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QI6A and QI7A in the Squaring Amplifier. Diode
CRI5 balances out the voltage drop across the base..
emitter junction of QI6B.
8-169. A 10 V dc full-scale output from the AC Con
verter appears at TP4 for full-scale inputs on the I , 10
and l OO V ranges (e.g. for a lOO V rms full-scale input
with the 100 V range selected, the output will be 10 V).
For the 1000 V range, 7 V dc is the output for 700 V rms
I ,
full-scale input. See Table 8-8 for the AC Converter
stage gains for the
10, 100, and 1000 volt ranges.
Table 8·8 AC Converter Stage Gains
10" , lit .. . l..,
Vllt ...
Oltput
,
.
> V
"2
,
,
1 0 V
1120
.
.
100 V
1/200
l000V'
1/400
1 . 1 5
.0025
'100 V ,m. m.x.
8-170. The dc output from the AC Converter connects
through a portion of the Input Switching (see Figure
8-33) on the way to the Input Amplifier. The Input
Amplifier is switched to a XI gain for the ac mode.
Refer to DC Volts Measurement Paragraphs 8-30, 8-40,
and 8-48 for circuit descriptions of the Input Switching,
Input Amplifier, and AID Converter respectively.
,
- -
-
- - - - -
- -
---
-
---
-
--
-
-
0 1 1 0
0103
�-----
------_. _ _
. _ . . _ . _ _
INPUT
AMPLIfIER
Figure 8·33. AC Converter, Output Signal Path.
llltolo ..
V,I
l""
RMS CG
...
••.
G.;n
G.iI
G.i.
Goi.
Tot.1
,
.
2.'
> 0
8
.0 '
8
2 '
1
,
.005
2.'
8
. 1
.
.01
8
---
-
. ,
. . _ .
8· 1 7 1 . RATIO MEASUREMENTS.
8-172. During a ratio measurement, three complete
measurement cycles are done. The first cycle is either a
DCV, ACV, or ACV + DCV measurement (dependent
upon the ratio function selected). During this cycle
Autozero
is
always
enabled
microprocessor for local operation. For remote opera
tion,
Autozero should not
intrument's controller. A controller error message will
be displayed if Autozero is disabled. The second and
third cycles are the DC Reference measurements with
Autozero
disabled
(disabled
Microprocessor). During the second cycle, a Reference
High Measurement is taken (see Figure 8-35). A
Reference Low is taken (see Figure 8-36) during the
third measurement cycle.
8-173. For DCV/DCV Ratio measurements, relay KI02
and FET switch QI09 (100 and 1000 V ranges) or KI03
and FET switch Q I 1 6 (.1, I, and 10 V ranges) are closed
during the signal voltage measurement (first cycle). The
relay (K102 or K103) for the selected voltage range re
mains closed during the Reference Voltage measure
ment (second and third cycle) but the associated FET
switch (QI09 or QI16) is open. For ACV/DCV or
ACV + DCV IDCV Ratio Measurements, FET switch
Q l lO is closed for the signal voltage measurement but is
open during the Reference Voltage measurements.
8-174. All of the voltages measured during the Ratio
measurement cycles are referenced to the VOLTS LOW
terminal. Measurement data is transferred from the In
guard Logic to the Outguard Logic where the Ratio
measurement is computed (see Ratio formula Figure
8-35). Measurement errors due to lead resistance (Rle ad )
between the RATIO REF 4WR LO and VOLTS LO afe
subtracted during these computations.
8-175. The voltage measurement circuit paths fOf the
Reference High (H4WH and LMES, FET's Q I 15 and
QI03 enabled) and the Reference Low (HGND, FET
QI05 enabled) are highlighted in the respective
Reference High (see Figure 8-35) and Reference Low
(see Figure 8-36) illustrations.
by
the Outguard
be disabled
by
the
by
O u t guard
8-29a
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