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SCOUT Interfaces for PXI

Challenge
A MAC Panel customer had an existing PXI ATE setup that was capable of testing a small family of products. The interface between the PXI instrumentation and the units under test was implemented as follows:

  • Off-the-shelf cables connected each PXI card to a terminal block. The terminal blocks were mounted in an open top box that was mounted inside the 19″ rack-mount chassis.
  • Discrete and twisted pair wire cables connected the terminal blocks to connectors mounted on the interface box.
  • External cables connected the UUT to the connectors mounted on the interface box.
  • The box also had electrical components mounted on a wire-wrapped prototype board that interfaced between some of the terminal blocks and the front panel connectors.

This test set had a number of inherent problems. Connections at the terminal blocks were often intermittent, with the wire sometimes breaking at the terminal block. The wiring was very hard to maintain, and sometimes the effort to fix one wire would cause other wires to break. Design changes were hard to implement and sometimes either wires would be omitted, or wires that needed to be removed would be left in place. Troubleshooting was tedious and sometimes destructive.

Due to a large increase in demand for their products, our customer needed an additional 20 test sets as quickly as possible. The effort to reliably replicate their existing design was not a viable option.

Solution
Our customer decided to modify their existing interface design to incorporate SCOUT interfaces and interchangeable test adapters (ITAs). Two different ITAs were designed to handle the entire product family on a single best tester. One dedicated to testing a higher I/O UUT (one at a time) and another to test any of the other products (two at a time).

For each ITA, a printed circuit card assembly (CCA) was mounted on the ITA. This CCA routed all signals from the UUT to the appropriate PXI instrumentation and contained all special interface circuitry such as load resistors and attenuators. MAC Panel designed ITA boxes that hinged on the right side to allow ribbon cables to be routed straight between the ITA modules and the CCA. This design almost eliminated discrete wires which greatly simplified building of the ITAs. Our customer could quickly populate the CCAs, mount them to the front door of the ITA, install ribbon cables and go to test.

Approximately 85% of these ITAs worked without any troubleshooting. The 15% that required troubleshooting were easily diagnosed and fixed because the system was easy to access. Our customer’s average troubleshooting instance was reduced from days and weeks to hours. In addition, our customer reported more accurate and repeatable test results with the new MAC Panel Solution. Finally, these test sets have been in use for over 3 years and have proven to be very reliable. In the rare case of failure, our customers manufacturing technicians have been able to fix them with minimal downtime due to the accessibility of the SCOUT design.

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