Philips PM 6303A User manual

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PM 6303A CONTENTS 0
-1
CONTENTS
1 SAFETY INSTRUCTIONS 1 - 1
1.1
SAFETY PRECAUTIONS 1- 1
1.2 CAUTION AND WARNING STATEMENTS 1- 1
1.3 SYMBOLS 1- 1
1.4 IMPAIRED SAFETY PROTECTION 1- 1
1.5 GENERALCLAUSES 1- 1
2 MAINS VOLTAGE SETTING AND FUSES
2-1
3 OPERATING AND MEASUREMENT PRINCIPLE,
BLOCK DIAGRAM, Figs. 1 to 5 3 - 1
3.1 DESCRIPTION OF THE BLOCK DIAGRAM. Fig. 3
3-1
3.2 MEASUREMENT PRINCIPLE
3-2
4 CIRCUIT DESCRIPTION, FAULT FINDING, Figs. 6 to 10
4-1
4.1 POWER SUPPLY. Fig. 52
4-1
4.2 CRYSTALCLOC
K, FREQ. DIVIDER. PHASE SELECTOR; Fig. 58
4-1
4 .3 COMPONENT CONNECTION. BUFFER. Rg . 56
4-2
4.4 CURRENTTO VOLTAGE CONVERTER. Fig. 56
4-2
4.5 PROGRAMMABLE AMPLIFIER. BAND-PASS FILTER 2. Rg . 56 4 - 3
4
.6 LEVEL DETECTOR. Fig . fiT
4 - 3
4
.7 PHASE SENSITIVE RECTIFIER. Fig. 57
4-3
4.8 ANAlOG TO DIGITAL CONVERTER. ADC. Rg . 57
4-4
4.9 CENTRAL PROCESSING UNIT. CPU. Fig. 58 4-6
4.10 KEYBOARD I DISPLAY. UNIT 2. Fig. 60 4-6
5 PERFORMANCE TEST 5 - 1
5.1 INTRODUCTION
5- 1
5.2 RECOMMENDED TEST EQUIPMENT 5 - 1
5.3 SELFTEST ROUTINE 5 - 1
5.4 PERFORMANCE VERIFICATION
5-2
6 TEST PROGRAM, Figs. 11, 12
6-1
7 DISASSEMBLING THE INSTRUMENT 7 - 1
7.1 GENERAL INFORMATION
7-1
7.2 REMOVING THE COVERS
7-1
7.3 UNIT 1
7-2
7.4 UNIT 2
7-2
7.5 UNIT 3 7
-2
7.6 TEXT PLATE 7
-2
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0-2
CONTENTS PM 6303A
8 CHECKING AND ADJUSTING
8-1
8.1 GENERAL INFORMATION
8-1
8.2 RECOMMENDED TEST EQUIPMENT 8-1
8.3 ADJUSTING PROCEDURE 8-2
9 SAFETY INSPECTION AND TESTS AFTER REPAIR AND
MAINTENANCE IN THE PRIMARY CIRCUIT
9-1
9.1 GENERAL DIRECTIVES 9-1
9.2 SAFETY COMPONENTS 9-1
9,3 CHECKING THE PROTECTIVE EARTH CONNECTION
9-1
9.4 CHECKING THE INSULATING RESISTANCE
9-1
10 SPARE PARTS,
Figs. 30 to 32
10- 1
10.1 GENERAL
10-1
10 .2 STANDARD PARTS
10- 1
10.3 SPECIAL PARTS
10- 1
10.4 TRANSISTORS AND INTEGRATED CIRCUITS
10- 1
10.5 STATIC SENSITIVE COMPONENTS
10- 2
10.6 HANDLING MOS DEVICES
10- 2
10 .7 SOLDERING TECHNIQUES
10- 3
10.8 MECHANICAL PARTS, HOUSING (Fig. 30)
10- 5
10.9 MAINS CABLES
10- 5
10. 10
MECHANICAL PARTS ON UNITS, CABLES,
10-7
PARTS NOT ON UNITS, MISCELLANEOUS (Fig. 31)
10 . 11
ACCESSORIES, ADAPTERS (Fig. 32)
10-7
10 .12 ELECTRICAL PARTS ON UNITS
10- 8
11
FIGURES
Fig. 51
Overall circuit diagram
Fig. 52
Unit 1, Power supply
Fig. 53
Un it 3, Flex print
Fig, 54
Unit 3, Flex print ; component la y ~ut
Fig. 55
Unit " Component lay--out
Fig. 56
Unit 1. Input circuit and amplifiers
Fig. 57
Unit 1, Analog to digital converter
Fig. 58
Unit 1, Frequency generation , CPU, counter
Fig. 59
Unit 2, Keyboard, display ; component lay-out
Fig. 60
Unit 2, Keyboard, display
Fig. 61
Accessories PM 9541 A, PM 9542A
12 ADDRESSES FOR
SALES AND SERVICE
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PM 6303A
SAFETY INSTRUCTIONS 1- 1
1 SAFETY INSTRUCTIONS
WARNING: These servicing instructionsareforuse by qualified personnel only. To reducethe
risk 01 efectric shock, do notperform any servicing otherthan that specified in the
Operating Instructions unless you are fully qualified to do so.
Read these pages carefully before Installation and use of the instrument.
The following dauses contain information. cautions and warnings which must be followed to ensure
safe operation and to retainthe Instrument
In asafe condlUon .Adjustment, maintenanceandrepair to
the instrument shall be carried out only
by qualified personnel.
1.1 SAFETY PRECAUTIONS
Forthecorrect and safeuseofthis inslrumenlit Is essentialthatboth operatingandseMcingpersonnel
tollowgenerally-accepted safetyprocedures inadditiontothe safety precautions specified In this man-
ual. Specific warning and caution statements, where they apply, will be found throughout the manual.
Where necessary, the wamlng and caution statements and/or symbols are
mar14:ed on the apparatus.
1.2 CAUTION AND WARNING STATEMENTS
CAUTION: Is used to Indicate correct operating or maintenance procedures in order to prevent
damage to or destruction of the equipment or other property.
WARN ING: Calls attention to a potential dangerthat requires correctprocedures or practices
in order to prevent personal injury.
1.3 SYMBOLS Protective earth (black symbol
on yellow background)
(grounding) terminal
1.4 IMPAIRED SAFETY PROTECTION
Whenever it is likely that safety protection has been Impaired, the Instrument must be made Inopera-
tive and be secured against any unintendedoperation.The mattershould then be referred to qualHfed
technicians.Safety protection is likelyto beImpaired if ,forexample,theInstrumentfails to perform the
Intended measurements or shows visible damage.
1.5 GENERAL CLAUSES
WARNING: The opening of covers orremoval of parts, except those to which access can be
gaines by hand, is likely to expose live parts and accessible terminals which can
be dangerous to live.
The Instrument shall be disconnected from all voltage sources before It Is opened.
Bearinmindthatcapacitorsinsidethe instrument can holdtheirchargeeven iftheinstrumenthas been
separated from all voltage sources.
WARNING: Any interruption of theprotectiveearth conductorInsideoroutsidetheInstrument,
or disconnection of the protective earth terminal,is likely to make the Instrument
dangerous. Intentional Interruption
Is prohibited.
Componentswhich are importantforthesafetyofthe instrumentmay only
be renewed by oomponents
obtained through yourlocal Philips organlzation (see also chapter 1 0) .
Afterrepairand maintenance in the primary circuit,safety inspectionand tests, as mentioned In chap-
ter
9, have to be performed.
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PM 6303A MAINS VOLTAGE SETTING AND FUSES 2
-1
2 MAINS VOLTAGE SETTING AND FUSES
The safety Instructions In previous chapters must be followed.
Before Inserting the mains plug
Into the mains socket, make sure that the instrumentis set to the local
mains voH:age.
WARNING: If the mains plug has to be adapted to the local sttuation,
such adapUon should be done by a qualified person onty.
On delivery from the factory the Instrument is set to one of the following mains voltages:
Type Coda no. Mains
Delivered
voltage mainscable
PM 6303A 945206303101 220 V Europe, Schuko
PM 6303A
945206303103 120 V North America
PM 6303A
945206303104
240 V England (U.K.)
PM6303A 9452 063 03105
220 V Switzerland
PM 6303A 9452 063 03106
240 V Australia
The set mains vohage and the corresponding fU58 are indicated on the rear panel.
Make surethatonlyfuses ofthe requiredcurrent rating,andofthespecified type,areusedforrenewal.
The use of repaired fuses and/orthe short drcutting of fuse holders are prohibited. The fuseshall be
renewed only by a qualtfied person who Is aware of the hazard Involved.
WARNING: The Instrument shall be disconnected from all vottage
sources when 8 fuse
Is to be replaced or when the
Instrument Is to
be adapted to a different mains vottage.
The Instrument can be
set to the followtng mains voh.ages: 100 V, 120 V, 220 V and 240 V a.c. These
nom inal voltagescan beselected by meansofthe voltage selector, located at the rear panel, adjacent
to
the mainssocket. The fuse is located In a holderat the same place. For mains vohageselection or
replacement of the fuse remove the mains cable and pry
open the compartment with a small
sO'ewdriver (see drawing
).
Select one of the vohage range s, as appropriate, by turning the selector. If necessary, insertthe ad ·
vised fuse (T0.
1A or TO . 2A ) into the fuse holderInstead of the one bulb·ln.
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PM 6303A OPERATING AND MEASUREMENT PRINCIPLE
3 OPERATING AND MEASUREMENT PRINCIPLE,
BLOCK DIAGRAM, Figs. 1 to 5
3.1 DESCRIPTION OF THE BLOCK DIAGRAM, Fig. 3
3-1
The 16 MHz crystal clock generates the basicfrequency for all signals, so the count pulses for the
analog
to digital converter ADe .
The frequency divider generates the 8 MHz clock pulse for the microprocessorand the 1 kHz mea-
surement frequency In 3 reference phases 0·. 90-. or 180· for the phase sensitive rectifier and the
ADC.
The band~pass filter 1 converts the TTL signal Into a 1 kHz sinewave signal.
The test yoltage amplifier amplifies the 1 kHz sinewavs signal to a 2 V open-circuit voltage at the
component connection. In the DC BIAS mode 2 V DC are added to the 1 kHz signal.
The isolating
buffer senses the voltage at the component.
The current to voltage converter converts the current through the component Into a proportional
voltage. The conversion factor (gain) can be switched by 8 factor 10.
For voltage or current measurement the input of the subsequent differential amplifier is switched
over by the voltage / current (VII) selector controlled by the CPU.
In the
programmable amplifier gainfactors x 0.1, x " orx 10areselected by the CPU depending on
the impedance
of the component. For reference measurement the Input is short-circuited.
The 1 kHz band-pass filler 2suppresses hum interlerenceand reducesthe harmoniccontents onthe
1
kHz measurement signal.
The level detector compares theoutput voltage of band-pass filter 2 wtth a presetreference value. If
this value is exceeded, the CPU swHches the programmable ampUllar to a lower galn factor.
The
phase sensitive rectifier generates DC voltages whichareproportional to thatcomponentofthe
measurement voltage being in-phase with the reference voltage.
The analog to dlgl1al convener ADC converts the output Signal of the rectifierInlo a binary number
which can be processed
by the CPU.
The central processing unit CPU with the miaoprooessor controls andmonltoresthe measurement
processaccordingtothekeyboard setting.computatesandstores the measurementvalues andtrans-
fers the result to the display. It also comprises the non-volatile memory forthe keyboard settingsand
the TRIM data .
On unit2 you find thebacklit liquid crystal display LCD wHh 2 backplanes controlled In duplex mode
by the decoder/driver.
Overmore on unit 2 you find the keyboard with Its assigned encoder .
The
power supply generates the required stabilized devoltages +15 V, -15 V, +5 V, and -5 V forthe
circuitries. It also comprises the power-down circuit for the non-volatile memory .
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3-2
OPERATING AND MEASUREMENT PRINCIPLE PM 6303A
3.2 MEASUREMENT PRINCIPLE
The component measurement Is based on the so-called current and vottage technique.The compo-
nent vohage and after that the component current ara measured and converted into binary values.
From these values the CPU calculates the ektdrica! parameters at the component. According to the
front panel parameter selection, etther the dominant component Is automatically displayed
(AUTO) -resistance. capadtance or inductance-or the sektcted parameter Is displayed.
Each measurementcycle lasts approx.0.5
S8oonds . It comprises 5singkl measurements, the results
of which are stored and arithmetically evaluated. Anal!y they are transferred to the display, S98 fig.2.
The 5 single measurements are as follows:
1. Reference measurement.
Althabeginningofeach measurementcycleareferencemeasurement Is performed, withtheoutputof
the programmable amplifiergrounded, caused by low
Signals PAl, PA2 at pins 1, 2 of the micro-pro-
cessor 0315 . The programmable amplifier is setto gain xO . 1. Afteradelaytime of50 msforeach ofthe
single measurements, necessaryforsettlingofthezero contr~ andband-passfltter2,Bmeasurement
without 1kHz signal
Is performed, comprehending all failures within the signal path from multiplexer
0103to the
AJO converter.Thecountercontents oftheAID conversion atthe end ofthis measurement
serves as reference for the subsequent 4 measurements.
2.
O· voltage measurement:
The voltage at the component
is measured.
The switchi
ng phase of the phase sensitive rectifler Is 0· .
For voltage sensing at thecomponentthe Inputs of the differential ampltfter are connected via the VII
selector.multiplexer 0101 ,to themeasurement Input.This is achleved by kM signal VIS from the m~
croprocessor 0315.3.The O· switchingphase is acttvated by low slgnal'sMct 4t', 0315. 14 .Thegain
ofthe progranmatNeampttfierls set to
xO .1.Atter5mssettlingtimeforthe 1kHzsignaltheoutputofthe
level detectorls sensed,OVR 0315.12. tf nooverrange Is detected, thegain Is set to xl; the level de-
tectorlssensed again. tf nowoverrangeis detected,the gain Is set backtoxO.l and an AJO conversion
Is started, 0315.5. For low-ohmic components the maximum gain xl0 Is set and, if no overrange Is
detected, the measurement Is performed.
3.
90· vottage measurement:
The voltage at the component
Is measured.
The switching phase of the phase sensitive rectifler
Is 90· .
The gain of the programmable amplifktr is not shered with respect to the O· v~tage measurement.
An AJO oonverslon is performed.
4. o· current measurement:
The current through the component is measured.
The inputsofthedifferential ampUfMK' are swttchedovertotheouputofthecurrentto vottage converter.
The switching phase of the phase sensitive rectifter Is 0· .
The gain of theprogrammable ampntieris set to x. l and, as forvoltage measurement. Increased to xl
with regard to the level detector. Next, if necessary, the conversion coeffk::ient ofthe IN converter is
increasedfrom xl to xl 0(highat0315. 4) andthe gatn ofthe prog . ampUfler Is Inc::reased to xl 0andevt.
set back to
xl after overrange detection. An AID conversion Is performed.
For low-ohmlc components the sequence Is slightly different:
Iffor vottage measurementthe gain
was setto xl or xl 0, theImpedance Is In any case very low, result-
ing in maximum current to flow. The current measurement Is perfonned at gain xO .l without trial for
gain changing.
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I PM6J03A illlIOmahC
RCl me Ier
B.B.B.B
M<Q
DE G
rp< R
OO M,,, ,o H f. r-it------;
DO I'IIN." T '~
noz+
potol ...... l .~
.. ,
AUTO
0
"""" "YO fllEO
lUI .
Fig. 4 Front view
jX Q
.. 500
0 .. 0.002
.rrn-
" ... "..... IEl ER
OC 81AS
AUTO 0 0 "
~,
D D ID 0 D
"
..
,
D 0 D
epOfl,p c ... L• •
D 0 D
OO "IN A HH~ Q - 0 - 1
- jX
a,. 500
0 .. 0.002
OO M'N A N T .~
0·500
Q .. 0.002
o ., 500
Q _ 0 . 002
OO M I N " N"~
PHILIPS I
TAl lO
D
,.... - .,
. ~
-. .
o @~@r-
O@ ~ @-=.
~
<:l'
Fig. 5 Equivalent-circuit symbol and dominant parameter in the sectors of the pha s or plane ( AUT O mode)
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3-4
OPERATING AND MEASUREMENT PRINCIPLE PM 6303A
The following phasediagramsandformulas show the mathematicbasicsfor Internal calculation ofthe
component value .
Vq -- ---- - -- V
I
I
I V: voltage
I: current
I
I
Vf . V2 : O· -voltage, 90 "-voltage
I
Iq - ------e-- I
<I> I
The phase angle between I and V is <p
The phase angle between I and V1 Is a
a Vp
Ip VI
In the diagram the phase relation between I and V is related to a lossy Inductance.
In each measurement cycle the following components are determined: Vp, Vq, Ip, Iq .
From these components the series resistance and reactance are calculated.
Rs _
Vplp + Vq Iq (1)
Xs.
Ip2+ Iq2
The following is valid:
jX
-c:J---fZZJ---
Rs XS
Quality factor:
0.lon<l> . 1/0_ IXsl (3)
Rs
Dissipation factor: 0 _ tan 6 _ 1/0 '" Rs
IXs I (4)
<I>
Vqlp-Vp Iq
(2)
Ip2+ Iq2
Z
6 xs
Rs R
The magnitude of a and the sign of Xs determine which parameter of the component is dominant.
The formulas for the various parameters are:
0 _ tX
sl see Z -V
R 2 Xs2
- S +
As equation (3 )
D _ 1
o
Rp-(1 +0
2) xRs
Rs
see
equation (1 )
Cp _ -,,--:-:::1'-,;,-,,.,--,-
00(1 + 1/0 2) IXs I
(1 + 1/0
2) IXs I
Lp _ '---'----'-'--'-='-
Cs - -,-7.:;:-;-
rolXsl
IXs I
Ls - - -
00
Impedance
Admittance
00
Z _ R+jX
Y _ lIZ
ifXs < O
ifXs > O
ifXs<O
ifXs > O
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PM 6303A OPERATING
AND MEASUAEMENT PAINCIPLE 3-5
Example:
By means of the 5 measurements the instrument has calculated As and Xs in accordance wtth formu-
las 1 and 2, e.g.:
From this the instrument calculated :
As • 3.037 kll
Xs. -15 .197 kll
0.IXSI.
5.
OO4
As
The instrument displays tne corresponding equivalent-CirCUit symbOl wittl the dominant component,
according to the criteria of the diagram on page 3 -4; In this case, as Xs is negative and 1 < Q < 500 :
Inn,
, LI.LI , n F
DOMINAHT ..C ~
AUTO
FREQ 1kHz
The calculation of the dominant component Cp was done according to the formula :
Cpo
Cpo
1
w(l + l/Q
2
)IXSI
1
.,----,-'---:----:--;;-----.10 .068 nF
2n '1 kHz (1 + 1/5.0042) '15.197 kll
whereby the instrument calculates at a higher resolution. The maximum disp'ay is 4 digits ±1 digit
tolerance .
The calculation 01 the further selectable parameters are pertormed as follows :
D • ..!... • ----L- .0 .199
o 5.004
Ap. (1 +02) 'As . (1 + 5.0042) '3 .037 kll .79 .08 kG
As _ 3.037 kQ (calculated by the instrument ace. to formula 1)
z • ~AS2 +Xs 2 • ~(3 . 037kll)2 +(15.197 kll)2 _15 . 497kll
Cs • .......,,;,-,
w l
XsI
- .10.472 nF
2n·' kHz ·15.197kC
CP : The Instrument calculates
tan CI> _ ~ _ 15.197 kO _ 5,004
As 3.037 kSl
and gets CI> from an I ntemal t~e
4>. -78 .7 DEG
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3-6 OPERATING AND MEASUREMENT PRINCIPLE PM 6303A
Cp
rC-r:J
y -
Rp
1 . C
Rp + Jto P
Z_
Rp (1- Iw CpRp)
1 + (wCpRp )2
jX D _ 1
/WC P
wCpRp
Cs _ (1 + D 2) X Cp
Rs-
D2
xRp
lI Rp
R 1 + 02
Cs
~
Z _ R . 1
S- I--
w CS
Rs
IX Rs R 0 _
wC sR s
~ W~S
Cp _ 1 x Cs Rp _ 1 + 02
Z 1 + 02 D2 X
Rs
Rs
~
Z . As+j w Ls
!.s
jX
D _ ~
/ W!.s
w!.s
Lp _ (1 + D 2) X Cp
Rp _ 1+ 02 X
Rs
As R
D2
Rp
c:vv:t:J
y-
1 1 Z _ Rp (1 + IRp/wLp)
- -j -1 + (RplwLp)2
Lp
Rp wLp
jX
lI Rp R 0 _ w
Lp
Rp
~ l / wlP
!.s _ 1
Rs_
D2
Y
1+0 2x Lp
1 +02 x Rp
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PM 6303A CIRC
UIT DESCRIPTION. FAULT FINDING 4-1
4 CIRCUIT DESCRIPTION, FAULT FINDING, Figs. 6 to 10
4.1 POWER SUPPLY, Fig. 52
Five voltagesaregeneratedbythepowersupply:+15V and-15 V are stabilized by the vo ltageregula-
tors N401. N402,adjusted by potmeters A402. R405.Z-diodes V403, V404 provide+5 V and-5 Vfor
the CMOS switches (muttiplexers) 0101, 0102 , and 0103 , fig. 56 . The +5 V supply for the digital cir-
cuitries is outputted by the voH:age regulator N403 .
When switching power off or when the powersupply fails,the power -dowrr reset circuit resets the mi-
croprocessor 0315 In fig. 58, thus preventing any further data 8 xdl ange until the i ntemal supply volt-
ages are completely down . Furthermore the non-volatile memory , SRAM 0314 in fig. 58, where the
actual keyboard setting and the TRIM data are stored, Is now backed-up by the battery G301 .
When switching off. the PO signal gets low before the 5VD supply disappears; hencelhe resellnput
RST of the microprocessor 0315 gets high. The same happens when pushing the concealed front
panel RESETswhd'l,figs. 59,
60 . When swttchlng on capadtor C309ln fig. 58provides a k)w signal tor
resetti
ng the microprocessor.
4.2 CRYSTAL CLOCK, FREQ. DIVIDER, PHASE SELECTOR; Fig. 58
The accuracy oltha 16MHz dock frequency ts moderate, ± 5 x 10~ . So fixed load capacitancesare
inserted; they nevertheless may be attered in test,
if necess8l)'. The output 01 the os cillator is de--
coupled byInverter 0307 . 0307 .61eeds the 16 MHz count pulses torthe counterintheanalogtodigital
converter
AOe .
The first dividerstage of the 4-bH binarycounter 0306 generatesthe 8 MHz clock pulse tor the micro-
processor. Its last stage feeds 1 MHz to the frequency divider chain. 0301 comprises two 4-bn BCD
counlers,the5:1division
otwhichis used for dividingthetrequency down 1040 kHz .Furtherdivisionby
10 results In a 4 kHzsignal at output 0302 .13,the bads frequency for generation of the 1 kHz signals
with different phase relations, seefig. 6.The trailing (high to low ) edges triggertheJK-fllpUops 0303 ,
0304 .The 1 kHz O· signal Is tedto the band-passfitter 1onfig.56.At output4 of themultiplex er 0305 a
O· or 90" signal Is available,selected (,select ~') by the microprocessor. At output7 a signalshtfted by
90· with relation to pin 4 is available for synchronization of the analog to digital converter.
0302 .13
4 kHz I
303.5 I r
I
303.6 J L
I I
0304 .5
-j
I
1 kHz 0"
I
I I
0304 .6
-..j
I
1 kHz 180" I
I I
0304 .9 I I r
1 kHz 90° I I
-----I2SOi<s_
I
I I
1-
1m.
" I
Fig. 6 Generation of the 1 kHz signals
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4- 2 CIRCUITDESCRIPTION. FAULT FINDING
PM 6303A
4.3 COMPONENT CONNECTION, BUFFER, Fig. 56
Forunderstanding the measurementof various types of components with respect to possible faults in
the instrument and tts accuracy, chapter 3.2 of this service manual Is helpful, in shorter tonn also
printedin the operating manual,chapter 3.6. In generalinfluences by series or parallel impedances In
the input/output connections of the component must be taken into account.
fig. 7 shows the circuitry for the four-wire connection of a pure ohmic component.
For two-wire measurement the component must be connected between +drive and -drive.
Depending on measuring either high-ohmic or low-ohmic components this figure can be Simplified.
The contad resistance at the sockets may Bpprox . be 50 mO .
buffer N110 l
2V
N101
~
curr oto voH.
V / 1
..
differential
test voltage converter selector amplifier
amplifier A107 xl I
xl0
~
N10B
A106
Ir t-
Nl02 , N103
400C 0101
Rl01 R102
100C
lkC
sense + -sense
9 9 :1-9-'-- --' 9line reslslances
component under lest
Fig. 7 Detailed circuitry for four-wire component conneC1ion
The 2 V measurement voltage is fed tothe •+. socket, sensed at the appropriate socket. The current
flows through the componenttothe "
-" socketandthe voltage at the lowendis sensed.The "-" socket
is no measurement earth contact
of the drcultries;the orcutt earth potential at the front plate is only
available at pins 1, 3, 5, 7 of the round connector or at the 4 mm centre connection of the 4-wlre test
cable. These connections must not be used to connect a protective earth conductor.
The
buffer amplifier Nl01 serves torImpedanceconversion from high-ohmicsensing the measure-
ment voltage to furthersignal processing.The signal
is ae coupled (ClOt) in orderto suppress the de
voltage in BIAS mode. .
4.4 CURRENT TO VOLTAGE CONVERTER, Fig. 56
The IIV converter Nll 0convertsthecomponentcurrent into aproporttonal outputvohage. Differential
sensing the current
at the leed-back resistor A104 or Rl0S allows measurement 01 low Impedances
down to 1 mO . Multiplexer0102switches the conversion factor (gain) to x 1orx 10 by selecting feed-
backresistor Al 04 or Al 05 .The tolerance of tha resistors mustbe0.05%, as ItdirectlyInfluences the
measurement accuracy of the instrument.
By separate switching the current path and the vohage
sensing at the resistors the on-resistances of the CMOS switches areeliminated.
Al0S and Z-dlodes
V119 N120 limit the amplitude at input 15 of the switch to ±4 .5 V. Vohages above ±S.O Vwould de-
stroy the swltchl
ArtekManuals => 2013

PM 6303A CIRCUIT DESCRIPTION. FAULT FINDING
4-3
4.5 PROGRAMMABLE AMPLIFIER, BAND-PASS FILTER 2, Fig. 56
In theInvertingamplifierN1 04 feed-back resistors are switched :Multiplexer 01 03 selects R114, R115,
or R116forgainseHingx D. ', x 1. orx 10depending on the Impedanceofthecomponent. Theabsolute
gain accuracy of the amplifieris of no importance; only the accuracy of the gain factors x
10 between
the 3 gain settings are Important; so the resistors mentioned have 0.05 % accuracy.
Capacitors C1121113 / 114 are paralleled to the resistors in order to achieve equal bandwidth and so
equal phase errors for the 3 gain settings.
2-pole switching ofthe feed-back resistors eliminates the on-resistances of the CMOS switch, Via the
lower contacts the high-ohm ic Input of Ie Nl0S senses the vohage at the resistors.
Signals PA 1and PA2 . binary coded from the CPU ,seled the gain at inputs 10 and 9of0103. Forthe
reference measurement within the measurement cycle. the Inputof the band·pass filter
Nl 05is set to
ground. code 00. pins 12 and 13of Dl03connected.Codes 01 to 11 correspond to gains x0.1to x 10 .
The BAND-PASS FILTER 2 suppresses hum interference coupled into the component and reduces
the harmonic contents of the 1 kHz signal. The gain at 1kHz is 0.98.
4.6 LEVEL DETECTOR, Fig. 57
The Level detector comprises comparator N206 and the retriggerable monostable multivibrator,
flipflop 0202. Ifthe positive peak value ofthe measurement signal exceeds
the reference value 2.8 V,
set by R251 ,R252,the comparatorgenerates 1kHz pulses,which triggertheflipflop.R254 and C212
determine the duration of the output pulse to 2 ms ; hence the output 12 Is low, as long as the
comparator detects overrange. The microprocessor detects the overrange Signal OVA and switches
the programmable amplifier to a lower gain, PA 1, PA2 .
4.7 PHASE SENSITIVE RECTIFIER, Fig. 57
The ci rcuit resolvesthecomponentvoltages Into vectors along thetwo reference phasesand converts
them to d.c. voltages.
It is essentially an onloff switch for the component voltage Vm .
WIthout Vm, i .e. during reference measurement,rectangular 1 kHz pulses of about 4.4 V (zero--peak)
are available at the buffer output N202.S.The pulse amplitude and rise and fall times are stat»e for at
least one measurement cycle, achieved by differential switch V2011202 and reference diode V212 .
The phase
of theswitching pulses In relation to the measurement voltage is selectable to O· and go-.
The measurement voltage Vm attheinputoftherectifieris superimposed onthe pulsesonlyduring the
ha" cycle:
N202.6 without Vm
Vm only, e.g. in.phase
N202 .6 with Vm
The maximum portion of Vm Is ± 30 % with respect to the d.c. pulse amplitude, achieved by
Vm -ca. 2 V eft being in-phase or anti-phase related to the switching signal.
ArtekManuals => 2013

4-4 CIRCUIT DESCRIPTION, FAULT FINDING
PM 6303A
4.8 ANALOG TO DIGITAL CONVERTER, ADC, Fig. 57
The outputsignal ofthephasesensitive rectifier isconverted intodigital data by a dual-slope analogto
digitalcoverter.
The ADe comprises Integrator N203, zerocontrol N204,comparatorN205. ADe con-
Irol
0204, 0205 and a 19-bltcounter. The latteris composed by the II -bitcounter 031 0 In fig. 58 and
an
B-bit counter within the microprocessor 0315 . Oscilloscope drawings In fig. 8 show one complete
measurement cycle. fig. 9 enlightens one conversion period wtthin one of the single measurement
cycles.
Highsignal STI oftha microprocessor 0315 .5preparestheconversion attt . The timet2-tl may vary
tromOto 1ms (1 pulseduration). Thestartpulseduration is I . Sms . Thetrailingedgeoftne 1kHzsignal
at 0205 .1 sets the output 5 to high to startthe Integration att2. ST2 switches the zero control off and
connectstheoutputofthephasesensitiverec1ifiervta
CMOS switch0201 to the inputof the integrator.
This is done duringthezero period
01 the measurement pulses. For this the 1 kHz 90- signal Is taken.
The integrator reference current, defined by R221 , R222, is equal for integration (12 to 14) and de-in-
tegration (discharge slope t4 to t5). The difference between input current. defined by measurement
voltagepulsesand resistorR220,and theintegratorreference currenteffectstheoutput vottage ofthe
integrator to go in negative direction. At t2 flipflop
0203 and counter 0204 are aC1ivated. The flipflop
divides the 1 kHz frequency by 2, feeding the down counter which was preset to 10.
At t3, counter
stage 7, high signal MR,
0204 . 6, resets the It-bit counterto zero. Low signal 0204 .7 resets flipflop
0203 ofthecomparatorenabledagain att4. At t4 thecounterstageiszero. Atthe trailing edgeofthe t
kHz signal the output 0204.13 generates a short low pulse resetting 0205 and so terminating the in-
tegration and starting the de-Integration. The integration period T1 _ 20 ms comprises 20 pulses; so
zero- and time--symmetrtcal50HznoiseandIts odd harmonicshavenoinfluenceon themeasurement
result.
When
0205 isreset att4,all 3enableinputs at NANDgate 0309, fig. 58,arehigh;so the 16 MHz count
pulsescan pass tothe
"-bit counter031 O. The carry ofthecountertoggles the8-bltcounterwtthinthe
mocroprocessor, input 15.
At t5 the output voltage ofthe integratorcrosses thezero level causing
the comparator an the flipflop
0203 .9to tum overto low.This signal EOI. 'endofintegration', disables gate 0309 tostopthe 16 MHz
count pulses. The counter state at t5 is proportional tothe integrator output voltage at t4 and conse-
quently to the measurement value. For reference measurement the integrator output is
ca . 5 V att4
resulting in
12. ca . 15ms, corresponding to 240.000count pulses. The maxlmuncounterstate is ca .
475.000 - T2 - 29 .7 ms, the minimum is ca. 5000 _ T2 _ 0.3 ms. So tor the measurement range ca .
±23S .ooo count pulses are available.
As thetilt ofthede-integrationIs independentofthe measurementvalue, the delay time betweenzero
crossing and comparator tum-over and
so the counter state for every single measurement is equal;
hence the dtfference of the counter states is not affected.
The output 0203 .9 ofthe comparatorIs sensed by the CPU. Low signal EOI at tS causes the CPU to
storethe 19-bltcountercontents into the memory.
The CPU sends a reset pulse RST at IS preparing
the
circuitrytorthe nextsinglemeasurement cyde :thezero controlisactivateddecreasing the integra-
tor output voltageto zero. In the rest position the zero control has to compensate theintegrator refe r-
ence current.
ArtekManuals => 2013