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CIRCUIT
DESCRIPTION
MODEL 615 ELECTROMETER
4.
Reference
Voltages.
A High and LOW Reference
voltage
is provided
by resistor
divider
R1114, R1115,
and R1116.
The voltages
are +8 volts
(High)
and +2
volts
(Low).
3-9.
POWER SUPPLIES (refer
ea Schematic
Diagram
24044E).
a.
*15 vole
Supply.
1.
The 115 volt
supplies
tap a-c power from a
secondary
of transformer
T101.
Diodes 0103,
D105,
0107
and
0108 and capacitors
CL04 and Cl05 compose
a full-wave
rectifier
with
filtering.
2.
Transistors
Q114 and Q115 form a differential
amplifier
which compares the voltage
at R115 with
the voltage
of zener diode
0110.
The difference
voltage
is amplified
by transistor
Q109 and fed to
Darlington
transistor
pair,
Q106 and Q107, which
series
regulate
the oueput
voltage.
3.
Transistors
Q116 and 4117 form a differential
amplifier
which compares the voltage
ae R123 with
respect
to la.
The difference
voltage
is amplified
'by transistor
Q113 and fed to Darlington
transistor
pair,
QllO and Qlll,
which
series
regulate
the -15
volt
aueput.
4.
Transismrs
Q108 and Q112 limit
rhe output
current
to about 200 milliamperes.
b.
t3.6
Volt
Supply.
1.
The ~3.6 volt
supply
taps a-c power from a
secondary
of transformer
TlOl..
Diodes DlOl and D102
2nd capacitor
Cl01 form a full-wave
rectifier
with
filtering.
2.
Transismr
4105 amplifies
the difference
be-
tween the ~3.6 volt
output
and a reference
voltage
derived
from the ~15 vole
supply
and determined
by
resistors
R103 and R104.
The difference
voltage
is
amplified
by rraneistor
Q104 which drives
a Darling-
ton tmnsistor
pair,
QlOl and Q102.
The Darlingto"
pair
series
regulares
the +3.6 volt
output.
3.
Transismr
4103 limits
the output
current
to
about 3 amperes.
C.
+170 Volt
Supply.
1.
The +170" supply
taps a-c power from a second-
ary of transformer
T101.
Diode Dill
and capacitor
Cl12 farm a half-wave
rectifier
with
filtering.
2.
Transistor
Ql19 amplifies
the voltage
devel-
aped by the resistor
divider
RUE and R129.
The
output
of Q119 controls
the series
regulator
cran-
sistar
Q118 to maintain
the +170 volt
output.
3.
When the electrometer
is overloaded,
and over-
load signal
drives
transistor
Q120 which
in turn
controls
the voltage
at the base of transistor
Q119.
The circuit
composed of diode
D112, transistor
Q120,
and resistors
R130, R131 and RI32 reduces
the +I70
volt
output
to +80 voles
when overloading
occurs.
Grounding
the overload
input
turns
off
transistor
Q120 causing
diode
0112 to conduct
and drive
Q119.
4.
The reduced
+80 volt
output
causes blanking
an
all
Numerical
Readout Tubes connected
co the +170
volt
supply.
d.
t210 volt
output.
The t210 volt
supply
is an
unregulated
voltage
supply
using
the, half-wave
fil-
tered
voltage
at diode
Dlll
and capacitor
C112.
e.
"9
Volt
Supplies
(shown an Schematic
24267E)
1.
The *9 "olt
supplies
tap a-c power from a sac-
ondary
of transformer
T1201 or T101.
Diodes
01201
to D1204 and capacitors
Cl216 and Cl217 for a full-
wave rectifier
with
filtering.
2.
Zener diodes
01205 to 01208 provide
regulated
*9 volt
outputs.
f.
1120 "0lC
Supplies.
I.
The 1120 volt
supplies
cap a-c power from a
secondary
of transformer
T1201.
Diodes D1211 and
D1212 and capacitors
Cl218 and Cl219 form a half-
we.ve rectifier
with
filtering.
2.
Zener diodes
01209 and 01210 provide
regulated
-rl20 vole
outputs.
28
0470
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