The document discusses the design of a practical ESR meter circuit that measures the equivalent series resistance of electrolytic capacitors. It begins by providing background on ESR and its importance in determining capacitor quality. The circuit uses an operational amplifier configured as an oscillator, amplifier, and comparator to measure capacitor ESR. The document provides details on the op-amp design and precision inverting amplifier circuit to explain how the ESR meter works and measures capacitor ESR without regard for other circuit components.

1. lot has appearedin recent issueso n the subject
of the ESR (equivalent series resistance) of an
electrolytic capacitor. The Capacitor Wizard
was reviewed by Martin Pickering in June 1998. It's
designed to measure a capacitor's ESR in-circuit while
'
ignoring any components that are connected to it. The.
unit described'in this. artible performs the same task, ..
and a lot of work has been put into achieving the end '
result. Even if you don't get around to building the
meter, this article will give you insight into the design
criteria and the way in which the instrument works. But
build it if you can: it's effective, very useful and inex-pensive.
ESR : . , '
' In view of Martin's review and also the articles by Ray
Porter on a capacitor's ESR (January and April 1993) I
won't say a lot about ESR here: it would simply be rep-etition.
To put it in a nutshell, a capacitor's measured
ESR (in ohms) is an indicationo f its 'goodness'.T he
Iower the ohms reading, the better the capacitor. An
ESR check can give an early indication ofcapacitor fail-ure,
and is far more useful than a capacitancem easure-ment.
Indeed many faulty electrolytics show OK when
checkedw ith a conventionalc apacitancem eter.
In recent months I've talked to many people who
don't appreciatet he importanceo f ESR and in what
senseit differsf rom capacitanceS.o I feel it worthwhile
including an extract from a technical bulletin on the
CapacitorW izard writtenb y Doug Jones,t he President
of IndependencEe lectronicsI nc. It sumsu p the ques-tion
of ESR well.
"ESR is the dynamicp urer esistanceo f a capacitort o
an AC signal.H igh ESRc anc auset ime-constanpt rob-lems,
c apacitorh eatingc, ircuit loading,t otal failuree tc.
A switch-modep owers upplym ay not startr eliably- or
start at all. Slight hum bars appear in the video of a
The subiecl of qn
elecfrolytic copocitor's ESR
hos generqted <r lot of
interesf in recent issues.
Alon Witlcox hos tqken it o
stoge further in designing
o procticol ESR meler. This
firsf porf deols wirh the
operotion of fhe circuitry
used in fhe meter .
Design.' ,uohf ''EM$ 6tBr
VCR ot monitor. A TV display may be pulled in from
the sideVtop/bottom. Diode and transistor failure can
occur over a period of time.
These and many other problems are often caused by
capacitors , with normal capacit'nce but high ESR,
which does not exist as a static quantity and therefore
cannot be measured using a conventional capacitance
meter or a:DC ohmmeter. ESR exists onlv when alter-nating
current is applied to a cdpacitorbr when a capac-itor's
dielebtric charge is changing state. It can be con-sidereda
s the total in-phaseA C resistanceo fa capaci-tor,
and includest he DC resistanceo f the leads,t he DC
resistanceo fthe connCctiont o the dielectric,t he capac-itor
plate resistancea nd the in-phaseA C resistanc-oef
the dielectric'material at a panitular frequency (my
italics) and temperature. ,' , ' r
The componentc ombinationt hat constitutesE SR can
be thought ofds a resistor in series with a capacitor: the
resistor does not exist as a physical entity, so a direct
measuremenatc rosst he,'ESRr esistor,i s not possible.
If, however, a method of correcting for the elfects of
capacitive reactance is provided, aid considering that
all resistancesa re in phase,t he ESR can be calculated
and measured using the basic electronics formula E = I
x R! This is the basis of the design of the Capacitor
Wizard."
Design Criterio
Capacitorm anufacturerqsu oteE SRv aluesm easureda t
l00kHz. So this is the test frequency I chose. The
impedanceo f inductorsi n the microhenriesre gionc an
be measureda t this frequency,e nabljngt he c-ondition
of video heads to be gauged --as they w6ar and the gap
deterioratest,h eir inductancefa lls.
The Wizard has a buzzer that sounds when the ESR
is below lCl or so. A capacitor with an ESR of less
than about lC) is generallyc onsideredto be good, so
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r 1 6 March 1999 TELEVISION

2. - " = ; ; - ; r ; 9 , ; : ,
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this is a very useful feature in situations where you
waht to cheik a number of suspect components,. it
means that you need refer to the meter ohly when
there's no beep. I've incorporated this facility, b'ut you'
must bear in mind that a lot of the capacitors in which
we'ire interested have ESR values of less than 0.5C)
when good. More on this later.
I'd like to stress this basic point before going any fur-then
as with the Capacitor Wizard, the meter described
in this article doein't measure a capacitor's micro-farads.
It simply lets you know if the capacitor is or
isn't up to the job. After gaining some practical experi-ence
with the meter, you will soon get to know"what
reading to expect from a good capacitor - taking into
accounti ts capacitancea nd voltage rating. But in'any
case the reading obtained with a faulty capacitor usual-lf
lea1e1 little doubt as to its condition.
The Op-Amp
The circuit'uses the basic opamp as an oscillator,
amplifier;' dslsctor, voltage-follower and .'comparator.
So'it's appropriateto devotes omes pacet o a description'
of the op-amp and its associated circuitry. Incidentally
the term'opcrational amplifier' relates to its use in ana-logue
computers and appeared in a paper by Ragaziuini
and others in 1947.T he first general-purposeo p-amp,
with.differential inputs and using the familiar triangular
symbol 'for circuit rcprcsentation, was :introduced;in.
1952 r 6Model K2-W, by'.George A. ' Philbrook
Re.searcheIsn c.). It's sobering to think that almost forty
years ago an early op-amp, the P2, cost $227 - an eighth'
of the cost of a VW Beetle at that time: now a superior
device can tie bought for less than a pound.
The op-amp is a high-gain (x100,000 or so) amplifi-er
that usually has two 'inputs, on-e non-inverting
Qabelled +) and the other inverting (labelled !). For
practical'purposes.the gain.rcan be considered as
infinitely high, with no cuirent flow at the inputs. The
opamp'isr,designed primarily to' operate stably'with
hcarlr- nefative. feedback' In 'fact from 'the' hisfelisal:;
poiriio"f:vlcw:de opamp andithe concept of negative'
feddb4k(the, invention :of fi,S.'r Blach-'workingrforr'
Bell_'[5t*iratories, in 1927) are synon5rmousB. lack'
wa5''w6ikihg'on telephones,t' is bu;ective biing to:.
achieve'stable gain independent of the characteristics':
of a valve (a thennionically-activated FET to youpg-sterSl).
When he tried to patent his negative-feedback
amplifier in 1928-the idea:was ridiculed. Over the
years however this concept has become one of the
most important in the field of electronics. Marconi had
much the same problem. It seems that people often dis-miss
things they don't understand.
' 'Anyway,
I digress. To get back to the point, the op-amp
usually:requiresa positivea nd a negatives upply
with respectt o a common earth. These.suppliesa re
often noi shown on circuit diagrams, being taken for
granted. Thq common earth (0V line) serves as a refer-eirce
point for the voltages that are present in the cir-cuit
and as a'return path to the power supply for any
currents generated by the device's operation.
The main point here is that if the voltage at the + input
increasesw ith respectt o the voltage at the - input, the
output voltage will be positive-going.C o,nverselyif the
voliage at the + input decreasews ith respectt o the volt-hge
at the 1 input the output voltage will be negative-going.
T hus in normal practicet he outputc orrespondsto
the difference between the inputs.
If the op-amp doesn't have any negative feedback
and the + input is at only 0'lmV above the - input, the
output voltage will be close to that of the positive sup-ply
rail. If the + input is lower than the - input by the
same amount, the output voltage will be close to that of
the negitive supply rail. Thus the gain is equal to the
average slope, which is typically l0V/0'1mV =
100,Q00.T his very sensitive property is used in com-parat<
ir circuits (it's'used in the ESR meter's buzzei
circuit). But the op-amp is far more useful when.the
output is restricted to narrower limits.
The Precision Inverting Amplifier
This is one cif the'riiost common opimpapplications
and is used in the second and third stages of the meter.
Circuit operation will hopefully be made clear by the
rather unusudl representation (due to Tom Hornack)
shown in Fig. l.
At (a) the op-amp is arranged to provide a voltage
gain of two. The fact that in this case the output is
inverted (the gain'is.minus two) is not important. The
heavy negative.feedback,viaresistoRr f forces the out-put
to be such that the voltage at the - input is equal to
that at the + input rjvhich is'oV. Remember that the op-
::a mp respondst'd the"d ifrerenceb etween its' inputs. As
;,point X is at earth'potential, there is "lV across Rin'
',O(lkh0m) 's .and,ther,cirrrdnt flow via Rin, calculated by
Law;.iS lmA. jTherc is no current flow at the
input of the op-amii So this lmA flows via Rf (2k0)
whiih thus has 2V'across it.
Notice how Rf and Rin behave like a seesaw as the
input goes from a positive to a negative value, with the
piVot at the null point X. This point is referred to as a
virtual earth. There is no current path between point X
and earth, and point X is always at zero voltage with
respect to earth.
The concept of a virtual earth is used as a short-cut
(ol {bt DSUd
Fig. 1: Precision inverting op-amp circuit, ia) witn a positive input, (b) with a negative input. Note how Rf
and Rin behave like a seesaw as the input goes from positive to negative, with the pivot at the null (virtual
earthl point X. The gain of the stage is RflRin, so the output is Vin x Rfl&in.
TELEVISIONM arch 1999 317

3. ESR METER
Fig.2: Jim Williams'original circuit, the firct
attempt at combining an op-amp with a Wien
bridge network to form an oscillator.
656t1
Fig. 3: An op-amp Wien bridge oscillator arrange-ment
with the output set at 6V p-p (positive peak
shownl. At the resonant frequency points a, b and c
are in phase and the waveforms at the op-amp's
inpuF are a third of that at its outpttt. The ratio
BflRin = 2.
when the operation of a current-to-voltage converter
is analysed. From Fig. I you can see that, because of
the virtual earth, Rf appears to be in parallel with RL.
So the voltage across Rf appears across the load as the
output voltage. But although the null point is cortsid-ered
to be at earth potential, at a microvolt level it's
very much active.
It can be seen from Fig. I that the stage gain, within
the limitations of trhe supply, is determined by the
ratio of Rf to Rin. Incidentally there's a frequency
limit on the gain: with common types of op-amp we
are limited to a gain of about x10 at 100kHz. If the
resistors in Fig. I are transposed the stage gain will be
0.5 - the circuit acts as an attenuator.
Overview
Before we go further, it would be as well to provide a
quick introductiont o the meter circuit presentedh ere
(see Fig. 5). The first stage consists ofa l00kHz oscil-lator,
whose output is fed to the capacitor being test-ed.
Put simply, the current flow through the capacitor
is sensed then amplified as a voltage. It's finally
detecteda nd measuredb y the meterm ovement.
The better the capacitor, the lower its ESR and the
higher the meter indication. It's not quite this simple,
becauset he meter must ignore the other components
connectedto the capacitorb eing tested.W e'll come to
the solution to this problem later.
The Oscillqtor - History
At the heart of the meter there's a Wien bridge net-work
oscillator. This form of oscillator has an inter-esting
history which is worth a few paragraphs.
In 1939 William Redington Hewlett (co-founder of
Hewlett-Packardp) roducedh is Stanfordt hesisA New
TypeR esistanceC apacityO scillator.It madeu seo f a
resonantR C networkt hat had beenc onceivedb y Max
Wien (pronounced Vene) in 1891. The American
inventor Lee DeForest (yes, we can blame him) had-n't
started the ball rolling yet with the creation, in
I 906, of the triode valve. So there had in I 89 I been no
means of obtaining electronic amplification and Max
couldn't have got his network to oscillate. That
wouldn't hav'e troubled him, as he was using the net-work
for AC bridge measurementA. mazing what peo-ple
got up to over 100 years ago, isn't it? I think it
was, once again, something to do with telephones.
But Hewlett had the pentode valve at his disposal.
He also had Harold S. Black's pioneering work on
negative feedback to assist him. In addition there was
Nyquist's Regenerative;Theory, which described the
conditions necessary for. oscillation.
Hewlett showed that the Wien network could be
made to oscillater A crucial problem had to be
resolved however, that of stage glin. With a gain of
less than unity there would be no oscillation. With a
gain of greater than unity there would be distortion.
With unity gain there,will be what Hewlett wanted, a
,'wsianse wave. He had a flash'of inspiration; the solution
literally staring him in the fate - the electric light
bulb. :
Hewlett's oscillator.was a two-valve affair, with a
6J7 as the oscillator and a 6F6 as the output stage. His
solution for gain stability was to wire a tungsten bulb
between the cathode of the 6J7 and earth. The nega-tive
feedback was applied between the anode of the
output valve back to the cathode of the triode oscilla-tor
valve. If the output increases for any reason, so
does the current flowing through the bulb. As it
warrns up, its resistancei ncreasesS. o doest he level of
negative feedback, thereby stabilising the oscillator's
output. Hewlett's idea of employing a light bulb was
brilliant in its simplicity. It survived in the Hp200
series audio oscillator during a fifty-year production
run - into the mid Eighties.
About fifty years after Hewlett built his oscillator
Jim Williams, who was working for Linear
Technology Corporation, was sitting in his den one
rainy Sunday trying to think of something to do. His
old HP200 caught his eye. Peering into the back, he
saw the light bulb where it had been placed half a cen-tury
ago, and wondered how Hewlett's oscillator
would perform using a modern op-amp. He went on to
knock one up - the original circuit is shown in Fig. 2
- and was pleased to find that it had a distortion fig-ure
of only 0.0025 pei cent.
Perhaps he could improve on it, by eliminating the
bulb? Jim was the first to use a JFET in place of the
bulb, but with this device the distortion figure rose to
a massive 0.15 per cent. Unfortunately there's not
space to explain why the use of a JFET gives such
inferior results compared to a bulb. In the event Jim
discarded the JFET in favour of an optically-driven
CdS photocell. This, in conjunction with five op-amps
etc., produceda n analyser-limitedd istortionf igure of
0'0003 per cent (three parts per million). At one point
during his quest Jim writes (Analogue Circuit Design,
Butterworth-Heinemann) "I could almost hear
Hewlett's little light bulb, which worked so well,
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4. 'i{ii;r-."
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laughinga t me". So no apologiesf or the useo f a light
bulb'in this design-
Operotion of the Oscillofor
Fig. 3 shows the Wien,bridge netwoik oscillator as
you probably won't have seen it drawn before. It.illus-trates
the situation at the peak of the positive-going
half cycle. The positive feedback network consists of
the series-paralleRl C (lead;lag) network: the negative
feedback loop consists of the preset Rf and'bulb Rin.
We'll consider the RC network first. At very high
frequencies the shunt capacitor in the lower arm of the
bridge will appear to be a short-circuit and there will
be no signal at the op-amp's + input. At very low fre-quencies
the series capacitor will appear to be open-circuit
and again there will be no input from the feed-back
network. At some point in between there will be
maximum output from the network. The frequency at
which this occurs is equal to ll(2nRC), which is called
the resonant frequency (fr) of the bridge network. At
' this point there is no phase shift across the bridge, and
the upper arm of the network has twice the impedance
of the lower arm, giving a transmission lgss of 1/3. To
overcome this loss and achieve the required stage gain
of unity, the closed-loop voltage gain (ACL), which is
set by thc ratio of Rf to Rin, must be three. The for-mula
for the closed-loop gain of a non-inverting
amplifieris ACL = M/Rin + 1, so Rf/Rin must be two
in order for ACL to equal three. , ....
At power up the negative feedback is low, because
the bulb is at its lowest resistance, and.the gain is
high. As,a rcsult oscillation begins immediately, aud
' the bulb is warmed by the current current flow. Within
a fraction of a second the resultant increase in its
resistance reduces the oscillator's output. It settles at
the level at which the bulb's resistance is half that of
the feedback resistor Rf. So the value.of Rf sets the
amplitude,of ,the"output.,Notet hat the bulb's thermal
delay means that it cannot follow oscillations at rela-tively
high frequencies. It.responds to the RMS.cur-
. rent,gnly, and phus lehavps,F a.n ordinary resistor. . i ;g
y. " { " '
- - b r ' . , i ] ; , t . r , f + ' i , . ' . . + , j r , ' , j : .
The Bulb ,: ' .:'.
. Although the Wien bridge oscillator is the accepted
statrdard'at frequencies up to say lMHz, the use of a
bulb for gain control, popular in the USA, has never
found favour on this side of the Atlantic. I think I.
know thc rcason for this., In most textbooks things
begin to get a bit vague iwhen it comes to the actual
type of light bulb to use.
It is often said that any low-yoltage, low-current
bulb can be used. This is not so. I have seen the fol-lowing
flawed reasoning in some books. Take a l2V,
50mA bulb-which has a resistance of l2Vl50mA =
240Q. The feedback resistor must be twice this, i.e.
480Q or a lk() preset. There's nothing wrong with
this value for the feedback resistor, but it won't work
with such a bulb. The point that's been missed is this:
the bulb must be operated at a current level that gives
a large change of resistance.
This occurs when the current is only a few mil-.
liamperes,a nd nowheren earb ulb incandescenceW. hat
we requirei s a bulb that hasa resistanceo f about 200f1
when cold. When the type of bulb normally specified is
used, the result is overloading of the op-amp, distor-tion,
heavyc urrentd rain and dependenceo n the supply
voltage for regulation rather than correct bulb opera-tion.
I didn't do what Hewlett did, which was to plot the
1/ characteristicos f variousb ulbs carefully. I simply
TELEVISIONM arch 1999
Fig. 1: Pr*ision rectifier circuit, (al with positive input, bl with negative
input. In (aJ the op-amp's orrtPttt goas as low as required to overcome the
forward voltage drop acrosli D'| and still satisfy Ohm's law as far as Bf and
R|n are concerned. D2.is off as the voltage at its anode is 2'6V le*s than
that at iE cathode. In (b) D.l is off, its cathode voftage being 0'6V higher
than its anode voltage. The conduction of D2 limits the positive o,ftptlt 8t
0.6V. This limiting factor speeds up the recovery of the op'amp when the
input goes positive again.
I ; : ' r . ; l ; : : i . . ' '
measured the resistauce of pulbs that I thought might
be'iuitable, and found that the cold resistance of a
28Y,24r.A hulb is l70Q-. fitis soemed to be about
right. When I tried it -,bingo! So when, in this con-nection,
you see "any low-voltage, 50mA or so bulb"
you can in future read "a28Y,24mA bulb". The oscil-lator,
will work a treat.
The Prbcision Rectifier
The final stage of the basic meteruses an op-amp as a
precision rectifier..Keeping to the type ofrepresenta-tion
we've used before, Fig. 4 shows its method of
operation.
With a conventional rectifier there's the drawback
that the signal must rise above the diode's forward-voltage
drop before conduction begins. This can be
overcome by the use of an op-amp in the circuit. At (a)
in Fig. 4 the input is positive and the output reduces
the voltage at the cathode of Dl. This enables the
input to carry on via Rf to the amplifier's output. As
in the case of the inverting amplifier circuit, the out-put
is again Vin x Rf/Rin. The diode's forward volt-age
drop, which is 0.6V with a silicon diode, is over-come
becauseth e op-amp'so utputg oesl ower by this
amount, satisfying Ohm's law as far as Rf and Rin are
concerned.
Point X is still held at earth potential by feedback
action from the output. D2 is off at this time, as the
voltage at its anode is lower than that at its cathode.
When the input goes negative however, as shown at
Yflt - 0v
D5UO
Vioa -lY
3 1 9

5. ESR MbTER
Fig. 5: The basic meter circuit. VBI sets the oscillator's output level. Pin 8 of tCl and tC2 is connected to the +ve suppty, pin
1 to the -ve supply.
(b), the op-amp's output rises to the point at, which
D2 conducts. The current then flows via Rin, point X
andD2. DI is now off and the output ib zero.-
Bosic Meter Gircuit
The circuit of the meter itself is shown in Fig. 5. The
Wien bridge oscillator, redrawn, is the same except
for the inclusion of a lf,l resistor (R3) between the
bulb and the 0V line. Depending,on VRI's setting, the
bulb's current ii typically 3.5m4 RMS.'As a resriit, in
the absence of a capacitor under test about lOmV
peak-to-peak at lOOkHz is developed across R3. " ' '
VRI sets the amplitude of the oscillator's ouq)ut. In
this case the butput is used only for feedback,ind is
set at 5V feak+o-peak; There is nothing magical
about this figure, and with this application no test
equipment is required to set it. It's just that'to get a
higher level output you would have to use a higher
supply voltage. In fact however the higher thb output
voltage the better.'
The ESR of the'capacitor being tested forms part of
-
a potential divider with thez.lQ resistor R4. The volt-age
waveform across this resistor, as a result of the
current in the capacitor, is amplified by the rest of the
meter circuit. Bear in mind thit with the range of ESR
values we are measuring an ideal mid-scale figure
would be about 3Q. With low. ESR'value'C (good
capacitor) the signal across R4 is high, while with a
poor capacitor it wlll be low - often, in relation to
2.7d2, there can be an effective open-circuit.
Now if, for example, the ESR is 2.7Q, half the
source voltagri across R3 would be passed to the meter
and a half-scale reading would be expected. It doesn't
quite work out like. this however, because the source
voltage is not independent of the lohd, and we will be
setting full-scale deflection with R3 and R4 in paral-lel
(test leads shorted).
If the ESR tends to go below the value of R4, it
becomes more effective in increasing the voltage
across R4. As the ESR rises above the value of R4, it
becomes less effective at incrEasing the voltage across
R4. Hence the non-linear scale, which is ideal with
this application. R3 and R4 are of necessity low in
value, because they compare with the values of ESR
in which we are interested..The bonus here is that
becauseo f their low valuest hi effect of associatedin -
circuit componentsb ecomesi nsignificant.
The design of this littlernetwork is such that the
waveforms across R3 and R4,are virtually in-phase
regardless ofthe value ofthe test capacitor. So we are
measuring the total in-phase AC resistance to which
Doug Jones refers (see quotation earlier).
You might wonder why the test.signal amflitude is
so small. It isn't because rfe warit tg avoid turning on
semiconductor devices - we could go up to a'coiple
of hundred millivolts before there'would- be:any wor-ries
about thit, It's'similly'i"mattef .bf power con-r
sumption. Even our tittle iOmV requires 3.5mA, irnd
in this case I have (dare I claim cleverly?) used a cur-rent
source thdt's already there. A l00mV test source
would require a hefty 35mA, quirc a drain on
resources. If anything the value of the lQ resistor
could be even lower, so that with respoect to2.7Qit
would more closely approximate a constant-voltage
source.
You may think that to test an electrolytic capacitor
effectively a fair old currentishould be pumped
through it. Not so. A healthy l,Q00trrF capacitor will
still present 0.05C1 or so to a couple of millivolts and
thus be produce a reading. :1 ': '
The signal across R4 passes through two stages of
amplification each with a gain of ten, and is then
detected for the meter movement. There is furtheri
amplification in the detector stage. The output iS inte-gated
by C4 to produce a DC output of about l.3V
with the test leads shorted - this corresponds to zero
E S R . , i : . . r : '
The basic meter circuit uses two dual op-amps. you'
will see that the signal path from the oscillatoi in ICI
passesto IC2 then back again.f hil is donet o prevent
the first, sensitive stage of amplification picking up a
strong oscillator signal in the same package.
The Power Supply
There is no need for a regulateds upply, becauseth e
bulb stabilisesth e oscillatora nd the implification fac-tor
of the op-amps is fixed by the ratio of the feedback
and input resistors.
_Thep ower supplya rrangemenut sedi s showni n Fig.
6. IC3a generates split rails from a single supply line.
The voltage at its output pin 7 is at half thC iupply
voltage,b ecauset he voltage ar its - input (pin 6) is
equal'to the half-voltage level set by R[2 and Rl3 at
its + input- (pin 5). This way of using an op-amp is'
known as the voltage-follower.T here is total negaiive
feedbacka, nd the c-losed-loogpa in is unity.
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320 March 1999 TELEVISION
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Fig. 6: The..iplit-rail generator and buzzer comPdrator circuits'
i ? t
ESR METER
-
The meter's total current requirement is only some
l0mA,.plus a ,couple of mA for the on indicator D6-
Two PF3 batteries in..series are ideal. Long life is
assured -. if the oscillator's output is, set-as described .
later, the meterls accuracy will be maintained until the
supply drops to-about 5V per battery.
ti tfrl fnt Uetween the batteries was connected to the ,
0V rail this split-rail arrangement would be unneces-.
sary. -an
It's included to enable a DC adaptor to be used
as
alternative power source. An adaptor with an
output from,I2V to 30V can be used. A regulated type
is best, as ripple on the supply c.puld cause problems.
i , , ' ' l i t '
The Buzzer
lC3b serves as a comparator forbuzzer operation. The
output froin the meter rectifier circuit, across C4, is
appiiea to the + input (pin 3) for comparison with the
vbitage,at the - input (pin.2). If the voltage 1t pin 3
e*""Jdi that at pin 2; ttre output at pin I goes high (see
comparator ciriuit.description earlier) and the buzzer
soun-dsA. bout lV is developed acrosst he series-con-inecied
diodes.D3 and D4.rWhen the ESR value of the
capacitor being tested is about lO or less, the yoltage
acioss C4 rises above this lV reference.
Next Month
In Part2 nextm ontfw, e will dealw ith construction,
'asdedttiitni-so unD . use and inductance measurement,a nd in
brovide a bit more information on ESR. A
detailed cbmponents list will be included.
TELEVISIONM arch 1999
321

7. .7t Suitable
'ier scale, ,relpro-ced
full size.
I n pu.t I lqt month the design criteria were spccified
I and a full description of the operation of the circuit
f was provided. The meter i3 simple to build and the
effort rcqufuedis well worthwhile. , : :::.:
Construction
Fig. 8 shows the board layout. For convenience,'0.lin.
matrix stripboard is used. The most common problem
qo.l9.".Tsi-lr 9 print cuts. If these are made by rwisting a
d.itl lit by hanp, as I do, instead of usingthe correct
tool, it's all too easy for the cut to be incoirplete orfor
some of the print to spread over qo an adjacent track.
If a double-pole on/off switch is used, ihis is a cbnve-nient
point for the connection of an on/off indicator. A
flashing LED with a l0kQ series resistor does the job
we-ll: althoughit takes only a couple of mA, the flashing
light does catch your eye.
It is best to use screened cable for the test leads, in
order to avoid pick-up of unwanted radiation from any
In fhis second pqrt Alon
Willcox deqls, wirh construc-fion
ond setting up of rhe
meter, upgrcides qnd use,
ond provides oddirionol
bockground informotion 'bler
workirg.TV line output stage in the vicinity. Rather than
use plugs and sockets, solder the test leads to the ICB:
we are often concemed wittr RSR values of less than
0.1O, and it doesn't take long for a plug-and-socket
connectiont o deterioratea nd producer esistance.values
greater than this. The length ofthe leads is not at all crit-ical.
I use a 24in. length of screened audio lead termi-nated
by two 8in. lengths of flexible wire.
On- a cold, frosty morning, before the workshop has
reached its normal comfortable, cosy (?) temperature,
$9 leter's readings may increase,slightly. Alttrougtr
this_increase may amount to the equivaleniof less thin
0JO, the fact that accurate low-rciistance readings are
often required justifies the use of an off-the-board set-zero
control rather than a preset type as used in the
Wizard ESR meter.
This control also comes in handy if you want to
squeeze the last ounce out of the batteries, but the
buzzerc an't be relied on when the batteriesp roducel ess
than 5V T9 th" output from the oscillator begins to fall.
Also useful in this respectis the ability to alte; the point-er
position easily at maximum output, to be able to
observe the operation of the bulb and the correct func-tioning
of the oscillator. This is covered in the set-up
notes later.
Probe clips were used for the all-important probes. The
hooks were cut off, the internal springs were removed,
then the plastic was cut back to expose more of the
probes. They have proved to be ideal in practice, and are
small enough to often be able to get under the capacitor
on the component side of the PCB. The probes are not
polarity conscious, and it doesn't matter which connec-tion
is used for the screen ofthe test lead.
The suggestedb oards ize (3 x 2in.) is slightly larger
7 5 4 3 2 I .5
ESR al 1OO kHz
426
April 1999 TELEVISION

8. ESR METER
-
. . r . : : i i . i + r , . . . .
_:{:f '
than it needs to be to.dccdmmodate the components.
There arc two reasons ifor this: First, so that it will slot
into the case that was selected, and secondly to allow
space for future upgrades. With this in mind the set-zero
control is offset to the right, allowing space for a modu-lar
preset shaft.
The batteries are securcd with self-adhesive Velcro.
It's a simple solution, and the Vrlcro will transfer sev-eral
times.
witli theWizard this meterdoes not dif-feientidte
between a $hort4ircuit capac.
itor and a really good one (with an ESR :
arc-und 0.050). Now although we all
kiiow ' that a short+ircuit electrolytic
capacitor is quite rare, it ciio'occur and
has caught me and others out. Allot of
time can be wasted when it occurs and is
missed. So I've been testing an addition
that gives an audible indication when a
short-circuit is present. A further refine-ment
is an auto power-off facility.
I've not included these extras at pre-sent
because I feel it best to present as
simple and economic a pdect as possi-ble
initially. But space has been left for
these additions.
Gomponenl Sources
I obtained most of the pans used in the
prototype from Maplin Electronics and
have included this company's part num-bers
in the componentsli st. The buzzer
and meter movement were obtained
from CPC. For correct operation of the
oscillator it's vital that Cl and C2 are
good-quality polystyrene capacitors.
TELEVISIOANp r i l 1999
: . ' . , .
Apart from the bulb, the sp&ifrcation 6f ttre other com-ponents
is not critical.
The Mefer Scole
The geometry of the meterls scale (see'Fig. 7) is dictar
ed by the relative values of R3 and R4. If the value of
R4 was'inbreased to say 10O, this would be the mid-scale
reading and R3, being low in comparison, would
hav,e less effecl Say a capacitorwith -aerESR iriil!
of l0O is
connected. Half the signal ai.ross R3
.be passed on,
andrtittb'6f ,its curreni will,be' diverteidt6,.reduce R3's
voltage;.rvhich is the result of i6i ibtii.Ent . ' l * i r * , - . through ' . the
. .1 . . ! , . . . i r . . ;
" ' :
X - lrocl cut!
Fig.8: Meiel.
circuit layovt
on stipboard.
Board size is 3
x 2in. lo allow
for upgrudes.
See jex].
continued on Page 436
. 4,27
:
',nl
ffi
lnlernal view oJ ihe meter.

9. ESR METER
continued from page 427
bulb' A mid-scale reading of this order may be more Leave the set-zero control at minimum appropriatef or testing and observe surface-mountede lectrolytic the-operationo f the bulb uy ttit.ting capacitors,w hich seem on with to the have higher ESR va.luei. qrgbei shorted together. vou *iir have no data on see this the pointer type of ! capacitor at the time of deflectrrlcrrtrren"lil;;ir";;;ui"iy.;".pdownrothe
writing however. stabilised"position.
Anyway, the value of R4 used here,2'7{1, doesa ffect Once the oscillator's output has the sourcev ciltaget beens et, o adjust an extent vR2 that has to be consid- for full-scale oenectionw -iirri ;;;.;;, ered.T he currentt hat shortedt ogeth- -flows through the bulb is con- er. ninaity, centret he controlk trolled_ nob. by the setting of VRl. R3, being only le, does
not af-fect$ e operationo f the oscillatoi. Using the Meter
scale calibration with an 0-100 dial ideally follows nxperi-encew ith the meter provides the rule the bestg uide as to wh;t ESR value to "ip""t oi ;;;; capaciror. Some
Read=in( Rg3 +R 4v(R+R 34 + E SRx r)0 0. ffiT*iJ,iff:il#t,::tiT'l#Y"""",T#"J,".TTi';
Inp ractitchees ignabre comse9rs o ray th ighE SRva r- ;#i%:!E:X'r?l3lY"'[119,1*ft,:"d:d#ti":il"#
uest hat somen on-linearityin the cjrcuitis apparent, electrolyticc apacitor_.otf0 the resultb 0pF einga oi-over -slightd value, lparnrre you from this rbrmura. a Becausoef readingc lose this,to i t's this and bettert o usee itherf ixed resistors below0 itgtJ^"Id cerrainly .5h.
to calibrateth e scaleo r copyF ig. 7. If a standard9 0' There * ,orn" moYemenotf exceptionsh owever.a differents I ,ll iif mention is usedi,t is easye nough trremt rerea s they toreduce.olenlargb-thqscalebyphotocopyinE. cani uur" "ooruri;;. A^irih*;lsR- valuei s to be eipectedy rth ltF, ligh-vorh;;ei;-
letrlnSU n .::'',-
The first consideratioins .t he oscillator's-outpulet vel. rtutt-up" o.pon"ni. n"iog pc with the 6p"raiJin specifiedl a amp, the context, oscillatorw il its wbrk down Fsi iJil;ilp"rr-r to JV peak-to-qeakB an e-xamplae ut new4 beari 50v.rype n mind that the oscilla- "tlt ;*;;;Uuce 4t a tor's readingo outputs etringi f theb s rdero not importantg f:30f,I ilryt{ At the deflectionissimplyadjustedby-vR2.w.i tt_ruh-.-tshceallee s, toletnaiqd esq:royi rq grhire;;.qonrtgnert.9r iua.oE "e*tir:nppr"pri,ooJo.buprr.,adingof0.le
sho{9!together'I,owsetting]ofthebircilIator:soutput<iireisiisau}f--:-:.i---:'.l1tr+-.lI
providesa longer battery-life,'iiedugintgh e livel it Table l, from whicht Dubilier,p rwides he bulb ceasest9 a functiona usefulg uide, l.1 in qery[tor. tests ignalc anh oweverb e so low at highEsR values Stre addition,i r ytu ar" unsurew hat readingto expecitt ,s "ury "nougtiio thata *ut"'u ccuracsyu "o-f*iro" ffersI.practicea *iiri",i-iili;; n no scillatoro utputo about5 V peak-to-peaisk -
f rr9- yoor?"il-stockedl uy-J"r""t oiyti"r. a goodc om-promise.
The-meterh as good rf an oscilloscopies protectiona gainstp not availablet,lacingt he h e followings im- probe, u"ros ple u .f,.g"d methodc .upu"it-, anb eu But sed.this C onnect shouldo a 1o f resistorb eiw""n "ourr" u" uuoia"a.thet r fr" estI onryi eadsa eui ndt Juut" urn thes for ^uie",concernis jiiig;:
et-zeroco ntrolV R2 (shown . the. 'mains mootfrinbgl ock,,i .". u *an,
incorrectlya s a preseti ri ric, .s*f as1-,g -.tql wise.A dvancbth es cttingo f wil slowly. [ti"r*t: "i;t il*]l'ii-""paciior. we att tnow tr,atn is capacitor. half wayp ointt heo scillatorw ill start Iust:aftetrh e. can abtlnb;" .rrif1f pun.l *n"o " piLr-suppty has,: up andt he meter's faibd l; siilt up. If you are-oft he typew ith a tendency pointerw ill deflect.c 1rry oq.yntil th-e-buzzeior unds ro sucha cciJent,i iwour,l ue steadilyA. r thisp oint the oscillator'so utputs hould fruiiiito wke a couple: be E F"fy ;F;; 6ack-to-babakc rossth e merer,sin pur.,, cloqet o 5v.peak+o-peakN. ote that with eacha dj.ust- rrris stiouta mentt he pointerw ill twitch briefly liotect the meter,b ut it won,t help your as the bulb se[des, heart- ot yo'otp robes- in the evento f sucha misfor- givingt hei mpressiotnh att hep otentiometeisr no5r, tune.rt's gLoJpracticet" al*rr*ga irtit capacitor with
Table 1: Typical ESR values at 100kH2...
I
Capacitance value Voltage rating lmpedance*
ltrF
2.21tF
4.7pF
10pF
221tF
471tF
471tF
100pF
100pF
2201tF
2201tF
4701tY
4701tF
1,000pF
1,000pF
2,2001tF
2,2001tF
63V
50v
2 5 V '
50v
16V
35V
16V
35V
16V
35V
16V
25V
25V,
35V
4Q
2.8A
2.4A
1.9c)
1.3c)
1.3cr
o.7a
0.scr
0.2scr
0.25fi
0.1 14Q
0.114c)
0.065fi
0.0650
0.041c)
0.036ct
0.034f)
50v
50v
50v
*When new - low-ESR type.
a mains-type bulb - it is always reassurine to have a
visual indication that little charge remains. See warning
note later.
Inductonce
As the meter operatesa t l00kHz, any inductancein the
circuit under test becomes significani. The loudspeaker
that reads.8C)o n your coqventionalo hmmetera pp"*s
to be nearly open-circuit wittr ttre ESR meter.
This propert_yc an be quite useful. When testinga line
oxtput stage for example you might find that there,s a
short-circuit across the hansistor. In this event there are
in general three possibilities, (a) the transistor is short-circuit,
(b) the line output transformer has a primary-to-secondary
short, or (c) the HT line has a short-circuit
across it. If the short-circuit is still present when the
ESR meter is used, the transistor is almost certainly the
culprit: in the other two cases the ESR meter will give
an open-circuitr eadingb ecauseo f the inductanceo f the
transformer's primaly winding.
. Video headt esterso perateb y measuring,in effect, the
inductanceo f the head.I ts impedancef alls as the gap
deteriorates with wear. Althou;h this meter operates at
a frequency that's inappropriate for a video heid, it can
436
April 1999 TELEVTSTON

10. give a irelative indication of the head's and considering the fact that ESR is an in-phase com-poient,
'don1t have,a collection of heads in various states of
health to be able to confirm any figures, but it seems
that new heads produce a reading of about 20 while
worn heads produce a reading ofabout lf).
Inductors with millihenry values, of the type used in
EW modulator circuits, normally give an open-circuit
reading. But ifa shorted turn is present the inductance
drops dramatically and the meter's pointer will deflect.
Anotogue v Digitol
In dealing with the problem of in-circuit ESR measure-ment
I've used traditional analogue technology. But, as
is often the case, there's another way of doing things.
Bob Parker, an engineet,fdown under' who was con-vinced
of the importance of such an instrument, hrst
tried analogue circuitry. After "a few fairly unsuccess-ful
attempts" he opted for a digital approach. His solu-tion'is
to use a 7)log processor,with, instead of a
,sinewavea s a test signal,s hortc urrent pulsesa ppliedt o
the capacitor being tested. The resultant voltage pulses,
which are.proportionil to the electrolytic's ESR, are
compared to the level existing on a fttmp generator.
Time measurement by the 286 processor determines
the amplitude of the pulses.
.As far as the power,requirement is concerned, tliere's
a parallel in the form of a remote-control handset. The
LED is pulsed with a high currentfor a short period, the
average curretrt drawl being low. The brief high cur-rent
is supplied by a reservoir of stored power in an .
electrolytic capacitor that's wired across the battery's
connections.
I have made the assumption in my calculations
that ESR amounts to the same thing as an equivalent
fixed resistor.
Other uses for the meter emerge the more it is used.
For'example, non-electrolytic capacitois can be mea-sured
and their capacitance estimatbd. But because of
' the different types of capacitor construction in use, I
can't coine up with any hard and fast rule. A lower limit
for measuremenits about 0:lFF. There seemst o be less
and less need these days to measure the actual value of
a capacitor. With line output stage tuning capacitors
and timing components'a conventional capacitance
meter is more appropriate.
The ESR meter is one of those things that, once you
have one, you wonder how you ever managed without
it. Hats off to whoever came up with the idea - it's not
mine. I've just taken this opportunity to share with you
the course I adopted to end up with the solution pre-sented
here. I haven't clapped eyes on the Wizard yet -
we can't afford one down here in Wales. I'd like to
know how the Wizard designer approached the prob-lem,
but no information has come my way.
The idea for my meter was triggered off by the
Wizard. When I first read about it I was impressed. It
would test that most troublesome of all components, the
electrolytic capacitor. Not only that but.it would do so
in-circuit, ignoring associatedc omponents.t liked the
'tiod-einat oefr par ecto nventiohalm eter movementw ith its easv-scale,
also the buzzer feature for quick
checking. But the meter was shrouded in mystery and
its price tag was beyond me. So I decided to have a go
myself.
Development
A clear picture formed in my mind as to how to go
about it. My idea was to supply a low-valuc resistor
(l0Q) with a constant-current l(X)kHz sinewave,
amptify and rectify the resultant ;voltage waveform
acroSs this resistor and feed it to h meter movement. [n
thii situation thb meter is to be set at full-scale deflec-tion.
The test leads were to be connected across the
resistor. Now ifthe capacitor being tested has an ESR
ofsay 10f,1, the voltage across the resistor would fall by
half. Thus half-scale deflection would correspond to an
ESR of 10Q and so on. A very low ESR (good capaci-tor)
would produce a near-zero reading while a poor
capacitor would have little effect, the pointer remaining
at near full-scale deflection. The result is a meter scale
in opposite sense to that of the Wizard.
Within a couple of months of the start of development
work on the project I had a working prototype and
decided to write an article about it. Then, at the
eleventh hour, I had second thoughts. Something was
nagging me. The meter looked OK, did its job, and oth-ers
were happy with it. But after using it for some time
I felt that something was not quite right.
My main concern was that it seemed to be very sensi-tive
to the inductance of the test leads. This impedance
meant that even with the test leads shorted the reading
could not be brought down to zero. I had introduced
measures to offset this, but in this connection a more
serious problem emerged after some further use.
When a capacitor with a very low (near zero) ESR
was being measured, the pointer would vary about the
zero point if the distance between the test leads was
altered. If they were close together, their inductance
would tend to cancela nd the reading would decreaseI.
was aware how important it was to be able to differen-tiate
between say 0.5O and 0. lfl or between 0'lfl and
Friendly rivalry between the analogue and digital
camps has existed for a long time. This brings to mind
an old story that sums it up well. Two male engineers,
. one specialising in digital design and the other in ana-logue
design, are working together in a lab. A nude
.: femalc appeel! at the door, attracting the attention of
,, both men. This vision of beauty announces.that every -
trlten'ieconds she'will reduce'the distance betrveen hei-r::
l'self and the engineers.by one half. The digital engineer
,r:lool3S disappginted and cries "that's terrible, she'll
. never get here". Xhe analogue engineer smiles and then
rcplies i'that's OK she'll get close enough".
More on ESR
,@oPb arke(rE /ear onicsA ustralraF,e bruar1y 996p) uts
it this way.
"The electrolyte has an electrigal resistance which,
along with the (negligible) resistahce of the connecting
leads and aluminium foil, forms the capacitor's equiva-lcnt
series resistance. Normally the ESR has a very low
value, which stays that way for many years unless the
rubber seal is defective. Then the electrolyte's water
gradually dries out and the ESR creeps up with time.
The electro gradually comes to act like a capacitor with
its own internal series resistor. . . Heat makes it worse.
If an electro is subjected to high temperatures, espe-cially
from heat generatedin ternally as a result of large
ripple currents, the electrolyte will start to decompose
and the dielectric may deteriorate - the ESR will then
increasefa r more rapidly. To make things worse,a s the
ESR increasess o doest he internal heatingp roducedb y
the ripple current. This can lead to an upward spiral in
the capacitor'sc ore temperaturef,o llowed by complete
failure - sometimes even explosive , . ."
Both Bob (Dick Smith Electronics) and Ray Porter, in
an article on ESR meter design in this magazine a few
years back, mention the use of fixed resistors to assist
with meter calibration. Armed with this information.
TELEVISIOANp r i l 1999 437

11. ESR METER
zero.T his.wasa designw eakness,a nd I was not happy.
At this time Bob Parker's K7204 ESR meter became
available. I had one with which I could make a com-parison,
and noticed the same sensitivity to inductance
that I was experiencing. Both meters monitor the volr
age across the capacitor, whereas the Wizard measures
the current through the capacitor - this was clear from
its scale.
I went on to build a little circuit to do just that and, lo
and behold,t his over-sensitivityd isappearedT. he effec_
tive lead impedance dropped dramitically, and that
which remainedc ould be iimply compensatedf or by
means of the FSD preset. So it seemed that the Wizard
yay yas the right way. All rhis can be explained using
the relevant maths, but I'm not about to brush up on my
thcory and extend this article longer than it is aieady.'
. Reluctantly, I-accepted that I had to scrap my original
ideaand starr all-over aggl Thir was by nbw becoiling
an obsession with me - I had to come up with the besi
solution, and it had to be .the simplest.
Certaiir things had to go. After s-ome use I realised that
qlugs and sockets for the test leads were out ofthe ques-tion.
Their increasing contact resistance made low-o-hms
readings unreliable. I had also been determined that the
meter should operate with a single pp3 batterv.
To this end I had built a DC-DC converter io provide
a negative supply line. This provided operation .iown to
7V. But it used 7mA and geatly increased the circuit
complexity. To do away with it meant that I needed a
higher supply voltage. The use of two pp3s in series to
obtaint his may seemt o be a backwardss tep,b ut isn,t
really. The meter now takes half the current used by the
first prototype, and will regulate down to less than 5V
per battery. In,fact the T:t9llgadinC remains unchanged
over the supply range l0-30V with the oscillator set at
5V peak-to-peak.
Now,- almost a year after building my first prororype
andq uitea few versionsla ter,I havep resented'th_is;y
final (?) solution!
Worning
It seems that forgetting to discharge the main smooth_
ing block or HT reservoir capacitor before measure_
ment is a more frequent occurrence than had been
expected. When this happens R4 at least will blow. As
replacing componentso, n stripboard is a messyj ob, I
strongly recommend that protection is built in. Aimall
board with two 1N4007 diodes wired back-to-back and
a lA (N25) circuit protector in series with one of the
test leads can be mounted on the back of the meter
movement.
Thonks
I have to thank Martin Pickering for his constructive
comments after testing an earlier, voltage-sensing proto-t)?
e meter.
Components list
Item
R1, R2
R3
R4
R5, R7, R9
R6, Rg, Rls
R10
R l 1
R12, R13, R14
R16
VR1
VR2
*Value for current,economy
C1,C 2 47OpF,1%p olystyrene
C3, C4, C7i 0.1!F miniitur'e ri;sin dipped
c5, c6 22iF,16V
[c1,l c2,l ca
D1,D2D, 3,D 4,D 5
D6
LP1
M1
SW1
Buzzer
Stripboard
Case
Knob
Batteries
Probe clips
Value/type
3kQ,1yo
1Q
2.70
1oka
100kf)
- 91kO
5.6kfi
56kO
2.7K1or 10kfl*
500Q cermet preset
10 kCtl inearp otentiometer
TL082CN ,
1N4148
FlashingL EDp lusc lip
Miniature wire-ended
28Y,24mAlamp
100pA meter movement
DPST switch
Miniaturea larm
ABS box type BM22
Two PP3s plus clips
Order code
M3K
M1R
M2R7
MlOK
MlOOK
M91K
M5K6
M56K
M2K7 or M10K
WR39
JM71
BX53
RA49
VH09
RA71
oL80
OY96 and W40
BT44
CPC code PM11125
RD17
CPC code LS-M3
JP47
cc83
YXOl
HF28
HF21
Order codes are Maplin,s unless otherwise indicated.
438
April 1999 TELEVTSTON

12. OHMS
-.oix7 5 4 3
compa re
ESR at lOO kHz

13. The equivolent series resistqnce (ESRI of qn electrolytic
copocifor is o relicrble indicqtion of its condifion.
Alon Willcox's firsr ESR mefer".detign, published in these
pqges some five yeors a9o, wqs very populor. This Mork 2
version incorporoles severql improvements, in porficulor q
simpler oscillotor design ond single-botfery operotion
simplified equivalent circuit
of an electrolytic capacitoq
see Fig. l, is usually shown
when providing a briefexplanation
of what ESR is all about. In addi-tion
to the ideal capacitor Xc, a
secondc omponenti s present.I t has
a significant effect on the capaci-tor's
performance, and is referred
to as the equivalent series resist-ance
(ESR). Electrolytic capacitors
are used mainly for decoupling and,
to a lesser extent, for signal cou-pling.
This being so it's important
that, for optimum performancet,h e
impedance( AC resistance)o f the
capacitoris as low as possible.
An electrolytic capacitor's ESR
is mainly determined by the condi-tion
of the electrolyte (paste) that
separatesit s foils. The electrolyte
increasetsh ec omponent'sc apaci-
Fig. 1: Simplified equivalent circuit
of an electrolytic capacitor. Xc
represents an ideal capacitor. lts
reactance moves towards zero
ohms as the frequency increases.
Xc = l/(Zt fcl. The value of the
equivalent series resistance ESR is
determined mainly by the condition
of the electrolyte.
tanceb ut, when it deterioratesi,t
increasesth e impedancep resent.
The lower the ESR, the better the
capacitor!
Electrolytic capacitors used in
switch-mode (chopper) power sup-plies
and those mounted close to
heatsinks tend to run hot. Heat is
inclined to dry out the electrolyte
and, in time, a capacitor may devel-op
a high ESR. This will itself
introduce a power loss - and more
heat! The effect offailure ofthis
type in a power supply can be cata-strophic.
For example, if the capac-itor
is in the HT monitoring section
of a TV set's power supply the HT
voltage might rise, damaging the
line output transistor and maybe the
field output IC.
This type of problem is more
significant when a set is started up
from cold, as the condition of a
faulty electrolytic capacitor is
worse when cold. Thus cold checks
are by far the best approach to test-ing!
Problemsw ith electrolytic
capacitorsp, articularlyt hoseu sed
in switch-modep owers uppliesa, re
caused not so much by a change of
capacitancvea luea sb y an increase
in thec omponent'EsS R.T hus
removalo f a suspecct apacitort o
checki t with a conventionacl apac-itance
meter is largely a waste of
time-F urthermorea faulty capaci-tor
may be overlookedb ecauseit s
capacitancvea lueh ash ardly
changedA. n ESR meterg ets
around this problem by using a test
frequency( or pulser ate)t hat'sh igh
enoughf or thec apacitivere actance
to be almost zero ohms, leaving
just the ESR as the measurement.
Meosuring ESR
ESR obviously cannot be measured
directly,u singa conventionaol hm-meter,
so a means has to be found
to 'get to'the ESR that's hidden
insidet he capacitorA. numbero f
ready-madem eterd esignsa ndk its
aren ow availablef or measuringth e
ESRo f an electrolyticc apacitorin -
circuit,u singc old checksT. hey
achieves uccessa nds implicityi n
varyingd egreesU. seo f a suitable
meter enables cold checks to be
made without the risk of any fur-therd
amageo ccurring.S trictly
speakingit is the impedanceth at's
beingm easuredb ut,o ver a particu-lar
rangeo flest parametersi,t can
be shown that this presentsm ore or
Iess the same value.
It is all too easy to over-compli-cate
things when it comes to ESR.
There are those who argue that
ESRm etersd on't measureth e ESR
preciselyB. ut, in ther eal world,
how precise does the reading need
to be? It really doesn't matter. The
servicee ngineerjustn eedst o
know,a s quickly as possiblew, hich
capacitoris causingt he trouble.A n
ESR meter does just that! Once
techniciansh ave becomea ccus-tomed
to using an ESR meter, they
wonder how they ever managed
without one. Although the ESR
varies somewhat with frequency,
we cani n practicer egardi t as
beinga constanitn -phasec ompo-nent,
a ndc alibrateo ur meteru sing
fixed resistorsT. his is useful,a st he
meter will also serve well as a low-ohm
meter.
So. if an ESR meter doesn't
measurec apacitancew, hatr eadings
can we expect from good and bad
capacitorsu sings ucha meter?
How do you know whether a
capacitoris OK or not?T he curve
showni n Fig.2 givesa practical
idea of the sort of ESR readings
thats houldb e obtainedr vithg ood
capacitorso f differentv alues.
Therei s no hard-and-fasrut le horv-ever-
it's nota n exacts cienceA. ll
it needsis a bit of gettingu sedt o.
Thisd oesn't akel ong:j ust meas-ure
the ESR of a f'ew nerv capacl-tors.
Try l, 10, 47, t00, 470 and
1,000pFY. ouw ill find thatv alues
of 47pFa nda bovem easurqeu ite
low.0 '5O or less.w ith theb uzzer
comingo n (theb uzzetru rn-on
pointc anb e varieds, eel ater)T. he
7 6 December2 004T ELEVISION

14. impo.rtanpt oint is just how low ES8(o)
capacito-iws ith valueso f 47u F and
abovem easurie A t 47018 and ovr.,
the reading is close to zero'ohms.
If, in practice, a 1,0004F capacitor
producesa readinga s high as O.SSI,
rt's no good! i:
Anqtd$i,i'ditiin"l ,
d t s P l g ) B . r i , . - . . ,
Digital..methodbsf measurement
and lisiildy are'generally regarded
as pro,vldrng& ore accurater esults.
F9r mpny applicationsr his is true.
but itjs nqr:,45pessarilsyo wi*r gSn
measureineriflTheriere two wavs
of interfacingt he,capacitobr einl
tested' eiffi the m6tir:ftre capaciicir
can be connectedin parallel-with
the test sign4l.g"ourqaes, showni n
Fis.3 (a);Wiii"i;?:iti#6'bri',e . irbi.'
_ If a digital ESR readout i; ii;ad.
the capacitor must shunt the test
signal.,Witha n deal,capabito4th e
resultrwill be:z0ro,ohmsa;n d .z&te.,:.t :
display:.-witha .b adcapacitort here
will be d hieh rcading;with linle
s_h_untlnagw ay of. the test-signal.
We are interbsted in ESR viues of
3Q or less,rbuat digital meter
gives readings far higher than this.
It's not a major problem, but can
grve nse'to superfluous information
aSf ar aSE SRtmeasUrementasr e r_j
concemed; A inore. important factor
is ftat the:bqraltdmetnoa results in
a signifiidrftlniiease in,tne read::^ :
ings obaiiied&ecauiff 'of,ejri:i:Ssive
i
sensitifi.df0lttiri[dluctiriie,ofithe,,l
$! le3+,frf is".ii,ii'b e.overcomtye
-
fi tting.twollehds.tor6actlprobe:;It
provides.cancellation"toi,laige - .
extent,;but:thissolution.ias U'it .. ,
rmsyi n.r'sea nd'to conshuct.T he ""cries method ofiinterfacing does ,;.,
not sufferrfrom,this.ilrawback; so
the use of;conventional test leads ,
becomesa' cceptablelll don't know
yhy thi sef fec toc cur s - I jus:t,.
found out the hard way. . .
Although we have 6ecome used
to_digital readouts nowadays, for
ESR measurementth ere is-little
doubt that a moving-coil meter is
the.bestt ype of display.I t gives a
raplo, ei$y-to-rnterpreitn dication
of the condition of the capacitor.
After somee xperienceo f using it,
oxe gets to know where the pointer
should approximately be with good
capacitorso f different values.
Indeed a meter scale becomes
almostu nnecessaryI .k now of
people who have used this type of
meter quite satisfactorily without
I t F *
,Qgq$anr;
gl9se
qf9:3lgt.'
Rsample. Value
cfiosen for
optimum
meter scale
ever having taken the trbuble to fit
a scale dedicated to ESR measure-ment.
To repeat: it's not an exact sci-ence
but, with some experience,
Layoui o( Non willcox's Ma* 2 ESRm eF,ro n stripboard. n" n4z incorporates severol.improyementsin, cludinga simpler" "riil.i";-i;;b" i,ii;igb_bottery operalion.

15. ptb
?d anp
Fig' 4: The basic ESR meter circuiL new version. lcl and IC2 require positive and -negative supplies at pins g Further circuitry is required, and 4 respeaiiely. see nert month, to generate tne sim-riit iujpfu and provide a buzzer comparator.
one soon gets to knoy whfglr- - lly capacitancew ill providen egli_ , capacitori s causingth e qo.ubleb y .- gible opposition ficjto it.
knowing roughly where the ESR'': :t '-
meter's pointer should be with a Waveform: Analysis of a square_
good one. one argument that's wave has been used, and l'vL triea
sometimes put forward against the ,this myself. The results are a bit
use of a moving-coil movementi s unpredictableh owever.I had a lot
that the movement will be dam- ofiroubre trying to preserve the
aged should the meter fall off the waveform intaci at the mv level to
bench. I have a solution to this give a useful, predictable indica-problem.
If you are inclined to be tion. It's not *:orth the effort. A
glumsy,a ttacha piece_ofs tring sinewavei s so easyt o generatea nd
between the merer and the bench, gnplify that I cannot sJe any.lusti
Iong enough so that the meter ncition for incorporating square_
comes to-a halt just before it hits wave analysis into the dEsien of an
the deck but not so short that you ESR metei.
' ' dorittgetabitofajolttoservLas'117'l'*"1*. ( . .
:a'ieminder. , ' -
An improved ESR. meter
Thr meter presented here is similar
to the one described in the
March/April 1999 issues of
Television. Since then the use of an
ESR meter to check quickly for
faulty capacitors has Lecome well
establishedT. he original circuit
works well and has stood the test
of time, but feedback from the
hade has prompted me to make
some improvements. These include
single-battery operation and
improved temperature stability.
The new circuit remains stable
down to 6.2Y, and consumes about
l3mA. Because of the improved
temperature stability of thl new
oscillator circuit, there is no need
for an externally-availables et-zero
control.
The oscilloior cirrcuit
An IIF oscillator or pulse generator
with a stable output over a reason-able
supply voltage range is the
heart of every ESR meter. ICla in
the new circuit, see Fig. 4, is the
sinewave oscillator in this design.
The simplestw ay of generatinga-sinewave.
ist o incorporatei n the
oscillator's positive-feedbackp ath
a network originated by Max Wien
in 1891.I t ensurest hat the feed-back
is an in-phase component at
only one frequency, which is fixed
by the rRC values used. At very
high frequenciesC 2 presentsi low-impedance
path, while at lower fre-quencies
Cl becomes an effective
open-circuit. At some point in
between there will be maximum
output from the network Cl, Rl,
C2,R2, which is refened to as a
Wien bridge. The RC values used
here'result in oscillation at about
lfi)kHz.
There are two simple methods
of stabilising the output level with
an op-amp Wien-bridge oscillator.
The method traditionally used is to
include a bulb in the nelative-feedback
path (between-pins I and
2here). This was the approach
used in my 1999 design. There
has been some misunderstandine
about the bulb, because of ttre Oif-ferent
specifications used in US
literature. I went into the maner
in some detail in the 1999 articles.
The corrects pecificationis
28Y,24mA.
The principle behind the use of
a tungstenb ulb is that its resist-ance
increases with the current
that flows through it. If a bulb's
resistanceis measuredt,h e small
current from the ohmmeter will
increaseit s resistanceW, hen
employed correctly in this applica-tion
the bulb does not come anv-wheren
eari ncandescenceI .d ecid-ed
to use the lamp then because of
its elegant simplicity and extreme-
Iy low distortion figure (0.0025Vo).
With the new design I wanted to
reduce the operating voltage of the
l.)ecemhcr
,)OO4
TFI F/lqlr.)l
TesFsignol porumeteru
Amplitude: To test for ESR or for
actual capacitance there are no con-.
straints on how low the test sisnal
can be as far as the capaciior ii
concernedT. aking into account
power consumption, and the prob-lems
associatedw ith lowJevel sig-nals
of the order of microvolts,
noisec onsiderationse tc., a level of
about 5mV peak+o-peak seems to
be a good compromise.
Frequency: The time period
should be short enough to zero out
the capacitiver eactance.1 00kHzi s
a popular choice. At about this fre-quency
the ESR and impedance
converge with the type of capaci-tors
in which we are interested.
Apart from that consideration,
lOOkHz is about the top frequency
at which a predictable gain of up to
ten times can be obtained with
readily-availablel,o w-cost opera-tional-
amplifier ICs.
Remember that if the rate-of-change
of the voltage is fast enough,
7B

16. whole mcter so that a single PP3
battery could be used as the porvcr
source while still achieving very
lorv po"vcr consumption. The
problem '"vith the use of a bulb is
that in thesec ondi t ionst he bulb's
temperaturei s not sufficiently far
away from the ambient tempera-ture
to ensufe good stability. so
this time I decided to use the
brute-force method of diode stabil-isation
(Dl, D2).
The idea here is that when the
output from the oscillator rises
above the conduction point of the
diodes the negative feedback
increasest,h e output settling at an
amplitude which depends on the
characteristicso f the diodes.I n
this case the net result is a
sinewave source signal across R5
, with an amplitude of about 6mV
L peak-to-p"uk. Diod. stabilisation
introduces greater distortion, but
this is not important here. To
maintain oscillation, the value of
R3 must be over trvice that of R4.
A preset resistor, adjusted to just
sustain oscillation (lorvest distor-tion),
is usually used in the R3
position. I decided to use a fixed
value that's a ferv ohms on the
high side, to ensure reliable oscil-lat
ionr egardlesosf distor t ion.
Interfoce with rhe copocitor
being tesfed
The interface with the capacitor
being tested is the crucial part of
the meter. It took me a long time to
get this right. See Fig. -5. The wave-form
across R5 (the source resistor)
is not an ideal, constant-voltage
source,b ecauseo f the needt o
'--,.nclude the sample resistor (R6),
rvhose value must be comparable to
the ESR values in rvhich we are
interestedT. he ESR of the capaci-tor
being tested forms part of a
potential divider rvith R6. Thus if,
for exanrple.a good 1,0007rF
capaci torrv i tha n ESRo f about
0' lO is connectedio r test ,R 6 is
c{ ' fbct ivcl iyn paral lcrl vi thR -5T. his
Incanst hatt hes upply-signaslo urce
i lcs hr ' t 'ausrr'v. l rcrtrr c i lp: rci loiIs
beingt cstcclt.l lc const i rnt -cur rent
sourcct o l l5 is shl r rctrlv i t l rt hc
t:SIl urrd [{6 in p l r a l l c l .
'['hc
vol taqcr i ,ur 'cl i r rni lrc vcl
o p c t la c r o s s1 1 6l t s : rr c s u l to l l h e
, l r i l , ' i l 1l l t t , ' t t . - llrl r e , l r P i r r ' i t r r t '
l r c i r r g{ c s t c t li s l r n r l l l i t i c cul n t l t h c n
r l c t c c t c cbi y t l r c r c . l o l t l r c c i r c u i t .
l l t h c t r S I { o l t l r ec r r p a c i t o rb c i r r g
t e s t e ( li s c q u a l t o t h c v a l u c t r l l { 6 .
l u r l l ol thc s t r p p l y w a v c l i r r r n r v i l l
- l ' l r c
bc passctl orr.
supply rvavc.
I r l r rn i s r rot i r r t l cpcnr l c r rot l l l re
Ioac ll tor v c v c r - .I l thc I :SI t i s l c s s
than the value of R6, as rn rnost
cases it is, the lvavefonn voltage
across R6 increases.
As the ESR rises above the
value of R6, the latter becomes
less effective. The result of all this
is a non-linear scale, expanded at
the lolver range and somewhat
logged out. This is ideal for the
presenta ppl icat ion,b ecauseI n
some cases it is important to bc
able to distinguish benveen a vcry
low value, close to zero, and onc
of about 0 -5Q.
I have achieved low current con-sumption
and circuit simplicity by
tusingt he feedbackc urrent and
comprornisings omervhato n the
ideal.c onstant-voltageso urce.
Nexf month
In thec oncludingi nstalmennt ext
r r ror r thI ' l l completct hec i rcui t
description,d eal rvith sonrep racti-cal
points and protection ntethocls,
provide a detailedc ontporren ts list
and a stripboard layor-rt. I
Internol view
of the new
ESR meter.
fhe test leod
connections are ol
the bonom, with
proteclion diodes
bet,tveen them.
6mV p-p under
0 6V P-P anncr2nr oPen-circuit
(lCla pin 2) : : ; : : : ' , " condirions
i Y " " " " ' i / I i t i
I lR4 1oo() I Esn
Constant-voltage
source
(from osc
feedback loop)
Fig.5: The method of test capacitor interface used in this nreter. The source voltage is not a true
constant voltage because of the need for R6, whose value nrust be cotrtparable to the ESR of the
capacitors in which we are interested.
Current economy and circuit simplicity are achieved by using feedback current front the
'logged'
oscillator circuit as the source fed to the capacitor under test. The outltttt is inversely
out in relation to ESR.
l l l l ' l l r r ' ,

17. This second, concl
Wittcox's lotest ESR meter, with o suggested stripboqrd loyout ond
component specificotions
I n Part I last month I dealt with
I gSn and its measuremenat,n d
I describedth e significantf ea-tures
of my latest ESR meter
design. I'll start this month with a
description of the basic circuitry
used.
Circuir description
Fig. 4 (see page 78 last month)
shows the basic ESR meter circuit.
The important features of the oscil-lator
and test interface sections
were covered last month. There is
no need for a regulated Power suP-ply.
Just to remind you, the amPli-tude
of the HF output waveform
obtainedf rom the oscillator( ICla)
is setb y the characteristicws,h ich
are virtually temperature-stableo,f
the two diodes Dl and D2 in the
negative-feedbacPka thb etween
pins I and2 . The amplificationa nd
detectionle velsp rovidedb Y the
others tagesa res etb Y the ratio of
lhe sourceln d feedbacrke sistor
valuesu sed.T his is standardo pera-tional-
amplificprr acticeT. he way
in whicho pcrationaalm Plifiers
work rvasc over edi n somed etaili n
my articlesin theM arch/APril
1999i ssuess, o only a briefdescrip-tion
is given here.
The frequency of the Wien-bridge
oscillator is approximately
equal to ll(zfiRq when resistors
Rl andR 2 andc apacitorsC l and
C2have equal values. At this fre-quency
there is no Phase shift
across the bridge and thus maxi-mum
positive feedback. At reso-nance,
the upPer section of the net-work
(Rl, Cl) has twice the imPed-ance
of the lower section (R2, C2),
so there'sa transmissionlo sso f
1/3.T o sustaino scillation,t he over-all
gain (ALC) must be greater than
unitv.T he transmissionlo ss
through the network is offset by the
gain determined bY the ratio I +
(R3/R4). In this circuit the ALC
would be more than the three times
requiredw erei t not for diodesD l
. and D2, which override the effect
of R3 as mentioneda bove.
The following two stflgeso f
amplification( IC2aa nd IClb) are
straightforward,r vith no needf or
conectionc ircuitry.C apacitoCr 3 in
thef eedt o the detectors tage( IC2b)
is includedto removea nYD C com-oonent
and also to rctlucc sensitivity
to low frequencies(m ainsh um or
whatever). Rl2 sets the gain in the
detectors tageB. ecauseo fthe high
intrinsic gain of an operational
amplifier, the forward voltage droP
across detector diodes D3 and D4 is
overcome and detection at even mV
level is not a problem.
SpliFroil genetator ond
buzzer
That is all there is to the basic cir-cuit.
But the operationaal mplihers
require positive and negative sup-plies.
T his requiremenist provided
by IC3b, see Fig. 6, which is config-ured
as a voltage-followerT. herei s
100 per cent negative feedback (pins
7-6), so the output voltage must set-tle
at half the supply voltage, set by
the equal ratio of Rl4 and Rl5. I
wasp leasedto find thatt hec ircuit
remainss tablew ith outputsa sl orv
as +3'lV. This lower supply voltage
range is quite consistent.
IC3a is configureda s a voltage
comparatoWr. hent heE SRr cading
is less than 0'5Q, the output from
thed etectogr oesh ighert hant he
forrvardv oltaged rop acrossD 8.
The output at pin I of IC3 thcrcfore
1 5 8 J r ruar y2 005T i l EVISION

18. :oes high, activating the buzzer.
.-fhe ESR level at which the buzzer
operatesis set by the overall gain.
This point can'easily be changed by
altering the value of Rl2. If its
value is increasedt,h e overall gain
rises and the buzzer will operate at
a higher ESR level.
The value of l00Q for Rl8 is
chosen to limit the current from an
external 12V source to a recharge-able
battery to the trickle level. The
overall consumption is so low that,
if you are one of those who remem-ber
to switch off battery-powered
equipment when it's not in use, an
ordinary battery is OK and will last
for quite a long time.
Although the basic meter circuit
is happy with a supply between 6-
30Y the buzzer and LED won't be.
The value of 2'7kf,J for R19, which
is in series with the power-on indi-
. rtor LED, gives good brightness
ver a supply range of 6-9V with
only a feg mA drawn.
Prqcficol points
As the meter operates at 100kHz,
any inductancein a circuit being
checked will produce a high-impedance
reading. If an EW coil
produces a reading, it has shorted
turns. Another use of the meter is
where the line output transistor
appearsto be short-circuit.A quick
check with the meter will isolate it
- if the short is elsewhere,in most
cases the impedance of the line out-put
transformer will be in the way
and will result in a high reading. If
there's a low reading, the transistor
is most often the culprit.
ESR meter users have come up
with new applicationsT. he non-polarised,
high-voltage capacitors
used in the line output stage (tuning
FromRl2lC4
f I Prlntcuts(24)
etc.) can be tested. I've not taken
the trouble to design a new meter
scale for this application, as I have
no practicale xperienceo f such
checks. It seems to me that if such
a capacitor gives any reading at all
other than short-circuit it will be
OK. This type of capacitor does not
change value.
I would like to think that the
present article just about sums
everything up with resPecto the
lcl,lcz
pin I
l c l , l c 2
pln 4
+ve supply
Meter +ve'
Top - Fig. 6: The
split-rail generator
and buzzer com-parator
circuits.
Centre- Fig.7:
Suggested layout
on stripboard,
Left - Layout of
the prototype
meter on strip-board
Bottom - Fig.8:
The ESB meter
scale, shown full
size l58mml.
'Connecl to track slde of board
t 5 t ! 2
o
ESR at 100kHz
Cr
TELEVISIOJNan uar2y0 05 1 5 9

19. Parts list
Item
R l , 2
R3
R4
R5
R6
R 7 , 9 , 1 1 , 1 6 , 1 7
R8, 10
R12
R13
R14, 15
R18
R19
...
Valueftype
3ka
220A
100a
1A
2.7A
10kc2
100ka
*68kQ
3.9kA
56kO
*100Q
*2.7kf2
CPC order code
REMFR4fo l lowedb y the value
Al l0.5W1, %m etal f i lm
VR1
c't,2
c3,4
c5, 6,7
1OkQ cermet preset
470pF low-loss high-stability*r
0.1 p F cer-amicm ultilayer
221tF,1 6V
RE01881
cA02068
cAo2098
cAo1613
sc1N4't48
sc1 N4004
sc1N4002
scTL802.
sc00023
PM11119
sw-z201lz
1S00654
EN55030.
1N00772.
PC00046
PC00066
8T02187
PWo0037.
D1 , 2 , 34, , 9 , 9
D5,6
D7
l c 1 , 2 , 3
LED
1N4148
1 N4004
1 N4002
TLO82CN
3mm Superbright
M1
S1
100pA moving-coil
Miniature toggle switch
Buzzer 5V DC
Case ABS box
Test leads 2mm plug to probes
Veroboard
Spot face cutter for Veroboard
PP3b atteryc lip lead
High-currenptr otectionc hoke
See text
See text
See text
quick in-circuit location of faulty
electrolyticc apacitors.I f anyone
contemplatetsh e designo f a PCB
for the project, it is important that
separateo perational-amplifei r chips
are used for the oscillator and the
first amplifier stage - to avoid
interferencbee tweent he oscillator
andt he sensitivefi rst amplifier
stageF. ig. 7 showsa stripboard
layout for the meter's circuitry. Fig.
8 shows the meter scale.
Don't be temptedt o usep lugs
ands ocketsfo r the testl eads- you
wouldi n timeg etp roblemsin the
low-ohmsr ange.S olderedc onnec-tionss
houldb c usedt hroughouIt.
use2 mmt estl eadsw ith thep lugs
cut off. Make surc that you file the
probesto gives harpp ointsT. he
coatingth at'so n then.hra sa signifi-cant
resistance.
Thec ases pccificdin thep arts
list is a bit on thed ccps ide.T o
achievea slimmera ppearanceI ,
boughta notherc ase,t ypeE N55029
(too slim), andc ombinedt he
halvesT. his might sounde xtrava-gant,
but you still end up with two
casesa ndt heyc osto nly aboutf 2.
Protection mefhods
In a letter in the August issue this
yearJ im Littler suggestewd iring
an inductora crossth e testl eadt er-minals
to protect the meter should
it be connectedto a chargedc apaci-tor.
I can see no problem with this,
andf ollowedu p with a letteri n the
Scptembeisr sueI.f a values ome-rvhat
lower than the l5(i7rH rccom-rnendedth
erei s used,p roducinga
readingo f say3 0Q,t hisr cading
rvill bep resenet acht irre then teter
is srvi tcheodn andy ou rvi l lk now
thlt it is workingc orrectlyI.t will
not al'fectt he useo f thc ntcter.W e
l r reo nlyi nteresteind vulucsth at
are much lower.
If this methodo f protectionis
used with a digital meter, the dis-play
will settle at a fixed reading.
This will show that all is well with
the meter and will also eliminate
superfluourse adingsI.n the caseo f
a moving-coild isplay,it will dou-ble-
upa s a power-oni ndicator.
The useo f a circuitp rotectori n
series with the test leads has been
suggestedT.h e problemi s that it
would tend to blow too easily and
requiref requentr eplacement.
To reitcrated, iodep rotection
(D5, D6) shoulda lwaysb e incluclcd.
Any contmentasb outh igh-cLrr-rentc
hokep rotectionw, hichs eenrs
to be a r"rniqri.dree a,a ndo n ESR
measurcntcirn)t g enerawl ouldb e
welconrc.
You can reach me by email at
alancsr(hlro trnal.ic om
I thinkt hatc overse verythinqt .
r 6 0 J ,uruar2y0 05T ELEVISION

20. Table 1: T.yRicaEl SRv alues at,1Q0(Hz.r. ,",
... t
Capacilaicb vatie Voltage rating tmpedih'ce*
:
lttF
2-21tF
4.71tF' '
.
10ttF ,
221tF
471tF
471tF
100pF
100pF
2201tF
22O1tF
47OpY
. a7O1tF
1,000pF
1,000pF
2,2001tF
2,2O0pF : .
50v
50v
50v
' 5603Vv
25V'
50v
16V
35V.
16V
35V
16V
35V
16V
25V
25V',
35V
4rl
2.8cr
2.4A
1.gfi
1.3cl
1.3fi
0.7ct
0.5c)
0.2scr
0.25cl
0.1 14cl
0.1 14ct
0.065cl
0.06sfi
0.041rt
0.036rl
0.034cl
*When new - low-ESR tYPe.

21. Anologupeo neml eters I
t - . #
I o n o e r s
s t * i l r e r i c .
FAnuetc zz 9 8 2 7 8
?*,rrlrrrrlrtrurrllttrr t l r, o
r ' r r ' 4
^ 1 t , t t l ' l ' l ' l r r r 7 , ,
a
a
a
a
a
Attrocfive md modern dextign
Clxfce of printed scdes
4 popdqr sizes
"Eosy-frf'scdes
Chss eO
A moderna nd attractiver angeo f qualityd c moMngc oil metersa vailblea t
veryc ompetitlvep rices.
Therea re4 populasr izesw hichc an be eithers urface or flushm ounted
behindt he panel througha rectangulacru tout.T he metersu tilisea well
proven and robust, 90 degree deflection, pivot and jewel moving coil
movemenl.
Meters are suppliedi n sensitivitieso f 100 microamps,1 00-0-100
microamps(c entrez ero),1 milliampso r as 4-20 milliamps( supressed
zero)f or signapl rocessin dication.
Pre-printesdc alesa rea vailablsee peratelgyr aduateda ndn umbered0 -10,
0-30,0 -100a nd1 00-0-100.
{ _ f i +
Fixing studs on all meters (Dimension G)are M3 x 12mm
Dimensions in mm
M o dA eB l c D E F H I J W S c a | e
Length
CV-15X 57 48 43 24 40 35 1.5 14.5 28.5 50x23.5 40
CV-16X 68 58 45 31.5 48 48 1.5 14.5 28.5 61.5x28 50
cv-18x 80 67 50 38.5 64 48 5 14.5 28.5 72 x35 63
CV-20X 100 83 50 51.5 80 64 1.5 14.5 28.5 92x45 78.5
Crder Code Size Range Rec. Price €:
1+ 5+ 10+ 25+ 50+
METERS
3V15X1MA CV-15X 0-1mA
:V15X100UA CV-15X 0-100F4
:Vl5XGZ100UA CV-15X 100-0-100!A
3Vi5XSZ20MA CV-15X 1004-1004
3V'OXIMA CV-16X 0-1mA
3Vi6X100UA CV-16X 0-100ttA
3V16XCZ100UA CV-16X 1004-100A4
M6XSZ20MA CV-16X 4-2OmA
;V18X1MA CV-18X 0-1mA
3V18X100UA CV-18X 0-100rA
;Vl8XCZ100UA CV-18X 100-0-100FA
3V18XSZ20MA CV-18X 4-20mA
3V20X1MA CV-20X 0-1mA
CV20X100UA CV-20X 0-100!A
3V20XCZ100UA CV-20X 1004-100pA
3V20XSZ20MA CV-20X 4-20mA
METER SCALES
S/CVISXB CV-15X Blank
s/cv15x10 cv-15x 0-10
s/cv15x30 cv-15x 0-30
s/cvr5x100 cv- 5X 0-100
s/cv15xczt00 cv 5X 100-0-100
9/CV16XB CV 6X
s/cv16x10 cv 6X Blank
s/cv16x30 CV 6X 0-30
s/cv16x100 cv 6X 0-100
s/cvl6xczl00 cv 6X 100-0-100
s/cv18xB cv- 8X Blank
s/cvl8x10 CV 8X 0-10
s/cv18x30 cv- 8X 0-30
s/cv18x100 cv- 8X 0-100
s/cvl8xcz100 cv 8X 100-0-100
S/CV20XB CV-20X Blank
s/cv20x10 cv-20x 0{0
s/cv20x30 cv-20x 0-30
s/cv20x100 cv-20x 0-100
s/cv20xcz100 cv-20x 100-0-100
AVA1ASIE FRort NATKta,lA!O lglRlBUtORs OR DIRECTF aOl ANO*S SUEJECTrO A mOQ OF 25 PC$ ANALOGUECVl Revision4 03/06/04
Onders electronicpsl c BayhamP laceL, ondonN Wl OEU UK
Tel: +44 (0)20 7380 8167 Fax: +44 (0)207874 1908 wwwmeters.anders.co.uk

22. SD80/0-100UAI M ULTICOMP I PanelM etersI ElectricaIl Farnell
Page I of I
2OO7/0 8/08
SDSOIO- IOOU-A MULTTCOM-P METER8, 1X81MMO - IOOUA
4S 60
Manufacturer: MULTICOMP
Order Code: 4433932
Manufacturer Part No: SD80/0-
lOOUA
Rol15 :
Description
, A v a i l a b i l i t y
Availability: 1
Price For: 1
Minimum Order Quantity: 1
Order Multiple : 1
U*it ?rice: 99"5$
Image is for illustrative purposes
only.
Please refer to product description
Technical Specifications
r*l Product Rang;e
Catalogue Page:
58s / UK2
ffirech::ical Oata $heet {i.95 kBi
Product Attributes
Weight (kg): 0.12
Approximate weight in primary packaging
Tariff No.: 90303399
Country of Origin: TW Taiwan
Country in which last significant manufacturing process was carried out
a
a
a
a
a
a
METER8, 1XB1MMO - lOOUA
Depth,e xterna:l 3 6.5mm
Diameter, panel cut-out:
63.5mm
Length / Height,
external:81mm
Meter Movement
FSD:100pA
Pitch:34mm
Resistan ce, coil: 15 00R
Width, external:81mm
_ _Qtv .._ . -^:":
O r i r e
:
i L - 4
. t - n
. L O - 2 4
: 2 5 - 4 9
List Price
€9.5B
f 9.38
89.t9
€8.96
E7.37
fi0ierL*qc
p:i,/acy $l:atcme nt I Site rflep j Te rrrs cf Prrchase I Te rmS lf Acce r :
Cc;:iTrlght ii-; 2307 l:rer*:er Ferne il UK Llmite d ALL R:Gli15
Copy! - rghti n t i l r whoie ar rd every par t of l | i is !1i r t isi le* el rn;s ic Prer : ier ?anet l i )4.L arni f . : l
i i cen$edt, r ans fer i -edc,o piei o. rep: 'oduleciin whole oT in 3a! - li n al y manner or : ' : t t : l ' : ; i r ' ;
acccrcancey , , l tht he terms of i re O'^ner 's agreer :ef l | , wi tno, , r tl n* pr t i ) t wr t '
Fainell is a d:vision of pren'r;er f*rnell UK Limited. Regist*:'*d in fnciard and Waies fi.: C{.}8(
Lecd:, i..gl: 2QQ.
Prcd ucer R cg lstration l'l u *r be r : '! f.f. I AK t), 4117.
http://uk.farnell.com/jsplElectricaliPanel+MeteTsAvIULTICOMP/SD80/0-100UA/dis0p8..1. 08/2007