Article: Enter PXI

The modularity of the PXI standard for creating test and measurement systems is allowing users to push the boundaries of what can be done, affordably. JON HANCOX introduces this exciting technology.

Industrial test, measurement and control systems need to withstand vibration, humidity, EMI, dust and more.

Which is where CompactPCI comes in. This is a high-performance industrial bus, based on the desktop PCI electrical specification standard found on almost all PCs, but using rugged 3U or 6U Eurocard packaging with a 2mm metric pin and socket connector system. Compact PCI also supports eight PCI slots (double the desktop PCI standard) which can be expanded by using PCI-PCI bridges.

PXI (‘PCI eXtensions for Instrumentation’) is a modular instrumentation platform specification that extends CompactPCI for measurement and control applications. It enables us to mix and match modules from multiple vendors, whilst retaining standard communication systems such as the 132 MB/s PCI bus. PXI also integrates timing and synchronisation into the system, allowing signals to be passed between instruments without additional cabling.

PXI delivers industrial-standard performance in relatively small, rugged packaging. It’s an ideal platform for automated test systems, as multiple vendors provide a wide array of instrumentation modules: there are estimated to be over 800 PXI products currently available, including oscilloscopes, multimeters, waveform generators, RF analysers and switch multiplexers.

Finally, because of the small size and tight integration, PXI systems are usually lower cost than traditional alternative approaches. That said, some manufacturers’ ranges are much more competitive than others’, and it was this which led the Adept Scientific data acquisition team to select ADLINK’s product range when users began to enquire about PXI systems some time back.

ADLINK has a range of 3U PXI instrument cards, data acquisition cards and instrument chassis systems which represent truly excellent price-performance. Take the new PXI-3710 controller, for example, which is a 3U PXI PIII 1.26GHz CPU module with 128Mb memory, a 20Gb hard drive and an optional floppy drive at a quite exceptional price point. The company also has a good range of chassis, with 5 slot ‘portable’, 7- and 17-slot 19in rack versions available. The 5- and 7-slot versions also have and optional 6.4in TFT LCD screen integrated into the chassis.

Or take the PXI-2010, a four-channel, 2MS/s simultaneous A/D multi-function PXI module. Yes, that’s true simultaneous sampling up to 2MS/s sampling rate. This exciting piece of kit has 14-bit resolution and uses the latest carrier-and-daughter modular design concept, which separates the analogue circuitry and digital circuitry into two cards, greatly reducing the signal noise generated by digital parts. It also has two 12-bit analogue outputs; two 16-bit counter/timers; and 24 digital I/O lines, again at an excellent price.

PXI’s use of standard PC technology offers performance at a much lower cost than with, for example, VXI, VME, or GPIB approaches. It also integrates with GPIB, serial or Ethernet instrumentation, allowing you to move technology on without abandoning earlier systems.

That’s why it’s the fastest-growing standard since IEEE-488 (GPIB). Commentators are suggesting that the measurement capabilities of PXI will possibly soon surpass traditional dedicated instrumentation, and thanks to the ability for users to combine innovative specialist technologies from multiple suppliers, we’re seeing the development of test and measurement systems which have never been possible before.

There are some exciting times ahead for PXI, and the Adept Scientific data acquisition team is now well-positioned to support you down that path. u