It's important to remember that the weakest part of your electronic test system will limit the effectiveness of the test. We’ve talked about the test plan and specifications, relay types, and cables. Now, let’s discuss connectors. The integrity and robustness of the connectors used and the quantity of them in the signal path are crucial. Let’s go a little deeper here.
Connector & Backshell
Wire size and insulation thickness cause physical issues when inserting hundreds of wires into a small connector backshell. Selecting the correct gauge of wire and insulation thickness can go a long way to resolving this and making the finished custom cable assembly more affordable.
Backshells are available with three different exit options. Consider which direction makes the most sense regarding ease of access and removal and working in tight spaces inside the tester cabinet.
Consider the Entire Signal Path
Watch that Capacitance
A long cable may have a fair amount of capacitance which can damage your switching, PXI instrumentation, or other instrumentation when discharging the energy within the cable. I worked on a defense application where the UUTs were in a chamber, and the cables from the chamber to the tester were 24 feet long! The wiring used polyurethane insulation. Standard Wire and Cable Co shows that this insulation can exhibit up to 6.5 pF per foot. A charge large enough to damage delicate instruments is possible with such long cables. Additional switching had to be added to discharge the cable between tests.
If all of these choices sound complex, they can be. I recommend that you work with a reputable cable manufacturer or become good friends with your component rep who is selling you wire and connectors.
For more information about cables, watch the webinar "Simplifying Test Interconnect with Pickering's Cable Design Tool" and check out our Connectivity webpage.