Data Acquisition

programming instruments with any hardware link. Figure 8.1 illustrates the relationshipsamong the standards.Figure 8.1IEEE 488.1, IEEE 488.2, and SCPI standardsApart from the three standards associated with the term IEEE 488 (IEEE 488.1, IEEE488.2, and the SCPI) the term GPIB is often used interchangeably.The GPIB is an interface design that allows the simultaneous connection of up to 15devices or instruments on a common parallel data communications bus. This allowsinstruments to be controlled or data to be transferred to a controller, printer, or plotter. Itdefines methods for the orderly transfer of data, addressing of individual units, standardbus management commands, and defines the physical details of the interface. These arediscussed in the following sections.8.2 Electrical and mechanical characteristicsThe GPIB bus is carried inside a shielded 24-wire cable with standard connectors at eachend. The connector used is the Amphenol MICRORIBBON, Cinch Series 57MICRORIBBON, or AMP CHAMP type, shown in Figure 8.2, which has both a plug andreceptacle (male/female). Adding a new device to the bus is done by connecting a newcable in a star or chain configuration. Screws hold each connector securely to the nextone. Since the 24-pin connectors are usually stackable, it is easy to connect or disconnectdevices to the bus.