B+K precision 177/V-95 Manual de usuario

@r77lv-ss

YACUUM

TUBE

VOLTMETER

DYNASCAN

COF|PORANCfN

TESTINSTRUMI]NT

SAI.'ETY

WARNING

Normal useof tcst cquipmcnt cxposes

you to a ccrtainamount of dangerfiom elcctrical

shock becausctesting must often be performed where exposedvoltageis present.

An electrical

shock causing 10 milliamps of ourrent to passthrough the heart will stop most human

hcartbeats. Higher voltages pose an even greatcr thrcat becausesuch voltage can more easily

producc a lcthal current. However, voltage as low as 35 volts DC or AC RMS should be

considered dangcrous

and hazardoussince it can produce a lcthal current under ccrtain

conditions. Your normal work habits should include all accepted

practices

that will prevcnt

contaot with cxposedhigh voltage,

and that will steer

current away

from your heartin cascof

accidental

contact with ahigh

voltage.

You will significantly

reduccthc risk factorif you know

and observethe following safety precautions:

1. Don't cxposehigh voltageneedlessly.Removc housings

and covers

only whcn ncccssary.

Turn off cquipmcnt while making tcst connectionsin liigh-voltagc

circuits.Dischargc

high-voltagccapacitorsafter removing power.

2. Use

an insulatedfloor materialor alarge,

insulatedfloor mat to stand

on, and

aninsulated

work surfaccon which to placc

cquipment;and make certainsuchsurfaces

arenot damp

or wet. Whereinsulated floor surfaocis not available,wcar hcavy gloves.

3. Use the timc-proven "one hand in the pocket" tcchniqucwhile handling

an instrunrcnt

probc. Be

particularly

carcfulto avoidcontactingancarbymctal

objcct that could provide

agoodgroundreturnpath.

4. Always usean isolation transformerto power transformerless

"hot chassis"

equipntcnt,

wherc onc side of thc AC power line is connected directly to the chassis.

This includes

most recent tclevision

sctsand audio cquipment. Without an isolation

transformer,the

chassis

of such cquipmcnt may be floating at line voltage(120 VAC, 60 Hz in USA),

dependingupon which way the 2-wire AC power plug is inserted.Not only does this

prescnt

a dangcrousshockhazardif the chassis

istouchcd,

but damage

to test

instrumcnts

or the cquipment undcr test may result from connectingthe ground lcad to some

test

instruments

to a "hot" chassis.Thegroundlead

of rnostoscilloscopcs

andmostother tost

instrumcntswith 3-wire power plugsis at earth ground. Thc B & K-PRECISIONModel

TR-l l0 IsolationTransfbrmerissuitablcfor mostapplications.

5. On test instruments

or any equipmcnt with a 3-wire AC power plug, usconly a 3-wirc

outlet. This is a safcty fcaturc to kccp tho housing

or othcr cxposedelcmcnts

at oarth

ground.

6. If possiblc,

larniliarize

yoursclf with the cquipmcnt bcing tcstcd

and thc location of its

high voltagc points. Ilowcvcr, rcmembcr that high voltagcmay appear

at uncxpcctcd

points

in defcctivccquipmcnt.

7. Also rcmemberthat AC line voltagc

is prcscnt

on somc

powerinput circuit points

suchas

on-offswitchcs,fuses,

powcr transformcrs,etc.,evenwhentheequipment

isturnedoff.

8. Ncvcr work alone.

Someoncshouldbc ncarbyto rcndcr

aidif nccessary.Training

on CPR

(cardio-pulmonary

rcsuscitation)firstaid ishighly rcoonrmendcd.

TABLE OF CONTENTS

Page

KeyFeatures......... I

Specifications

lmportant Notes

Advantages of the VTVM

Accessories

D.C. VoltageMeasurements

A.C. VoltageMcasurements

ResistanceMeasurements

Reading the Meter Scale

Using the db Scale

Circuit Descriptiou

Maintenance Suggestions

Warranty Service Instructions

KEY FEATURES

1. Wide vision 6" x 4" meter scale for efiortless reading.

2. Anti-parallax mirror permits maximum scale-reading accuracy.

3. rnput impedance of 11 megohms on all D.c. voltage rzrnges. This is a very

important feature when measuring oscillator grid-bias, AGC/AVC voltage i-i

high impedance circuitry.

4. special 0-.5 volt D.c. range, useful for accurate measurements of critical

circuit parameters in solid state circuitry.

5. Measures D.C. voltage up to 1500volts.

6. Measures A.C. RMS voltage up to 1500

volts.

7. Measures A.C. peak-to-peak, sine and complex voltages up to 4000 volts.

8. Measures resistances up to 1000megohms.

9. Calibrated DB scale.

10. Zero center on meter scale, useful for F.M. discriminator aligmment'

11. "Transit" switch position automatically clemps and protects meter movement.

SPECIFICATIONS

DC VOLTMETER. ELEC'TRONIC:

8 Ranges ...0-.5,r.5,5, 15,50,

150,500,

1b00

volts

fulr

scale.

Input Resistance . .11 Megohms (1 I\4egohm

in probe).

Sensitivity .7[ Megohms per-volt on 1.5

volt range.

Circuit ..

..Ralanced

bridge using twin triode.

Accuracy .,1-3% full scale.

AC VOLTMETER. ELEC'TRONIC:

7 Ranges (R.M.S.) .......0-1.5, 5, 15,

50,150,

500,1500volts

full scale.

7 Ranges (Peak-to-peak) ... .. ....0-.4, 14,

40,L40,400,1400,4000

volts.

Frequency Response (5V Range). . -+1 db 40 Hz to 4 MIIz (600 ohms source).

Accuracy ..isTo full scale.

DB Scale ..-6 to +16db, +4 to +26db, f 14

to +36db,

*24 to +46db, *34 to +56db, +44 to

l-66db (0.775 volts into 600 ohm

line on 0-5 volts AC scale - 0db).

OHMMETER, ELECTRONIC:

TRanges ...0-1000 (x1),10,000 (x10),100,000

(x100),

I meg (x1000),

10 meg (x10K), 100 meg

(x100K), 1000 meg (xl meg). 10 ohms

center scale on Rx1.

No battery required for ohmmeter.

METER . . . . .100 p.A movement, plastic case.

Anti-parallax mirror.

MULTIPLIERS ....t% precision

type.

TUBE ......12AU7, twin triode bridge.

POWER REQUIREMENTS lO5-L25 volts 50-60 cycle AC.

OPERATING

WARNINGS

whe

n this

v'rvM isused

to make

measurements

equipmcnt

that

contains

high

voltage,thcrc is always a certain amount of danger

fiorn elcctric shock.The

person

using

theVTVM should

qualified

electronrcs

technician

orothcrwise

traincd andqualifie

d to work in such

conditions.

obscrve

thc ..Test

Instrument

Safety"

recomme

ndations

listeci

on theinside

front cover

of this

manual.

There t:utt

bc a shock h.azurtr.lrom

touchirlgthc (asco.r

tht'vrvrl u,hcrt

trtt,

cotnrt,, .r gr.urttl leutl,J tha ilrcter

iscttnncc,tetl

t. u ltighvortugc

p.irtt. The

chassis

and case

of the VTVM are

isorate

d from carth

ground to pcrrnityou to

"float" the metcr for measuring

voltage

betweenrwo polnts,

'crther of which

ts grouaded' Howevcr,

this rnust

bedone with caution. The

t,rnitrt.n ,r gr.uttd

leutlof the meterist;ottnectatl

tn thc cltassis

utttlcusc

of the VTVM untlshould

nortnulll' bc corre(ted to ugrcturttrecr

pr.tirt

tn the equipmentundertest.

If thc

common read

is conncctcdto a high vortage

point, thc case

of the VTVM rises

to that potential.The metercasc

shoulcl

beiniurated

from ground und it. ..r.

should

not be

touchcd

while

connccted

in this

manner.

obscrve

Cuution.

one of the most com"only encountercd

shock hazards

is testing

of ,,hot

chassis"

transformerless

ac-powercd

equiprnent

(see

item + on tne in'siae

front

covcr

of this manual

for a fu[ explanation

of the

hazard).

If the

common

lead

of the VTVM is conncctedto a "hot" chassis,

the case

of the vrvM wrll also

become"hot." For safety,always

uscan isolated

transformer

betweenthc ac

power line and any "hot chassis"

ccluipment

undertest.

To beon the sate

side,

treat any ac-powcred

equipment as"hot chassis"

unlessyou o." rurait t u, un

isolated

chassis

or earth

grouncl

chassis.

when handling the test probe, touch onry the rnsurated

portion. Nevertouch

theexposed

tip portion.

f^ *"*--

ADVANTAGES OF THE VTYM

'I'he greatest of the many advantages ofiered by the VTVM is its high input

impedance. This feature makes possible the measurement of voltages in high

impedance circuits such as oscillator grid circuits and AGC networks with a much

higher degree of accuracy. As a simple illustrative example of this, we have

showl in Figure 1A two 500K resistors connected in series across a 100 volt

source of voltage. A simple knowledge of basic fundamentals makes it obvious

here that the voltagc drop across each resistor will be 50 volts. I\4easuring the

voltage acrosseither resistor with a 20K ohm-per-volt non-electronic type instru-

ment on the 0-100 volt scale however, we obtain a reading of only 44 volts. Why

the discrepancy. As shown in Figure 1A the meter (on the 100

volt range) can be

considereda resistor of 2 meg.,which is connected in parallel with the 500K resis-

tor. A simple Ohm's Larv calculation rvill readily shorvthe total resistanceof the

parallel circuit to be 400K, resulting in a redistribution of the voltage drops in

the circuit. Now the first 500K resistor has approximatety 56 volts across it, and

R(rorAL)

(ruerER

PARALLEL

wlrHRz)=ffiffffi;aoo K

\oLTAGEAcRossRzAND

METER=Eoffi

xtQQ=44

voLTs

(APPRox')

FIGURE

R=5OO

E=51

-t-

loo

_l_

-T-

loo

_.1_ /ruec.oN\

\ANY SCALE/

R(roTlt-)=4goK

E=49V

R(rorAu

(METER

rNPARALLEL

wrrHnz)=*#Hili$F. .48MEG.=48oK

VoLTAGEAcRoss

R2ANDMETan=#|ft5xloo=4e

voLTs

FIGURE

the other 500K resistor in parallel with the meter has approximately 44 volts across

it. The low resistance meter is loading or changing the impedance of the circuit

when it is connected. When a VTVI\{ is used as shown in Figure 18 we have a

total of 11 megohms connected in parallel with the 500K resistor, and the total

resistance of our parallel network is now approximately 480K, resulting in the

voltage across

the meter and resistor dropping only to 49 volts or a mere 2/6 lowet

than the actual operating voltage. More accurate readings can only be obtained

with a high-impedance instument such as the VTVM.

R:5OO

E=56V

--MULrrMetEd-' E_q?rf;.Ll"4ooK

ONIOOVSCALE=2MEG. I

VTVM

Additional aclvantages

of the VTVM in solid state measurements are:

A t/2 volLfull scalesensitivity range which permits the accurate reading of the

fractions of a volt, (which are often applied between baseand emitter of transistor

devices). 'I'he VTVM input impedance is important, so that the connecting of the

meter doesnot causefalse readings due to current injection in the transistor base.

Other advantagesin the high impedance characteristics of the VTVM include the

ability to acculately measure voltages,without upsetting circuit operation, on AGC

lines, high impedance osciilator grid and other grid circuits, insulation resistance

measurements.

ACCESSORIES

(Available on separate order)

*F*ffi

re d-g]', ^€

ifl n. dry

*-t

MODET AV-2A. Increoses DC voltoge ronge up lo

50,000 volrs.

MODET AV-lA. R.F. Probe. lncreoses frequenq

rqnge up to 250 MHz.

The AV-IA RF PROBE enables the operator to make measurements of sine

wave voltages at frequencies up to 250 MHz.'rhis probe employs a crystal diode

which is useclas a half wave rectifier. The half wave rectifier circuit develops a

DC voltage proportional to the peak value of the sine wave input signal. A cali-

brating resistor convertsthis peak reading to the proper reading on the VTVM.

The AV-2A HIGH VOLTAGE MULTIPLIER PROBE has been developed

as an Accessory item (available at your distributor) to extend all DC voltage

rangesof your VTVM by a factor of 100.

The heavy duty plastic handle and safety-type connector insures maximum

operator safety. Two oversizedflashover guards protect the operator's hands from

leakage at the test point on the probe head.

One of the most u:;eful applications of the AV-2 High Voltage Probe is the

measurernent of 2nd anode voltage in TV sets.

The DYNASCAN Models AV-1A and AV-2A Probes can be used with the

following vacuum tube voltmeters:

- B&K Model 177

- B&K Model 375

- B&K Model 175

- Precision Apparatus Model V-95

- Precision Apparatus Model V-75

- Precision Apparatus Model 48

and most other VTVM's with 11 megohms input resistance

SeeOPERATING

WARNINGS

on page

3 concerning

connection

of aommon

lead

ofVTVM.

DC VOLTAGE MEASUREMENTS

Io nrerrsur,,DC

r.oltages

with the V'l'VM, connecttlte commonlearl

to the

common B-, or "grouncl" gide of the voltage to be measured. This is the chassis

in most instances although in many transformerless sets, the chassis is isolated

from the electrical circuitry and the common or B- side must be determined

rom the schematic diagram. Set the function switch to -DC or tDC as

requirecl, ancl set the range switch to a range greater than the voltage to be

measured,

if known. If not known, set to the highest, (0-1500

volt) range. set

the AC-OHMS, DC switch on the test probe to the DC position, then touch the

pro|e to the voltage point to be measured. If the reading obtained is less than rf

fuli scale (500 volts rvhen on the 0-1500volt range) move the range switch to the

next lower position. (0-500 volt range in this example.) For greatest accuracy,

always select the range which permits you to obtain a reading nearest full scale

deflection without having the pointer go off scale. IJseonly the scales

marked DC-

RMS for reading DC uoltages. Use the 0-5 scale for reading DC voltages between

0 and .5

volts.

You rvill notice that your vTVM has a convenient

center scale

zero position

for special applications such asbalancing FM discriminator circuits. You may use

this center scalezero feature when the range switch is on either the *DC or -DC

position by simply adjusting the ZERO ADJ. control to bring the pointer to the

center scalemarking.

set Function switch to "-DC or *DC" volts position, and switch in tlre

orobe to "DC".

VOLTAGE TO

BE MEASURED SET RANGE

SWITCH TO READ FROM

SCALE MULTIPLY

READING BY

0to.5V

0to 1.5V

1.5

to5V

5to 15V

15to 50V

to 150V

150to

500V

500to 1500V

.5V

1.5V

15v

50v

150v

500v

1500v

0to5

0to 1.5

0to5

0to1.5

0to5

to1.5

0to5

to1.5

100

1000

AC VOLTAGE MEASUREMENTS

To measure AC voltages

with the VTVM, connect the common leatl to one

side of the voltage to be measured, set the function switch to AC, and the range

switch to a range greater than the voltage to be measured,if known. ff not known,

set to the highest (0-1500

volt) range.set the AC-OHMS, DC switch on the test

probe to the "AC-OHMS" position, then touch the probe to the other side of

ihe voltage to be measured. If the reading obtained is less than % full scale

(500 volts when on the 0-1500 volt range) move the range switch to the next

iower position. (0-500volt range in thi." exampie.) For greatest accuracy, always

selectthe ra-nge

which permits you to obtain a-reading ne"arest

iutl scale deflection

without havingthe pointer go off scaie. It is importani to remember that 1500

volts

is the highest RMS AC voltage that can be measur.ed

with your v.fvM. The

scalesof the meter are calibrated to read both RMS an.l pe,,i-to-peak voltages.

Read the RMS values on the black scalesmarked "DC-RMS" u.rd.

tn" peakito-

peak values on the red scalesmarked "P-p". peak-to-peiik voltages are equal to

2'83 times the RMS values of sine-rvave

voltages and the scalesa'reso calibratecl

that when a voltage of 10 volts RMS for "*u-pl" is applied to the insirument, the

meter pointer will indicate 10 volts on the 0-15 volt scale, and 28.3 volts on the

0-40 P-P red scale. use the scalemarked "l.bv RMS low AC" and ..0-b.0VRMS

low AC" for AC voltagesthat fall within these ranges.

See the charts below, indicating scalesto be usecl.

AC RMS VOLTAGE MEASUREMENTS: set Function switch to ,.AC",

and Switch in the probe to "AC-OHMS".

IiMS VOL'TAGE TO

t]I] MEASURED

0to 1.5V

1.5

to5V

5to 15V

to 50V

50to 150V

150

to 500V

500

to 1500V

SET RANGE

SWITCH TO

1.5V

15V

50v

150V

500v

1500v

READ FITOM

SCALI]

1.5

RMS,LOW AC

5RMS, LOW AC

1.5

DC or RMS

5 DC or RMS

1.5

DC or RMS

5 DC or II,MS

1.5

DC or RMS

MULTIPLY

READING BY

100

1000

AC PEAK-TO-PEAK VOLTAGE MEASUREMENTS: set Function

switch

to "AC", and Switchin the probe

to "AC-OHI\{S,'.

T)EAK-TO-PDAK VOL READINGS IN RED COLOR

TO BE MI'ASURED

0to4V

4 to l4Y

to40V

to 140V

140

to400V

400

to 1400V

1400

to4200V

SET RANGE

SWITCH TO

14V

40v

140V

400v

1400v

4000v

RI'AD FROM

SCALE

4 P-P,

LOWAC

P-P,

LOWAC

40P-P

140

P-P

140

P-P

MULTIPLY

READING BY

100

Note that the "DC or RMS" scales are correct for AC voltages only when

sine-rvavevoltages are being measured. The peak-to-peak scales"i., l" used for

both peak-to-peak of sine and non-sine (complex) ,'oitag". such as are measured

in TV receivers

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