Mass interconnect for PXI

In a mass-interconnect system, patch cables bring the PXI test equipment’s front-panel signals to a series of receiver modules, which mount onto a panel. The receiver modules mate to a corresponding set of panel-mounted test assembly plugs, which connect to the unit under test (UUT).

The UUT may be hard-wired to the test-assembly plugs, connected with patch cables, or plugged into a test fixture. Often, the receiver-module panel and the test-assembly panel use a levering mechanism to overcome the insertion forces for the modules.

Mass interconnect thus reduces the hook-up between the UUT and the test equipment to a single, multi-pin connector. All of the cabling complexity resides in the links between the receiver panel and the test equipment and in the links between the test assembly plugs and the UUT. Once the links are established, connection to all of the signal lines becomes a single, plug-in operation. Mass-interconnect systems can handle as many as 14,000 connections.

A mass-interconnect system has several parts and turns complex wiring setups into a single connection.

A number of companies offer the building blocks for a mass-interconnect system, including MAC Panel, MEI Technologies, TTI Testron, and Virginia Panel. These companies also offer receiver modules with preconfigured patch cabling for many PXI modules. Test-chassis vendors are also beginning to support mass interconnect. The Geotest GX7102 chassis, for instance, has a hinged front cover that can accommodate a receiver module panel and associated patch cabling.

Bill Berger, applications engineer at Virginia Panel, explained that a mass-interconnect system can be used to support a series of related tests, such as production tests of devices or boards in a family of similar products. He said that a PXI test chassis equipped with a mass-interconnect receiver panel can handle a number of product variations. The test assembly provides all of the wiring changes necessary for accommodating the differences among the UUTs. The test equipment and its receiver module wiring remain the same.

Berger further explained that with a mass-interconnect system, you can easily replace a PXI module with a new or upgraded model. You simply remove the patch cables that run to the module and attach them to the replacement unit.

If the cables are designed with some slack to them, Berger said that you can reconfigure the placement of PXI modules in the chassis without changing the cabling. If the new module has reorganized, different, or additional I/O ports, only the patch cables and receiver modules associated with that one module require changes.

Berger advised that, when designing the receiver panel, you should leave room for extra receiver modules to enable the system to handle the additional I/O of an upgraded PXI module as well as the I/O of any additional modules you want to add.

The major drawbacks to using a mass-interconnect system are the initial cost and the need to develop a different test assembly for each product. These factors may seem to preclude the use of mass interconnect for unique tests or exploratory lab testing, but even in these situations, Berger said that mass interconnect offers advantages. One is the reduction of wear-and-tear on the PXI modules. The receiver panel takes all the abuse. The module connectors only see a small number of insertions and removals and are protected from damage caused by bumps and spills.

Another advantage is that mass interconnect can simplify the use of a PXI test chassis as a series of virtual instruments. By developing mass-interconnect assemblies with labeled connectors corresponding to the front panel of a bench instrument, you can quickly reconfigure the PXI test chassis from, say, a spectrum analyzer to an oscilloscope. You would simply attach the mass-interconnect assembly and load the software on the test chassis to configure the inter-module connections and turn the test chassis into an instrument that offers a labeled I/O panel.