Reference Design for Synchronizing DSA Devices in Two PXI Chassis using GPS

Publish Date: Mar 08, 2016 | 0 Ratings | 0.00 out of 5 | Print | Submit your review


This example demonstrates how to synchronize two PXI chassis connected to a single controller with either PXI-4461/4462 or PXI-449x devices to GPS. The GPS Time Coordinator will synchronize multiple systems together which allows you to create a very large and flexible synchronized measurement system.

Table of Contents

  1. Hardware Required
  2. Hardware Setup
  3. Software Required
  4. Software Setup

Setup Instructions

1. Hardware Required

·         PXI Chassis and controller

·         MXI interface

·         PXI-4461/4462 or PXI-449x

·         PXI-6682

·         PXI-6651

·         GPS Antenna

·         Trimble Thunderbolt E (or other GPS receiver which can provide a GPS disciplined 10MHz signal)

·         GPS Splitter (recommend part number ALDCBS1X2-B/5 from GPS Networking)

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2. Hardware Setup

·         Connect GPS Antenna, GPS Splitter, Thunderbolt and PXI-6682 together appropriately.

·         Connect 10MHz output from Thunder to PXI-6682 Clk In terminal.

·         Connect PXI-6682 ClkOut  to PXI-6651 Clk In (10 MHz signal)

·         Connect PXI-6682 PFI 1 to PXI- 6682 PFI 0 (wrapback of triggers)

·         Connect PXI-6682 PFI 2 to PXI- 6651 PFI 0 (triggers)



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3. Software Required

·         LabVIEW 8.5 or later

·         NI-Sync 3.0 or later

·         Simple TCP Messaging Protocol (

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4. Software Setup

After connecting all of the signals and booting the system, you will need to wait for the self survey of the PXI-6682 to complete.  The self survey process takes about 15 minutes to complete.  By default, the PXI-6682 will perform a self survey each time it is reset.  To change this behavior so that a self survey only one time, open Measurement & Automation Explorer (MAX), right-click on the PXI-6682 and select “Properties”.  The following screenshot shows the option to uncheck.


You will only need to perform a self survey if you move the PXI chassis from its current location.

After the self survey is complete, you should calibrate out any offset errors in the PXI-6682’s GPS time reference.  This is accomplished by measuring the amount of error between the PPS signal from the Trimble Thunderbolt and the timestamps from the PXI-6682.  Calibration code is included in the code set.  Once an adjustment has been made, you can make the adjustment persist through resets by applying the settings in MAX.  Below is another screenshot of the PXI-6682’s property page:



In a 14 or 18 slot PXI chassis, the PCI bus and the trigger bus are divided into three segments.  In order to route the triggers through to all slots, you need to manually configure this in MAX.  PXI_Trig4 and PXI_Trig5 need to be routed “Away from Slot 1” as shown in the screenshot below.  These are the triggers lines which will route the Sync Pulse and Start Trigger to the DSA devices.



Now, we are ready to make some measurements.  On the measurement system, open the “GPS Sync with 446x or 449x – Single CPU Multi Chassis 6682 only –”.  Configure the inputs and run the VI.  On the same PC or a different one, open the “GPS Time”.  Configure the inputs appropriately and run the VI.  The measurement system will stream to disk all of its data and send one channel back to the GPS Time Coordinator over TCP/IP.



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GPS Sync with 446x or 449x - S
ingle CPU Multi Chassis 6682 o
nly -



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