Agilent Technologies 34970A, User Manual, Page: 64 / 356

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Chapter 3 System Overview
Data Acquisition System Overview
The 34970A/34972A Data Acquisition/Switch Unit
As shown below, the logic circuitry for the 34970A/34972A is divided into
two sections:
earth-referenced and floating . These two sections are
isolated from each other in order to maintain measurement accuracy and
repeatability (
for more information on ground loops, see page 263 ).
The earth-referenced and floating circuitry communicate with each other
via an optically-isolated data link. The earth-referenced section
communicates with the floating section to provide PC connectivity. The
34970A is shipped with both an GPIB (IEEE-488) interface and an RS-
232 interface. Only one interface can be enabled at a time. The 34972A is
shipped with Local Area Network (LAN) and Universal Serial Bus (USB)
connectivity.
The earth-referenced section also provides four hardware alarm outputs
and external trigger lines. You can use the alarm output lines to trigger
external alarm lights, sirens, or send a TTL pulse to your control system.
Optional
Analog Bus
100
200
300
= Optical Isolators
Control
GPIB,
Floating
Logic
Earth
Referenced
Logic
AC Power
External Trigger
Alarms
To Computer
IN
Plug-In
Slots
Digital
Internal
DMM
OUT
Bus
RS-232
(34970A)
USB
LAN,
(34972A)
34970A Refresh UG.book Page 64 Wednesday, February 17, 2010 12:34 PM