Kenwood VT-175 User manual

©PRINTED INPAN
KENWOOD
2 CHANNELACVOLTMETER
VT-175
INSTRUCTIONMANUAL
KENWOOD CORPORATION

CONTENTS
1. GENERAL3
2. FEATURES 3
3. SPECIFICATIONS 4
4. FUNCTIONAL CONTROLS6
5. OPERATION8
6.APPLICATIONS10
7. MAINTENANCE13
8.ALIGNMENT14
9.CAUTIONSFORUSE••16
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1. GENERAL
2. FEATURES
The Model VT-175 isdual-channelelectronicvoltmeter
sets havingtwoindependentACvoltmetersina single
cabinet.Two-pointermeterallows easy dualmeasurements
andinter-channelcomparisons.
MODEL VT-175 iswideband,highsensitivevoltmeterfor
use anywherevoltagemeasurementsaremade, with a
remotecontrol unit. Theeasy-to-usevoltmeterprovides
frequencyresponseaswideas5Hzto 1 MHz,measurable
range from 1mVto300V,and input impedanceof
10MO.
a. Twopowersourcecircuits,positiveandnegative,
are providedforverystableDCbiasandrecover
from anyoverloadina veryshorttime.
b.Small-sizedcompactconstructionis easy tocarry
andlarge-sizedtwo-pointermeteris easy toread.
c. Four-scaledialplateandredandblackpointers
allowquick,andaccuratevoltagereading.
d. Numberofadjustingtrimmersareminimized with
amplifiersthatarepreciselycalculatedinopen loop
gains andarenegativefeedbacked through metal-
film resistorsasaccurateas1%
Amplifiercharacteristicsthereforeare from secular
change.
e. Inputimpedanceisashighas10MOonallranges
anditsparallelcapacitance less than45pF
f.IndirectattenuatorswitchingbyrelayandFET
(field-effecttransistor)switchprovideshigher
reliability,signal-to-noiseratio,andinter-channel
crosstalk thanmostpreviousdirectmethodofrotary
switch.
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9- RangescanberemotelyselectedusingtheRT-61
(option).
h.Twochannelrange setting canbemadeeither
individually or together (ininterlockedmanner).
i.A ground mode selectormay float measuringcircuit
aboveground.
3.SPECIFICATIONS
[Meter Section]
Measurablevoltages: 1 mV-300Vin12ranges:
1 mV,3mV,10mV,30mVr100mV,
300mV,1V,3 V,10V,30V,100Vand
300V. full scales.
dB: -80~+50dB(0dB= 1V).
dBm: -80~+52dBm(0dBm= 1 mW,600n).
Error : Within ± 3%of full scaleat1kHz.
Frequencyresponse: ± 10%at5Hz— 1 MHz,
±5%at10Hz-500kHzand
±3%at20Hz-200kHzas
±2% at30Hz~100kHz
referencedto 1 kHzresponse.
Input impedance: 10MO±5%, with less than
45pF parallelcapacitance.
Durable input voltage:500V(DC+ACpeak)
at1V—300Vrange
100V(DC+AC peak)
at1mV~300mVrange
Stability: Within±0.5%of full scale fori 10%
linevoltage fluctuation.
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Residual voltage: Less than 20^V with input shorted
on 1 mVrange-
Crosstalk,Individual: Less than -80dB with other
input terminated with 600O
Inetrlock: Less than -50dB with other
input terminated with 600O.
[Amplifier Section]
Gain : Approx.60dB.
Output voltage: 1Vrms(Full scale) ±20%
Output impedance:600X1+20%
Distortion : Less than 1%at full scale. (Rated
bysignal-to-noise ratio in 1 mVand
1V ranges.)
Signal-to-noise ratio: Over40dBat full scale.
Frequencyresponse: Within ± 3dBat5 Hz—500kHz
[Environmental]
Coefficient:± 0.08%/°C
Temperature (within specification): 10~40°C
(full operation): 0~50°C
Relative humidity : Less than 80%
[PowerSupplySection]
Line voltage: 100,120,220VAC+ 10%,
216- 250VAC,50/60Hz
Powerconsumption:Approx.7W
[Dimensions]Wx190(212)Hx238(268)Dmm.
Values in( ) includeprotrusions.
[Net weight] 3 kg
[Accessories ]
Powercable: 1 pc.
Input cable: BNCcord,2pes.
Replacementfuse: 0.3A2pes.
0.5A 2pes.
Instruction manual: 1 copy.

4.FUNCTIONALCONTROLS FrontPanel(seeFigure1)
Figure 1 - FrontPanelView
REFER-
ENCED.
IDENTIFICA-
TION
DESCRIPTION
® Power-onindicator
(LED)
© ONOFF
on-off switch
©
RANGE-CH 1/2
Channel 1 and2 atten-
uatorselector
®
INPUT 1
Channel 1 input
connector
©
CH2 SELECTOR
Individual-interlock
rangesettingselector
©
CH2 INPUT
Channel 2 input
connector
©
RANGE-CH 2
Channel 2 attenuator
selector
©
GND MODE Negative
input floating
switch
© Dual-pointermeter
® Meterzero-adjust
trimmer
•CH1(left),CH2(right}
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RearPanel(seeFigure2)
Figure2 - RearPanelView
REFERE-
NCE No.
IDENTSFSCA-
.TION
DESCRIPTION
® GND
Casing grounding
post
@
CH2 OUTPUT Channel2
monitor
output connector
® Line
voltage selector
andfuse holder
® Power
Gable connector
©
CH1 OUTP' Channel1
monitor
output connector
©
CONT. INPUT Remote
control
mounting hole
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5.OPERATION
•Set-up
(1) Press the ON/OFF Pushswitch©in.ThePower-on
indicator®,a light-emitting diode,will light, indicat-
ingthatpowerhasbeenapplied.
(2) Plugthesignalcalbes into theCH1 INPUT andCH2
INPUT connectors® and© .
(3) CH2SELECTOR©, with theswitch released(JH),
takes singlemodeinwhich Ranges CH 1 andCH2 are
changedoverugingAttenuatorsCH1/2©andCH2®,
respectively.' . ' •
Withtheswitchpressed (-—-), the SELECTOR takes
interlockmodeinwhich both Ranges CH 1 andCH2
are simultane-ouslychangedoverusingAttenuator
CH 1/2®.Intheinterlookmode,AttenuatorCH2®
is nolongeroperabletoselecta Range.
Select eithersingleorinterlookmodeaccordingto
yourparticularmeasurement.
(4) Setthe RANGE-CH 1/2selector©andthe RANGE-
CH2 selector® to"300V/TomeasureanACvoltage
superimposedona DCvoltage,besuretosetthe
selectors tothepositionsbeforeconnectingthecables
topointstobemeasured.rerwise,theDCvoltage
causes a highsurge,whichcouldburnvoltmeter.
(5) GNDMODE®iseffected with theswitchreleased
(•)r inwhich both CH 1 andCH2areconnectedto
thegroundingterminalofthecasing,takingGND
state, with theswitchpressed(-•».),thegroundingof
CH 1 andCH2isfloatedto OPEN stateinwhich
youmovetheearth point tothesignalsourceside.
NormallyusethedeviceintheGNDstate.
(6) Connectthecablestopointstobemeasure.
(7) Turntheselectors® and© forproperranges until
each Meterpointerswitngsoverone third ofthe
fullscale.
(8) OUTPUTS CH2@ andCH 1 @ provide output
signals byamplifying input signalsinsuch
a degreeasthesignalamplitudeofa meterfull-
scale becomes1 Vrmsnomatterwhichrangeisset.
(9) Read theMeter.
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(1) Voltage Scales
See Figures
There aretwoblackvoltage scales : a scale ®
graduated0 to10anda scale © 0 to3.Whenthe
RANGE selector® isat"1V,forexample,the
division10onthe scale ® indicates1V.Atthe"300
mV"position,thedivision3 onthe scale ® indicates
300 mV.Similarly,theother RANGE selectorpositions
showtheir full scale values.
(2) dB Scale
Ingeneral,thedBvaluesareexpressedindBVwhich
is a unit referencedbyOdBequalto1 V.Thedivision
10 atthe scale ® correspondsto0 dBonthedB scale,
whichisa voltage ratio scale. Sincethe RANGE
selectorhas12rangepositionsinstepsof10dB,the
voltage ratio of1 mVto300Vis110dBattenuation.
Assume a referencevoltagelevelonthe scale ® be
1V with the RANGE selectorat"1V,"a givenvoltage
can bereadaslowas-60dB(1mV)by turning the
selectordownward.Further,asthe scale A allows
readingto—20dB(0.1mV),youcancontinuously
measure thevoltage ratio as high as-80dB(0.1mV
to1V).Thereadof-80dBmeansa signal-to-noise
ratio ofaround10dB.Also,thedB scale allows
continuousmeasuringupto+50dB(1to300V)by
turning theselectorupward.
(3) dBm Scale
Ingeneral,voltmetershavea referenceleveldivision
ofOdBmequalto0.775V(1mWpower)inducedacross
a 800Oresistanceload.Therefore,thedBm scale is
available tomeasurea powerlevelreferencedto0
dBm, with theimpedanceofthegivenpowercircuit
being60012pureresistance.Wheremeasuredacross
specific resistanceloads,forexample,10kO,other
thanthe600Oload,thelevelsaresometimes
expressed indBs.
Figure 3 - Meter Scale Graduation
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•HowtoUseRemoteControl 6.APPLICATIONS
The RT-61option,a remarkablefeatureofthe VT-175,
providesa remotecontrolcapability.Tousetheoption,
removethe case andtherear-panelblindplate,install
theconnectorsuppliedwiththe RT-61, thenplugthe
RT-61 into the16-pinconnectoronthe print circuit
board. Fordetails,refertotheRT-61Instruction
Manual.
The basic useofyourvoltmeteristomeasuresinusoidal
wave voltagesasanACvoltmeter.Inaddition,it
providesa widevarietyofapplicationsasdescribed
below.
AmplifierGainMeasurement
Voltmeteriscapableofmeasuringanamplifiergain,
whichisa signalmagnificationfrom point A toB in
Figure 4 witha signalgeneratorconnectedtotheamplifier
input.IfthemeasuredsignallevelsatpointsA andB
are a andb dB,respectively,thenthegainis(b-a)dB.
Figure 4 - AmplifierGainMeasurement
Also themethodisapplicableformeasuringanopen
loop gainofeachamplifiercircuitwiththenegative-
feedback signal leaves applied.Further,themethodc
beusedformeasi"thefrequencyresponsesofgiv
SIGNAL
GENERATOR
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