Kenwood HM-250 User manual

©PRINTEDIN*N
KENWOOD
DISTORTION METER
HM-250
INSTRUCTION MANUAL
KENWOODCORPORATION

CONTENTS
1. GENERAL. 3
2.FEATURES3
3.SPECIFICATIONS4
4.PANELEXPLANATION6
5.PRECAUTIONFORUSE8
6.OPERATINGPROCEDURE ........................... 8
A product of
KENWOODCORPORATION
17-5, 2-chome, Shibuya, Shibuya-ku, Tokyo 1 50, Japan
2

1. GENERAL
2. FEATURES
The modelHM-250isa precision distortion meter.
Itfeaturescontinuousmeasurement from 20Hzto20kHz,
0.1% full scale and0.01%(typ.)ofresidual distortion
rate.
Pushbuttonswitchesonthepanelofferone-touch
operationandsimplifiedcalibrationregardlessof
measurementranges.Automatic tuning isadoptedin
thebasicwavereductioncircuittoeliminatecompli-
catedadjustments,enablingeasy-to-useautomatic
operation.
The HM-250canalsobeusedasa 10Hz-to-200kHz,
100V full scale highly-sensitiveACvoltmeter.
a. Automatic tuning offers easy operation.
b.Highsensitivity: 0.1% full scale (distortion meter)
100V full scale (voltmeter)
c. One-touchcalibration
d. Has"X"and"Y" axis outputs forwaveform
observation.
e. small-sized, lightweight and easy toinstalland
move.
3

3. SPECIFICATIONS
[Distortion Rate Measurement]
Range ofmeasurement:
0.1to100%/ F.S.in7 ranges,
in1-3steps(distortionrate^ 30%)
Inputlevelrange: 100mVto100V(with100%
calibration)
^ 30mVormore(automatic
tuning possible)
Basic wavefreq.range:
20Hz to20kHzin3 ranges, with
a finecontrol
Residual distortion rate: 0.01%(Typical)
(at 1kHz, SENSITIVITY
Control: max)
Higherharmonics: Within±1dBat20Hzto10kHz
(2ndto5th)basicfrequency
Within±2dBat10Hzto20kHz
basic frequency
*(Higherharmonics^ 60kHz,
distortion rate^ 30%)
Basic waverejectionratio:
80dB ormore
[AC VoltageMeasurement]
Range ofmeasurement:
100i"V to 100V/F.S. in
1-3steps
Indicationaccuracy: within ± 3%of full scale (at1kHz)
Residual noise: 5%or less ofmeter full scale
(in0.1mVrange with closed
input)
Frequency response: ± 0.5dB from 20Hzto20kHz
±1dB from 10Hzto200kHz
(withrespectto1kHz)
[CommonSpecification]
Meterindicationsystem:
Average valuedetection,
effectivevalueindication
(Calibrationbasedon input sine
wave)
X-outcharacteristics: Outputsbasicwavecomponents
inDMmode.
Outputvoltage: Approx.1Vrms
(when tuned with 100%calibra-
tion)
4

Output impedance: Approx.2.2kO,
unbalance
Y-outcharacteristics: OutputshigherharmonicsinDM
mode.
Outputs input signalsinVM
andCALmodes.
Output voltage: Approx.0.5Vrms
(inmeterF.S.mode)
Output impedance: Approx.2.2kO,
unbalance
Input impedance: Approx.100kO,lOOpFor less
Max. input voltage: AtOdBattenuation
120Vrms or less (^60Hz)
200VDC or less
(AC peakvalue+ DC)^ 200V
At30or60dBattenuation
140Vrms or less
200VDC or less
(AC peakvalue+ DC)^ 200V
[Environmental]
Operatingtemperatureand humidity :
0to40°C,10to90%RH
(Nodewconcentration)
Storagetemperatureand humidity :
-10 to50°C,10to80%RH
(Nodewconcentration)
[PowerRequirements]
Voltage& frequency: 100/120/220/240VAC±10%
(max. 250V), 50/60Hz
Power consumption: Approx.5W
[Dimensions] 212Wx 133Hx 272Dmm
Max.dimensions: 212Wx 156Hx 288Dmm
[Weight] Approx.3.7kg
[Accessories] Signalcable(withbanana-
alligatorclips,1 meter): 1
Instructionmanual: 1
Power cable: 1
5

4.PANELEXPLANATION
6

® Power Switch• ( jb-ON/JB.OFF)
A push-buttontypeswitchthatturnsthepower
source onandoff. Pressing theswitchturnsthe
poweron. Pressing itagainturnsthepoweroff.
(D Meter
Indicates measured values.
© INPUT Terminal
Inputsignalstobemeasured into thisthrminal.
® ATT(dB)Switch
Attenuates input signals. Three attenuation levels
are available: 0,30and 60dB.
© SENSITIVITY control
Controls thecalibration level.
© RANGE selectorswitch
Selects themeterrange.7 rangesareavailable
in1-3 steps.
© Measurementrangeindicatorlamps
Indicate themodeselected with the FUNCTION
switch © andthemeterrangeselected with the
ATT switch®.
® X-OUTPUT terminal
This terminaloutputs basic waveintheDMmode.
Used together with the Y-OUTPUT terminalfor
easy frequencyadjustmentbydisplaying Lissajous
waveforms onanoscilloscope.
® I
GND terminalofthismeter.
© Y-OUTPUT terminal
This terminaloutputshigherharmonicsinthe
DMmode,oritoutputsthe input signalinthe
VM orCALmode.IntheDMmode,theterminal
is usedthe same wayasthe X-OUTPUT terminal.
© FUNCTION selectorswitch
Selects anyofthe following threemeasurement
modes :
VM : ACvoltmetermode
CAL : Calibrationmode
DM: Distortionmetermode
© MULTI Switch
Selects 10,100,or1kHzrange.
Set the FREQUENCY dialtox10,xl00orxtGOO
positionfor each range.
© FINE adjustment
A knobforfrequencyfineadjustment.
@ FREQUENCY (Hz)adjustment
A dialforfrequencyroughadjustment.
7

5. PRECAUTION FORUSE
a. Donotapply excessively highvoltagetotheinput
terminal.
b.Donotapplyvoltagetothe output terminal.
c. Donot press anypushbuttontwiceormore.
d. Thesupplyvoltageshouldbewithintherating
voltage±10%(Max. 250V).
e. Usethemeteratanambienttemperaturefrom
15 to35°C.Donotplacethemeterclosetoa
heat generatingobject.
f.Donotapply excessive forcetothemeter,dial,
inputterminal,etc.
g. Wipe dirt offthepanel,etc.withsoftcloth.
Use weakneutraldetergentfor dirt ifitcannot
bewipedoffwithclothonly.
h.Ifpowersupplycontainspulsenoise,a higher
value maybeindicatedormonitorwaveformmay
beinfluenced.
6. OPERATING PROCEDURE
©PowerON
connecttheattachedpowercabletothemeter
and a wallsocket. Press the POWER switch®
and powerissuppliedtothemeter.
®Priortoapplyinginputsignal
Excessive inputsignalmaydamagethismeter.
Before applyinginput signal, settheswitchesas
follows:.
ATT switch® : 60(dB)
RANGE switch® : Press theleftbutton.
IntheVMmode,the full scale ofthismeteris
100V undertheabovesetting.
Note: Thefollowingtableshowstherelationship
betweenthemaximuminputvoltagesand
settingsoftheATTswitch®.Ifapplied
voltageishigherthanspecifiedinthe
followingtable,themeterisdamaged.
Never applya voltagehigherthanspecified.
8

6-1ACVoltageMeasurement
DependingonthesettingsoftheATTand RANGE
switches, thismetermeasures input voltage from
0.1mVto100V.IftheATTswitchissettoOdB,
theupper scale ofthe RANGE switch0.1mVto
lOOmVisselected.IftheATTswitchissetto
30dB, themid scale 0.003V.to3Visselected.
IftheATTswitchissetto60dB,thelower scale
0.1Vto100Visselected.Ifthelevelof input
signalisunknown,selectthelowestsensitivity
rangeasdescribedinthepreviousparagraph.
The impedanceofthe input terminalis tOOkO.
The maximum input voltageisasshowninTable1.
AdjusttheATTand RANGE switchesso that the
meterreadsa value from 1/3ofthe full scale
andthe full scale.
(1) Howtoreadvoltage
Three meterrangesareavailableforACvoltage
measurement.The right lampindicatesa selected
range.Thenumbersabovethepressed RANGE
switchintherowindicatedbythelampshow
theselectedrange.
IntheexampleshowninFig.1,the0.1Vrange
is selected.Division10onthemetercorresponds
to0.1V.TheATTswitchandthemeasurement
rangeindicatorlampcorrespondtoeachotherin
theverticaldirection.
Note : Ifthelevelof input signalisunknown,be
sure tosettheATTandmeterrangetothe
minimumsensitivity,thenapply input signal.
9
'* (ACpeakvalue+ DC)^ 200V
Table 1 Maximum Input Voltage
ATT Setting Max. Input Voltage*
0(dB)
120 VACrmsor less, 200VDCor less
30 (dB)
140 VACrmsor. less, 200VDCor less
60 (dB)
140 VACrmsor less, 200VDCor less

These twobuttonsare pressed.
(2) HowtoreaddBvalue
Numbersbelowthe RANGE switches© indicate
dB values. Numbers-20dBto-80dBcorrespond
tothevoltageswhentheATTswitch© isset
toOdB.InotherATTsettings,dBvaluescorre-
spondingtothevoltagesareobtainedbyadding
thesetting(number)oftheATTtothenumber
ofdB scale.
Inotherwords,OdBonthemeterineachsetting
can beobtainedbyaddingthedBvalueofa
pressed RANGE switchtothedBvalueofthe
I ATTswitch.IntheexampleshowninFig.1,OdB
j onthemeteris-20dB(-50dB+ 30dB= -20dB).
Nc|te: The input impedanceofthismeteris100kO.
Ifimpedanceofthe input signalsourceishigh,
I usecareforerrors(duetoloadeffect).
6—MeasurementofDistortionRate
^1) Howtosetcalibrationlevel
For measuring distortion rate, input signalmust
becalibratedtoa constantlevel. This iscalled
calibrationoperation,whichisperformedasfollows
onthismeterusingtheATT(dB)and SENSITIVITY
©(calibrationlevelcontrol):
1. Press theCAL button ofthe FUNCTION ©.
2. AdjusttheATT(dB)and SENSITIVITY so
thatthemeterreadsthe full scale value(at
theCALposition).
Ifthelevelof input signalisbetween0.1to3V,
set theATT(dB)toOdB.Ititisbetween3 to
100V, settheATT(dB)to30dB.Thelevel
between0 to30dBcanbeadjustedcontinuously
with the SENSITIVITY ©.For distortion rate
measurement, donotsettheATT© to60dB.
10
Fig. 1

(2) Tuning
Distortion ratemeasurementrequires tuning of
thenotch filter forremovingthe basic waves.
This meterprovidesautomatictuning.However,
rough adjustmentshallbecarriedoutmanually.
1. Press theleftmost button (100%) ofthe
RANGE ®.
2. Press theDM (distortion ratemeasurement)
button ofthe FUNCTION ©.
3. SettheMULTI(frequencyrangeselector)
switch @ inaccordance with the basic
frequency. Thefrequencyrangesareas
follows:
10 : 20Hzto200Hz
100 : 200Hzto2kHz
1k : 2kHzto20kHz
4. Adjustthe FREQUENCY dial@ (frequency
rough adjustment)and FINE knob@
(frequency fineadjustment)todecreasethe
value indicatedonthemeter.Whenthe
value indicatedonthemeterlowersbelow
15%, increasethemeterrangesensitivityto
read indication.Thenumbersinthelowest
row(withlampON)indicatetherangefor
distortion ratemeasurement.
Frequency adjustmentisfacilitatedbycon-
nectingtheX ® andY © OUTPUT termi-
nals ofthismetertoanoscilloscopeas
shown inFig.2 andobserving Lissajous
waveforms ontheoscilloscope.
Note that automatic tuning isdeactivated
ifthemeterrangeissetto100or30%.
The scale onthe FREQUENCY dialisfor
rough adjustmentandisnotaccurate.
The FINE knodenablesfineadjustmentof
±10% for20divisionsonthe FREQUENCY
dialand± 1%for2 divisions.Setthe FINE
knobtothecenterusually.
11

HM-250
Oscilloscope
Waveformonoscilloscope(in100%range)
Incompletetuning Completetuning
Fig. 2 Lissajous Waveform Monitoring
(3) Measurementofsignallevelto distortion rate
characteristics
Tuningisneedlessforsignalsatthesamefre-
quency with differentlevel.Measurementcanbe
performedina shorttimeasfollows:
1. Press theCAL button ofthe FUNCTION ©.
2. Adjustthemetertoits full scale with the
ATT (dB)® and SENSITIVITY ®.
3. Press theDM button ofthe FUNCTION.
4. Setthemeterrangeagain,if necessary, and
read indication.
5. Repeatoperations1 to4 above.
Ifthefrequencyhasbeenchanged, tuning is
required.Followtheinstructionsbelow:
1. Press theCAL button ofthe FUNCTION.
2. Adjustthemetertoits full scale with the
ATT (dB)and SENSITIVITY.
3. Setthemeterrangeto100%.
4. Press theDM button ofthe FUNCTION.
5. Setthemeterindicationtoa valuebelow
15% with the MULTI, FREQUENCY and FINE.
6. Boostthesensitivityofthemeterandread
itsindication.
7. Repeatoperations1 to6 above.
(4) Analyzinghigherharmonicsusing Lissajous
waveform
Observing Lissajous curveformedbythecomparison
of distortion (higherharmonics)andthebasicwaves
enables simpleanalysisofhigherharmonics.
Fig. 3 showsanexample.
12
Signal
generator
Test piece
(Amplifier,etc.)

(a)Much2ndharmonicsarecontained
(b)Much3rdharmonicsarecontained
(c) Muchhigherharmonicsarecontained
Fig. 3 HigherHarmonicsAnalysisusing Lissajous
Waveform
6-3Usageas Band-Pass Filter
The X OUTPUT terminaloutputssignals through
a band-pass filter. Usageofthisterminalisthe
same asdescribedinparagraph6-2Distortion
Rate Measurementabove.TheX OUTPUT termi-
nal isinvalidforACvoltagemeasurement.The
meterrangeshallbesetto100%or30%.
To setthecenterfrequencyoftheband-pass
filter, maximizethelevelofintendedsignalwhile
observingthelevelofthesignals output from
theX terminal.Atthistime,adjustthesignal
level properly through calibrationdescribedin
6-2—(1) toavoidsaturationoftheinternal
circuit.
The selectivityoftheband-pass filter Q isapprox.
approx.5.
Q=(centerfrequency)/(band width at-3dBpoint)
6-4Outputs
Details oftheX andY outputsofthismeter
are asfollows:
X output : Outputsthebasicwave(for distortion
ratemeasurement)
Approx.IVrmswhentunedto100%
calibration.
Y output : Outputshigherharmonics(for distortion
ratemeasurement)or input signal
(forACvoltagemeasurement).
Approx.0.5Vrmsatthe full scale
ofthemeter.
The impedanceofthe both outputsisapprox.2.2kl2.
.UsingtheY OUTPUT terminalenablestheuserto
use thismeterasa lownoiseamplifier.Itsgain
varies dependingonthemeterrangesettings.
13

Itis74dB(5000times)inthe O.fmV range,or
-46dB(0.005 time) inthe100Vrange. Note that
theY output signalsa certaincrossover distortion.
Note : Ifsignalsare applied totheX orY OUTPUT
terminal,the meter isdamaged.Never apply
signalstotheseterminals.
14