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The system configuration shown on the previous page offers the
following advantages:
• You can use the 34970A to perform data storage, data reduction,
mathematical calculations, and conversion to engineering units.
You can use the
PC to provide easy configuration and data presentation.
• You can remove the analog signals and measurement sensors from
the noisy
PC environment and electrically isolate them from both the
PC and earth ground.
• You can use a single PC to monitor multiple instruments and
measurement points while performing other
PC-based tasks.
The Computer and Interface Cable
Since computers and operating systems are the subject of many books
and periodicals, they are not discussed in this chapter. In addition to the
computer and operating system, you will need a serial port (
RS-232) or
GPIB port (IEEE-488) and an interface cable.
Serial (RS-232) GPIB (IEEE-488)
Advantages Disadvantages Advantages Disadvantages
Often built into the computer;
no additional hardware is
required.
Cable length is limited
to 45 ft (15 m). *
Speed; faster data and
command transfers.
Cable length is limited
to 60 ft (20 m). *
Drivers usually included in
the operating system.
Only one instrument or
device can be connected
per serial port.
Additional system flexibility,
multiple instruments can
be connected to the
same GPIB port.
Requires an expansion
slot plug-in card in PC
and associated drivers.
Cables readily available
and inexpensive.
The 34970A is
shipped with a serial cable
(if internal DMM is ordered).
Cabling is susceptible to
noise, causing slow or
lost communications.
Varying connector pinouts
and styles.
Direct Memory Transfers
are possible.
Requires special cable.
Data transfers up to
85,000 characters/sec.
Data transfers up to
750,000 characters/sec.
* You can overcome these cable length limitations using special communications hardware.
For example, you can use the Agilent E5810A LAN-to-GPIB Gateway interface or a serial modem.
3
Chapter 3 System Overview
Data Acquisition System Overview
51