Kenwood VT-171 User manual

ACVOLTMETER
VT-171
VT-171E
©PRINTED . >APAN
INSTRUCTION MANUAL
KENWOODCORPORATION
KENWOOD

CONTENTS
1. GENERAL3
2. FEATURES 3
3.SPECIFICATIONS4
4. FUNCTIONALCONTROLS7
5. OPERATION• 8
6. APPLICATIONS10
7. MAINTENANCE 12
8. ALIGNMENT 13
9. CAUTIONSFORUSE• ••14
A product of
KENWOODCORPORATION
2-5, 1 -chome Shibuya,Shibuya-ku,Tokyo150,Japan
(2)

1. GENERAL
2. FEATURES
Your KENWOOD'S ElectronicVoltmeter,Model VT-171,
r"VT-171EJ , isa voltmeterofabsolute-meanvalue
indicationtypecapableofmeasuringACvoltages
from ImVTSOO^VJ to300Vr 100VJ inthefrequency
rangeaswideas5Hzto1MHzonroot-mean-spuare
value scales. Your VT-171 TVT-171EJ isavailablein
varietyofapplicationsasitishighlysensitiveandresponds
accurately togivenvoltagesinsucha widefrequency
range. Foruseonproductionlines,itcanbecontrolled
bya remotecontroldevice(option).
This manualooverstwomodels,
the VT-171
and
VT-171E.
Mostdestdescriptionsarecommonto both
models.
Where therearedifferences,the descriptions for
the VT-171E areshownenclosed byT J.
a. Dualpowerdifferential input amplifiersusedinthe
entirecircuitprovidea highreliabilityand good
characteristic ofrestoration from possiblesaturation
dueto excessive inputs.
b.A large-sizedTaut-bandmeterhasa highsensitivity
andreliability.
c. Thenumberofadjustingtrimmersareminimized
with theuseoftheamplifierswhichareprecisely
calculated intheopen loop gainsandarenegative-
biased through metal-filmresistorsasaccurateas1%.
The amplifiercharacteristics,therefore,arefree from
any secularchange.
d. The input resistanceisashighas10MOinall
ranges anditsparallelcapacitanceis45pForlower.
e. Themeter scales aregraduatedintheroot-mean-
square valuesforsinusolidal waves. Also,themeter
has a dBanddBm scales convenientformeasuring
relative values.
f.The output terminalallowsyour VT-171 TVT-171EJ
touseasa high-gain,wide-bandamplifier.
<3>

9- The input attenuatorsareswitchedbya so-called
"logic control circuit"so that a desiredrangecan
beselected with useofa remote control device
(option).
h. A relayandFETswitchforrangeselection, controlled
bythelogic control circuit, provide higher reliability
thanusual rotary switchdirectswitching.
3.SPECIFICATIONS
[Meter Section]
Messurablevoltages: 1mV-300mVin12ranges:1mV,3mV,
10mV,30mV,100mV,300mV,1V,3V,
10V, 30V,100V,and300V full scales.
ro.3mV-100mV in12ranges:0.3mV,
1mV,3mV,10mV,30mV,100mV,
300mV,1V,3V,10V,30V,and100V
full scales.J
dB : ' -80~+50dB r-90~+40dBJ (0dB=1V)
dBm: -80~+52dBm r-90~+42dBmJ
(0dBm=1mW,600O)
Error : Within±3%of full scale at1kHz.
Frequencyresponse: ±10%at5Hz-1MHz,
±5%at10Hz-500kHzand
±2% at20Hz-100kHzas
referencedto1kHzresponse.
Input impedance: 10MO± 5%, with less than45pF
parallelcapacitance.
Durable input voltage: 500V(DC+ACpeak)
1V to300Vr 100VJ range
100V (DC+ACpeak)
1mV ro.3mVJ to300mVrange

®
Stability: Within±0.5%of full scale for
±10%linevoltagefluctuation.
Residual voltage: Less than20^VF3Gj«VJ with
input shortedon1mV TO.SmVJ
range.
[AmplifierSection]
Gain : 60dB±1dB T Approx. 70dBJ
Output voltage: 1Vrms±20%
Output resistance: 60012± 20%
Frequency response: Within±3dBat5Hz-500kHz.
Distortion: Less than1%at full scale.
(Rated bysignal-noiseratioin
1mVand1Vranges.)
T (Ratedbysigal-noiseratioin
0.3mV,1mVand1Vranges.)J
Signal-to-noiseratio: Over40dBat full scale.
rover30dBat0.3mVrange J
[Environmental]
Temperature
coefficient: ± 0.08%/°C.
Within specifications
tenperature: 10~40°C
Full operating
temperature: 0~50°C
Relative humidity : Less than80%
[Power SupplySection]
Line voltage: 100,120,220VAC±10%,
216-250V AC,50/60Hz
powerconsumption: Approx,4W.
[Dimensions]128(130)Wxl90(2l5)Hx238(260)Dmm.
Valuen in( ) includeprotrusions.
[Netweight]2.9kg
[Accessories]
powercable: 1 pc.
Input cable: CA-41, 1 pc.
Replacement fuse: 0.1A2 pes. 0.2A2 pes.
Instructionmanual: 1 copy.

Figure1-FrontPanelView. Figure2-RearPanelView.
<8>

4.FUNCTIONALCONTROLS
Figure3 - PresetControlsonSide Panel.
1)FrontPanel(seeFigure1)
1. Power-onindicator
2. POWER : ON/OFF switch
3. RANGE : Measurablevoltagerangeselector
switch
4. INPUT, 10MO,: Input connector,10MOimpedance
5. OUTPUT, 60012: Output connector,60012
impedance
6. RELATIVE REF: Relativereference control
7.UNCAL: Uncalibrationindicator
8.Meter
9. Meterzero-adjustscrew
2)RearPanel(seeFigure2)
10. Powerconnector
11. Linevoltageselectorandfuseholder
12. Remote control connector
(option) blind.
3)PresetControlsonSidePanel(seeFigure3)
The following controls,placedontheMainPCboard
(X65-1370-00), aretobepresetonthe right-hand
sidepanel.
13. TC101: First Attenuator preset trimmer
capacitor
14. VR101: First Attenuator presetvariable
resistor
15. VR102: MeterAmplifiergainpreset
variableresistor

5.OPERATION
•Set-up
1. Press the ON/OFF pushswitch©in,ThePower-on
indicator®,a light-emitting diode, will light,
indicatting that powerhasbeenapplied.
2. Plugthemeasuringcable into theINPUTconnector
®.
3. Setthe RANGE selector®to "300V"T100VJ .
To measureanACvoltagesuperimpsedona DC
voltage,besuretosetthe RANGE selector(3)before
connectingthecabletoa point tobemeasured.
Otherwise,theDCvoltage causes a high surge,which
couldburnyourVT-171 TVT-171EJ out.
4. Connectthecabletothe point tobemeasure.
5. Turnthe RANGE selector© until theMeterpointer
swings overone third ofthe full scale.
6. Read theMeter.
(1) Voltage Scales
There aretwoblackvoltage scales : a scale @ graduated
0to10anda scale ®0to3.Whenthe RANGE selector
3 isat"1V",forexample,thedivision10onthe scale
®indicates1V.Atthe"300mVposition,thedivision
3 onthe scale ©indicates300mV.Similarly,theother
RANGE selectorpositionsshowtheir full scale values.
(2)dBScale
Ingeneral,thedBvaluesareexpressedindBVwhich
is a unit referencedby0 dBequalto1V.Thedivision
10 atthe scale @ correspondsto0 dBonthedB scale,
whichisa voltageratio scale. Sincethe RANGE
selectorhas12rangepositionsinstepsof10dB,the
voltageratioof1mVro.3mVJto300Vr 100VJ is110dB
attenuation.Assumea referencevoltagelevelonthe
scale @ be1V with the RANGE selectorat" 1V"a given
voltagecanbereadaslowas-60dB(1mV)l~-70dB(0.3mV)
by turning theselectordownward.Further,asthe scale
@ allowsreadingto-20dB(0.1mV)[~-20dB(0.03m V)J,
youcancontinuoslymeasurethevoltageratioas high as
-80dB(0.1mVto1V)P-90dB(0.03mVto1V)J.Theread
of-80dBl~-90dBJmeansa signal-to-noiseratioof
around20dB F~10dBJ. Also,thedB scale allowscontinuous
measuringupto+50dB(1to300V)l~+40dB(1to 100V)J
by turning theselectorupward.
®

(3) dBm Scale
Ingeneral,voltmetershavea referenceleveldivision
ofOdBmequalto0.775V(1mVpower)inducedacross
a 600Oresistanceload.Therefore,thereddBm scale
is availabletomeasurea powerlevelreferencedto0
dBm, with theimpedanceofthegivenpowercircuit
being60012pureresistance.Wheremeasuredacross
specific resistanceloads,forexample,10kOrother
thanthe600X1load,thelevelsaresometimes
expressed indBs.
•HowtoUseRemoteControl
Availabilityofthe optional RemoteControlisoneof
outstandingfeaturesofyourVT-171 ["VT-171EJ.
To attachtheRemoteControl,removethe blind plate
attherearofyourVT-171 ("VT-171EJ. Installand
plug the optional con-nector into the16-pinconnector
onthePCboard.
The RT-61 option, a remarkablefeatureofthe VT-171,
providesa remote control capability.Tousethe option,
removethe case andtherear-panel blind plate,install
theconnectorsupplied with the RT-61, then plug the
RT-61 into the16-pinconnectoronthe print circuit
board.Fordetails,refertotheRT-61Instruction
Manual.
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.
Figure 4-Meter Scale Graduations.
®

6.APPLICATIONS
The basicuseofyour VT-171 ["VT-171EJ istomeasure
sinusoidal wavevoltagesasanACvoltmeter.Inaddition,
itprovidesa widevarietyofapplicationsasdescribed
below.
(1)AmplifierGainMeasurement
Your VT-171 ["VT-171EJ iscapableofmeasuringan
amplifiergain,whichisa signalmagnification from
point A toB inFigure5 with a signalgenerator
connectedtotheamplifier input. Ifthemeasured
signal levelsatpointsA andB area andb dB,
respectively, thenthegainis(b-a)dB.
Also, themethodisapplicabletonegative-feedback
amplifiers;thatis,itisavailableformeasuringan
open loop gainofeachamplifiercircuit with the
negative-feedbacksignal leaves applied.
Further, themethodcanbeusedformeasuringthe
frequencyresponsesofgivencircuitsbychangingthe
signal generatorfrequency.
As anexample,letuscalculatetheopen loop gain
(from point A toB)ofthenegative-feedbackamplifier
showninFigure6.Assumethatthemeasuredlevelat
point A be+1.5dBinthe-60dBrangeandthatof
point B -4dBinthe+10dBrange.Thegain from point
A toB is
(+l0dB-4dB)-(-60dB + 1.5dB)= 64.5dB.
SIGNAL
GENERATOR
Figure 5-AmplifierGainMeasurement.
SIGNAL
GENERATOR
Figure 6-NegatveFeedbackAmplifierGainMeasurement.
®

(2)Root-Mean-SquareandPeakValueCalculations
Your VT-171 FVT-171EJ, anvoltmeterofabsolute-mean
value 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.
a. Assume that themeterreadsV.
2\Tl
•Absolutemeanvalue=• V ^ 0.9V.
TZ
•Root-mean-squarevalue=(Absolutemeanvalue)
x(formfactor).
• Peak value=(Root-mean-squarevalue)x (crest).
b.Forrectangular waves, their form factoris unity
(1) andthecrestunit(1).
2v/~2~
•Absolutemeanvalue=-V^0.9V.
7C
• Peak value=0.9V.
c. Forsawtooth waves, their form factoris2/v/3_and
thecrest \/3".
•Absolutemeanvalue= V ^ 0.9V.
7T
•Root-mean-squarevalue=
x -=V= --^-V^ 1.04V.
• Peak value=-^x^—1.8V.
7TV3 %

7.MAINTENANCE
(1) Removingthecasing(seeFigure7)
1. Removethesixscrews holding thecasingonthe
both sidesandtopusinga Phillipsscrewdriver.
2. Widenthe bottom ofthe7-shapedcasinga little
and pull itupforremoval.
(2) Mounting thecasing(seeFigure8)
1. Widenthe bottom ofthecasinga little when
coveringitoverthemainbody.
2. FitthecasingPCboardretianertothePCboard
retainer.
3. Alternately tighten thesixscrewsfor uniform
torque.
(3)Replacingthefuse(seeFigure9)
REPLACING FUSE
Whena fusegoesout,thedeviceisnolongeroperable.
Ifgoneout,checkfora trouble cause, remedyit,remove
thecapofthefuseholderontherearpanelusinga
minusscrewdriverandtakeitoutandreplacethefuse
with a newone.
Whenreplacingfuse,be sura, tocheckthecapacityofa
newfusefora specifiedvalueasfollows:
AC 100V,120: 0,2A
AC 220V,240V : 0.1A
CHANGEOVER OF VOLTAGE IN SWITCHING
REGULATOR
Remove thefuseholderontherearsidedeviceset,
usinga minussurewdriver,adjustyourpreferred
voltageindication with T markand plug theholderin.
For changing100Vor120Vto220Vor240V,change
thefuseof0.2Ato that of0.1A.
Figure 7-CasingRemoval.
CASING MOUNTING
SCREWS, 6 PIECES

Figure 8-PCBoardRetainer,
Figure 9-Replacingthee.
8.ALIGNMENT
Your VT-171 waspreciselypresetatthefactory.How-
ever, itcanbealignedthroughtheadjustholeslocated
ontheright-handsidewithleavingithousedinthe
casing, ifrequired.Inrealignment,firstadjusttheline
voltagetothevoltage,usea preciselycalibratedmeasur-
inginstruments,andproceedasfollows (also, seeFigures
1 through3).
1. Beforeturningthe ON/OFF switch"ON",adjustthe
Meterzero-adjustscrew until thepointercorrectly
indicates "0".
2. Connecta voltmetercalibrator 1 kHz(or400Hz)
output tothe INPUT connector®.
3. Setthevoltmetercalibrator output voltageto30mV
and setthe RANGE selector© onyour VT-171 I~VT-
171EJ tothe" 30m V" range.
4. Adjust VR102 until thepointerswingstothe full
scale.
5. Inturn,setthevoltmetercalibrator output voltageto
10V andsetthe RANGE selector3 tothe"10V"range.
6. AdjustVR101 until thepointerswingstothe full
scale.
7. Disconnectthevoltmetercalibratorandconnecta

wide-bandsignalgeneratortothe INPUT connector®.
8. Setthesignalgeneratorfrequencyto 1 kHzandset
the RANGE selector© onyour VT-171 [""VT-171EJ to
the"1V"range.
9. Adjustthesignalgenerator output voltage until the
pointerswingstothe full scale.
10. Changethesignalgeneratorfrequencyfrom 1 kHzto
50kHz.
11. AdjustTC101 until thepointerswingstothe full
scale.
12. Repeat Steps 2 through11.
®
9,CAUTIONSFORUSE
1. Your VT-171 TVT-171EJ willworkjustwhenthe
POWER switchispressedin.Foraccuratemeasure-
ments, waitaroundfiveminutesforwarm-up.
2. Avoidplacingyour VT-171 fVT-171 EJ wheremagnetic
fieldandelectricfieldaretoostrong.
3. Theinputcableotherthanthesuppliedoneshouldbe
low-capacitance shieldedcord,orcoaxialcable.
4. Thecontinuousmaximuminputvoltageallowablefor
your VT-171 FVT-171EJ is100V(DC+ACpeak)with
the RANGE selectorat"~60dB l~-70dBJ "to"-10dB
["-lOdBJ ".Fullcareshouldbeodservedinmeasuring
highvoltages.
5. Becarefulofa linenoiseandsimilarsmallnoisesas
your VT-171 fVT-171EJ isa highlysensitivevoltmeter.
6. Donotleaveyour VT-171 TVT-171EJ atanyofhigh
temperatureandhumidityplacesfora longperiodof
time.
7. The ON/OFF switchof thit isdesignedtoactonthe
secondary sideofthepowertransformer.Theprimary
side ofthetransformerremainsenergizedevenifthe
ON/OFF switchissetto OFF.Therefore, iftheunit
is tobeunusedfora longtime,thepowercordshould
beunplugged: n thereceptacleoutlet.