2
GENERAL
The Noisemeter is an ultra-sensitive electronic
voltmeter
having a
maximum
sensitivity
of
1O#V fullscale
(:lO
pV,
tor
the
VT
-125)
Its
wide
frequency range covers
from
10
Hz
to
500
kHz (1
mV
~
300V)
and the five types
of
weighting
are
selectable. In addition, DIN or
CCI
R quasi-peak or average
detection
with
RMS
display
is
selectable. making possible
S/N
and noise measurements in accordance
with
JIS-A.
DIN NOISE, DIN AUDIO.
CCIR
and
CCIR/ARM
standards
The
units
are also provided
with
an overload indicator and a
10
dB range relative reference adjustment. AC and DC
out-
puts are provided and remote control
of
range
switching
is
available
to
facilitate
use on
the
production line.
CONTENTS
GENERAL
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. 2
FEATURES
.................................................
2
SPECIFICATIONS......................................
3
CIRUIT
DESCRIPTION
..............................
9
CONTROLS
AND
INDICATORS
................
10
OPERATION
..............................................
13
PRECA
UTI
0 N
............................................
14
MAINTENANCE
......................................... 15
ADJUSTMENT
...........................................
15
APPENDIX
.................................................
17
PARTS LIST
...............................................
21
P.C.
BOARD
AND
CIRCUIT
DIAGRAM
................................
30
*
VT-126:
10
J.N
fullscale
maximum
sensitivity
with
0.2
J.N
graduated scale for measurements
down
to
-120
dB
VT-125:
Maximum
sensitivity
of
30
J.-tV
fullscale.
*Button
selection
of
JIS-A
DIN NOISE. DIN
AUDIO.
CCIR
and
CCI
R/
ARM
weighting
filters make possible noise
measurements and
S/N
measurements in accordance
with
a variety
of
standards.
* In addition
to
average
detection
and
RMS
display, DIN
and
CCI
R semi-peak
detection
with
R
MS
display is
available for measurements
in
accordance
with
those
standards.
*
AC
OUT and DC OUT
terminals
are
provided
to
facilitate
waveform
observation, recording
of
measured values or
use
of
the
unit
as
an amplifier.
* A relative reference
adjustment
from
0
~
- 10 dB
makes possible relative measurements
of
signals
with
respect
to
an arbitrarily set reference level. particularly
useful in
S/N
measurement.
*
An
overload indication prevents
measurement
errors
caused
by
distortion
not
detected
by
the
operator by
viewing
the
meter
level for use
with
the
weighting
filters.
* Logic control is used
for
range selection
making
this
func-
tion
remote
controllable (option).
