© National Instruments
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Introduction
This chapter contains a description of the GPIB-120B, lists what you need to get started and
optional equipment you can order, and explains how to unpack the GPIB-120B.
Description of the GPIB-120B
The GPIB-120B is a high-speed bus isolator/expander with the following features:
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It is transparent to user software.
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It electrically isolates two GPIB systems from each other and from the power supply.
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It expands the GPIB to interface up to 28 devices.
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It extends the GPIB by effectively doubling the 20 m cable limit.
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It has optional rack or DIN rail mount hardware accessories.
The high-speed GPIB-120B bus isolator/expander connects two GPIB (IEEE 488) bus systems
in a functionally transparent manner.
The two bus systems are electrically isolated from each other. The two bus systems are also
isolated from the power supply. Isolation is maintained up to 2500 VDC (withstand 5 s).
Isolating an instrument or group of instruments from an IEEE 488 bus Controller can eliminate
ground loop noise and induced common-mode noise, which may cause measurement problems
in both analog and digital systems. The two isolated bus systems are physically separate, as
shown in Figure 1-1; however, the devices logically appear to be on the same bus, as shown in
Figure 1-2.
Figure 1-1.
Typical GPIB-120B Expansion System (Physical Configuration)
Computer
(Controller, Talker,
and Listener)
Printer
(Listener)
GPIB-120B
GPIB
GPIB
Multimeter
(Talker and Listener)
Signal Generator
(Listener)
Unit Under Test
