Kenwood VT-176 User manual

2 CHANNELAC VOLTMETER
VT-176
VT-177
INSTRUCTIONMANUAL
KENWOODCORPORATION
©PRINTED INJ,,N
KENWOOD

CONTENTS
1. GENERAL3
2. FEATURES3
3. SPECIFICATIONS4
4. FUNCTIONALCONTROLS6
5. OPERATION••8
6. APPLICATIONS10
7. MAINTENANCE 13
8. ALIGNMENT 14
9. CAUTIONSFORUSE16
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1. GENERAL
2. FEATURES
KENWOOD'S Model VT-176, and VT-177 aredual-
channel electronicvoltmeter sets havingtwoindepen-
dentACvoltmetersina singlecabinet.Two-pointer
meterallows easy dualmeasurementsandinter-channel
comparisons.
VT-176, and VT-177 alsoarewideband,highsensitive
voltmeterforuseanywherevoltagemeasurementsare
made, with a remotecontrolunit.Theeasy-to-use
voltmeterprovidesfrequencyresponseaswideas5 Hz
to1 MHz,measurablerange from 0.3mVto100V,
and input impedanceof10MI2.Theoptionalremote
controlfeatureisconvenientformeasurementin
productionlines.
The Model VT-177 issameas VT-176 typeindesign
andspecifications.Rangeindicatorlampisprepared
onthetopsideofdualpointermeterandremote
controlofrangeswitchingisavailabetocheckthe
input range.
VT-177 ismeasuringrangecanberemotelycontrolled
by RT-62. (VT-176 : RT-61)
a. Twopowersourcecircuits,positiveandnegative,
are providedforverystableDCbiasandrecover
from anyoverloadina veryshorttime.
b.Small-sizedcompactconstructionis easy tocarry
andlarge-sizedtwo-pointermeteris easy toread.
c. Four-scaledialplateandredandblackpointers
allowquick,andaccuratevoltagereading.
d. Numderofadjustingtrimmersareminimized with
amplifiersthatarepreciselycalculatedinopen
loop gainsandarenegativefeedbacked through
metal-filmresistorsasaccurateas1%.
Amplifiercharacteristicsthereforearefree from
secular change.
e. Inputimpedanceisashighas10MOonallranges
anditsparallelcapacitance less than45pF
f.IndirectattenuatorswitchingbyrelayandFET
(field-effect-transistor)switchprovidehigher
reliability,signal-to-noiseratio,andinter-channel
crosstalk thanmostpreviousdirectmethodof
rotaryswitch.
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g. Remoterangeselectionispossibleina simpleway
that optional remote control unit " RT-62" canbe
connectedto VT-177, sinceisattachedremote
function.(VT-176: RT-61)
h.Twochannelrangesettingcanbemadeeither
individuallyortogether(ininterlockedmanner).
i.A ground modeselectormay float measuringcircuit
aboveground.
3. SPECIFICATIONS
[Meter Section]
Measurablevoltages: 0.3mV-100Vin12ranges:
0.3mV,1mV,3mV,10mV,
30mV,100mV,0.3V,1V,3V,
10V, 30Vand100V full scales.
dB : -90~+40dB(0dB=1V).
dBm: -90~+42dBm
(0dBm=1mW,60012).
Error : Within ±3%of full scale at
1kHz.
Frequency response: ±10%at5Hz~1MHz,
±5% at10Hz~500kHzand
±3% at20Hz~200kHzas
±2% at30Hz~100kHz
referencedto1kHzresponse.
Input impedance: 10MO±5%, with less than
45pF parallelcapacitance.
Durable input voltage: 500V(DC+ACpeak)
1V—100V range
100V (DC+ACpeak)
0.3mV~300mVrange
Stability: Within ±0.5%of full scale for
±10% linevoltagefluctuation.
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Residual voltage: Less than 30A/ V with
inputshortedon0.3mVrange.
Crosstalk, Individual: Less than-80dBwithother
inputterminatedwith 60012.
Interlock: Less than-50dBwithother
inputterminatedwith 60012.
[AmplifierSection]
Gain : Approx. 70dB.
Outputvoltage: 1Vrms(full scale) ±20%.
Outputimpedance: 600O±20%.
Distortion: Less than1%at full scale.
(Rated bysignal-to-noiseratio
in0.3mV,1mVand1V ranges.)
Signal-to-noise ratio: Over40dBat full scale.
(Over 30dBat0.3mVrange)
Frequency response: Within±3dBat5Hz~500kHz.
[Environmental]
Coefficient : ±0.08%/°C
Tempe rature
(withinspecification):10~40°C
(fulloperation):0~50°C
Relative humidity: Less than80%
[Power SupplySection]
Line voltage: 100,120,220VAC±10%,
216-250V AC,50/60Hz
Power consumption: Approx.7W
[Dimensions] 128(138) Wxl90(212)Hx238(268)Dmm.
Values in( ) include
protrusions.
[Netweight]Approx.3kg.
[Accessories]
Power cable: 1 pc.
Inputcable: BNCcord, 2pcs.
Replacement fuse: 0.3A 2pcs.
0.5A 2pcs.
Instructionmanual: 1 copy.

4.FUNCTIONALCONTROLS FrontPanel(seeFigure1)
Figure 1 - Fron*PanelView
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REFER-
ENCENo.
IDENTIFICA-
TION
DESCRIPTION
® Power-onindicator
(LED)
-j-- ON/JBLOFF
Power on-off switch
®
RANGE-CH 1/2
Channel 1 and2 atten-
uatorrangeselector
©
CH1 INPUT
Channel 1 input
connector
©
CH2SELECTOR
Individual-interlock
rangesettingselector
©
CH2 INPUT
Channel 2 input
connector
©
RANGE-CH 2
Channel 2 attenuator
rangeselector
®
GND MODE
.OPEN/mGND
Negative input float
switch
© Dual-pointermeter
® Meterzero-adjust
trimmer
CHI(left), CH2(right)

Rear Pane! (seeFigure2)
REFERE-
NCE No.
IDENTIFICA-
TION
DESCRIPTION
© GND
Casing grounding
post
@
OUTPUT-2
Channel 2 monitor
output connector
@
Power cableconnector
@
Power cableconnector
© OUTPUT-1
Channel 1 monitor
output connector
©
CONT-INPUT
VT-176 type:
Remote control
mountinghole
VT-177 type: Connectc
for' remotecontrol
VT-177typeOnly
Figure 1 - Rear PanelView
©
Range indicatorlamp
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5BOPERATION
•Set-up
(1) Press the ON/OFF pushswitch© in.ThePower-
onindicator©,a light-emitting diode,will light, (5)
indicatingthatpowerhasbeen applied.
(2) Plugthesignalcalbes into theCH1andCH2
INPUT connectors® and©.
(3) CH2SELECTOR©, with theswitchreleased(m),
takes individualmodeinwhichrangesCH1and
CH2 arechangedoverusing RANGE selectorCH1/
2®andCH2®,respectively.
WiththeswitchpressedtheCH2 SELECTOR (6)
takes interlockmodeinwhich both rangesCH1U)
andCH2aresimultaneouslychangedoverusing
RANGE selectorCH1/2®.Intheinterlookmode,
RANGE selectorCH2© isnolongeroperableto(8)
select a range.
Select eitherindividualorinterlookmodeaccording
toyourparticularmeasurement.
(4) Setthe RANGE-CH1/2 selector© andthe RANGE-
CH2 selector© to100V.TomeasureanAC
voltagesuperimposedona DCvoltage,besureto
set theselectorstothepositionsbeforeconnecting
thecablestopointstobemeasured.Otherwise,
theDCvoltage causes a highsurge,whichcould
burnvoltmeter.
GND MODE© iseffected with theswitch
released {ML), inwhich both CH1andCH2are
connectedtothegroundingterminalofthecasing,
takingGNDstate, with theswitchpressed (-**-),
thegroundingofCH1andCH2isfloatedto
OPEN stateinwhichyoumovetheearth point
tothesignalsourceside.Normallyusethe
device intheGNDstate.
Connect thecablestopointstobemeasure.
Turn the RANGE selectors® and© forproper
ranges until eachMeterpointerswingsoverone
third ofthefullscale.
OUTPUTS CH2® andCH1@ provide output
signals byamplifying input signalsinsucha
degreeasthesignalamplitudeofa meterfull-
scale becomes1 Vrmsnomatterwhichrangeis
set. Outputinpedanceof60012.
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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"0.3V"
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 of0.3mVto100Vis110dBattenuation.
Assume a referencevoltagelevelonthe scale @ be
1V with the RANGE selectorat"1V,"a givenvoltage
can bereadaslowas-70dB(0.3mV)by turning the
selectordownward.Further,asthe scale ® allows
readingto-20dB(0.03mV),youcancontinuously
measure thevoltage ratio as high as-90dB(0.03mV
to1V).Thereadof-90dBmea»~~a signal-to-noise
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ratio ofaround10dB.Also,thedB scale allows
continuousmeasuringupto+40dB(1to100V)by
turning theselectorupward.
(3) dBm Scale
Ingeneral,voltmetershavea referenceleveldivision
ofOdBmequalto0.775V(1mWpower)inducedacross
a 600Oresistanceload.Therefore,thedBm scale is
available tomeasurea powerlevelreferencedto0
dBm, with theimpedanceofthegivenpowercircuit
being600Opureresistance.Wheremeasuredacross
specific resistanceloads,forexample,10kO,other
thanthe600Oload,thelevelsaresometimes
expressed indBs.
Figure 3 - Meter Scale Graduation

•HowtoUseRemoteControlFunction 6.APPLICATIONS
This equipmentischaracterizedbyanoptionalremote
controlfunction.
For the VT-177, inserttheconnectorplugattheend
ofthecord from the RT-62 (option) into theconnector
onitsrearpanelforremotecontrolofrange
selection.
The VT-176allowsremotecontrolbyusingthe RT-61.
Remove theblankboard from therearpanelofthe
VT-176.
Connect theaccompanyingreceptacletothe RT-61.
Connect. theconnectorconnectedtothereceptacleto
theoneontheprintedcircuitboardofthe VT-176.
For details,refertotheinstructionmanualforRT-61
or RT-62.
The basicuseofyourvoltmeteristomeasuresinusoidal
wave voltagesasanACvoltmeter.Inaddition,it
providesa widevarietyofapplicationsasdescribed
below.
AmplifierGainMeasurement
Voltmeteriscapableofmeasuringanamplifiergain,
whichisa signalmagnification from point A toB in
Figure 4 with a signalgeneratorconnectedtotheamplifier
input. IfthemeasuredsignallevelsatpointsA andB
are a andb dB,respectively,thenthegain is(b-a) dB.
Figure 4 - AmplifierGainMeasurement
Also themethodisapplicableformeasuringanopen
loop gainofeachamplifiercircuit with thenegative-
feedbacksignal leaves applied.Further,themethodcan
beusedformear^ngthefrequencyresponsesofgiven
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SIGNAL.
GENERATOR