CompactPCI Switches and PXI Switches

CompactPCI switches and PXI switches are backplanes that are used in industrial systems to connect test points, or other peripherals, to instruments for the purpose of testing, measuring or monitoring the system. CompactPCI switches and PXI switches are designed to be highly scalable with flexible architecture, to provide high performance. CompactPCI is high performance industrial bus based on the PCI electrical specifications. Its form factor is specified to be the rugged 3U and 6U Eurocard format.

PXI (PCI eXtensions for Instrumentation)is a specification developed by National Instruments that extends CompactPCI for measurements and automation systems. CompactPCI / PXI is used in many industrial applications including computer telephony, industrial automation, real-time data acquisition, real-time machine control, instrumentation, military systems, and others. Compared to desktop PCI, Compact PCI supports 8 PCI slots (the desktop PCI standard supports only 4) that can be expanded by using PCI-PCI bridges, and is more robust and sturdy for use in industrial applications.

There are three main types of functional topologies for CompactPCI switches and PXI switches, general-purpose switches, multiplexers, and matrices.  General-purpose switches consist of independent and isolated relays or FET switches. They can connect one input to one output.  A multiplexer connects one input to several outputs, or several inputs to one output.  A matrix switch is an arrangement with several inputs and several outputs. Any number of inputs can be connected to any number of outputs.  It is also possible to locate multiplexer / matrix switch arrangements that can be connected as either a multiplexer or as a matrix, as the situation dictates.

CompactPCI switches and PXI switches are available in a number of switch types.  Most common among these are relay switches, solid-state switches and radio frequency (RF) switches.  Other switches, such as optical, are also available.

Relay switches use a mechanical relay to rout or switch signals. They are used to switch or to scan high voltage signals.  There are three types: armature, dry-reed, and mercury-wetted switches. The relay type can be: SPST (single-pole, single-throw), SPDT (single-pole, double-throw), or DPDT (double-pole, double-throw).

Solid-state CompactPCI switches and PXI switches use transistors (FETs and others) to route or switch signals. They are used in applications that require high-speed scanning of low-level signals (±10 V). Because they do not have any moving parts, these switches have a very long life.

RF switches are ideal for routing high-frequency signals.

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