Kenwood VT-173 User manual

KENWOOD
©PRINTED II.PAN
AUTORANGEVOLTMETER
VT-173
INSTRUCTION MANUAL
KENWOODCORPORATION

CONTENTS
1. GENERAL3
2. FEATURES 3
3. SPECIFICATIONS4
4.FUNCTIONALCONTROLS6
5.OPERATION8
6.APPLICATIONS11
7. MAINTENANCE13
8.ALIGNMENT14
9.CAUTIONSFORUSE• 16
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! GENERAL
The KENWOOD ElectronicVoltmeter VT-173 isan
absolute-mean valueindicationtypeautomaticelectronic
voltmeterwhichcanmeasureACvoltagerangingfrom
10Hz to1MHzontheroot-mean-squarevalue scale.
Ithasa wide full scale rangescoveringfrom1mVto
300V and selects theoptimummeasurementrange
automaticallyinaccordancewithinput level.
The measurementrangecanbefixedmanually.Foron-
production-lineuse,a remotecontrolunit(option)is
available.
2. FEATURES
a. Dualpowerdifferentialinputamplifiersusedinthe
entirecircuitprovidea highreliabilityandgood
characteristic ofrestorationfrompossiblesaturation
dueto excessive inputs.
b.A large-sizedTaut-bandmeterhasa highsensitivity
and reliability.
c. Thenumberofadjustingtrimmersareminimized
withtheuseoftheamplifierswhichareprecisely
calculated intheopen loop gainsandarenegative-
biased throughmetal-filmresistorsasaccurateas 1 %.
The amplifiercharacteristics,therefore,arefreefrom
any secular change.
d. Theinputresistanceisashighas 10 Milinall
ranges anditsparallelcapacitanceis 45pF orlower.
e. Themeter scales aregraduatedintheroot-mean-
square values forsinusolidal waves. Also, themeter
has a dBanddBm scales convenientformeasuring
relative values.
f.The output terminalallowsyour VT-173 touseasa
high-gain,wide-bandamplifier.
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g. Anelectroniccircuitautomaticallyselectstherange
mostsuitableformeasuring input voltage.
A desiredrangecanalsobeselectedmanually.
h.ACandDC outputs areavailablefor monitoring.
3. SPECIFICATIONS
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[ Meter Section]
Measurablevoltages: 1mV-300mVin12ranges:1mV,3mV,
10mV,30mV,100mV,300mV,1V,3V,
10V, 30V,100V,and300V full scales.
dB : -80~+50dB(0dB=1V)
dBm: -80~+52dBm(0dBm=1mW,60012)
Error : Within±3%of full scale at1kHz.
Frequency response: ±10%at10Hz~1MHz,
±3% at20Hz-200kHzand
±2% at50Hz-100kHzas
referencedto 1 kHzresponse.
Input impedance: 10MO±5%, with less than45pF
parallelcapacitance.
Durable input voltage: 500V (DC-f AC peak)1Vto300Vrange
100V (DC+ACpeak)
1mVto300mVrange
Stability: Within±0.5%of full scale for
±10%linevoltagefluctuation.
Residual voltage: Less than20^V with
input shortedon1mVrange

[PowerSupplySection]
Line voltage: 100,120,220VAC±10%
216-250 V AC, 50/60Hz
Power consumption : Approx,5W.
[ Dimensions ] 128(130)Wx190(215)Hx238(270)Dmm.
Valuenin( ) includeprotrusions.
[Net weight ] 3.2kg
[Accessories]
Powercable: 1 pc.
Input cable: CA-41, 1pc.
Replacementfuse: 0.3A2 pes.0.5A2pes.
Instruction manual: 1 copy.
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[AC output AmplifierSection]
Output voltage: 1Vrms±20%
Output resistance: 60012±20%
Frequencyresponse: Within ±3dBat10Hz-500kHz.
Distortion : Less than 1%at full scale.(Rated
bysignal-noise ratio in 1 mVrange.)
Signal-to-noise ratio : Over40dBat full scale.
[DC Output AmplifierSection]
Output voltage: 1V±20%4-offsetvoltageat
fullscale
Offsetvoltage: ±100mV
Output resistance: 60012±20%
Ripple: Less than 10mVrms
Frequencyresponse: Within ±3dBat10Hzto1MHz
[ Environmental]
Temperature
coefficient: ±0.08%/°C
Within specifications
tenperature: 10—40°C
Full operating
temperature: 0~50C
Relative humidity : Less than 80%

4.FUNCTIONAL CONTROLS
Front Panel(seeFigure1 )
Figure 1 - Front Panel View.
REFER-
ENCE No.
IDENTIFICATION
DESCRIPTION
® ON/OFF
ON/OFF switch
-INPUT
Input connector
©
AUTO/HOLD
Mode selectorswitch
® DOWN
Range DOWNswitch
©
UP
Range UPswitch
©
AC OUTPUT
AC output terminalctor
®
RELATIVE REF
RELATIVE REF
controller
®
UNCAL
Uncaliblationindicator
®
VOLTES/DECIBELS Meter
RANGE RANGE
indicatorlamp
©
METER zero-adjust
trimmer
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Figure 2 - Rear Panel View.
Figure 3
Figure 4
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Rear Panel(seeFigure2 )
REFER-
ENCE No.
IDENTIFICATION
DESCRIPTION
@
Power connector
©
Line voltageselectoi
andfuseholder
®
DC OUTPUT
DC output terminal
©
CONT. INPUT Remote
control connec-
tor(option) blind plate
5.OPERATION
The VT-173hasthreerangesettingmodes; Auto,Hold
andRemote(option). With thesemodes,theVT-173
providesa wideapplications.
[HowtoUseAuto Mode]
(1) Bypressingthe ON/OFF switch®,the RANGE
indicatorlamps© goonsequentially from 300V
rangeindicator.The1mVindicatorgoesonfinally.
(2) Whensignalis input totheINPUTconnector®,
theVT-173automaticallyselectsthemeasurement
rangewherethemeter pointer indicatesa value
from 27%to102%ofthe full scale (standard
value ).
(3) Ifthelevelofthe input signalcorrespondstoa
value from 85%to102%ofthe full scale (standard
value), a 1 levelhigherrangemaybeselectedto
indicatethevoltage within 27%to32%(standard
value). Insucha case, thesensitivitycanbe
increased by1 range with theDOWNswitch@ to
indicatethevoltage within 85%to102%(standard
value).
Note:The "full scale" denotesthedivision10on
the scalr"
Preset ControlesonSidePanel(seeFigure3 and4 )
REFER-
ENCE No.
IDENTIFICATION
DESCRIPTION
©
TC 101
First Attenuatorpreset
trimmercapacitor
©
VR 101
First Attenuatorpres.
variableresistor
VR 102 Meterfullscalepreset
variableresistor
©
VR 201
Range uplevelpreset
variableresistor
VR 202
Range downlevelpreset
variableresistor
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(4) Tofixtherange,settheMODEselectorswitch©
toHOLDposition.Therangeimmediatelybefore
settingtheselectorswitchisheldhereafter.
[HowtoUseHoldMode]
(1) Press the ON/OFF switchCDtofixindicationof
the RANGE lamps© to300V.
(2) Supplysignaltothe INPUT connector®.
(3) Whileobservingtheswingofthemeter pointer,
select a desiredrange with theDOWNswitch®.
(4) Theselectedrangeischanged into the1 level
higherrangebypressingtheUPswitch© orthe
1 levellowerrangebypressingtheDOWNswitch®.
[Scale (SeeFig.5)]
(1)Voltage Scale
The meterhasdouble-graduatedblack scales: the
scale © graduated from 0 to10andthe scale ®
graduated from 0 to3.Inthe1Vrange,division
10 onthe0—10 scale @ indicates1V.Inthe
300mVrange,division3 onthe0~3 scale ®
indicates300mV. Scales correspondtovoltages
likewiseinotherrancje.
(2)dB Scale
The dB scale, marked with dBVingeneral,
indicates1VasOdB.The0—10 scale © has
voItage-ratio-baseddivisionsanddivision10onit
correspondstoOdB.
Ifthemeterreads-6dBinmeasurementusingthe
20dB (10V)range,themeasuredvalueis20dB-6dB
= 14dB. This correspondencealsoappliestoother
ranges.
(3)dBm Scale
Ingeneral,voltmetershavea referenceleveldivision
ofOdBmequalto0.775V(1mVpower)induced across
a 6000resistanceload.Therefore,thereddBm scale
is availabletomeasurea powerlevelreferencedto0
dBm, with theimpedanceofthegivenpowercircuit
being600Opureresistance.Wheremeasured across
specific resistanceloads,forexample,10kll,other
thanthe600Oload,thelevelsaresometimes
expressed indBs.
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[HowtoUseRelativeReferenceControl]
The RELATIVE REF control iskeptat"CAL"in
general cases ofreadingcalibrated,absolutevalueson
theMeter.Tomeasurerelativelevelssuchasfre-
quencyresponses, turn the control foruncalibration
state(UNCAL) until thereferencelevelissettoa
desiredvalue,forexample,OdBm.Thisallowsreading
therelativelevels.
[HowtoUseRemoteControl]
The RT-61 option, oneofthefeaturesofthe VT-173,
providestheVT-173 with remote control capability.
To attachthe RT-61, removethe blind plate from
therearpanelofthe VT-173, installtheconnector
supplied with the RT-61, then plug theRT-61 into
theconnectoronthePCB(voltmeterunit).
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Then, settheMODEselectorswitchontheremote
control boxto REMOTE position.Bythis,the
measurementrangesoftheVT-173canberemote-
controlled with the RANGE selectorontheremote
control box.BysettingtheMODEselectoronthe
remote control boxto PANEL, theVT-173canbe
operatedonthepanel.
For details,seetheInstructionManualofthe RT-61.
Note:TousetheVT-173intheRemotemode,be
sure tosettheMODEselectoronthepanel
toAUTOposition.
[HowtoUseACOUTPUTandDCOUTPUTConnectors]
The AC OUTPUT connector outputs 1VrmsAC
voltagewhenthemeterreadsthe full scale,
regardless ofthemeasurementrange.
Output impedanceis600O.
Likewise, theDC OUTPUT connector outputs approx.
1V DCvoltagewhenthemeterreadsthe full scale,
regardless ofthemeasurementrange.
Output impedanceis600O.
Figure 5 - Meter Scale Graduations.

6. APPLICATIONS
The basicuseofyour VT-173 istomeasuresinusoidal
wave voltagesasanACvoltmeter.Inaddition,itprovides
a widevarietyofapplicationsasdescribedbelow.
(1) AmplifierGainMeasurement
Your VT-173 iscapableofmeasuringanamplifier
gain, whichisa signalmagnification from point A to
B inFigure6 with a signalgeneratorconnectedtothe
amplifier input. Ifthemeasuredsignallevelsatpoints
A andB area andb dB,respectively,thenthegainis
(b-a) dB.•
Also, the method isapplicabletonegative-feedback
amplifiers; that is,itisavailableformeasuringan
open loop gainofeachamplifiercircuit with the
negative-feedbacksignal leaves applied.
Further,the method canbeusedformeasuringthe
frequencyresponsesofgivencircuitsbychangingthe
signalgeneratorfrequency.
As anexample,letuscalculatetheopen loop gain
(from point A toB)ofthenegative-feedbackamplifier
showninFigure7.Assume that themeasuredlevelat
point A be+1.5dBinthe-60dBrangeand that of
SIGNAL
GENERATOR
Figure 6 - AmplifierGainMeasurement.
SIGNAL
GENERATOR
Figure 7-NegatveFeedbackAmplifierGainMeasurement.
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point B -4dBinthe+TQdBrange.Thegain from point
A toB is
(+10dB-4dB)-(-60dB + 1.5dB)= 64.5dB.

(2) Root-Mean-SquareandPeakValueCalculations
Your VT-173, anvoltmeterofabsolute-meanvalue
indicationtype,readsroot-mean-squarevaluesof
sinusoidalwaveinputs.Also,itdeflectsthe pointer in
proportion totheabsolute-meanvalueofa given input
wave.
Ifthe form factor(=root-mean-squarevalue/absolute
meanvalue)ofthe input waveandthecrest(= peak
value/root-mean-squarevalue)areknown,thenthe
root-mean-squarevalueandpeakvaluecanbe cal-
culatedasfollows.
Be suretousetheHOLD(manual)modetomeasure
non-sinusoidalwavevoltage.
a. Assume that themeterreadsx.
2-v/T
•Absolutemeanvalue=x = 0.9x.
71
•Root-mean-squarevalue=(Absolutemeanvalue)
x (formfactor).
• Peak value=(Root-mean-squarevalue)x (crest).
b.Forrectangular waves, their form factoris unity
(1) andthecrest unit (1).
2 ^/~2~
•Absolutemeanvalue=x ^ 0.9x.
71
• Peak value=0.9x.
c. Forsawtooth waves, their form factoris2/v^and
thecrest A/3".
•Absolutemeanvalue= x ^ 0.9x .
7Z
•Root-mean-squarevalue=
2vT2 4VT
—x7¥x=^x%104x"
• Peak value=~=x v
/Tx= -^-^x=i.8x.
K V 3 71
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7. MAINTENANCE
(1)Removingthecasing(seeFigure8)
1. Removethesixscrews holding thecasingonthe
both sidesandtopusinga Phillipsscrewdriver.
2. Widenthe bottom ofthe7-shapedcasinga little
and pull itupforremoval.
(2) Mounting thecasing(seeFigure9)
1. Widenthe bottom ofthecasinga little when
coveringitoverthemainbody.
2. FitthecasingPCboardretianertothePCboard
retainer.
3. Alternately tighten thesixscrewsfor uniform
torque.
(3) Replacingthefuse(seeFigure10)
REPLACING FUSE
Whena fusegoesout,thedeviceisnolongeroperable.
Ifgoneout,checkfora trouble cause, remedyit,remove
thecapofthefuseholderontherearpanelusinga
minusscrewdriverandtakeitoutandreplacethefuse
with a newone.
Whenreplacingfuse,besuretocheckthecapacityofa
newfusefora specifiedvalueasfollows:
AC 100V,120: 0,2A
AC220V,240V : 0.1A
(4)CHANGINGTHE SUPPLY VOLTAGE
Remove thefuseholderontherearsidedeviceset,
usinga minussurewdriver,adjustyourpreferred
voltageindication with • markand plug theholderin.
For changing100Vor120Vto220Vor240V,change
thefuseof0.2Ato that of0.1A.
CASING MOUNTING
SCREWS, 6 PIECES
Figure 8-CasingRemoval.
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Figure 9 - PCBoardRetainer.
Figure 10- Replacingthe fuse.
8.ALIGNMENT
The VT-173 isfactory-adjustedprecisely.However,it
can beadjustedthroughtheadjustholesontheside
whilebeinghousedinthecasingif necessary. Forre-
adjustment,checkthesupplyvoltagefirst,thenfollow
theinstructionsbelowusinga preci se I y-ca I i bra ted meas-
uringinstrument.
1. Priortoturningonpower,adjustthemeterpointer
indicates exactlyzerowiththe ZERO ADJUST screw
©ofthemeter.
2. Turnonthepowerofthe VT-173, thensetthe
MODE selectorswitch(3)toHOLDposition.Rotate
the RELATIVE RFFcontrol® clockwisetoactivate
it.
3. Connectthevoltmetercalibrator output (1kHzor
400Hz) tothe INPUT connector©.
4. Setthecalibrator output voltageto300mVtoset
therangeofthe VT-173 to300mV.Control VR102
©sothatthemeterreadsthe full scale.
5. Then, setthecalibrator output voltageto3Vto
•settherangeofthe VT-173 to3V.ControlVR101
©sothatthemeterreadsthe full scale.
6. Disconnectthecalibrator.Connecta wide-bandsignal
generatortothe INPUT connector@.
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7. Adjustthefrequencyand output voltageofthe
signalgeneratorto50kHzand3Vrespectivelyto
set therangeofthe VT-173 to3V. Control TC101
©so that themeterreadsthe full scale.
8. Repeatsteps from 5 to7.
9. Fully rotate VR201 •©clockwiseand VR202 ®
counterclockwise.
10. Setthefrequencyand output voltageofthesignal
generatorto1kHZandapprox.120mVrespectively.
Set theMODEselectorswitch(3)ofthe VT-173 to
AUTO position.
11. Adjustthemeasurementrangeofthe VT-173 to
100mV with theDOWNswitch® andUPswitch©.
12. Control the RELATIVE REF© so that themeter
reads 102mV.
13. Rotate VR201 © counterclockwiseslowly untill the
measurementrangeischanged into 300mV.
14. Control the RELATIVE REF© so that themeter
reads approx.80mV, then setthemeasurement
rangeto100mV with theDOWNswitch®.
15. Rotatethe RELATIVE REF© clockwiseslowlyand
check that the measurement rangeisautomatically
changed into 300mVrangewhenthemeterreads
102mV.
16. Control the RELATIVE REF© so that themeter
reads 75mVinthe300mVrange.
17. Rotate VR202 © slowly until themeasurement
rangeischanged into 100mVrange.
18. Rotatethe RELATIVE REF© clockwiseslowlyun-
tilthemeasurementrangeisautomaticallychanged
into 300mVrange, Then, rotate itcounterclockwise
slowlyandcheck that themeasurementrangeis
automaticallychanged into 100mVrangewhenthe
meterreads75mV.
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9. CAUTIONSFORUSE
1. Your VT-173 willworkjustwhenthe POWER switch
is pressedin.Foraccuratemeasurements,waitaround
five minutesforwarm-up.
2. Avoidplacingyour VT-173 wheremagneticfieldand
electric fieldaretoostrong.
3. Theinputcableotherthanthesuppliedoneshouldbe
low-capacitance shieldedcord,orcoaxialcable.
4. Donot leave your VT-173 atanyofhightemperature
and humidity places fora longperiodoftime.
5. Themaximumallowablecontinuousinputvoltage
ofthe VT-173 is100V(DC+ AC peak) whenthe
measurement rangeissetto1mV~300mV.
Thus, usegreat care.
6. Beware ofline noises orotherlow-level noises since
the VT-173 isa highlysensitivevoltmeter.
Great care shouldbeusedwhena longcableoran
instrumentofpoorisolationisconnectedtothe
MONITOR OUTconnector.
7. Besuretousethe HOLD (manual)modetomeasure
non-sinusoidal wavevoltage.
8. The ON/OFF switchof thit isdesignedtoactonthe
secondary sideofthepowertransformer.Theprimary
side ofthetransformerremainsenergizedevenifthe
ON/OFF switchissetto OFF.Therefore, iftheunit
is tobeunusedfora longtime,thepowercordshould
be unpluggedfromthereceptacleoutlet.
A productol
KENWOOD CORPORATION
17-5, 2-chome, Shibuya, Shibuya-ku, Tokyo150, Japan
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