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.
®