Kenwood VT-172 User manual

©PRINTEDIN JAPAN
NOISE METER
VT-172
INSTRUCTION MANUAL
KENWOOD CORPORATION
KENWOOD

CONTENTS
1. GENERAL3
2. FEATURES 3
3.SPECIFICATIONS4
4.CONTROLSANDINDICATORS7
5.OPERATION10
6.PRECAUTION11
7.MAINTENANCE12
8.ADJUSTMENT. 13
9.APPENDIX16
-2-

1. GENERAL
The Noisemeterisanhigh-sensitiveelectronicvoltmeter
havinga maximumsensitivityof10M/fullscale.Its
widefrequencyrangecovers from 10Hzto500kHz(1mV
~300V) andthefivetypesofweightingareselectable.
Inaddition,DINor CCIR quasi-peakoraverage
detection with RMSdisplayisselectable,making
possibleS/Nandnoisemeasurementsinaccordance
with J IS-A, DIN NOISE, DINAUDIO, CCIR and CCIR/
ARM standards.
The unitsarealsoprovided with anoverloadindicator,
a 10dBrangerelativereferenceadjustmentandACand
DC outputs.
a. 10#Vfullscalemaximumsensitivity with 0.2/^V
graduated scale formeasurementsdownto-120dB.
b.Buttonselectionof JIS-A, DIN NOISE, DINAUDIO,
CCIR and CCIR/ARM weightingfiltersmake
possiblenoisemeasurementsandS/Nmeasurements
inaccordance with a varietyofstandards.
c. In addition toaveragedetectionandRMSdisplay,
DINand CCIR semi-peakdetection with RMS
displayisavailableformeasurementsinaccordance
with thosestandards.
d. ACOUTandDCOUTterminalsareprovidedto
facilitatewaveformobservation,recordingof
measured valuesoruseofthe unit asanamplifier.
e. A relativereferenceadjustment from 0 10dB
makes possiblerelativemeasurementsofsignals
with respecttoanarbitrarilysetreferencelevel,
particularlyusefulinS/Nmeasurement.
f.Anoverloadindicationpreventsmeasurementerrors
caused by distortion notdetectedbytheoperator
byviewingthemeterlevelforuse with the
weightingfilters.
2. FEATURES
-3-

3.SPECIFICATIONS
-4-
[Voltmeter Section]
Voltage ranges: > 10/A/-300V(10/A//30/<V/100M//
300M//1mV/3mV/10mV/30mV/
100mV/300mV/1V/3V /10V/30V/
100V/300V)fullscale
dB: -120~+50dB(0dB=1V)
dBm: -120~+52dBm(0dBm= 1mW/600O)
Displayaccuracy: With average detection in FLAT
mode:
10#Vand30/A/ranges: within
±5%offullscale
100/xV—300Vranges: within ±3%
offullscale
With quasi-peak detection and
DIN NOISE, DINAUDIOor
CCIR weighting filter:
W/AV range: within ±7%of
fullscale
30/tV~3G0V ranges: within ±5%
offullscale
Frequencyresponse: With average detection andRMS
display
10/iVrange:20Hz~10kHz±5%
10Hz~30kHz±10%
30/A/—300/A/ranges:
20Hz~20kHz±5%
10Hz~100kHz±10%
1mV~300Vranges:
20Hz~100kHz±3%
15Hz~300kHz±5%
10Hz~500kHz±10%
With quasi-peak detection and
RMS display
10/iVrange:30Hz~15kHz±5%
20Hz~20kHz±10%
10Hz~30kHz±20%
30/A/—300Vranges:
30Hz~20kHz±5%
20Hz-50kHz±10%
10Hz~100kHz±20%
input impedance: 1MO±5%
Parallelcapacitance:
50pFor less

-5-
Overloadvoltagelevel: 10/A/—300/A/ranges:
AC 10Vrms,DC500V
1mV~300mVranges:
AC 80Vrms
500V(DC+ACpeak)
1V—300V ranges:
500V(DC+ACpeak)
Relative referenceadjustment:
0~approx.-12dB
Over level: Lightsuporflickerswhena
signalofmorethan+15dBfor
maximumvalueisapplied.
This indicates that thereisa
possibilityoferroneous
indication duetoover input
whena level weighting filter is
used.
Residual noise: Average detection :
10AV range input shorted, Input
equalityvalue
Below1.5M/rms(1.0/iVrmsTYP.)
30/iVrange, input shorted, Input
equalityvalue
Below5/iVs(3.0/A/rmsTYP.)
Peak detection :
10/A/ range input shorted, Input
equalityvalue
Below2.0/iVrms(1.0/iVrmsTYP.)
30M/range input shorted, Input
equalityvalue
Below5/iVrms(3.0/A/rmsTYP.)
Stability: Within ±0.5%offullscalefor
± 10% linevoltagefluctuation.
[AmplifierSection]
AC AMPLIFIER :
Gain : Approx.100dB
Output voltage: 1Vrms± 10%
Output resistance: 800O± 10%
Distortion : Below1%offullscaleat1kHz
This distortion isdeterminedby
theS/Nfortheranges10M/~
300/W
S/N : With respecttofullscale:
1mV~300Vranges:40dB minimum
300/^V range:30dB minimum
10U«Vrange:25dB minimum
30MArange:20dB minimum
*~'Vrange:16.5dB minimum

Frequency response: 1mV~300Vranges:
10Hz~500kHz within ±3dB
30/A/—300M/ ranges:
10Hz~150kHz within ±3dB
10/iVrange:
10Hz~30kHz within ±3dB
DC OUTPUT AMPLIFER :
Output voltage: 1V±10%forfullscale
Output resistance: 600O±10%
Frequency response: Approxthesameasthemeter
indication.
[Environmental]
coefficient: 0.08%/°Cor less
(at 1mVrangeormore)
Operatingtemperatureand humidity for within
specification: 15~35°C,80%RHmaximum.
Full operatingrange: 0~50°C,80%RHmaximum.
[PowerSupplySection]
Supplyvoltage: 100/117/220/240VAC ±10%
(Max. 250VAC)50/60Hz
Power consumption: Approx.15W
[Dimensions] Width 128mm,Height190(214)mm
^Depth285(315)mm
( ) dinsionsincludeprotrusions
from thebasic case.
[Weight] 4.6kg
[Accessories] Powercard1
Input cable(CA-41)1
Instructionmanual............1
-6~

4.CONTROLSANDINDICATORS
FRONT PANEL
© POWER (ONj>l/OFF* ) Switch
AC powerswitch.
®PowerLamp
IndicatestheVT-172ispoweredup.Lightswhen
POWER isdepressed.
(D RANGE SelectorSwitch
Attenuatorselectorswitch.16positionsin10dB
steps. Toprevent excessive inputs,thisswitchis
startedinthehighest,300Vrangeandgradually
workeddownrangetoprovideaneasilyreadable
meterdeflection.
®INPUT Juck
BNC signal input connector.
© RELATIVE REFControland© UNCALLamp
Sensitivityadjustmentanduncalibratedannunciator.
More than10dBofadjustmentispossible.When
the control isturned fully clockwise,thesetrange
is calibrated.This control canbeusedtoadjust
themetertoanappropriatelevelforrelative
measurements. - Whennotsetat fully clockwisethe
UNCAL lamplightstowarntheoperator.
Fig. 1 Frontpanelview
-7-

® OVERLEVEL Lamp
Whenusingweightingfilterstheeffectofthe
filter istomask from theoperatorthepresence
ofanexcessively high input level.Thus distortion
andtheresultingerrorscanoccur without the
operatorbeingawareofthiscondition.Toprevent
thisthe OVERLEVEL warninglampalertsthe
operatorwhenthe input levelgoes+15dBabove
the full seal level (OdB). .
® AVERAGE/PEAK Switch
This switchisusedtoselectthedetectionmethod.
Inthereleased position averagedetectionand
RMS displayareineffect.Depressingtheswitch
selects eitherDINor CCIR quasi-peakdetection
andRMSdisplayofthesignallevel.When CCIR/
ARM isselectedthedetection method isauto-
maticallyswitchedtoaveragedetectionandRMS
displayregardlessofthe position ofthisswitch.
® WEIGHT Switch group
This six position selectionswitch group allows
selectionofoneof FLAT or JIS-A, DIN NOISE,
DINAUDIO, CCIR or CCIR/ARM weighted
response. Selectionofthe FLAT position turns
the unit into a widebandACvoltmeter.Ifno
button isdepressed,themodeisautomatically
CCIR/ARM.
JIS-A :
Used fornoiselevelmeasurementsinaccordance
with JSS:C1502A, JIS"C5551A, IEC-A, and IHF-A
standards.
DIN NOISE ;
Used fornoiselevelmeasurementsinaccordance
with DINstandard45405.
DINAUDIO: "
Used for1QHz~2.0kHz:.audiolevelmeasurementsin
accordance with DINstandard45405.
CCIR :
Used formeasurementsofnoiselevelinaccordance
with CCIR standards..
CCIR/ARM :
Used fornoiselevelmeasurementsinaccordance
with CCIR/ARM standards.
This measuringequipmentisrecommendedby
DolbyLaboratorie.
Whenthe CCIR/ARM filter isused,average
detectionisusedregardlessofthe AVERAGE/
PEAK switch.
-8~

The appropriate AVERAGE/PEAK switchsettings
thevariousfiltersare:
for.
Filter : AVERAGE PEAK
JIS-A
O
DIN NOISE
-o
DINAUDIO o o
CCIR
-o
CCIR/ARM
o
® METER
® METER Zero-adjustTrimmer
Fig. 2 Rearpanelview
»9-

REAR PANEL
©AC OUTPUT Juck
This output isusedforwaveformobservationor
forusedoftheVT-172asanamplifier.
@ DC OUTPUT Juck
This output isusedforrecording off-line measured
values.
®GNDTerminal
Groundconnection.
©AC POWER Connector
This isACpower input connector.Usethepower
cordprovided with the unit.
@ AC LINE VOLTAGE Selector
Set the plug ofthisselectortothelocalline
voltage(100/117/220/240VAC).
@ FUSE HoWer
Use a screwdrivertoopenthisholderfor
replacementofthefuseofspecifiedrating.
For 100or117V: 0.5A
For 220or240V: 0.3A
5.OPERATION
1. Checkthemechanicalzeroingofthemeter.
2. Connectthesignalcableto INPUT ©
3. Setthe RANGE switch® tothe300Vrange.
4. Connectthepowercordandpressthe POWER ®
switchto turn the unit ON.TheredLED©
should light indicatingthe unit isreadyforuse.
5. Input thesignaltobemeasuredandifnecessary
graduallyswitchtolower(moresensitive)ranges
until an easy toreadmeterdeflectionisobtained.
USING RELATIVE REF
To makemeasurements with respecttosomearbitrary
referencelevel, input thesignaltobeusedasthe
referencelevelanduse RELATIVE REF© to obtain a
OdB meterdeflection without changingthe RELATIVE
REF settingmeasurementofothersignalscanbemade
andreaddirectlyoffthedB scale indB with respect
tothereferencelevel.
The adjustmentrangeofthe RELATIVE REF control
is from 0 to-12dB(negativeonly)sotosetOdBfor
signalunderOdBswitchingdownrangemustbedone.
-10-

READING THEMETER SCALES (SeeFig.3 )
(1) VOLTAGE SCALES
These scales consistofa 0—10and0~3 scale
whichareusedtoreadrangeswhicharemultiples
of10and3 respectively.Therangesettingalways
refers tothemeterfullscaledeflection.Theranges
are designedtooverlaptoallowvaluesonthe
lower portion ofonerangetobemoreaccurately
readontheupper portion ofthenextmore
sensitive range.
(2) dBm SCALES
A levelof1 mW into a 600Oresistanceistake
as OdBm(0.775V)andreadingsaremadeinOdBm
with respecttothisstandardreferencelevel.
Fig. 3
6.PRECAUTIONS
1. Toassureaccuratemeasurementsallowa five
minutewarmingupperiodbeforeactual
measurementsarebegin. Note that switching
between1Vand300mVandbetween1mVarid
300M/ and10/A/ upon poweringthe unit upmay
resultinthedeflectionofthemeter.
2. Topreservethe high sensitivityofthis unit, be
sure touseeitherthe input signalcableprovided
oranotherlowcapacitanceshieldedcable.Useof
singleconductorsorotherunshieldedcablesor high
impedancesignalsourcescanresultinnoisebeing
introduced into themeasurementcircuit.
3. Besuretotakecarenottoexceedthemaximum
allowable input levels:
10/A/—300/A/ ranges:AC: 10Vrms
DC : 500V
1mV~300mVranges:AC: 80Vrms
500V(DC+ACpeak)
.1V—300Vranges: 500V(DC+ACpeak)
For excessively high inputsinthe10/A/to300/A/
ranges the input impedancedropstoapproximately
10012.
-11-

4. Please note that this unit OVERLEVEL LED
lightswhenthe input exceeds15dBabovethe
fullscale readingforuse with weightingfiltersto
warnagainst distortion duetohighly excessive
signallevels.Italsonormallylightswhen
switchingbetweenthe300Vand1Vorbetween
the300/iVand1mVranges,butthisisnormal
andnotanindicationof excessive signallevel.
5. Thedynamicrangeoftheunitsis40~80dB
makingitimpossibletomeasuretheinternal
weighingfilter'sfrequencyresponsewhiletheyare
installedinthe unit.
6. A signalorDCvoltageshouldneverbeplaced
betweentheinstrument case andground.
7. Whenthisinstrumentisusedina locationwhere
theAClinehaspulsenoiseofa levelhigher
thantheinterna] filter canhandle,performance
maybeaffected.Ooitsideration sttould begiven
to providing a cleanpowersourceinsucha
situation.
8. Temperaturecoefficientis0.1%/°CTYP. with
10A<V~300J«V ranges.
7.MAINTENANCE; •
Removingthe CASE
Using a screwdriver,removethetwoscreweachon
the left side, right sideandtopoftheinstrument.
Openthe bottom ofthereceptacleshaped case to
removethecover.
Removal ofthe four screwsretainingthe bottom cover
will exposetheshield.
Replacing the fuse (seeFigure4)
REPLACING FUSE
Whena fusegoesout,thedeviceisnolongeroperable.
Ifgoneout,checkfora trouble cause, remedyit,remove
thecapofthefuseholderontherearpanelusinga
screw driverandtakeitoutandreplacethefuse with
a newone.
Whenreplacingfuse,besuretocheckthecapacityofa
newfusefora specifiedvalueasfollows:
AC 100V, 120V: 0.5A
AC 220V,240V: 0.3A
-12-

CHANGEOVER OF VOLTAGE IN SWITCHING
REGULATOR ^^^^^^^^^^^)
Remove the fuoo Keride*-ontherearsideofthedevice
set, usinga minussurewdriver,adjustyourpreferred
voltageindication with j markandplugtheholderin.
For changing100Vor117Vto220Vor240V,changethe
fuse of0.5Atothatof0.3A.
Fig. 4
8.ADJUSTMENT
Althoughthisinstrumentisshippedina calibratedand
adjustedstate,shouldrecalibrationbe necessary,
performtheproceduresoutlinedbelowusingcalibrated
instrumentsafterverifyingthatthelinevoltagesetting
is correct.
Meter accuracy adjustment
1. Removethe case and bottom cover.
2. Without applyingpowermechanicallyzerothemeter
using thezeroadjustmentscrew.
3. Usinga metercalibratorapplyeithera 400Hzor
1kHz signaltotheINPUT©ofthisinstrument.
4. Setthe AVERAGE/PEAK switch® to AVERAGE
and the WEIGHT switch© to FLAT.
5. Setthemetercalibrator output to10mVandthe
meter RANGE switch© to10mV.AdjustVR2of
theOutputUnit(X73-1390-00)fora fullscale
deflectionof10mV.
6. Setthemetercalibrator output levelto30mVand
themeterrangeswitchto30mV.AdjustVR4on
theInputUnit(X73-1380-00) (bottom side) fora
-13-

fullscale deflection.
Nextsetthemetercalibrator output levelto1Vand
themeterrangeswitchtothe1Vrange.
AdjustVR1oftheInputUnitfora fullscale
deflection.
7. Foradjustmentofthe10/4Vto300/A/rangesuse
a calibratedresistiveattenuatortoobtainan output
of100iN. Setthemeterrangeto100/iVand
adjustVR2oftheInputUnitfora fullscale
deflection.
8. Toadjustthe10/iVrangeofthe VT-172, set
thecalibrator output to10/iVandsetthemeter
rangeswitchtothe10/A/position.Adjust VR201
oftheInputUnitfora fullscaledeflection.
9. Depressthe AVERAGE/PEAK switchandleavethe
WEIGHT switchesinthe FLAT condition.Aswas
doneinstep5,adjustVR7oftheOutputUnit
fora fullscaledeflection.
10. Removethecalibratorandconnecta wideband
oscillatortothe INPUT. Settheoscillator
frequencyto1kHzandthemeterrangeswitchto
1V. Adjusttheoscillator output levelfora .
fullscale deflectioninthiscondition.
11. Shifttheoscillatorfrequencyto100kHzanduse
theTC1ontheInputUnittoadjustthemeterfor
fullscale deflection.
12. Repeattheaboveprocedure.
AC-DC OUTadjustment
Depress the AVERAGE/PEAK switchonthepaneland
leave the WEIGHT switchesinthe FLAT condition.
1) AC-OUT adjustment
Applya signalsothatthemeterreadsforfullscale.
AdjustVR8sothattheACOUTis1Vrms.
2) DC-OUT adjustment
Short circuitthe input andadjustVR10sothat
theDCOUTisOV.Applya signalsothatthe
meterreadsforfullscale.
AdjustVR9sothattheDCOUTis1V.Repeat
aboveprocedure until thespecifiedvalueisobtained.
-14-

Fig. 5 InputUnitAdjustits(BottomView)
Fig, 6 OutputUnitAdjustments(Left Side View)
Fig. 7 FilterUr,Adjustments(Right Side View)
-15-

9.APPENDIX
AdjustmentofWeightingFilterReference Level.
The referencelevelofeach filter isadjustedso that
thislevel(theOdBlevelonthe weighting curve)yields
thesamemeasuredvalueasthe FLAT conditon.Usea
frequencycountertoaccuratelysetthefrequencyofthe
oscillatorforthisadjustment.
Weighting
Filter
Unit
Control
Oscillator
frequency
Adjust
For:
JIS-A
VR1 1kHz OdB
• indicatio
DINNOISE VR2 1kHz OdB1
indicatio
DINAUDIO VR3 1kHz 0«
indicati onf
CCIR VR4
6.3kHz
. 12.2dB
indication
CCIR/ARM VR5
6.3kHz
6.6dB
indication
Table1
With regardto CCIR recommendationsandDIN45405
standardsforsemi-peak detection ofnoiselevels,the
following characteristicsarespecified.
1. One tone burstistobe input andthemeasured
valuetobeverifiedtobe within the limits
summarizedbelow.The tone burstistobesine
wave of5kHzfrequency.The duration timesare
listedinthetablebelow.
Tone burst duration (ms),
1
2 5 10 20 50 100 200 oo
Measured value(%) 17.0 26.6 40 48 52 59 68 80 100
Allowable range(%)
Lower limit
13.5 22.4 34 41 44 50 58 68
Allowable range(%)
Upper limit
21.4 31.6 46 55 60 68 78 92 -
Table 2
2. Input a tone burstsignalasshownbelowandverify
a response within the limits shownbelow.The tone
burstfrequencyis5kHz.
Tone burst repetition freque rcy(Hz) 2 10 100
Measured value (%) 48 77 97
Allowable
range (%)
Lower limit (96) 43 72 94
Allowable
range (%)
Upper limit(%)
53 82 100
Table3
"-16™

1) NoiseMeasurementFilter JIS C1502A, J IS
C5551A IEC-A, IHF-A
2) NoiseMeasurement
Filter DIN 45405 (NOISE)
3) NoiseMeasurement
Filter DIN 45405(AUDIO)
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance
(dB)
25
-44.6
±2.0
31.5 -39.2
±2.0
40 -34.5
±2.0
50
-30.2
±2.0
63 -26.1 ±2.0
80 -22.3
±2.0
100
-19.1 ±1.0
125 -16.1
± 1.0
160 -13.2
± 1.0
200 -10.8
± 1.0
250
- 8.6
±1.0
315 -
6.5
± 1.0
400
- 4.8
± 1.0
500
- 3.2
± 1.0
630
- 1.9
±1.0
800'
- 0.8
±1.0
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance
(dB)
1000 0 C
1250 +0.6
±1.0
1600 +1.0
± 1.0
2000 +1.2
± 1.0
2500
. +1.2
±1.0
3150 +1.2
± 1.0
4000 +1.0
± 1.0
5000 +0.5
±1.0
6300
-0.1 ±1.0
8000
-1.1 ±1.0
10000
-2.4
± 1.0
12500
-4.2 ±2.0
16000
-6.5
±2.0
Table 4
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance
(dB)
^ 20
<-40
^ 31.5 <-38
63
-31.6 ±1.5
100
-26.1
±1.5
200 -17.3
± 1.5
400
- 8.8
±1.5
800 - 1.9
±1.5
1000 0
±0.5
2000 + 5.3 ±1.5
4000
+ 8.2 ±1.5
5000 + 8.4
±0.5
6300
+ 8.0 ± 1.5
7100 + 7.1
±1.5
8000
+ 5.1 ±2.0
9000
- 0.3
+ 3,-2
10000 - 9.7
4- 3.-2
16000 <-21
20000 <-23
31500 <-30
-17-Table
5
Table 6
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance
(dB)
4 ^ -20
10 S - 5
31.5 0 ± 0.5
1000 0
± 0.5
20000
0
± 0.£
25000 ^ - 3
50000
S -40

4) NoiseMeasurementFilter (CCIR standard),
(Rec. 468-2)
5) NoiseMeasurementFilter
(CCIR/ARM standard)
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance \
(dB)
31.5 -29.9 ±2.0
63
-23.9 ±1.4
100 -19.8 ± 1.0
200 -13.8 ± :.35
400
- 7.8 ±0.7
800
- 1.9
+ : 55
1000 0
•rj.5
2000 + 5.6
± 'J. 5
3150
+ 9.0
±0.5
4000 + 10.5
±0.5
5000
+ 11.7
±0.5
6300
+ 12.2 0
7100
+ 12.0 ±0.2
8000
+ 11.4
±0.4
9000 + 10.1 ±0.6
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance
(dB)
10000 + 8.1 ±0.8
12500
0 ± 1.2
14000
- 5.3
± 1.4
16000
-11.7 ± 1.65
20000
-22.2
±2.0
31500
-42.7
±2.8
----- oo
Table 7
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance
(dB) .
31.5 -35.5
!
• ±2.0
63
-29.5 ±1.4
100 -25.4 ±1.0
200 -19.4
±0.85
400 -13.4
±0.7
800
- 7.5 ±0.£~
1000
- 5.6 ±0.5
2000 0
±01
3150
+ 3.4
±0.5
4000
+ 4.9
±0.5
5000
+ 6.1 ±0.5
6300
+ 6.6 0
7100 + 6.4 ±0.2
8000
+ 5.8
±0.4
9000
+ 4.5 ±0.6
Frequancy
(Hz)
Response
(dB)
Responsed
tolerance
(dB)
10000 + 2.5 ±0.8
12500
- 5.6
±1.2
14000 -10.9 ± 1.4
16000 -17.3
± 1.65
20000 -27.8
±2
31500 -48.3,
Table 8
-18-

Table9 Noise Weighting Characteristics
-19-
JIS A
DINNOISE'
DINAUDIO'
CCIR
CCIR/ARM-

A productof
KENWOOD CORPORATION
17-5, 2-chome,Shibuya,Shibuya-ku,Tokyo150,Japan
-20-