Choosing a Switch Platform: PXI or SCXI

This document describes some benefits of the PXI and SCXI form factors in switching.

PXI Switch Benefits

• Low-cost channel expansion
• Minimum footprint
• Utilize unused slots in PXI chassis
• Direct communication to controller
• Access to PXI trigger backplane for switch synchronization

The PXI platform offers an excellent low-cost, high-density environment for tightly synchronized switching applications. Switches can be easily incorporated into an existing PXI systems. Direct communication between PXI measurement devices and switch modules ensures optimal throughput in the system by taking advantage of several trigger lines built into the PXI backplane. These lines can be used to synchronize the switch and measurement device to eliminate delays between the switch closure and measurement-complete steps. Control of PXI switch modules is achieved from either the embedded controller of the PXI chassis or through a MXI connection to a host computer. Whether used in conjunction with other PXI instruments or as a stand-alone switch box, the PXI platform provides an industry-standard solution for modular switch systems.

SCXI Switch Benefits

• Low-cost channel expansion
• Maximum relay density
• Excellent addition to Signal Conditioning systems
• High-channel-count
• High-voltage Analog Bus (HVAB)
• Up to 250 VDC, 250 VAC, or 8 amps

SCXI switches provide a low system cost, and high capacity for maximum relay density. The SCXI platform continues to excel in high-channel-count applications. Switch modules are controlled through a SCXI-capable communicator such as a Multifunction DAQ card or a High-precision DMM. National Instruments provides SCXI switch modules capable of switching voltages up to 250 VDC/250 VAC, currents up to 8 amps, and frequencies from DC to RF. Large matrix applications are easily addressed with matrix expansion cables and plugs, allowing the interconnection of rows and columns from multiple modules in seconds. Also, a high-voltage analog bus (HVAB) allows routing of signals along the SCXI backplane between several modules or directly to instruments.

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