CIRCUIT
DESCRIPTIONS 3-15
I 1
Figure 3.
7
Schematic diagram attenuator
section
•
Detailed circuit deacription
See figure 3.7 ar^d circuit diagram A2a (figure 10.4).
input eoupHng
The incoming signal first passes the AC/DC coupling section
(C2202). When re\ay K2201 i$ opened,
the signal is AC coupied via
C2202.
H.F. (high frequency) path
After the coupling section, the L.F, pan of the signal
Is
Olocked
by capacitor C2203. Only the H.F. part
of the input signal enters the H.F. attenuator. This is
a
triple capacitive divider,
consisting of a 1 to
100, a
1
to 10. and a 1 to 1.46 divider
The 1
to
1 .48 divider
section is switched on when relay switches K2202 and K2203
are In the "upper"
position (as shown on circuit diagram A2a, figure 10.5).
The 1 to 1.48 divider cc^sists of C2203 and
C2209
in parallel with
some parasitic capacitors. The
attenuation of 1 .48 times in this straight-on
path
is
compensated for later in the circuitry.
The separate sections are switched
In
the signal
path, depending on the attenuation
required:
Table 3.2 Sections used in various attenuator settings.
Attenuator Settings
|
Sections Used
Attenuation
5 mV/div 1 00 mV/di
V
1.48X 1.48 times
200 mV/div 1 V/dlv 1.48X. 10x
14.8 times
2 V/dlvIO V/div
|
1.48x, lOOx
148 times
20 V/dlv 1O0 V/div
i
1.48X.
lOx,
lOOx
1460 times
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