HP 8340B Manual page 213

As shown in Figure
E-1,
analog
and digital trace layers are
separated by
ground plane layers. These
layers were designed to disperse any digital noise
into
the ground planes and
act as an electrostatic
shield
between the
digital and analog signal traces. The ground planes extend to each
edge
of the
motherboard and are connected to STAR
GND.
This provides isolation between analog and digital
grounds while reducing signal crosstalk.
•
REFERENCE GND
—
is
connected to STAR GND and
is
used as a
very stable low current
refer¬
ence
for
integrated
circuits
and cable shields.
•
MISCELLANEOUS GROUND PLANES:
A.
The ground plane under the
20/30
Loops' aluminum casting completes
a
radio frequency
interference
(RFI) "box" comprised of
the casting, assembly
covers, and the
20/30
loops'
ground
plane. This
ground plane
is
connected to
STAR GND
via
a
GND
trace, and
to chassis
GND through the
aluminum casting.
B.
A
ground plane under the
M/N
Loop's aluminum
casting
connects to STAR GND and
is used
as an RFI shield.
•
CHASSIS GND
—
All
grounds and ground planes are mechanically secured to the chassis (CHAS¬
SIS GND) around the instrument's perimeter and
to various other parts of the
A62 motherboard.
MOTHERBOARD REPLACEMENT
The A62 motherboard is
not customer/field replaceable. Direct any questions concerning mother¬
board replacement to your nearest HP service center for more specific
instructions.
Refer
to the HP
service center listing at the end of
this manual.
E-2
A62 Motherboard Overall
Descriptfon
HP 8340B/41B