HP 3457A Service Manual page 41

3457A Installation
TO MULTIMETER
7 INPUT CURRENT
HfL HfL
1? | —@ a = 4
| VA WA
<A whl
1.5A] 1.58)
ele]
og 7!
Q 2
=
~?
2 2
4
CH cH CH CH
5
Figure 2-9. HP 44491A 2-Wire Input Configuration
2-32. Plug-In Assembly Configuration
2-33. The Wiring Block Assembly configuration is dependent upon the particular Plug-In Assembly installed
(HP 44491A or HP 44492A) and the user's application.
2-34. HP 44491A Configuratio
. The HP 44491A Armature Relay Assembly can be configured for eight
2-wire input channels, four 4-wire input channels or a combination of 2 and 4-wire input channels. The as-
sembly also has two 2-wire input channels which are used for measuring current or as actuator outputs. The
Wiring Block Assembly must be wired for the particular configuration used.
The HP 44491A Armature Relay Assembly uses latching relays. The state of
these relays can only be altered under program control. This is an advantage in the
sense that, under most conditions of failure, the relays will remain in whatever state
the program has set them, However, in case of a power failure, any application
requiring a fail-safe method of ensuring that the circuits under control are in a
known state must be provided by the installer.
In case of component failure or programming error, any voltage input toa plug-in
assembly may be present on any other terminal of the plug-in assembly.
2-35. Figures 2-9 through 2-11 show simplified schematics of the HP 44491A Armature Relay Multiplexer
Assembly configured for 2-wire inputs, 4-wire inputs and current/actuator applications.
2:9