An Efficient PXI Test System Hardware Architecture
Test system architecture can be the critical difference between money well spent or money wasted. Quality instruments, components and software are essential ingredients, but without a sensible architecture, achieving an efficient system is not likely.
Like most any subject, a lot can be learned by history. Test systems have been designed for years and several commercial systems have long term success. Recently, powerful hardware architecture has emerged that points the way for the design of a new tester. The implementation of this architecture, called ABex takes today’s instrumentation bus, PXI and extends it to create a versatile measurement bus for ATE systems.
Many electronic test systems today are based on the PXI architecture. PXI is a form factor centered on the PC bus eXpanded for Instrumentation. It is essentially a card cage with the expanded PC bus as the backplane. The cage is equipped with power supplies and cooling.
A wide variety of instrument manufacturers provide a very diverse set of instruments on a card that plug into the PXI cage. Somewhere there is a PC also plugged into the PXI cage. This architecture facilitates communication between instruments and the computer, and in some cases directly between instruments. It is a very powerful and popular concept featuring well designed instruments coupled with software for plug and go.
The concept of instruments plugging into a card cage has been around for decades. Long before PXI arrived, ATE manufacturers were building such systems. Usually they were built using more or less proprietary bus structures. What makes PXI unique is that so many manufacturers have agreed on a common useable mix and match format. Today a system builder can buy a set of components from various manufacturers and successfully roll his own system – with one exception.
The ATE guys from decades ago were smart enough to recognize that computers, card cages, and instruments were not enough. (Software, yes! But that is not the topic of this paper.) The critical factor is interconnect.
The PXI approach provides marvelous, consistent communication and control between instruments and the computer. The instruments may even include various switching systems allowing for versatile connection topologies. But the PXI bus does nothing to connect the measurement end of the instruments to the switches. This is left to the integrator. The ATE systems of yore – and also today – put another bus/backplane on the measurement end of the instruments. This bus/backplane gets various names from various vendors but we’ll call it the instrument bus, or simply BUS. The BUS is a set of pathways that allow measurement signals (stimuli and responses) to be connected from the switches to the measurement instruments.
The ABEX Architecture
The BUS is a critical piece for efficiency. Without the BUS these pathways have to be provided by point to point wiring. This wiring is almost always done in the test fixture or ITA . Since there may be several or many different fixtures, this wiring gets replicated. And it can be a lot of wiring.
BOO! PXI doesn’t provide any BUS solution.
YEA! Konrad does! Konrad Technologies has introduced a system call ABEX, Analog Bus eXtension for PXI.
This system provides the BUS. With ABEX a signal can come from the fixture into the PXI switching system, and then get passed through ABEX to the proper instrument. No more redundant messy fixture wiring. With ABEX signal integrity is consistent. System flexibility is maximized. System efficiency is achieved with Superior Architecture.
Money Well Spent.