Testing as an art (Part 2)

The concept that any manufactured product should be tested was introduced in the first instalment of this series. Of course, a key aspect to testing is controlling the test. There are numerous approaches to creating the circuitry required to test any board. It is vital to remember that the test equipment documentation is as important as the product itself. The product life cycle can extend beyond expectations. Test jigs are shipped back and forth to subcontractors, stacked on shelves, and abused in many other ways (sometimes intentionally), so they have to be rugged.

Quick and dirty
It is sometimes possible to make your test equipment very quickly and cheaply, as you can see in figure 1.

This approach has some problems as well. The second unit takes just as long to build as the first and is rather fragile. Nevertheless this piece of test equipment has worked for 18 years with only one solder connection breaking.

Design your own
Sometimes there is just no commercial equipment available to meet your unique requirements and you simply have to design your own. For example, we required a method of generating a stable 100 amps AC, preferably without high voltage or heat. Of course, creating the equipment can be a huge project in its own right. The problem with this approach is that it drains corporate resources and—if the project needs multiple iterations—you may have to compromise on the requirements.

Self–test
If you have a microcomputer on board, and provided you have sufficient memory, the whole test can be implemented as an integral portion of the firmware.