Test Benches and ATE

Comprehensive Test Solutions

Every embedded system, sub-system or module needs to be tested to various degree independently, before being deployed for field installation / integrated with other entities. After basic testing in the design and development phase is completed, there is a need to test the unit as a black box, by feeding simulated input signals and monitoring the output signals for verifying expected behaviour.

Test systems designed for specific testing needs of embedded units may be of different types:

• PC based Systems
• Embedded Test Systems with PC connectivity
• Standalone Test Jigs

In general, the test jigs provide a set of input signals to the Unit underTest (UUT), as per specifications, thereby simulating the field signals / environment. The output signals provided by the UUT are monitored by the Test Jig, and compared with predetermined / expected values, with suitable tolerance.

Sigma has designed, configured, manufactured and deployed various types of test systems to address specific testing needs of various embedded units.

PC basedTest Systems

PC based systems typically employ a set of add-on cards, which provide the required signals (typically analog, discrete and pulse). These signals are fed to the UUT. Similarly, signals from the UUT are also monitored by connecting them to suitable PC add-on cards.
 

This approach of testing may be carried out either using the existing application software on the UUT or by specially writing a diagnostics software on the UUT. Usually the later approach facilitates a more detailed test / diagnostics, unless the application software itself sufficiently caters to Built-in-Test (BIT) and diagnostics.
 

As an extension of the above concept, it is possible to use a communication card, to cater to interfaces like MIL-STD-1553, ARINC-429, ARINC-573, ARINC-717 or even simple serial ports. Using a GPIB card enables usage of standard Test and Measurement (T&M) equipment like power supplies, oscilloscope, spectrum analysers and signal generators to test the UUT, under the overall control and test philosophy adopted on the PC based Test System.
 

Sometimes, it is also necessary to generate complex waveforms and timing-critical signals for the UUT. Such requirements are usually addressed with custom-designed add-on cards, usually based on FPGA / CPLD devices.
 

PC based test systems may be typically configured with:

• Desktop PC, with COTS / custom PCI add-on cards
• Industrial PC, with COTS / custom PCI / ISA add-on cards
• Compact PCI / PXI platform, with COTS / custom compact PCI add-on cards
• Custom signal-conditioning cards
   

Each of the above configuration addresses specific testing needs and has its advantages and disadvantages. While compact PCI / PXI offers very reliable performance, it is considerably more expensive, compared to desktop PC or even industrial PC configurations. Industrial PC configuration offers a good trade-off between reliability and cost, while desktop PC offers the most cost-effective solution for lab environment
 

Configuring a test system, besides the selection of the platform and overall configuration, involves the selection of individual boards:

• COTS / custom-designed boards: The core boards - CPU module and backplane would invariably be COTS boards.
• Add-on cards may also be COTS, if it is one-time requirement, and a suitable configuration is readily available. This helps in cutting down the lead-time. Another important factor is the availability of device drivers and software support. Occasionally, it is necessary to design and develop add-on cards, when a suitable configuration is not readily available, or where long-term support is needed. The main add-on cards provide standard range of I/O signals, which may need further signal-conditioning, to be able to interface with the UUT.
• Signal conditioning cards are invariably custom-designed, being specific to each project.
   

PC based Test System offers the following distinct advantages:

Automation: Tests can be automated to a large extent, thereby minimizing human intervention. This facilitates testing with large data sets and testing over long times (for endurance tests, burn-in tests, environmental tests), without skipping tests or taking short-cuts.

Flexibility: A variety of test approaches can be taken, allowing for automated tests with multiple data sets, and also for more close monitoring in manual modes
Data Logging: Test results may be logged and printed, so that it can used for detailed analysis and annexed to test summaries.

Ease of hardware support and upgradation / maintenance: PC based systems may be upgraded to more powerful configurations, with minor software changes, if any
Ease of software development and maintenance: Since the PC offers a more friendly and familiar environment, software may be more easily developed and deployed. Several standard data acquisition / monitoring software packages may also be used, which permits developing test suites with simple scripting languages.
 

Software solutions for PC basedTest System include:

Custom-software: This approach involves developing the software, which is completely customized and tailor-made for the specific needs. The development is usually done, usingVisual C++ on MS-Windows platform. Alternatively, solutions can be also be provided on Linux environment. The software is usually fully GUI based and menu-driven, with extensive usage of ActiveX controls / widgets to represent familiar objects like switches, knobs, meters, LED's and such others. This gives a 'soft' control panel look to the test operator, easing the learning curve. The advantage of this approach is that it is totally tailor-made and suits specific needs. The disadvantage is that it needs more development time and effort

 

Standard software packages: The other approach is to use standard data acquisition / instrumentation software package, which provides out-of-box support for a large number of standard cards. This enables developing test suites, using scripting languages. The main advantage is the ease of development, while the disadvantages are that it is more generic. Support for custom developed boards is also an issue. Cost of the standard package is also another important factor to consider.

 

Sigma can provide solutions on both approaches.

Embedded Test Systems, with PC connectivity

Certain applications need to use an embedded test system for reasons like portability, signal timings, power consumption and such other factors. Such test systems usually comprise of an embedded processor-based board, with custom test software. The test system then simulates the I/O signals for the UUT.
 

The test system usually initiates tests, under the supervisory control of a PC host. Test inputs and results may be transferred between the PC host and the embedded test system. Usually these type of test system features some basic local display and control, so that limited tests may be carried out without PC connectivity.

Standalone Test Jigs

Standalone test jigs are used for basic testing, using local controls like potentiometers, panel meters, switches, LED's and test-points. These jigs are typically non-intelligent, low-cost and usually meant for simulating and monitoring simple signals. It is quite suited for board-level testing and basic trouble-shooting / debugging, and usually very economical and cost-effective.

Datasheet