The Challenge:

Developing an integrated and configurable data acquisition and test system, that can conduct an assortment of test on various types of Power Modules (PM) and Differential Buffer Amplifier (DBA). Configuration flexibility, testing efficiency and accuracy, data recording reliability and effective report generation are significant performance challenges.

The Solution:

Manufacturing an automated, highly flexible and scalable test system using National Instruments SCXI Platform, DMM module, NI DAQmx, GPIB interface and LabVIEW Development Environment.

Introduction:

Our client a leading R&D organization specializes in developing Power/Energy Modules for vehicles. So before integrating these modules should be subjected to rigorous testing. Those Modules underwent through various standard simulated testing environments. The Client wanted a test system that would:

• Simulate different input voltage ratings in between 26-32V for Power Modules.
• Simulate different input voltage ratings in between 0-5V for DBA.
• Provide facility to monitor and control the tests performed.
• Perform online result data presentation and report generation of processed data.
• Provide a software interface to automate test sequences thereby requiring minimal user intervention.
• Provide a software and hardware architecture that support future expansion.

System Design:

Each part of the system had a unique requirement met by NI hardware and LabVIEW software. The major application of this system is measurement of various parameters at high precision. These measurement parameters are as given below:

• 1 mV accuracy; 0.1 mV resolution for dc voltage measurement
• 10 mA accuracy; 1mA resolution for current measurement
• 1 mΩ accuracy; four wire measurement of resistance

Earlier this combination of accuracy and speed was available only with high resolution digital multimeters. Now NI PCI-4070 FlexDMM card is available with all these characteristics at very low cost compare to those particular high resolution digital multimeters. The DMM card receives data from switch modules and passes this data to PC. Another PCI-GPIB card is connected to PC, which controls the Ammeter and Power supplies for both Power Modules and DBAs. Systematic hardware setup diagram is shown below:

Broadly 2 types of modules are there: Power Module and DBA. A 32X1 (2 wires) high density multiplexer switch NI SCXI-1127 with SCXI-1331 terminal block connects Power Module output lines to the PCI-4070 FlexDMM,. A GPIB controlled Power supply gives 28V to Power Modules. Current measurement is carried out through a single GPIB controlled ammeter. NI 6221-DAQ card driven relays establish and break connections between ammeter and output lines.

DBA modules output lines also connect with the NI switch SCXI-1127 card. For powering of these DBA modules, a ±15 V dual Power Supply is provided. 28 V power Output of DBA connects via SCXI-1332 Terminal block

Software Implementation:

The software had to be modular, scalable and easy to debug. So in the design phase a layered architecture was proposed. A brief explanation of layered architecture is given below.

The application software contains four layers, which are functionally independent of each other. Each layer carries out a set number of functions, which are logically similar. Each layer communicates only with its adjacent layer. There are separate interfaces for read and write between layer to make to make both the process independent of each other. The following figure gives a graphical representation of the layered architecture.

The four layers are as follows:

LabVIEW along with NI DAQmx proved to be a perfect choice for developing the checkout software. Even though we had to acquire data from a wide range of sensors, the hardware we used along with NI DAQmx driver helps us in easily blending all these data together. The layered architecture was easy to build in LabVIEW due to its modular design. Also toolkits like report generation greatly reduced development time. The great GUI features provided by LabVIEW come handy in creating a user friendly user interface.

Conclusion:

Using National Instrumentation LabVIEW Development Software and DAQmx and SCXI platform, we were able to implement a high-performance, flexible, and powerful system within a reasonable cost, with minimal user intervention. This checkout system enabled our client to efficiently test his UUTs and provide the facility to configure it for various kinds of test setups. In addition the test system is automated so analyzed test reports are now ready within minutes of completing a test, saving the client’s few days in manual testing, collecting, analyzing and preparing reports.