Inguard Logic (A30 Board); Isolation Logic; Simplified Block Diagram - HP 3456A Operating And Service Manual

Model 3456A
8·176. INGUARD lOGIC (A30 BOlrd).
•
8·177. Generll.
8-178. For the theory of operation, the functions per­
formed by the lnguard Logic circuits are divided into
the following three major operations (see Figure 8-37
Simplified Block Diagram, Inguard Logic):
a. Interfacing (Isolation Logic) between the Inguard
and Outguard.
I . R�eiver-Paragraph 8-183
2. Transmitter-Paragraph 8-186
b. Controlling the different ranges and functions.
1 . Inguard Microprocessor-Paragraph 8-189
Range and Function Control-Paragraph 8-191
2.
c. Controlling the timing and the AID Converter cir-
cuits during the actual measurements.
I .
ALE and ALE Synchronizer-Paragraph 8-198
2. ALE Clock for AID Converter-Paragraph
8-199
FRAC and Rundown Operation-Paragraph
3 .
8-200
4. Rundown Timing-Paragraph 8-206
5 . FRAC Circuit Description-Paragraph 8-2 1 1
LOVL (Low Overload)-Paragraph 8-221
6.
7. RunlTest Operation-Paragraph 8-222
lNH��U'T " lit A�AnAIIU'
D E T HT
ISOLATION
UCEJYER
ISOLATION
l O'1 C
TflANS"lTHR
Figure 8·37. Simplified Block Diagram, Inguard logic.
8-179. Set-up information from the Main Controller
(Outguard) is received by the Inguard through the Isola­
tion Logic. This information is used by the Inguard
microprocessor (PP) and the "Range and Function Con­
trol Logic" to control the various relays and FET swit­
ches for the specified measurements. The Range and
Function Control Logic section, although physically
located on the A20, is an extension to the A30 board's
control logic.
8-180. Another major section on the A30 is the analog
to digital (AID) controller circuits. These provide the
critical counter and timing signals for fast, pr�ise
measurements. Digitized measurement information is
sent through the Isolation Logic to the Outguard for
conversion to useable information (e.g. front panel
display).
8·181. Ilolation logic.
8-182. General.
a receiver which
Outguard and a transmitter which sends information to
the Outguard (See Figure 8-37). Both use transformers
for coupling. Each transformer consists of windings on
a torodial core and a single wire passing through the
center of the core for coupling. Transformer coupling
allows the Inguard ground (connected to low input ter­
minal) to be isolated from the Outguard ground which is
connected to earth ground.
PORT
U HMNOHt
I N' ''' R O
COl/Nail
".
SLOP{
CLOCK ,.,NO
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5TNCHAONI2f�
The Isolation Logic on A30 consists of
receives information from the
DECODER
UAlrc
Dn'MU
,,, . .... "
Service
8-31