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1.
INTRODUCTION
The Motorola
Transistorized AC Voltmeters
offer many
advantages not found
in
a-c
vacuum
tube
voltmeters.
Small
physical
size,
light
weight
and
full
transistorization
permit
com-
plete
portability
for
field
use.
Тһе absence
of heat
producing
elements,
such
as
tubes
and
transformers,
lessens
the need for
frequent re-
calibration
and
increases
component
life,
The
.Model S1051C.is battery
operated.
The
Model
„ 51053С, in addition to being battery operated,
con-
tains an a-c power
supply which operates froma
117уа-с,
50-400 срв source.
A detachable power
cord
is
supplied
with
the
Model
51053С.
Тһе
SKN6009A 230/117 Volt Adpater Cable Kit (an op-
tional item not furnished with the standard Model
$1053C) permits
operation
from
а 230 volt,
50-
400 cps power
source.
2.
DESCRIPTION
а.
Functions
These
transistorized
a-c
voltmeters
are
ca-
pable of accurately performing the following func-
tions:
(1)
AC voltage measurement from 0.1 milli-
volt to 300 volts in а frequency
range of20 cycles
per second to 1 megacycle.
(2)
Power
measurements
from
-72 to +52
dbm when measured across 600 ohm impedance
(0 dbm - 1 milliwatt into 600 ohms).
(3)
Comparative
power
measurements from
-72 to +52 db (when measured
at the same imped-
ance level).
(4)
High gain isolation
amplifier
with
high
input resistance and low impedance output for amp-
lification of low level audio or r-f signals.
b.
Instrument
Characteristics
This instrument is similar to many other a-c
voltmeters
in that the meter movement
responds
to average
values
of applied voltages.
The meter
Scale
is calibrated
to
read
the
rms
value
of a
sinusoidal waveform.
When the input waveform
departs from a pure
sine wave,
the meter indica-
tion will be in error by the
ratio
of the
average
value to the rms
value of the incoming waveform.
(See figures 1 and 2 in paragraph 8.)
c.
Construction
Although
primarily
designed
for
laboratory
use,
these
instruments,
being
self-powered,
are
quite suitable for portable use without
sacrificing
the accuracy
or versatility ofalaboratory instru-
ment.
A detachable metal cover protects the front
panel from
damage
that might
occur
in portable
use.
Clips for storing the meter
cable
or
other
accessories
are mounted
on the inside of the cov-
er;
d.
AC
Power
Supply
The power
supply of the Model
51053С
con-
tains a conventional
half-wave
diode
rectifier cir-
cuit with а capacitor input filter connected to the
output.
А Zener
diode is connected
across
the
output for voltage regulation. The input step-down
transformer
is installed in the
line cord
circuit
and isolates
the
instrument
case
from
the
a-c
source,
Тре ground pin of the
line
cord
is
not
connected to the instrument
case.
Тһе line cord
is detachable
when portable operation with an in-
ternal battery is desired.
3.
METER SCALES
The meter
is calibrated
in two
linear
a-c
voltage
scales,
a decibel
scale
anda battery con-
dition scale,
It uses
а 0-50
microampere
taut-
band movement
with non-linearity
less
than
19
of full-scale deflection.
Damping
is adjusted
to
eliminate
'overshoot''
for convenience
in reading
the pointer indication.
The meter scales and their
applications
are as follows:
a.
AC Voltage Scales
The two linear scales (black) are used to mea-
sure
rms
values
of a-c voltages,
The upper scale
is graduated to a full-scale value of 1.0
and
the
lower
scale is graduated to a full-scale
reading
of 3.2.
АП a-c voltages from 0. 1 millivoltto
300
volts
rms
are
read
directly
from
these
scales
using the full scale factors appearing onthe range
selector
switch positions.
b.
Decibel
Scale
The DECIBEL
scale (red)
is used
for
dbm
measurement
when measuring
power level into а
600 ohm impedance
or comparative db levels when
measured
at the same impedance level. The scale
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