Chapter 3 System OverviewData 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 and earth ground.

∙ You can use a single PC to monitor multiple instruments and

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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 port (IEEE-488) and an interface cable.

Serial (RS-232)

HP-IB (IEEE-488)

 

 

 

 

Advantages

Disadvantages

Advantages

Disadvantages

 

 

 

 

Often built into the computer;

Cable length is limited

Speed; faster data and

Cable length is limited

no additional hardware is

to 45 ft (15 m). *

command transfers.

to 60 ft (20 m). *

required.

 

 

 

 

 

 

 

Drivers usually included in

Only one instrument or

Additional system flexibility,

Requires an expansion

the operating system.

device can be connected

multiple instruments can

slot plug-in card in PC

 

per serial port.

be connected to the

and associated drivers.

 

 

same HP-IB port.

 

 

 

 

 

Cables readily available

Cabling is susceptible to

Direct Memory Transfers

Requires special cable.

and inexpensive.

noise, causing slow or

are possible.

 

The HP 34970A is

lost communications.

 

 

 

 

 

shipped with a serial cable

Varying connector pinouts

 

 

(if internal DMM is ordered).

and styles.

 

 

 

 

 

 

 

Data transfers up to

Data transfers up to

 

 

85,000 characters/sec.

750,000 characters/sec.

 

 

 

 

 

*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.

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