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9
INSTRUMENTATION SYSTEM
INTEGRATION AND INTERFACES
9-0 INTRODUCTION
Technical evolution and economic influences have combined to define the integra-
tion of contemporary multisensor instrumentation systems relative to a delineation
of applications. A hierarchical instrumentation taxonomy is accordingly described
as illustrated by discrete automatic test equipment, remote measurement environ-
ments, automation system virtual instruments, and analytical instrumentation for
aiding sensed-feature understanding. The integration of each of these instrumenta-
tion categories is also defined by bus and network structures appropriate for meet-
ing application performance requirements.
Chapter highlights include the description of virtual instrument capabilities for
elevating fundamental sensor data to a higher attribution, enabling more complex
cognitive interpretation. Such attribution is then extended to analytical instrumenta-
tion employing hyperspectral sensing of multiple spatial and spectral data for im-
proved feature characterization. This is shown to be useful in advanced process
control systems for comparing product states to goal states during manufacturing
for the purpose of synthesizing compensating online quality control references.
9-1 SYSTEM INTEGRATION AND INTERFACE BUSES
Electrical measurement has been evolving for nearly two centuries since the inven-
tion of the galvanometer in 1820. Continued development has provided an expand-
ing range of sophisticated measurement, signal conditioning, analysis, and data
presentation capabilities with the instrumentation taxonomy, shown in Figure 9-1,
that can accommodate the comprehensive data requirements of advanced hierarchi-
cal sensor and actuator systems. Four distinct instrumentation integration structures
are defined, each of which involve different implementations for meeting their re-
Multisensor Instrumentation 6
␴
Design. By Patrick H. Garrett

9-1 SYSTEM INTEGRATION AND INTERFACE BUSES
189
FIGURE 9-2. Basic computer bus classifications.
agement lines for communication utilities. When ATN is high, all instruments must
listen to the DIO lines. When ATN is low, only designated instruments can send
and receive data.
External information exchanges with the host computer for all of the instrumen-
tation architectures of Figure 9-1 can be aided by the Gigabit Ethernet, especially
when high resolution graphics are involved. The efficiency of the Gigabit Ethernet
relies upon full-duplex transmission employing all four wire pairs of common Cate-
gory 5 cable, plus enabling terminal equipment shown in Figure 9-4. Performance
is facilitated by five-level PAM coding, Trellis forward error correction, and DSP
received signal equalization. Conventional Ethernet parameters are also introduced
in the following section.
Computer-based automatic test equipment (ATE) has evolved as an effective
application of parallel buses to link modular instruments in a systematic quality
control structure for evaluating and documenting the performance of complex
electronic systems, which may also include radio frequency signals. This structure
is illustrated by the example of Figure 9-5 for discrete units under test, such as ex-
ercised during the preflight countdown of the Space Shuttle. Compared with man-
ual stimulus and measurement, ATE offers improved test productivity, consistent
test repetition with objective results, and more comprehensive test options and du-
rations. Contemporary ATE software test executives typically are multisequence
programs in both scripted and graphical languages, such as C++ and LabVIEW,
with automatic report generation to ASCII, HTML, and database files including
Access and SQL Server. The abbreviated test language for all systems (ATLAS)
is an IEEE standard that was created for aviation electronic system maintenance,
and eventually adapted to many ATE applications. ATE programs typically con-
sist of macros with symbolic parameters that are combined by a linker to imple-
ment test applications.

FIGURE 9-6. Serial bus network structure.
FIGURE 9-7. RS-232C Full-duplex terminal interconnection.
whereas extended channel-encoded transmission generally employs a multinode
bus topology.
Alternatively, public LANs rely upon external network access devices such as
Ethernet. Ethernet is a universal network currently employed worldwide because of
advances in performance to 100 Mbps and, separately, economy of implementation
enabled by twisted pair connectivity. This LAN further offers the versatility of
coax, twisted pair, and fiber media. Its carrier-sense multiple access, collision de-
tection (CSMA/CD) datalink protocol benefits from simplicity and effectiveness.
Frequently applied twisted-pair Ethernet (10 Base T) supports data rates to 10
Mbps, whereas fast Ethernet employs fiber media (100 Base FX) supporting data
rates to 100 Mbps. Ethernet employs a bus topology and packet data format with a
48-bit unique worldwide address and allowable message size ranging from 512 bits
to 1512 bytes, where twisted-pair segments may extend to 1640 feet and fiber seg-
ments to 3600 feet. Note that Ethernet source encoding/decoding does not rely upon
the terminal devices shown in Figure 9-6 because of its higher data rate. Gigabit
Ethernet (1000 Base T4) utilizing four twisted pairs was described in the preceding
section.
The growing number of process instrumentation and control systems from multi-
ple vendors that require integration compatibility has led to the evolution of stan-
dardized public LANs for industrial applications that provide error checking and
the economy of multinode device connectivity. These networks are exemplified by
Foundation Fieldbus and the controller area network (CAN). Fieldbus employs
twisted pair connectivity with a data rate of 31.25 Kbps and a transmission distance
to 1 mile. It is intended for distributed process automation systems, and usefully
permits remote devices to be powered over the same signal pair. CAN was initially
designed to economically link onboard automotive digital functions. However, its
low-speed and high-speed data rate options, respectively 125 Kbps and 1 Mbps,
plus reliability provided by a multiple error checking protocol has resulted in a vi-