TABLE OF CONTENTS William M. Hayes
Modular instruments employ a frame (Fig. 25.6.1) that serves as a host. These frames allow multiple switch, measurement, and source cards to share a common backplane. This makes it possible to configure instruments that can accommodate a range of input/output (I/O) channels. It also makes possible tailoring measurement capabilities to the specific applications being addressed.
The modular standards described below are industry standards:
VME standard
VXI standard
Personal computer (PC) plug-ins
CompactPCI standard.
PC plug-ins are not part of a formal instrument standard. However, the ubiquity of the personal computer has made the PC motherboard I/O bus a de facto standard for instruments. Although all these standards are used for instrument systems, only VXI and a derivative of CompactPCI, called PXI, were developed expressly for instrumentation. For general-purpose instrumentation, VXI has the most products. PXI is emerging in the market, and generally offers the same features as VXI.
Open standards-based modular instruments are compatible with and can therefore accept products from many different vendors, as well as user-defined and constructed modules. Modular instruments generally employ a computer user interface instead of displays and controls embedded in the instrument s frame or package. By sharing a computer display, modular instruments save the expense of...
