Test fixtures are often at risk for the same kinds of errors found in the harness assemblies you are testing. Test fixtures can have shorts, opens, and miswires. They can have poor insulation between wires and they can have connections that have too high of resistance. The bigger problem is that you usually make just one test fixture. So how do you make sure that the one you have works?

The most common method is to "beep it out" by hand. This process takes a lot of time, usually by two people, and is subject to problems easily being missed.

Another method would be;

1. Prepare and load a known good test program that defines the harness to be tested.
2. Connect up the fixturing and a known good assembly and perform a test.
3. If it does not pass, start looking for errors

Despite this effort, you could still have opens, shorts, or miswires in the fixture. Opens can happen if your assembly has unused connector contact positions wired in the fixture. These points are not really tested for opens or miswires.

If you properly used the "attach fixturing" process in easy-wire software when you set up your test program, then you would not have opens, shorts, or miswires but you could still have poor quality insulation or poor connections. To learn how to be "safe rather than sorry" read about how to verify test fixturing with easy-wire testers.

To build good assemblies you need good fixturing.

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• Wire Processing Expo May Milwaukee, May 21-22
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