VME, VPX and VXI Switches

VME, VPX and VXI switches are used to connect test points or devices to instruments for testing, measuring, or monitoring. They provide a variety of switching and routing functions for test systems based upon the popular open-standard VXIbus architecture, VPX, and the older VMEbus. The VersaModule Eurocard bus (VMEbus) provides asynchronous transfer, an addressing range between 16 and 32 bits, data path width between 8 and 32 bits, and a 40-MBps bandwidth. VPX is an ANSI standard based on the VMEbus that supports switched fabric using a high speed connector. VMEbus extensions for Instrumentation (VXIU) are a platform that defines a multivendor instrument-on-a-card standard for industrial applications. Most VME, VPX and VXI switches and switching modules come in the form of a bus card or a backplane, which is then interconnected with the rest of the network system. The highest switching density is available in VXI systems because of the large size of the plug-in modules. 

VME, VPX and VXI switches carry specifications for switch topology, switch type, relay type, and configuration. There are four choices for switch topology: general-purpose, multiplexer, matrix, and multiplexer/matrix. General-purpose devices are simple switches that consist of independent, isolated relays or field-effect transistor (FET) switches. They are designed to connect one input to one output. By contrast, multiplexers can connect one input to several outputs, or several inputs to one output. Matrix switches have multiple inputs and multiple outputs; any number of inputs can be connected to any number of outputs. Configurations include 4 x 4; 8 x 2, 8 x, 4 and 8 x 8; 10 x 2 and 10 x 4; and 16 x 2, 16 x 4, 16 x 8, and 16 x 16. Multiplier/matrix VME, VPX and VXI switches can be connected as either a multiplexer or a matrix.  

VME, VPX and VXI switches differ in terms of form factor, operating system, electrical specifications, and features. Form factors are measured in millimeters (mm) and often have lettered designations. Support for standard operating systems is commonly available. Electrical specifications for VME, VPX and VXI switches include maximum AC and DC switching voltage, maximum AC and DC switching current, maximum real switching power per channel, and maximum reactive switching power per channel. Operating speed, switch operating time, CE Marking, and FCC certification are often listed as features.

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