Hardware Reference
In-Depth Information
8 The IEEE-488 bus
The IEEE-488 bus, also known as the
Hewlett Packard Instrument Bus (HPIB)
and the
General-Purpose Instrument Bus (GPIB)
, provides a means of inter-
connecting a PC controller with a vast range of test and measuring instruments.
The bus is ideally suited to the implementation of
automatic test equipment
(ATE)
and it has become increasingly popular over the last two decades with
a myriad of applications that range from routine production test to the solu-
tion of highly complex and specialized measurement problems. This chapter
introduces the IEEE-488 standard and describes the programming of a typical
IEEE-488 interface.
In the past, IEEE-488 facilities have tended to be available within only on the
more expensive test equipment. The necessary interface is, however, becoming
increasingly commonplace in medium- and low-priced instruments. This trend
reflects not only an increased demand from the test equipment user but also the
availability of low-cost dedicated IEEE-488 controller chips.
Nowadays, most items of modern electronic test equipment (such as digital
voltmeters and signal generators) are either fitted with the necessary IEEE-488
interface as standard or can be upgraded with optional IEEE-488 interface cards.
This provision allows them to be connected to a PC controller via the IEEE-488
bus such that the controller can be used both to supervise their operation and
process the data that they collect.
Automated measurement is important in many applications, not just within
the production test environment. Advantages of IEEE-488-based measurement
systems incorporating PC-based controllers include:
•
Elimination of repetitive manual operation (freeing the test engineer for more
demanding tasks).
•
Equipment
settings
are
highly
repeatable
thus
ensuring
consistency
of
measurement.
•
Increased measurement throughput (measurement rates are typically between
10 and 100 times faster than those which can be achieved by conventional
manual methods).
•
Reduction of errors caused by maladjustment or incorrect readings.
•
Consistency of measurement (important in applications where many identical
measurements are made).
•
Added functionality (stored data may be analysed and processed in a variety
of ways).
•
Reduction in skill level of operators (despite the complexity of equipment,
user-friendly software can guide operators through the process of connection
and adjustment).
The original IEEE-488 standard is often referred to as IEEE-488.1 whilst
the
most
recent
developments
of
the
standard
are
known
as
IEEE-488.2.
