RCA WV-38A Manual

SUGGESTED PRICE 5QCENTS
operatingand
maintenanceinstructions

RCA Volt-Ohm-Milliammeter
SafetyPrecautions
For properoperation,theground(black)leadofthe WV-38A
should beconnectedtothegroundoftheequipmentunder test, before
anyotherconnectionsaremade.Animportantpointtorememberis
that there isalwaysdangerinherentintestingelectricalequipment.
Therefore, theoperatorshouldthoroughly familiarize himself with the
equipmentunder test before working onit,bearingin mind that high
voltagesmayappearatunexpectedpointsindefectiveequipment. Addi-
tional precautions which experienceintheindustryhasshowntobe
importantarelistedbelow:
1.Itisgoodpracticetoremovepowerbeforeconnecting test leads
tohigh-voltagepoints.Ifthisisimpractical,beespeciallycarefulto
avoid accidentalcontact with equipmentracksandotherobjects which
can providea ground. Working with onehandinyourpocketandstand-
ing ona properlyinsulated floor lessensthedangerofshock.
2. Filter capacitorsmaystorea chargelargeenoughtobelethal.
Therefore, discharge filter capacitorsbeforeattaching test leads.
3. Remember that leads with brokeninsulationprovidetheaddi-
tional hazardofhighvoltagesappearingatexposedpointsalongthe
leads.Check test leadsforfrayedorbrokeninsulationbefore working
with them.
4. Tolessenthedangerofaccidentalshock,disconnect test leads
immediately after test iscompleted.
5.Remember that the risk ofsevereshockis only oneofthepos-
sible hazards. Even a minorshockcanplacetheoperatorinjeopardyof
moreseriousrisks,suchasa bad fall orcontact with a sourceofhigher
voltage.
6.Theexperiencedoperatorcontinuouslyguardsagainstinjury
anddoesnotworkonhazardouscircuitsunlessanotherpersonis avail-
abletoassistincaseofaccident.
3/71
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RCA Volt-Ohm-Milliammeter
Description
The RCA WV-38A Volt-Ohm-Milliammeter isa completelyportable,
all-purposemeasuringinstrument.The WV-38A will measurermsvaluesof
AC sine-wavevoltages from 0.1 volt to5000volts;DCvoltages from 0.005
volt to5000volts;DCcurrent from 1 microampereto10amperes;resistance
from 0.2ohmto20megohms;anddecibels from —20dbto+50db.Input
resistanceis20,000ohms-per-voltonDC,and5000ohms-per-voltonAC.
Featuresofthisversatile test instrumentincludetheuseofprecision
resistorsinallmeasuringcircuits,anda large,easy-to-readmeter with
sensitive 50/zA movement.Thepanelhasbeenspeciallydesigned with
two-color markingsfor simplified operation.*
A convenientfunctionswitchisprovided with AC, +DC,and—DC
positions. The+DCand —DC positionsofthisswitchreversethepolarity
of the test leads—afeature that isalso helpful incheckingthefront-to-back
resistanceratioofelectrolyticcapacitorsandmanytypesofsemi-conductor
devices.
Two special silicon diodesareusedtoprotectthemetermovement
againstburnoutduetoaccidentaloverload.*A fuseprotectstheprecision
multiplier intheohmsnetwork.
The WV-38A iscompletelyportable,requiringnoexternalpower
source. Five internalbatteries(notprovided)areusedfortheohmsfunction
(4penlightcellsand1 "D"-size flashlight cell). Theunitweighs only 3V2
pounds,andmeasures6%inchesby5^4inchesby SVs inches.Convenient
clips areprovidedonthehandleforcarryingthe test leads.The WV-38A
is attractivelystyled, with a rugged,lightweight,bakelitecase.
^Included on wired instruments with serial numbers above 20,000, andon kits with
serial numbers above 66,000 K.
Items Supplied with WV38A
1—RedTest Lead andProbe1—BlackTest Lead with Alligator
1—Slip-on Alligator Clip andRed Clip and Black Boot
Boot 1—Warranty- Registration Card
1—Instruction Book
(BatteriesNotSupplied)
Available Accessories forWV-38A
WG-297 High VoltageProbe
WG-210 Resistor900 Megohm forH.V.Probe(10x multiplier for5000
V. range)
WG-211 Resistor495 Megohm for H.V. Probe(100x multiplier for250
V. range)
WG-270A Vinyl Carrying Case
3

RCA Volt-Ohm-Milliammeter
Specifications
Electrical
DC Voltmeter (at full scale):
Ranges 0 to .25, 1.0, 2.5,10,50,250,1000,5000volts
Inputresistance20,000ohms-per-volt
Circuit loading 50 microamperesbleedercurrent
Accuracy ±3%
AC Voltmeter (at full scale):
Ranges .. .." ...0to 2.5, 10,50, 250,1000,5000volts
InputResistance5000ohms-per-volt
Circuit loading200microamperesbleedercurrent
Accuracy ±5%
Frequency Response(reference1000cps)flat within *4db
from 10cpsto50kconthe2.5,10,and50 volt ranges.
DC Current (at full scale):
0 to 50microamperes
0 to 1 milliampere
¥?o«Mo 1 0to 10milliamperes
Kanges•• ' " " ^ 0 to100 milliamperes
0 to 500milliamperes
0 to 10 amperes
Insertion Loss .0.25 volt
Accuracy ±3%
DC Ohms:
Ranges ScaleEndsCenterScale Full ScaleCurrents
R X10-200012ohms 120 MA
R X1000-200,0001200ohms MA
R X 10,0000-20,000,000120,000ohms 0.06 MA
Accuracy ±3°of pointerposition for exactvalue
Internal Batteries:
RX1 SizeD Cell, 1% volts
R X 100 Size D Cell, iy2volts
R X 10,000 . .4 Penlite Cells in series with D cell, 7% volts
AF Output (at full scale):
Ranges 0 to 2.5, 10,50,250volts
InputResistance5000ohms-per-volt
Circuit Loading 200 microamperes
Accuracy ±5%
Note :
An internallyconnected 0.1 *ifDC blocking capacitorpermitsout-
put measurements in presence ofDC voltages.
4

RCA Volt-Ohm-Milliammeter
Decibel Levels (Zero DBis1 milliwatt in600 ohms) :
2.5V,range
10V.range
50V.range
250V.range
-20to+10DB
- 8to+22DB
+6to+36DB
+20to+50DB
(May bereadonOutputorACpositions)
Mechanical Specifications
Dimensions—(less handle)
Height
Width
Depth
Weight
. 6%inches
.5x/4 inches
:3Y$ inches
3l/2pounds
Meter Scales
Thereare five separate scalesonthemeter.Thetopblackscaleis
usedwhenmeasuringOhms.ThesecondblackscaleisusedtoreadDC
voltagesandcurrents.ThetworedscalesareusedwhenmeasuringAC
voltages,theloweronebeingused only forthe2.5V.range.Thebottom
scaleonthemeterisusedfordecibelmeasurements.A chart,located
atthelowerrighthandcornerofthescaleforconvenience,isusedwhen
making decibelmeasurements.
The Range Switch, locatedatthecenterofthecontrolpanel,has
12positions.TheRange Switch maybeturnedineitherdirectionto
obtain thefunctionandrangedesired.
The Function Switch locatedattheupperleft-handcornerofthepanel
has three positions, "AC", "+DC", and "—DC".
To measureallACVoltagesandtomakedecibelmeasurements,the
switch mustbesettothe "AC" position.
For positivedirectcurrentandDCvoltagemeasurements,theswitch
mustbesettothe"+DC"position.
9 The "—DC" positionreversesthepolarityofthe "—COMMON" and
"+"jacks,permittingdirectmeasurementofnegativedirectcurrentand
DC voltage. This switchpositioncanalsobeusedasa convenientmeansof
reversing thepolarityofthe test leadswhencheckingthefront-to-back
resistanceratioofelectrolyticcapacitorsandmanytypes ofsemiconductor
devices.
Range Switch
Function Switch

RCA Volt-Ohm-Milliammeter
Operating Section
Zero Setting of Pointer
Thepointerofthemetermustindicatezerowhenthe WV-38A isin
thenormaloperatingposition.Ifthepointer does notindicateZero,the
adjustmentscrewlocatedatthelowercenterofthemetercovershould
bereadjusted.
Useof Range andMeter Scales
Themeterscalesonthe WV-38A havebeendesignedtoprovide
ease ofoperationandquickreadabilityovera wide range ofmeasure-
ments.Scaleshavebeengroupedaccordingtothetypeofmeasurement
for which theyareused.
Becauseofthewidenumberofmeasurement ranges providedon
the WV-38A, itisoftenpossibletotakevoltageorresistancereadings
on two ranges andscales.For greatest accuracyinvoltageandcurrent
measurements,alwaysusethe range which will provideanon-scale
reading which is nearest tothefull-scalepoint.Forexample:48DC
Volts canbereadfromeitherthe50 Volt orthe250 Volt range.Because
the50 Volt range will providea reading nearest thefull-scalepoint,the
50 Volt range onlyshouldbeusedifa readingof best accuracyistobe
obtained.ThisgeneralruleappliestoallACandDCVoltageranges.
For resistancemeasurements,however,the range selectedshouldbethe
one which providesa reading nearest thecenterofthescale, because the
WV-38A providesthemostaccurateOhmsreadingsatmid-scalepoints.
For some measurements it will benecessarytousea multiplying
factor with thescaletoobtainthecorrectreading.Therequired multi-
plication isindicatedbythesettingofthe range switch.Forexample:
when the range switchissettothe1000V.positionforvoltagemeasure-
ment,the0 to10scaleisused,butthereadingis multiplied by100times.
CAUTION:
When makingvoltageorcurrentmeasurements,itisgoodpractice
tomakea trial measurementata higher range settingthanisconsid-
erednecessary, because repeatedoverloadmaydestroythemetermove-
mentorimpairtheaccuracyofindications.
Itisalsogoodpracticeforpersonalprotectiontoturnoffallpower
tothecircuitunder test whenconnectingordisconnectingthe test leads.
Thepowertothecircuitunder test mustbeturnedoffwhen in-circuit
resistance measurements aremade,otherwisedamagetothe WV-38A
mayresult.
6

RCA Volt-Ohm-Milliammeter
Figure1.D-CVoltageMeasurement
DC Voltage Measurement (SeeFig*1.)
1.Setthe AC-DC Switchtothe"+DC"or "—DC" positionasrequired.
2. SettheRangeSwitchtoa positionconsiderablyhigherthanthe
voltagetobemeasured.
3.Plugtheblack test leadintothe "—COMMON" jackonthecontrol
panel.
4.Plugthered test leadintothe"+"jackonthecontrolpanelwhen
the2.5V.,10V,,50V.,250V.or1000V., range isused.
5.Connectthe test leads tothevoltagesourc**^ bemeasured.
6.ResettheRangeSwitchtoa positionw ^ givesa suitablepointer
deflection.
7.ReadtheDCvoltagefromf1scalecorrespondingtothe range
selected.
Note: In rare applicationswherehighenergyrfis present, suchas measur-
ing dc"keep-alive"voltageonTR tubes in radar equipment,itmay
be necessary todisconnectmeter-protectiondiodesCR3andCR4.
Special .25Volt,1 Volt,and 5000 Volt Ranges
Note: Whenusingthe.25V and1 V jacks,theFunctionSwitch must be
settothe"+DC"position.Meterpolarity must beobservedby
applying thered test leadtothepositivecircuitpointandtheblack
test leadtothenegativecircuitpoint.
8.Tousethe.25volt range, settheRangeSwitchtothe".25"position,
andplugthered test leadintothe"+.25 V/50/*A" jack.
9.Tousethe1 volt range, settheRangeSwitchtothe"1.0V"position,
andplugthered test leadintothe"+1V"jack.
10. Tousethe5000volt range, settheRangeSwitchtothe5000V posi-
tion, andplugthered test leadintothe"DC5 KV" jack.

RCA Volt-Ohm-Milliammeter
Figure2.A-CVoltageMeasurement
AC Voltage Measurement (SeeFig.2.)
1.Setthe AC-DC Switchtothe "AC" position.
2. SettheRangeSwitchtoa positionconsiderablyhigherthanthe
voltagetobemeasured.
3.Plugtheblack test leadintothe "-COMMON" jackonthecontrol
panel,
4.Plugthered test leadintothe"+"jackonthecontrolpanelwhen
the2.5V,10V,50V,250V,or1000V range isused.Whenthe5000
V range isused,thered test lead must bepluggedintothe "AC5KV"
jack.
5.Connectthe test leads tothevoltagesource tobemeasured.
6.Reset theRangeSwitchtoa positionwhichgivesa suitablepointer
deflection.
7.ReadtheACvoltagefromthescalecorrespondingtothe range
selected.
8

RCA Volt-Ohm-Milliammeter
Figure3.D-CCurrentMeasurements
DC Current Measurement (SeeFig.3.)
1.Setthe AC-DC Switchtothe"+DC"or "—DC" positionasrequired.
2. SettheRangeSwitchtoa positionconsiderablyhigherthanthecur-
rent tobemeasured.
3.Plugtheblack test leadintothe "—COMMON" jackonthecontrol
panelforall ranges withtheexceptionofthe10 AMPS range.
4.Plugthered test leadintothe"+"jackonthecontrolpanelforall
ranges withtheexceptionofthe10Aand50/iA ranges.
5.Connectthe test leads in series withthecurrent flow tobemeasured.
6.ResettheRangeSwitchtoa positionwhichgivesa suitablepointer
deflection.
7.ReadtheDCcurrentfromthescalecorrespondingtothe range
selected.
8.Tousethe50/iA range, settheRangeSwitchtothe"50aA"position,
andtheFunctionSwitchto"+DC".Plugthered test leadintothe
"4-.25 V/50/*A" jack.Meterpolarity must beobservedbyapplyingthe
red test leadtothemostpositivecurrentconnectionandtheblacklead
tothenegativeconnection.
9.Tousethe10 AMP range plugtheblack test leadintothe "—10A" jack,
andthered test leadintothe"+10A"jack.Onthiscurrent range the
AC-DC Switch must besettothe "-f DC position,andtheRangeSwitch
settothe10Aposition.Meterpolarity must beobservedbyapplying
thered test leadtothemostpositivecircuitconnectionandtheblack
leadtothe other circuitconnection.

RCA Volt-Ohm-Milliammeter
Figure 4.DCOhmsMeasurement
Ohms Measurement ( SeeFig.4.)
1.SettheFunction Switch tothe"+DC"position.
2. SettheRange Switch totheappropriateposition.
3. Plug theblack test leadintothe "—COMMON" jackonthecontrol
panel.
4. Plug thered test leadintothe"+ " jackonthecontrolpanel.
5.Shortthe test leadstogetherandadjustthe ZEROOHMS control
until thepointerindicates"0" (full scale clockwise).
6.Connectthe test leadstotheresistancetobemeasured.
7.ResettheRange Switch ifnecessarytoa position which givesa suit-
ablepointerdeflection.Ifthisisnecessary, repeat steps 5 and6
beforeproceeding with step 8.
8.Readtheresistance from the OHMS scale,and multiply bytherange
factor.
CAUTION: Low-current,low-resistancedevices,suchasthermo-
couplesandmetermovements,maybedamagedunlessa rangeabove
"RXI" isused,becausethe WV-38A appliesupto1.5voltsacrossthe
resistanceundermeasurementwhentherangeselectorissetat"RX 1".
To facilitatecheckingthefront-to-backresistanceratioofelectrolytic
capacitorsandsemiconductordevices,the test leadpolaritycanbereversed
simply bysettingtheFunction Switch tothe "—DC" position.
10