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Synchronize DSA Devices

The Digital Signal Analyzer (DSA) product family is designed to make highly accurate audio frequency measurements. You can synchronize other PCI and PXI product families using Trigger Connections and Clock Connections. To synchronize PXI and PCI family of DSA devices you need to use a sample clock with time-based synchronization or a reference clock time based synchronization. The AutoSyncDSA property allows you to automatically enable both homogeneous and heterogeneous synchronization between PCI and PXI device families. AutoSyncDSA property automatically configures all the necessary clocks, triggers, and sync pulses needed to synchronize DSA devices in your session.

PXI DSA Devices

PXI devices are synchronized using the PXI chassis backplane, which includes timing and triggering buses. You can automatically synchronize these device series both homogeneously (within the same series) and heterogeneously (across separate series) in the same session.

  • PXI/e 446x series

  • PXI/e 449x series

  • PXI 447x series

Hardware Restrictions

Before you synchronize, ensure that your device combinations adhere to these hardware restrictions:

PXI/e 446x and 449x Series

Chassis restriction

You can synchronize these series using either a PXI or a PXIe chassis. Make sure all your modules are on the same chassis.

Slot placement restriction

You can use any slot on the chassis that supports your module.

PXI 447x Series

Chassis restriction

You can synchronize this series both homogeneously and heterogeneously only on a PXI chassis. You can use them on a PXIe chassis to acquire unsynchronized data.

Slot placement restriction

On the PXI chassis, only the system timing slot can drive the trigger bus. Refer to your device manual to find the system timing slot. This image shows the system timing slot on a PXIe 1062Q chassis.

  • Homogeneous synchronization: You can synchronize PXI 447x devices homogeneously as long as one device is plugged into the system timing slot of a PXI chassis.

  • Heterogeneous synchronization:

    • You can synchronize a PXI 447x device with a PXI 446x device when the 446x is plugged into the system timing slot of a PXI chassis.

    • You cannot synchronize PXI 447x devices with PXI 449x devices.

    • You cannot use hybrid-slot compatible 446x devices.

DSA Device Compatibility Table

 446x Series447x Series449x Series
446x Series
  • PXI chassis only

  • Standard 446x device, not hybrid-slot compatible

  • 446x device in system timing slot

447x Series
  • PXI chassis only

  • Standard 446x device, not hybrid-slot compatible

  • 446x device in system timing slot

  • PXI chassis only

  • One device in system timing slot

χ
449x Seriesχ

Synchronize Dynamic Signal Analyzer PXI Devices

This example shows how to acquire synchronized data from two Dynamic Signal Analyzer DSA PXI devices, NI PXI-4462 and NI PXI-4461.

Create an acquisition session and add one voltage analog input channel from each of the two PXI devices

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

Acquire data in the foreground without synchronizing the channels:

[data,time] = startForeground(s);
plot(time, data)

The data returned is not synchronized.

Synchronize the two channels using the AutoSyncDSA property:

s.AutoSyncDSA = true;

Acquire data in the foreground and plot it:

[data,time] = startForeground(s);
plot(time, data)

The data is now synchronized.

PCI DSA Devices

PCI devices are synchronized use the RTSI cable. You can automatically synchronize these device series both homogeneously (within the same series) and heterogeneously (across separate series) in the same session when they are connected with a RTSI cable.

  • PCI 446x series

  • PCI 447x series

    Note:   If you are synchronizing PCI devices make sure you register the RTSI cables in Measurement and Automation Explorer. For more information see the NI knowledge base article What is RTSI and How is it Configured? (Document ID: 2R5FK53J)

Synchronize DSA PCI Devices

This example shows how to acquire synchronized data from two DSA PCI devices, NI PCI-4461 and NI PCI-4462.

Connect the two devices with a RTSI cable.

Register your RTSI cable in Measurement and Automation Explorer.

Create an acquisition session and add one voltage analog input channel from each of the two PXI devices

s = daq.createSession('ni');
addAnalogInputChannel(s,'Dev1', 0, 'Voltage');
addAnalogInputChannel(s,'Dev2', 0, 'Voltage');

Synchronize the two channels using the AutoSyncDSA property:

s.AutoSyncDSA = true;

Acquire data in the foreground and plot it:

[data,time] = startForeground(s);
plot(time, data)

Handle Filter Delays with DSA Devices

DSA devices have a built in digital filter. You must account for filter delays when synchronizing between heterogeneous devices. Refer to your device manuals for filter delay information. For more information see the NI knowledge base article Why Is My Data Delayed When Using DSA Devices? (Document ID: 2UI8PGX4).

Account for Filter Delays

This example shows how to account for filter delays when you use the same sine wave to acquire from two different channels from 2 different PXI devices. Perfectly synchronized channels will show zero phase lag between the two acquired signals.

Create a session and add two analog input channels with Voltage measurement type, from National Instruments® PXI-4462 and NI PXI-4472.

s = daq.createSession('ni');
ch1 = addAnalogInputChannel(s,'PXI1Slot2', 0, 'Voltage');
ch2 = addAnalogInputChannel(s,'PXI1Slot3', 0, 'Voltage');

Acquire unsynchronized data and plot it:

[data,time] = startForeground(s);
plot(time, data)

Use AutoSyncDSA to automatically configure the triggers, clocks and sync pulses of the channels to synchronize the devices:

s.AutoSyncDSA = true;

Acquire synchronized data:

[data,time] = startForeground(s);
plot(time, data)

Calculate the phase lag between the two channels, using the device data sheet:

NI PXI 4462 data sheet specifies the phase lag to be 63 samples when EnhancedAliasRejectionEnable property is disabled. Check to make sure this property is set to false or 0:

ch1.EnhancedAliasRejectionEnable
ans =

           0

To synchronize signals from these devices the phase lag should be 63-38 or 24 samples. Confirm that the data returned is 24 samples apart.

NI PXI 6672 data sheet specified the phase lag to be 38 samples when EnhancedAliasRejectionEnable property is disabled. Check to make sure this property is set to false or 0:

ch2.EnhancedAliasRejectionEnable
ans =

           0
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