The Need for Functional Testing
Testing is a vital part of ensuring quality for electronic modules. Ensuring quality is important to reduce the total cost of ownership (including warranty costs) for a product. The sooner a problem unit is identified the lower the cost to rework or replace the unit. The costs of late detection of faulty units include extra shipping, field service costs, supply interruptions (when many units are affected by the fault) and most importantly customer dissatisfaction.
The Problem for Automated Functional Testers
Functional testers are used to test units for correct operation at the end of the production line. Because each product is different it is impossible to make a generic tester that can thoroughly test even a wide range of different modules. It is therefore necessary to design a test system that can do the final configuration and test for correct overall function of the module. Unfortunately the need for this configuration and testing is often overlooked in the project until mass production is about to start. In a panic to have some sort of tester ready and operating without a budget the configuration and functional testing is often done by a mix of bits that come to little more than “Plug it in and see if it goes”. While at the surface this may even seem reasonable – what more real world test is there? The problem is that many service calls start with “It works but …” or “It works until ….” Real world faults are more subtle than “plug it in and see if it goes” tests can reliably reveal.
When functional testing is not adequately addressed a substantial opportunity to reduce the overall cost of ownership is lost. To make matters worse a good approach to configuration and functional testing also assists in controlling IP and product ownership. A well designed functional tester at the end of the production line will only program units that pass the tests and which the owner of the product have authorized to be programmed. This makes it hard for the manufacturer to simply make more units. Further special serialization and encryption methods can be used so the product owners software is never revealed.
What makes a good Automated Functional Tester
As a designer of products that often carry 3 and 5 year warranty we understand the importance of good end of production line functional testing and configuration. We also understand the must haves for the effectiveness of functional testing. The essential features and flow on benefits are shown below.
|Don Alan Functional Tester
|The test specification comes from understanding the module design as well as the functional specification. The tester is designed to meet the test specification needed rather than adapting the test specification to a test system.
|All tests are integrated into a single system. Units only have functional software installed if all tests are passed.
|Provide timely results
|Results are reported live and available to all stake holders anywhere in the world
|Results of high integrity
|By reducing the operator influence on tests and reporting directly to all stakeholders there is higher trust in the results. Efforts can concentrate on product and manufacturing improvements rather than on the quality of data.
|High Availability and Scalability to volume.
|The unit cost of the testers is low enough to allow multiple testers to provide redundancy and scalability.
|There is a lot of concern about ‘extra units’ being made for the non-genuine market. The tester only allows as many units as are licensed by the product owner to have software loaded.
|Provide insight into the manufacture process
|Disorganised and poorly controlled manufacturing can be identified straight away by monitoring the amount of rework and retesting.
|By providing interlocks that are not easily bypassed the chance of unsafe work practices are reduced. Automated systems lend them selves to safer test arrangements.
|Units are electronically serialised so returned units can be retested and compared to their original test results.
|Flow On Effect
|Don Alan Functional Tester
|Better assessment of field returns
|The low unit cost of the tester means that the product owner can use the same tester to assess units returned from the field. Field returns are often ‘set aside for later’ due to the high cost of assessing the units. This misses the opportunity to nip production and design issues in the bud.
|Reduced and Simplified Incoming Quality Control (IQC)
|Because of the transparency of test results there is less need for IQC testing by the product owner but the low unit cost for the tester means the product owner can duplicate testing on a sample basis or if an issue arises (damage in shipment etc).
The old approach to Automated Functional Testers
It is extremely difficult to make a piece of test equipment that can ‘test anything’ and it would be too expensive anyway. So the general approach to testers is to build systems by integrating ‘modular’ components. It is an effective way of reducing the design cost but it increases the unit cost because the modules are expensive. The design cost is not eliminated because the integration process is a substantial exercise in design.
The compounding problem of these systems is that the biggest market for the modular pieces of test equipment is R&D, scientific and defence. Mostly the equipment is not designed for rapid and high repetition work. The modules and the systems are often based on desktop operating systems that are just not designed for mission critical systems.
The Don Alan Approach
The Don Alan approach is to accept that there is a lot of design to be done – and do it. When we design a tester we draw from past designs and even use some standard modules. We have a standard software core that forms the test platform. But all of the custom parts, the inevitable quirks and special requirements of a particular job is handled by a custom designed module.
The result is that the cost for a single test system is competitive but when more than one tester is required (and it usually is) the Don Alan approach is game changing.
But it is not easy to design testers of the level of the Don Alan testers. It requires component level design skills, deep firmware and software skills and a good understanding of testing. These are all things that Don Alan has through its core business of designing and supplying specialised electronic assemblies.
The Don Alan Tester Platform
Each testing system has at least 3 processors in it. This may sound like an unnecessary complication but because each processor only has to deal with one of responsibility many of the issues that would normally arise again and again through the development never arise at all. Three processors are not expensive – solving the problems they eliminate is.
The Communication Processor
The communication processor handles the logging and communication of test data, set up information and firmware updates. Don Alan’s approach to transferring data to a server uses outgoing HTTP connections. This means that any internet connection that allows access to the web will do for the tester. No need to allow incoming connections, no need for a static or even a public IP address, no need for special firewall configurations etc. Data is logged so interruptions to internet connections do not delay testing or cause data to be lost.
The Test Manager Processor
The test manager sequences the tests and also handles communication with any external test equipment if used.
The Test Processor(s)
The test processors perform the deep down testing. Due to an innovative test structure it is possible to perform Hi Pot testing (electrical safety testing) and parametric functional testing in the same unit without large expensive relays. This is achieved by using multiple Test Processors with high isolation between each processor and the rest of the system.