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ж +
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Model 427A
РУ А2
RG
OF 4127
<, RESISTANCE
<, OF ATTENUATOR
<, (IO MEGOHMS)
Y
4274-8-0560
Figure 4-5.
DC Offset Circuit
would then be zero.
Ап alternative method of mini-
mizing the effects of Іс would beto zero the instru-
ment with the impedance of the measurement source
connected
to Ще
input terminals rather than with the
input
shorted,
A2CR1
has а temperature
charac-
teristic quite similar to that of A1Q6.
"Therefore,
01791-2
Е
Iu
|
|
|
Section IV
both Теса and Ig change by approximately
the same
amount with temperature and the amount
of additional
error at higher temperatures
is lessened.
4-19.
AC METERING
CIRCUIT (A2).
4-20.
Figure 6-3 contains the schematic
of the AC
Metering Circuit.
The
ac
input from the ac post at-
tenuator is applied through A2C1 tothe base of A2Q1.
A2Q2 is an emitter follower that provides impedance
matching
to common
emitter
output
stage
A2Q3.
Capacitor A2C4 provides an ac feedback path for gain
stabilization.
4-21.
The output from the collector of A2Q3 is recti-
fied by A2CR3 and A2CR4 and applied to the meter
movement.
4-22.
Resistor A2R17 is used to calibrate the ampli-
Нег
at low frequency
ага
is adjusted
for full scale
meter deflection witha 10 ту,
400 Hz input. Capacitor
А2С3
is used to calibrate the amplifier
at high fre-
quency.
With а 10 mV,
1 MHz input, A2C3 is adjusted
for full scale,
4-23.
BATTERY REGULATOR Ai (See Figure 6-3).
4-24.
The Battery Regulator regulates the dc voltage
fromthe 22, 5 volt battery or from the optional power
supply.
The voltage drop across
A1CR2
and the
emitter-base
junction of A1Q3 provides the -6, 7 volt
referencefor the power supply andthe -6. 7 volt output.
A1Q5 senses changes in the +6. 7 volt output and соп-
trols A1Q2, the positive series regulator.
А101 isa
current
source for A1Q5,
and diodes A1CR3,
CR4,
and CR5 provide temperature
stabilization.
Тгап-
sistor A1Q4 provides
a current shunt for A1CR2 to
keep its voltage constant under heavy current loads,
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