3 System Overview
80 Keysight 34970A/34972A User’s Guide
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 273).
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
Digital
Internal
DMM
OUT
Bus
RS-232
(34970A)
USB
LAN,
(34972A)
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