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Cable, Harness and Backplane Testing Made Easy! | |
When using automatic test equipment to test wiring harnesses, you are not only testing your Device Under Test (DUT) you are also testing the mating harness, or test fixturing, used to connect your DUT to the tester. In order to successfully test your DUT, you MUST have good interface fixturing. When using a harness, cable, or other adapting device, how do you know that it is good?
Perhaps you have customers auditing your process who require you to verify test fixturing, or perhaps you have just found an error(s) in the device under test and would like to narrow down whether it is really the device or whether it is the fixture that you are using to test with.
Cirris' easy-wire testers, CR, CH+ and CH2, have a built in Fixture Verification feature that eliminates the need to have two operators painstakingly "beep out" a test fixture with a multi-meter to verify its validity. With this Fixture Verification software a single operator can quickly and easily check the fixture to verify that each conductor is present, is connected to the correct pin in the mating connector and that it is not shorted to any other conductors.
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Fixture verification in the easy-wire software is a snap to use, since you have already created your test program you have already done all the work. The process involves two simple button clicks, then probing each point in your mating connectors as prompted by the software. Step 1:From the main menu in the easy-wire software select the test program for the interface fixture you wish to Verify. It can be for the CR, CH+, or CH2 testers. (Example, 'Testing Rules') | |
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Step 2:Click the "Verify" button, then, from the "Verify" menu click "Fixturng" You will be prompted to remove the DUT from the test fixture. Since you are verifying the FIXTURING ONLY, it is important that nothing else is plugged in at this time. You will also need to plug the test probe (supplied with your tester) into the probe jack of the tester. (Any standard banana jack probe will work.) 
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Step 3:The software will now prompt you to probe each point of the fixture, one connector at a time. The test program determines the probe order. It will start at the top of the list and work down each one of the defined connectors contained in Tab 1 of the test program editor. The tester will display the next point to be probed. If you probe the correct pin you will get a 'ding' sound and will then be prompted for the next pin in the sequence. If you probe a point out of order, or the wrong test point, you will get a 'click' sound and the display will show you the point that you are currently touching. If you have Easy-Wire 9.0 or 2008.2 (or later) software, then you can also enable our 'text to speech' feature to make this process even more simple. The software will speak to you and actually tell you from across the room what point you should be probing and what point you are probing. For more information on how to enable and use this feature please click this Text to Speech link. Once you've probed all of the points in the test fixture as prompted, if everything was correct you will get the "Good" result, just as with a passed test. If you are using a CR you are finished at this point. | |
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Step 4:High Voltage Fixture Verify (For CH2 and CH+ testers only.) If you are using a CH2 or CH+ tester, after the good screen appears from above, your tester will now prepare itself to run a hipot test on the fixture only. It will use the same Hipot parameters contained in the easy-wire test program that you are verifying. All you need to do is click Hipot, if for some reason you do not want to do a hipot test on the fixture click Abort. You may want to verify your test fixture at a higher voltage than that used in the actual test. In this case use the 'Save as' command in the editor to make a copy of the test program, then set the High Voltage parameters where you want and use that test to verify the fixturing. Once the Hipot test passes, you will be back at the good screen. That's it! You have now verified your test fixturing and can perform tests on your DUT's with confidence, knowing that your interface fixturing is good. | |
While the above process will verify that your test fixturing is wired properly (no opens, shorts or miswires) it does NOT check the resistance of your mating cables. Why check the resistance? It is possible that your harness-under-test is perfect, but fails due to "high resistance" in the interface wiring. This is usually due to wear on the mating connectors. The best way to check this is with "shorting blocks" plugged into each mating connector of your interface fixture. Use the same connectors as on your harness to be tested, only short each point together to make the "shorting block." Plug all of the shorting blocks into the mating fixture and do a "learn." You can set the connection resistance as low as you wish to verify that your fixture resistance is within the range that you deem appropriate. For more information on how to build shorting blocks see our page on "Bad Cable or Bad Test Fixtures?"
NOTE: the easy-wire software also has a "Fixture Tare" capability that allows you to set a single "Tare" setting to further help deal with the effects of fixture resistance. For more information search "Set Fixture Tare Values" in the Help system of easy-wire software.
Cirris recommends that you use the Fixture Verify process described above:
1. Any time a new test interface fixture is created, whether it is a first-time fixture or a duplicate of a previous fixture.© Cirris Systems Corp.