The Challenge:

The challenge was to develop a test system for functionality checks on electronic sub assemblies capable of handling large amounts of data, high speed measurements, high speed logging, and real time analysis on a windows environment

The Solution:

Using the capabilities of National Instruments high speed multifunction DAQ devices and the graphical and analysis features of LabVIEW a portable, flexible, and functional solution was provided.

Introduction:

Reliable sub systems are the secret to any successful large system. In this project we had to perform complete functional tests for electronic sub assemblies that were later integrated into larger systems. Detailed test reports were to be generated for easy reference.

System Requirements

The requirement was to provide a portable test system that could perform complete functional tests for subassemblies. There were four parts to the project.

Event Monitoring and Analysis: The subassemblies communicate amongst each other using current pulses. There were a maximum of 64 channels on which the pulses could occur. The test system had to measure the occurrence time for each pulse and its pulse width with an accuracy of 100 microseconds. After detecting a pulse the system had to compare the pulse with records in a look up table. Depending on the comparison the system determined if the pulse had ‘passed’ or ‘failed’. Logging of the entire data was also required.

Arbitrary Waveform Generator: The arbitrary waveform generator was used to simulate pulses to the sub assemblies. The user could create custom waveform patterns and store them as files for later use.

General Purpose Analog and Digital Acquisition: The system could also be used for various checks like vehicle sign checks, Frequency/Step response, and battery characterization. The system had a maximum of 64 analog channels and 96 digital lines. The system could also read data from 24 isolated digital lines and generate outputs on 24 isolated digital lines for driving relays.

High Speed Digitizer: The High Speed Digitizer needs to be used as a scope to debug faulty channels in the subassemblies.

Hardware selection

Since the system had to be portable and had to be used in an industrial environment a PXI based system was used. The PXI-6071E was used as the multifunction DAQ card for the application. The maximum sampling rate of 640kS/s was well within the limits of the card. To generate the custom waveform patterns the PXI-5411 Arbitrary Waveform Generator card was used. For General Purpose Analog and Digital Acquisition the same PXI-6071E was used as the analog card. The digital card selected was the PXI-6508 for its 96 DIO lines. The PXI-6527 was used for the isolated digital I/O lines. For debugging faulty channels the PXI-5112 High Speed Digitizer was provided which was used as a high resolution scope. A LCD unit was used as display with an integrated keyboard for user inputs.

A custom connector block using D3A999 connectors was provided along with the system for easy connection/disconnection to the electronic subsystems. A 15” TFT foldable Display with built-in keyboard was also provided this along with the PXI based system made for a rugged, portable and powerful test system.

System Configuration and Data Display

The following are some of the features of the custom application developed by Captronic Systems Pvt. Ltd.

• User Management:
  Two levels of entry for the system were implemented. The administrator had the rights to add/remove or modify user information on the system.
• System Configuration:
  The user could configure individual channel parameters on the system. In addition to channel configuration for Event Monitoring and Analysis the user could update the lookup table containing the various pulse entries. Through the user permissions, any user could use this application to view the system configuration, but only authorized administrators could change values.
• Offline Analysis and Report Generation:
  The user could easily view any previously stored data, and generate various reports for printing.

Software Implementation:

The requirements suggested that the custom solution developed would have to manage large amount of data, high speed acquisition, high speed logging and real time analysis and display. All these features were developed using LabVIEW software. The modular approach in LabVIEW helped in developing and testing of individual features. Using LabVIEW’s multithreading features we were able to optimize our application to performs tasks simultaneously. For example data acquisition, real time processing and data logging tasks were simultaneously executed but were independent of each other to guarantee smooth program flow. Similarly for ‘Event Monitoring and Analysis’ the pulse data had to be extracted in real time and processing done to compare if it was a valid pulse or not. To implement this, independent modules for pulse extraction, pulse processing, and pulse comparison were developed and executed simultaneously. Data was passed between modules using queues. This approach ensured data acquisition, and logging at high speeds.

Efficient execution of the application was guaranteed by setting appropriate priorities to tasks. For example display tasks were assigned low priorities while acquisition tasks were assigned high priorities.

Powerful graphical features of LabVIEW helped us build a functionally rich GUI rapidly. Powerful offline analysis features were included in the application using LabVIEW feature rich libraries.

A test panel for General Purpose Analog Acquisition is shown below.

Conclusion

Upon completion of the project, all design specifications were met in a cost-effective solution that paired the user-friendly strengths of LabVIEW and the capabilities of NI products. With the assistance of NI products and the power of LabVIEW we were able to acquire better data in less time, increasing reliability and throughput for our customer.