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Chapter 3 System Overview
Data Acquisition System Overview
The system configuration shown on the previous page offers the
following advantages:
You can use the HP 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
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
HP-IB
Serial (RS-232)
Advantages
Often built into the computer;
no additional hardware is
required.
Drivers usually included in
the operating system.
Cables readily available
and inexpensive.
The HP 34970A is
shipped with a serial cable
(if internal DMM is ordered).
*
You can overcome these cable length limitations using special communications hardware.
For example, you can use the HP E2050A LAN-to-HP-IB Gateway interface or a serial modem.
and earth ground.
port ( IEEE -488) and an interface cable.
Disadvantages
Cable length is limited
to 45 ft (15 m). *
Only one instrument or
device can be connected
per serial port.
Cabling is susceptible to
noise, causing slow or
lost communications.
Varying connector pinouts
and styles.
Data transfers up to
85,000 characters/sec.
HP-IB (IEEE-488)
Advantages
Speed; faster data and
Cable length is limited
command transfers.
to 60 ft (20 m). *
Additional system flexibility,
Requires an expansion
multiple instruments can
slot plug-in card in PC
be connected to the
and associated drivers.
same HP-IB port.
Direct Memory Transfers
Requires special cable.
are possible.
Data transfers up to
750,000 characters/sec.
3
Disadvantages
51
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