: ''
                         Connections: ''
                           IsRunning: false
                           IsLogging: false
                              IsDone: false
         IsWaitingForExternalTrigger: false
                   TriggersRemaining: 1
                           RateLimit: ''
                         ScansQueued: 0
               ScansOutputByHardware: 0
                       ScansAcquired: 0

Change the IsNotifyWhenDataAvailableExceedsAuto to false.

s.IsNotifyWhenDataAvailableExceedsAuto = false

s = 

Data acquisition session using National Instruments hardware:
   Will run for 1 second (1000 scans) at 1000 scans/second.
   No channels have been added.

Data Types: logical

IsNotifyWhenScansQueuedBelowAuto — Control if NotifyWhenScansQueuedBelow is set automatically

true (default) | false

Indication if the NotifyWhenScansQueuedBelow property is set automatically, or you have set a specific value.

• When the value is true, then NotifyWhenScansQueuedBelow is set automatically.

• When the value is false, you set NotifyWhenScansQueuedBelow to a specific value.

Example: Enable Notification When Scans Reach Below Specified Range

Change the IsNotifyWhenScansQueuedBelowAuto to be able to set the NotifyWhenScansQueuedBelow property to a specific value.

Create a session and display the properties by clicking the Properties link.

s = daq.createSession('ni')

s = 

Data acquisition session using National Instruments hardware:
   Will run for 1 second (1000 scans) at 1000 scans/second.
   No channels have been added.
   
Properties, Methods, Events

                         AutoSyncDSA: false
                       NumberOfScans: 1000
                   DurationInSeconds: 1
                                Rate: 1000
                        IsContinuous: false
      NotifyWhenDataAvailableExceeds: 100
IsNotifyWhenDataAvailableExceedsAuto: true
          NotifyWhenScansQueuedBelow: 500
    IsNotifyWhenScansQueuedBelowAuto: true
              ExternalTriggerTimeout: 10
                      TriggersPerRun: 1
                              Vendor: National Instruments
                            Channels: ''
                         Connections: ''
                           IsRunning: false
                           IsLogging: false
                              IsDone: false
         IsWaitingForExternalTrigger: false
                   TriggersRemaining: 1
                           RateLimit: ''
                         ScansQueued: 0
               ScansOutputByHardware: 0
                       ScansAcquired: 0

Change the IsNotifyWhenDataAvailableExceedsAuto to false.

s.IsNotifyWhenScansQueuedBelowAuto = false

s = 

Data acquisition session using National Instruments hardware:
   Will run for 1 second (1000 scans) at 1000 scans/second.
   No channels have been added.

Data Types: logical

IsRunning — Indicate if session operation is in progress

Read-only: true | false

This property is read-only.

Session running indication, returned as true or false.

The read-only IsRunning property indicates the session operation is started and in progress, whether or not the hardware is acquiring or generating data at the time.

Tip

• IsRunning indicates the session has started, but the hardware might not be acquiring or generating data. It is still true while the hardware is waiting for a trigger, and while transferring data in the process of stopping.

• IsLogging indicates the hardware is actively acquiring or generating data.

• IsDone indicates the session object has completed its operation, including all necessary transfer of data.

Example: Create an acquisition session, add a DataAvailable event listener and start the acquisition.

s = daq.createSession('ni');
addAnalogInputChannel(s,'cDAQ1Mod1','ai0','voltage');
lh = s.addlistener('DataAvailable', @plotData);

function plotData(src,event)
         plot(event.TimeStamps, event.Data)
end
startBackground(s);

See if the session is in progress.

s.IsRunning

ans =

    1

Wait until operation completes, and see if the session is in progress.

wait(s)
s.IsRunning

ans =

     0

Data Types: logical

IsWaitingForExternalTrigger — Indicates if synchronization is waiting for an external trigger

Read-only: false (default) | true

This property is read-only.

Indication if the acquisition or generation session is waiting for a trigger from an external device. If you have added an external trigger, this property displays true, if not, it displays false.

Example: true

Data Types: logical

NotifyWhenDataAvailableExceeds — Specify number of acquired scans to fire DataAvailable event

numeric

The DataAvailable event is triggered when the number of scans available to the session object exceeds the quantity specified in the NotifyWhenDataAvailableExceeds property.

By default the DataAvailable event triggers when 1/10 second worth of data is available for analysis. To specify a different threshold, change the value of NotifyWhenDataAvailableExceeds.

You cannot set the NotifyWhenDataAvailableExceeds property when the session is in the prepared state, which can happen after running startForeground. In this case, call release on the session before setting this property value.

Example: Control Firing of Data Available Event

Add an event listener to display the total number of scans acquired and fire the event when the data available exceeds a specified amount.

Create the session and add an analog input voltage channel.

s = daq.createSession('ni');
addAnalogInputChannel(s,'Dev4',1,'Voltage');
lh = addlistener(s,'DataAvailable', ...
			@(src, event) disp(s.ScansAcquired));

The default Rate is 1000 scans per second. The session is automatically configured to fire the DataAvailable notification 10 times per second. Increase the Rate to 800,000 scans per second, while the DataAvailable notification automatically fires 10 times per second.

s.Rate = 800000;
s.NotifyWhenDataAvailableExceeds

ans =
        80000

Running the acquisition causes the number of scans acquired to be displayed by the callback 10 times.

data = startForeground(s);

               80000

               160000

               240000

               320000

               400000

               480000

               560000

               640000

               720000

               800000

Increase NotifyWhenDataAvailableExceeds to 160,000. NotifyWhenDataAvailableExceeds is no longer configured automatically when the Rate changes.

s.NotifyWhenDataAvailableExceeds = 160000;
s.IsNotifyWhenDataAvailableExceedsAuto

ans =

     0

Start the acquisition. The DataAvailable event is fired only five times per second.

data = startForeground(s);

               160000

               320000

               480000

               640000

               800000

Set IsNotifyWhenDataAvailableExceedsAuto back to true.

s.IsNotifyWhenDataAvailableExceedsAuto = true;
s.NotifyWhenDataAvailableExceeds

ans =
                80000

This causes NotifyWhenDataAvailableExceeds to set automatically when Rate changes.

s.Rate = 50000;
s.NotifyWhenDataAvailableExceeds

ans =
                 5000

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

NotifyWhenScansQueuedBelow — Specify number of queued scans to fire DataRequired event

numeric

When generating output signals continuously, the DataRequired event is fired when you need to queue more data. This occurs when the ScansQueued property drops below the value specified in the NotifyWhenScansQueuedBelow property.

By default the DataRequired event fires when 1/2 second worth of data remains in the queue. To specify a different threshold, change this property value to control when the event is fired.

Example: Control When DataRequired Event Is Fired

Specify a threshold below which the DataRequired event fires.

Create a session and add an analog output channel.

s = daq.createSession('ni')
addAnalogOutputChannel(s,'cDAQ1Mod2', 0, 'Voltage')

Queue some output data.

outputData = (linspace(-1,1,1000))';
s.queueOutputData(outputData);

Set the threshold of scans queued to 100.

s.NotifyWhenScansQueuedBelow = 100;

Add an anonymous listener and generate the signal in the background:

lh = s.addlistener('DataRequired', ...
@(src,event) src.queueOutputData(outputData));

startBackground(s);

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64

NumberOfScans — Number of scans for operation when starting

numeric

Use the NumberOfScans property to specify the number of scans the session will acquire during the operation. Changing the number of scans changes the duration of an acquisition. When the session contains output channels, NumberOfScans becomes a read-only property and the number of scans in a session is determined by the amount of data queued.

Tips

• To specify a time length for the acquisition, use DurationInSeconds.

• To control the length of an output operation, use queueOutputData.

Example: Change Number of Scans

Create an acquisition session, add an analog input channel, and display the NumberOfScans.

s = daq.createSession('ni');
addAnalogInputChannel(s,'cDAQ1Mod1','ai0','Voltage');
s.NumberOfScans

ans =

                 1000

Change the NumberOfScans property.

s.NumberOfScans = 2000

s = 

Data acquisition session using National Instruments hardware:
   Will run for 2000 scans (2 seconds) 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

Rate — Data scan rate

numeric

Data scan rate, specified as a numeric value of samples per second. You can set the rate to any positive nonzero scalar value supported by the hardware in its current configuration. Many hardware devices accept fractional rates.

Tip

On most devices, the hardware limits the exact rates that you can set. When you set the rate, Data Acquisition Toolbox™ sets the rate to the next higher rate supported by the hardware. If the exact rate affects your analysis of the acquired data, obtain the actual rate after you set it, and then use that in your analysis.

Example: Set the Session Rate

Create a session and add an analog input channel.

s = daq.createSession('ni');
addAnalogInputChannel(s,'cDAQ1Mod1','ai1','Voltage');

Change the rate to 10000 scans per second.

s.Rate = 10000

s = 

Data acquisition session using National Instruments hardware:
   Will run for 1 second (10000 scans) at 10000 scans/second.
   Operation starts immediately.
      Number of channels: 1
      index Type  Device   Channel  MeasurementType      Range        Name
      ----- ---- --------- ------- ----------------- ---------------- ----
      1     ai   cDAQ1Mod1 ai1       Voltage (Diff)  -10 to +10 Volts

Data Types: double

RateLimit — Lower and upper scan rate limits

Read-only: array of doubles

This property is read-only.

Lower and upper scan rate limits, returned as a 1-by-2 vector of doubles indicating minimum and maximum allowed scan rates in samples per second. The scan rate limits depend on the hardware and its configurations. In devices that multiplex channels to a converter, the rate limit is impacted by the number of channels you use.

RateLimit changes dynamically as the session configuration changes.

Example: Find the Session Rate Limits

Create a session and add an analog input channel.

s = daq.createSession('ni');
addAnalogInputChannel(s,'cDAQ1Mod1','ai1','Voltage');

Examine the session rate limits.

format("longG")
s.RateLimit

ans =
    0.1        250000

Data Types: double

ScansAcquired — Number of data scans acquired during operation

Read-only: numeric

This property is read-only.

Number of scans acquired after you start the operation calling startBackground. This value is reset each time you call startBackground.

Example: Display Number of Acquired Scans

Acquire analog input data and display the number of scans acquired.

Create a session, add an analog input channel,

s = daq.createSession('ni');
ch = addAnalogInputChannel(s,'Dev1','ai1','voltage');

See how many scans the session had acquired before and after running.

s.ScansAcquired

ans =
    0

startForeground(s);
s.ScansAcquired

ans =
    1000

ScansOutputByHardware — Number of scans generated as device output

Read-only: numeric

This property is read-only.

Number of scans output by the hardware after you start the operation using startBackground. The value depends on information from the hardware.

Example: Display Scans Output by Hardware

Generate data on an analog output channel and to see how many scans are output by the hardware.

Create a session and add an analog output channel.

s = daq.createSession('ni');
ch = addAnalogOutputChannel(s,'Dev1','ao1','voltage');

Queue some output data and start the generation.

s.queueOutputData(linspace(-1, 1, 1000)');
startForeground(s);

Examine the ScansOutputByHardware property.

s.ScansOutputByHardware

ans =
    1000

ScansQueued — Number of scans prepared for device output

Read-only: numeric

This property is read-only.

Number of scans queued to the device output channels. Add scans to the queued with queueOutputData. The ScansQueued property value decreases when the hardware reports that it has successfully output data.

Example: Monitor Scans Queue

Queue some output data to an analog output channel and examine the session properties to see how many scans are queued.

Create a session and add an analog output channel.

s = daq.createSession('ni');
ch = addAnalogOutputChannel(s,'Dev1','ao1','voltage');

Queue some output data, then examine the ScansQueued property to see the number of scans queued.

s.queueOutputData(linspace(-1,1,1000)');
s.ScansQueued

ans =
    1000

StandardSampleRates — Standard available scan rates

Read-only: double array

This property is read-only.

Standard sample rates supported by your audio device. You can choose to use the standard rates or use values within the supported range. See UseStandardSampleRates for more information.

View the standard sample rates for DirectSound audio devices:

s = daq.createSession('directsound')
s.StandardSampleRates'

ans =

        8000
        8192
       11025
       16000
       22050
       32000
       44100
       47250
       48000
       50000
       88200
       96000
      176400
      192000
      352800

Data Types: double

TriggersPerRun — Number of digital triggers per session acquisition run

numeric

Number of digital triggers per session acquisition run, returned as a double. This is the number of times the specified trigger executes for one acquisition or generation session.

Example: Specify Number of Triggers Per Operation

Create a session and add channels and trigger to the session.

s = daq.createSession('ni');
addAnalogInputChannel(s,'Dev1', 0, 'voltage');
addAnalogInputChannel(s,'Dev2', 0, 'voltage');
addTriggerConnection(s,'Dev1/PFI4','Dev2/PFI0','StartTrigger');

Display the session TriggersPerRun property.

s.TriggersPerRun

ans =

     1

Set the trigger to run twice during the operation.

s.TriggersPerRun = 2

s = 

Data acquisition session using National Instruments hardware:
   Will run 2 times for 1 second (1000 scans) at 1000 scans/second.

   Trigger Connection added. (Details)

   Number of channels: 2
      index Type Device Channel MeasurementType      Range       Name
      ----- ---- ------ ------- --------------- ---------------- ----
      1     ai   Dev1   ai0     Voltage (Diff)  -10 to +10 Volts
      2     ai   Dev2   ai0     Voltage (Diff)  -10 to +10 Volts

Data Types: double

TriggersRemaining — Number of digital triggers remaining in acquisition

Read-only: numeric

This property is read-only.

The number of triggers remaining for this acquisition or generation session, returned as a double. This value depends on the number of triggers set using TriggersPerRun.

Example: Display Number of Triggers Remaining in Operation

Create a session and add channels and a trigger to the session.

s = daq.createSession('ni');
addAnalogInputChannel(s,'Dev1', 0, 'voltage');
addAnalogInputChannel(s,'Dev2', 0, 'voltage');
addTriggerConnection(s,'Dev1/PFI4','Dev2/PFI0','StartTrigger');

Display the session TriggersRemaining property.

s.TriggersRemaining

ans =

     1

Data Types: double

UserData — Custom data

any data

Custom data, specified as any MATLAB^® data type and format.

Example: Create a session and define its UserData property as a struct with custom fields.

s = daq.createSession('ni');
s.UserData.Data = [];
s.UserData.TimeStamps = [];
s.UserData.StartTime = [];

Set the start time, and append event information to the log fields stored in UserData.

s.UserData.StartTime = eventData.TriggerTime;
s.UserData.Data = [s.UserData.Data; eventData.Data];
s.UserData.TimeStamps = [s.UserData.TimeStamps; eventData.TimeStamps];

Data Types: single | double | int8 | int16 | int32 | int64 | uint8 | uint16 | uint32 | uint64 | logical | char | string | struct | table | cell | function_handle | categorical | datetime | duration | calendarDuration | fi

UseStandardSampleRates — Configure session to use standard sample rates

true (default) | false

Use this property to specify if your audio channel uses standard sample rates supported by your device or a user-specified value. To use non-standard sample rates, set the value to false and set the session Rate to the desired value.

Example: Configure a nonstandard sample rate

Add an audio channel to a session and change the UseStandardSampleRates property.

s = daq.createSession('directsound');
addAudioInputChannel(s,Audio1,1);
s.UseStandardSampleRates = false

s = 

Data acquisition session using DirectSound hardware:
   Will run for 1 second (44100 scans) at 44100 scans/second.
   Number of channels: 1
      index Type Device Channel MeasurementType     Range     Name
      ----- ---- ------ ------- --------------- ------------- ----
      1     audi Audio1 1       Audio           -1.0 to +1.0

Specify a different scan rate.

s.Rate = 8500

s = 

Data acquisition session using DirectSound hardware:
   Will run for 1 second (8500 scans) at 8500 scans/second.
   Number of channels: 1
      index Type Device Channel MeasurementType     Range     Name
      ----- ---- ------ ------- --------------- ------------- ----
      1     audi Audio3 1       Audio           -1.0 to +1.0

Data Types: logical

Vendor — Data acquisition hardware vendor information

Read-only: vendor object

This property is read-only.

Data acquisition hardware vendor information associated with the session, returned as a vendor object with the following properties:

ID
FullName
AdaptorVersion
DriverVersion
IsOperational

This object is the same as the corresponding vendor object returned by the daq.getVendors function.

Example: Create a session and get information its vendor.

s = daq.createSession('ni');
v = s.Vendor

v = 

Data acquisition vendor 'National Instruments':

            ID: 'ni'
      FullName: 'National Instruments'
AdaptorVersion: '3.3 (R2013a)'
 DriverVersion: '9.2.3 NI-DAQmx'
 IsOperational: true

Version History

Introduced in R2010b