I Milliard I

MULLARD-AUSTRALIA PTY. LTD. (Mullardl

VOL 5 — No. 5 SEPT.-OCT., !962

Editorial Office: 35-43 Clarence Street, Sydney. Telephone: 29 2006 “Oh, wad some Pow’r the giftie gie us, Editor: To see oursels as ithers see us.” JOERN BORK Robert Burns. All rights reserved by Mullard-Australia Pty. Ltd., Sydney. Information given in this pub­ lication does not imply a licence under any patent. Original articles or illustrations re­ produced in whole or in part must be The Insignia and the Image accompanied by full acknowledgement: Muliard Outlook, Australian Edition. Both noticed by the other fellow and always linked— the

TABLE OF CONTENTS image more elusive with pulse and personality, for it can surge Editorial ...... - ...... 50 with the progress of the company, by its products and its Viewpoint w ith Muliard ...... 51 The Range of Muliard Transmitting personnel, its aggressiveness and its humility, by its Service— or Valves for SSB ...... 52 Thermistors ...... 53 wither for the lack of it! Repairing Ferroxcube Aerial Inductor Rods ...... 55 Use of Quarter-Track Heads with An insignia, perhaps a few minutes work by an artist, an Muliard Tape C irc u its ...... 55 image evolved through the years from the painstaking efforts Muliard Semiconductors with CV Approval ...... 56 of a dedicated team with a craft and a tradition to be nurtured ORP94 High Sensitivity Cadmium Sulphide Cell ...... 56 and preserved. Muliard Omegatron Type O.l 56 A Transistor Tester for Educational Purposes ...... 57 Humility softens our ego to talk about a Muliard image, North Queensland Distribution ...... 58 Luminance— Light Units— whatever it may be, but we are not unmindful of the key— the Illumination ...... 59 continuity and ever-expanding support of our customers, for it is you—our readers—who see the Muliard image.

M.A.B.

The Vacuum Pumping system shown on the front cover utilises a Muliard Omegatron which is a simple form of mass spectrometer, providing a means MULLARD DISTRIBUTORS:— of analysing the residual gases and vapours in vacuum systems. It can New South Wales South Australia Q ueensland also trace the evolution of gases C. A. Pearce & Co. Pty. Ltd. within a sealed-off system, the action Martin de Launay Pty. Ltd. Agents: of getters and the permeation of glass Cnr. Druitt & Clarence Sts., 33 Bowen Street, Brisbane. and other materials by various gases. Sydney. Phone: 29 5834 Woollard & Crabbe Limited Phone: 2 5860, 2 8510 For a brief description of the Cnr. King & Darby Streets, 180 Wright Street West, 13 Palmer St., Townsville. Phone: 5864 Omegatron, see page 56. Newcastle. Phone: 2 4741 Adelaide. Phone: LA 4713 T asm ania 144 Keira St., Wollongong. MULLARD-AUSTRALIA PTY. LTD. Phone: B 6020 Medhursts Wholesale Ltd. Western Australia 163 Collins Street, Hobart. 35-43 CLARENCE STREET, SYDNEY V ictoria Harris, Scarfe & Sandovers Phone: 2 2911 Phone: 29 2006 Howard Electrical & Radio Limited. 136 Wellington Street, 123-129 VICTORIA PDE., COLLINGWOOD, N.5 Company. Launceston. Phone: 2 2091 VICTO RIA Vere Street, Richmond, 495 Newcastle Street, Perth. 106 Wilson Street, Burnie Phone: 41 6644 Phone: JB 4716 Phones: 28 1171, 28 0131 Phone: 1919 Associated with MULLARD LTD., LONDON and all leading wholesalers throughout the Commonwealth

50 I MullardO' I VIEWPOINT WITH MULLARD HOW REMOTE, REMOTE? MULLARD-AUSTRALIA

Near 16 feet, if it be remote control of The Ultimate PERSONALITIES a television receiver and maybe 16 million miles for a space vehicle! In appraising the ultimate as a require­ ment, it would no doubt be a cordless Much of mankind's inventiveness hasremote unit and these are available in one been directed to leisure and for ease of or two forms—ultrasonic keys and small control and often remote, be it the harness radio-bearer transistorised units, but both reins of a horse and cart or more recently, somewhat costly, when the other factors the controls of a television receiver. such as brightness, contrast, volume, between-channel muting and so on are considered. Nevertheless, with the present Requirement stage of the art and local production costs, it would appear that remote control At this time, rather than set out a specification of what form a control device units, with cord, are a reasonable com­ promise for the time being at any rate. might take, it is as well to decide just where remote control fits into the picture, how useful it might be and whether it is Additional Advantages a gimmick or of practical value. The Apart from channel selection and the answer is self-evident in that a remote adjustment of picture brightness and so control device with channel selection andon, the ability to mute some of the less ancillary facilities such as brightness, tuneful and jarring theme music is an contrast and volume are certainly worth­ added sales feature and these points have while and particularly attractive to the already been well covered by the manu­ existing owners of television receivers, facturers of remote control television more particularly, to the “constant receivers. viewers.” Remote Control of Radiograms Obsolescence Sound reproduction has reached a fine Having undersold the 17", 21" 90° andlevel of technical achievement but surely Mr. George A. Aungle 21" 110° market, apart from cabinet here is the ideal unit to apply remote control. styling and presentation, remote control is Mr. Aungle joined the Company in perhaps the only worthwhile obsolescence factor to encourage the sale of new tele­ Concert Illusion 1957 after a wide experience in Tele­ communications, Broadcasting and vision receivers. Moreso because of the This Writer has always considered that wider programme scope with the addi­ half of the pleasure of record reproduc­ Television. As a sales engineer in our tional channels coming into service, sometion was to have the loudspeaker at one Transmitting and Industrial Valve and overlapping and some with useful fringe end of the room and the player and coverage, for example the third com­ Semiconductor Department, his activi­ controls near the listener in that, not only ties are more closely linked to Govern­ mercial channel in some Metropolitan can one control the level and bass and areas; and Sydney to have four local treble reproduction at the listening point, ment Departments and Public Utilities. stations and four with a useful signal level but the isolation of the loudspeakers He is a member of the Institution from outside the area. inspires the imagination of remoteness in the concert hall or even intimate theatre. of Radio Engineers Australia and It has been suggested that 45% to 50% served with the Royal Australian of the new TV receivers sold in the Metropolitan areas of Sydney and Mel­ A Feature for Stereo Navy. bourne in the year 1962/63 will be Striving once more for the ultimate, Formerly a top-grade swimmer and against a traded-in receiver and, whilst could it not be argued that a “must” for water polo player, readers in Tasmania many of these will be 17" and the early stereo is the adjustment of the channel 21" receivers, the motive of remote control balance at the listening point? We feel so may be interested to know that he has, as a sales feature cannot be neglected. —and with the knowledge of manufactur­ on several occasions, taken part in the It can also be supported that the few ing costs and familiarity that receiver classic annual Hobart event of swim- purchasing a television receiver for the manufacturers have in their developmentming the Derwent. first time are leaning towards remote of remote control devices for television control with the philosophy of “waiting receivers, the adding of remote control Now, like many of his Mullard col­ for the latest developments.” for stereo radiograms is relatively leagues, he is a keen fishing and boat­ straight-forward. Again, the same argument is applied in selling an article of higher ing enthusiast, indeed we can now Demonstrate in the Home unit value and larger profit margin. muster a flotilla. In a recent survey made with a group We can picture the astute salesman of Metropolitan retailers, each volunteered weaving a sales story around the fact, that remote control television was best that with a mixture of records on a record demonstrated in the home, with all of the changer, some “loud” and some “soft”, household present, when the first the listener can adjust the volume of each. OUTLOOK, 1963 “gimmick” impression is soon dissipated It is therefore not without enthusiasm, and the practical benefits are readily that we look at remote control of not To ensure delivery of your copies appreciated. It would be naive of us to only television receivers but also stereo­ remind retailers that here is an article grams, as a vital factor in maintaining a for 1963 please complete the form “to sell up to” and make a larger profit satisfactory manufacturing and sales value enclosed with this issue and mail to­ margin. Nevertheless, it is a very true level when exploiting the obsolescence one for the profit-conscious retailer. factor. day.

51 iMullardl------—------

The Range of Milliard Transmitting Valves for SSB The Table below has been compiled to acquaint designers with the range of Mullard transmitting valves available for SSB communication purposes and to facilitate the selection of suitable types for given applications. The figures in the Table are for frequencies below 30 Me/s. The extent to which a valve may be used at higher frequencies with reduced output may be obtained from individual data sheets which are available on request. The data sheets should, of course, be consulted before commencing the design of new equipment. Problems of selectivity, brought about by These types, with an outline of their per­ valve characteristic with the required so many adjacent transmissions, coupled formance, are listed in the Table. degree of linearity. It will be seen from with selective fading, have resulted in an The latest addition to the range of the Table that this valve achieves both increasing number of station-operating Mullard SSB transmitting valves is thehigh power outputs and an unusually authorities to investigate single sidebandQY5-800 which has been developed pri­ favourable figure of intermodulation dis­ techniques. marily for SSB systems. Investigation of tortion. SSB techniques are already being used the severe load distortion requirements has The operating conditions shown for each to great advantage in special communicationled to the adoption of control grid andtype refer to operation as a linear amplifier services and inter-continental telephonescreen grid geometry which provides a for SSB suppressed carrier service. Other channels. details, such as the heater requirements, base connections and any special requirements Transmission regarding cooling may be found in the in­ The SSB method of transmission, by dividual data sheets (Vol. 3 Mullard Tech­ dispensing with one sideband, permits more nical Handbook). channels to be established in any one fre­ The following operating notes apply to quency band than can be accommodated all the types in the Table:— where conventional amplitude modulated Vgi (the control-grid voltage) is adjusted transmissions with a carrier and two side­ so that the recommended anode current bands are in use. (Ia), is obtained at zero signal. Further advantages of SSB operation Pi<>a

LINEAR RF POWER AMPLIFIER, CLASS, AB, SSB SUPPRESSED CARRIER SERVICE TYPICAL OPERATION AT f<30Mc/s ‘Two tone’ modulation, max signal conditions

QV06-20 QY3-65 QV1-150A QV08-100 QY3-125 QV2-250B QY4-250 QY4-400 QY5-500 QY5-800 QY5-3000A v„ 600 3000 1250 750 3000 2000 4000 4000 5000 4000 5000 V V ^ • 200 360 300 310 600 350 500 ■ 700 700 600 1000 V VK, -42 -85 -45 -45 -108 -56 -93 -120 -90 -110 -117 V I»(o) 26 15 100 130 23 100 50 85 56 150 200 mA I„ 72 45 180 270 77 190 115 180 180 330 380 mA I* 5.0 1.5 4 .4 26 7.0 4.0 3 .0 5.0 15 40 25 mA I*. 0 0 0 0 0 0 0 0 0 0 1.5 m A V in(pk) 4 7 85 45 45 108 56 93 115 90 100 134 V Pload(driver) 0.25 1.0 1.0 1.5 1.0 1.5 1.0 1.5 2.0 1.5 2.5 w Pa 20 70 140 93 117 220 188 427 495 670 111 5 w

Pk2 1.0 0.5 1.3 8.0 4.2 1.4 1.5 3.5 3.8 24 25 w P E P (o u t) 46 130 172 220 228 320 454 586 810 1300 1570 w P out(mean) 23 65 86 110 11 4 160 272 293 405 650 785 w 11a 54 48 38 55 49 42 56 41 45 49 41 % P E P (lo a d ) 38 111 146 187 194 272 383 498 688 1110 1335 w D i.m . 3 0 28 33 28 29 28 36 40 28 35 30 dB r n i r r t l

THERMISTORS In Outlook Vol. 5, No. 2, an article was published describing the properties and applications of voltage-dependent resistors. Another type of non-linear resistor is the thermistor. Thermistors are thermally sensitive semiconductors and are characterised by a large negative temperature coefficient of resistance. The variation of resistance of a thermistor may be caused by self-heating due to power dissipated in the device, by a change of ambient temperature or by a combination of these factors.

In general, the resistance of a conductor For small currents, the power consumption Manufacture of Thermistors increases with an increase of temperature. of the thermistor is too small to produce There is, however, a class of materials in a noticeable rise in temperature and cor­ As well as the conventionally sized which the resistance decreases when the responding fall in resistance. The thermistor thermistors shown in the photograph in Fig. temperature increases. These materials are therefore behaves as a normal linear resistor 4, miniature thermistors are also made and semiconducting oxides of iron, nickel andand has a straight-line voltage/current a selection of this type (magnified) is cobalt with small quantities of other characteristic. At point A, however, the heat shown in Fig. 5. The normal-sized therm­ materials added. Curves of specific resistance produced by the current through the ther­ istors are made by extruding or pressing a (the resistance of a cube of the material with mistor is sufficient to cause a fall in resist­ mixture cf the thermistor material and a sides of 1cm) plotted against temperature ance and so the characteristic departs from plastic binding material into the shape of a for various thermistor materials are shown the straight line. For the particular rod or a disc. The rods and discs are then in Fig. 1, and these clearly show the fall thermistor used to plot Fig. 2, point A fired and the electrical connections fitted. in resistance with an increase in tempera­ corresponds to a dissipation in the thermistor Miniature thermistors are made by placing ture. In other words, these materials have of approximately 0.01W. At a certain a bead of the thermistor material between a negative temperature coefficient of resistance.

0-1 0-3 0-5 1-0 3 5 10 30 50 100 300 500 1000 C urren t (mA)

Fig. 2 — Voltage/current characteristic of thermistor.

current value, the voltage reaches a maxi­ mum value and will decrease if the current is increased further. For the thermistor of Fig. 2, this point occurs when the temperature of the thermistor is 50°C above the ambient temperature. Beyond the point corresponding to 300°C above ambient temperature, the voltage starts to rise again with an increase in current. Fig. 1 — Specific resistance plotted against temperature. The resistance value of the thermistor does not change instantaneously with the change of temperature. There is a time lag If a current is passed through a thermis­ between the temperature change and the tor, heat is dissipated within the unit and thermistor reaching equilibrium. Similarly, the relationship between this current and the if the thermistor has been working for applied voltage when thermal equilibrium some time and the current through it is has been reached is shown by the curve of switched off, there will be a time lag before Fig. 2. (Thermal equilibrium is reached the resistance *of the thermistor rises to its when the heat lost to the surroundings just room-temperature value. The cooling curves equals the heat generated in the thermistor.) for two thermistors are shown in Fig. 3. The current and voltage are plotted onFrom curves such as these, designers can logarithmic scales and the voltage values find the time that a certain thermistor will are those developed across the thermistor take to react to current or temperature when thermal equilibrium has been reached. changes. Fig. 3 — Cooling curves for two thermistors.

53 I Mullard

THERMISTORS — continued two parallel platinum wires, as shown in Fig. 6. The beads are then dried and sintered. The sintering process shrinks the bead onto the wires to ensure good electrical contact. The beads are usually enamelled for protection. Applications of Thermistors The applications of thermistors can in general be classified into three groups. These are: (a) Applications which use the dependency of the resistance of the thermistor on temperature. (b) Applications using the negative tem­ perature coefficient of the thermistor. (c) Applications using the time taken by the thermistor to reach equilibrium. The most obvious application of ths, first group is the measurement of tempera­ ture. If the resistance of the thermistor at various temperatures is known, a calibration chart of resistance against temperature can be plotted. The thermistor can then be placed in an enclosure, allowed to reach equilibrium, and the resistance measured to give the temperature of the enclosure. It is important that the measurement of the resistance does not affect the tempera­ ture of the thermistor. An extension of this idea is to pass a known current through a thermistor and measure the voltage de­ veloped across it, or alternatively use a Fig. 5 — Enlarged view of miniature thermistors known voltage across the thermistor and measure the current through it. These methods can be adapted to temperature control since the variations of current or a television receiver. A typical circuit is tion occurs in transistor radio receivers voltage caused by the variations in tem­shown in Fig. 7. An increase in the resist­ where a thermistor is sometimes used in the perature can be used to control heating ance of the field deflection coils caused by base bias network of the output stage. A equipment through relay circuits. the flow of deflection current is accompanied typical circuit is shown in Fig. 8. An by a decrease in resistance of the thermistor increase in temperature causes a decrease An application of the second group is caused by the same current. The thermistor in the resistance value of the thermistor. compensation. One example of this which is chosen so that the fall in resistance The base voltage Vbe therefore decreases, will be familiar to the service engineer is matches the increase in resistance of the compensating for the rise in collector the use of a thermistor to compensate for coils and so the load on the output valvecurrent with temperature. By over-compen- changes in resistance of deflection coils in is constant. Another example of compensa- sating for the changes in Vbe, changes in the leakage current of the transistor with temperature can also be counteracted. A final example illustrates the third group of thermistor applications, those using the thermal inertia or time taken for the ther­ mistor to reach equilibrium. It is sometimes required that a relay should operate after a delay and this can be easily done with a thermistor. The thermistor is connected in series with the relay coil as shown in Fig. 9. To prevent the relay “chattering”, the paral­ I / lel circuit consisting of a resistor in series with one of the relay contacts is used. As soon as the relay starts to change over the parallel circuit is interrupted and the relay is fully energised.

I \ Thermistor

Fig. 4 — Standard-sized thermistors. Fig. 9 — Circuit for delayed action of relay.

54 E gB jSP

REPAIRING FERROXCUBE AERIAL INDUCTOR RODS

Enquiries have been made recently about the possibility of using an adhesive to repair fractured Ferroxcube aerial tods. Usually the receiver can be made to operate again satisfactorily, provided the fracture is a simple one and the coils are undamaged. Most commercially available adhesives except those requiring heat treatment can be used.

The physical dimensions of a Ferroxcube aerial govern its performance in the re­ ceiver. Therefore care should be taken not to remove any portion of the Ferroxcube material by the uses of abrasives, etc., on Fig. 6 — Manufacture of miniature thermistors. the mating surfaces. The adhesive should be applied according to the maker’s instruc­ tions. It is important to ensure that the two parts are in proper alignment and that the -Vcc amount of adhesive used is kept to a mini­ mum consistent with a firm joint.

Under no circumstances should the rod be subjected to excessive heat treatment as this is likely to permanently impair the magnetic properties of the Ferroxcube.

The aerial circuit of the receiver may require readjustment for good sensitivity Therm istor after the aerial has been repaired. This is done in the usual way by moving the coil axially along the rod for best signal sen­ sitivity at the low frequency end of the band. It is useful to note the initial posi­ tion of the coil on the rod, the final adjust­ Fig. 7- ■ Temperature compensation in a Fig. 8 — Temperature compensation ments being made about this position. television receiver. transistor radio. USE OF QUARTER-TRACK HEADS WITH MULLARD TAPE CIRCUITS By and large, quarter-track operation in recording current is required, the gain Equalisation does not introduce any new principles of into the recording output stage may be re­ In principle, equalisation is not affected the design of tape amplifiers, and therefore duced by taking the output to the bias re­ the published Mullard designs are suitable. jection network from a suitable tap in the by a change from half-track to quarter- However, some slight modifications may anode be load of the stage through a 0.1 |iF track operation. However, many modern required, and the following points arecapacitor. in­ It should be noted that the feed heads have an improved high-frequency tended as a general guide. to the record-level indicator should still be response, and a change in equalisation may At first sight, a quarter-track head would taken from the original point at the anode therefore be beneficial. As this depends on be expected to give less than half the signal of this stage, through the original 0.1 ^F capacitor and 470kf! resistor. the actual head, the type and make of tape output of a comparable half-track type, but in use and, to some extent, the level of improvements in head construction have, in many cases, made the difference in output Bias Current bias, individual recommendations cannot be made. Where required, adjustment of the considerably less. In any case, the sensi­ A similar situation to that described for tivity of the Mullard circuits is, in practice, the recording current also applies with treble-boost frequency can always be made adequate for use with most high-impedance respect to bias .current, but the adjustment by altering the capacitor in parallel with the quarter-track heads. is now simply made by varying the value treble-boost inductor—the frequency of of the bias feed capacitor until the correct boost is proportional to 1/-\/C —while the Recording Current level of bias is found. As the reactance of amount of boost can be varied by adjust­ The recommended peak recording cur­ a capacitor is proportional to 1/C, an rent may differ from that for the corre­ increase in the value of C will increase the ing the value of the damping resistor in sponding half-track head and, in general, itlevel of bias, and a reduction in value willparallel with the capacitor, an increase in may be expected to be lower. If a reduction lower the bias. R increasing the boost. 55 I Muliard I------

ORP94 HIGH-SENSITIVITY CADMIUM SULPHIDE CELL M u lia rd The high sensitivity of the ORP94. the SEMICONDUCTORS WITH CV APPROVAL most recently introduced Muliard Cadmium Sulphide Photoconductive Cell, enables it to Additional types are constantly under review for inclusion in CV listings and for additional fulfil a wide variety of switching functions information on these and other CV types please contact the Muliard Professional and at extremely low light and low voltage Industrial Department. levels, with the utmost safety of operation. With only 10V across the cell and an illumination of 54 lux the resistance Services Muliard Description of the ORP94 falls from 800 kO to Type No. Type No. 200Q, permitting a current flow of 50mA, AF Low Power GermaniumTransistors which is more than adequate for the opera­ CV2389 OC71 Medium gain general purpose transistor tion of a relay. CV2400 OC71 Medium gain general purpose low nois The simplicity of operation of the CV7001 P03 Germanium transistor ORP94 conveniently fits several major ap- CV7002 P 04 Germanium transistor plicational requirements, particularly where CV7005 OC71 Medium gain general purpose transistor low voltage supplies are already available. CV7006 OC72 Output transistor It can be used in motor cars, for daylight- CV7007 High voltage low power switching trar controlled parking lights; and in industry OC77 CV7008 AC 107 Low noise transistor for safety alarm and many other light- CV7009 OC83/84 General purpose transistor controlled systems. The maximum cell dissi­ CV7074 OC83/84 General purpose transistor pation is 1W at an ambient temperature of CV7118 OC72 General purpose switching transistor 25 °C. Up to 70V can be applied to the ORP94, the spectral response of which Diodes peaks at 0.67|im in the red region and CV425 — General purpose diode extends to beyond 0.8(im in the near infra­ CV442 OA73 Detector diode red. CV448 OA81 High voltage general purpose diode CV7040 OA202 Silicon general purpose diode A CV7041 OA95 Subminiature high voltage diode 1 JKSS'WP CV7047 OA5 High voltage gold-bonded diode CV7048 AAY12 High voltage gold-bonded diode CV7049 OAIO High current computer diode CV7076 OA47 High speed switching diode CV7127 AAZ17 Gold-bonded diode Rectifiers CV7113 OA210 Silicon rectifier CV7114 OA211 Silicon rectifier m m AF Power Transistors CV7083 OC29 High gain transistor TnT CV7084 OC35 General purpose power transistor Ultrasensitive Cadmium Sulphide Photo- CV7085 OC28 Close tolerance high voltage transistor conductive Cell ORP94 CV7086 OC36 High voltage medium gain transistor Abridged Advance Data for ORP94 Germanium RF Transistors Characteristics CV7003 OC44 RF transistor CV7004 OC45 IF transistor (at Tamb ;= 25°C, D C conditions) HF transistor Nominal cell resistance at 54 lux 200 Q CV7089 OC171 Equilibrium cell current at 10V D C , 54 lux, Germanium Switching Transistors lamp colour temp. 2700°K CV7042 OC41 Low power transistor Min Nom Max Core driver transistor 25 50 100 mA CV7054 OC23 CV7087 OC43 Low power transistor D ark current at 70V D C * 140 nA CV7111 OC139 n-p-n medium speed transistor Absolute Maximum Ratings CV7112 OC14Q n-p-n medium speed transistor V cell (dc Or ac pk) ITiaX 70 V Peon max Silicon Transistors At Tamb = 25 °C 1.0 W CV7043 OC200 Low gain general purpose transistor At Tamb = 70°C 350 mW CV7044 OC201 Medium gain general purpose transistor *20 seconds after removal of illumination CV7075 OC201 Low noise transistor of 54 lux CV7117 QC203 High voltage transistor MULLARD OMEGATRON TYPE 0.1 The omegatron is similar in principle to will thus move in a spiral path and will At pressures below 10-7 torr the the magnetic resonance accelerator (now eventually be collected by an electrode on resolution is sufficiently great to provide known as the cyclotron). Ions formed by the perimeter of the system. All ions of complete separation up to mass 30. From electron bombardment are made to travel other types will continue in circular paths, mass 30 to mass 100 the separation is in a circular path through a magnetic and will therefore not be collected. The less complete but is adequate for identifica­ field, at a frequency of revolution equal detection of ions of any specific mass is tion of the ions present. to their cyclonic resonant frequency. This therefore achieved by the choice of fre­ frequency, for a constant magnetic field, is quency for the RF field. Operating Conditions a function of the mass of the ion and Magnetic field 3000 to 3500 gauss number of its electron charges. If an ion Performance RF field (for mass of a particular type is present, it can be The ion collector efficiency is high, and numbers 1 to 100) 50kc/s to 5Mc/s accelerated by the application of an RF the device operates satisfactorily as a Vh max (adjusted for field at right-angles to the magnetic field, spectrometer in the pressure range 10-5 required emission) 1.5 V the applied frequency being equal to the to 10-9 torr. Measurement of pressure is Iu max 10 mA cyclonic frequency of the ion. The ion possible down to 10-12 torr. Accelerating voltage 67 V 56 A Transistor Tester For Educational Purposes This transistor tester has been designed switch SW2 is now operated, a current of specifically with the needs of the school 10|iA is fed into the base from the reference laboratory in mind. Without such a device circuit. The meter reading then indicates the the laboratory staff may often be faced increase in collector current (I,) resulting with the problem of establishing whether an from a 10nA increase in base current (lb) experimental transistorised circuit is in­ and hence the current amplification factor operative because of a failure in a com­ ponent, faulty design or failure of the 1= transistor itself. By the use of a transistor — can be calculated. tester and a resistance-capacity bridge, two Ib of these possibilities can quickly be investi­ The grounded base amplification factor gated. The tester described in this leaflet a, can also be calculated from the relation is extremely simple in design and operation. It can make reasonably accurate measure­ ments of the two leakage current I„<, and I'co and also the common emitter amplifi­ I + B' cation factor a'. The common base amplifi­ cation factor can be calculated from this The Complete Circuit latter parameter. The complete circuit is shown in Fig. 5 The circuit has been simplified consider­ where a three-pole four-way switch SW3 ably as the instrument has been designed to test low power p-n-p transistors, the now selects which measurement is to be transistors falling into this category being taken. The diagram shows:— those most commonly used for educational (a) in switch position 1 the correct refer­ purposes. ence voltage is set up; Principles of the Tester (b) in switch position 2 I'co is measured; It is easier to understand how the tester (c) in switch position 3 is measured operates if the various sub-circuits are and in the final position a' can be explained separately before considering the measured. complete instrument. Fig. 1 shows the sub-circuit which pro­ The only additional components in the unit vides a fixed reference potential of 2.5V are a low consumption pilot lamp and an (X-X) used for all measurements. The refer­ on/off switch SWi. ence transistor, TR1( is connected in an emitter follower (grounded collector) circuit, Practical Construction the current through the load resistor R: being adjusted by means of bias potentio­ Fig. 6 shows the prototype tester, all the meter RV» for a meter reading of 2.5V. components, including a meter measuring In the prototype instrument, a 0-lmA move­ 4 x 4 in. and a large bell battery, fitting ment meter was used in conjunction with into a box measuring 12 x 6 x 3 in. deep. a multiplier resistor of appropriate value Three terminals marked c, b and e (emitter, to measure 2.5V full scale. collector and base) for connection of the Fig. 2 shows the circuit used to measure transistor under test are also shown. the leakage current I'co. Here the transistor under test, TR2, is connected across the Meter Calibration reference voltage (X-X) and the collector current is measured with the base open The basic 1mA movement is used in the circuit. The meter reading givesI'co direct. various switch positions to measure 0-2.5V, R5 is a limiter resistor to protect the meter 0-1000|iA and a' readings from 0-100 movement should the transistor have an internal short circuit from collector to Ic 1000[iA emitter. Ib 10|iA The circuit for measuring the leakage under test is now connected across the 4.5V current I„, is shown in Fig. 3, the only supply and a load resistor R0 is in series In the prototype it was found most con­ difference in this measurement being that with the collector. The meter measures the venient if the meter scale was therefore the base of the transistor is now connected signal output current from the transistor calibrated from 0-1 with 100 subdivisions, to the emitter. and initially will indicate a current which each one representing 1 OllA. Thus the meter Measurement of a' is carried out using is reduced to zero by adjustment of the reading is multiplied by 100 when measuring the circuit shown in Fig. 4. The transistor “a' adjust” resistor RVS. If the press-button a' and read off directly forI™ and I'co.

57 I Mullard

For the reference voltage the reading is multiplied by 2.5. LIST OF COMPONENTS R. 6800 carbon resistor RVs lkfi linear potentiometer r 3 lkfl carbon resistor R, Value must be calculated accurately for a given meter R5 1.5kfi carbon resistor Ro 2.2k fi carbon resistor Rj 220kfl carbon resistor, high stability 1% Rs 22kQ carbon resistor, high stability 1% RVo lOOkn linear potentiometer SW, Single-pole, two-way toggle switch SW2 Single-pole, push button switch SW3 Three-pole, four-way rotary switch Pilot lamp 6.3V, 0.04A TRi Mullard OC72 transistor Mi 0-lmA, DC moving coil instrument. Using the Transistor Tester To simplify operation of the Tester, details are shown in the Table.

NORTH QUEENSLAND TABLE DISTRIBUTION Position of Adjustments Measurement Note Switch 3

1 Adjust reference potentiometer — RV. for a reading of 2.5V 2 I'co in nA 11 the transistor is short circuit, meter reads a maxi­ mum. If transistor is open circuit, meter reads zero.

3 Ico in (iA If transistor is short circuit, meter reads a maximum. If transistor is open circuit, meter reads zero. Mr. C. A. Pearce 4 Adjust balance resistor RVS If transistor is short circuit, C. A. Pearce & Co. Pty. Ltd., sole Queens­ for zero reading or open circuit it is not land distributors for Mullard-Australia, possible to zero meter have recently opened a branch in Towns­ reading. ville to cover the area between Home Hill and Cairns, including the Atherton Table­ Press a' If pointer goes off scale this land. button The new branch is located at 13 Palmer indicates that the a' is Street, South Townsville, telephone Towns­ greater than 100. ville 5864. The premises feature showroom and warehouse facilities and, no less, a Mullard Valve and Picture Tube ServiceAccuracy: Centre. The accuracy of the I'co and I,,, tests depends upon the accuracy of the meter. The The new branch is in the capable hands a' measurements are within 10%. of Lester Anderson, former C. A. Pearce country representative. Note: Managing Director Mr. Clive Pearce, Mullard-Australia Pty. Ltd. cannot offer this unit either as a complete instrument formed his Company in Brisbane in 1948 or as a kit of parts. The prototype illustrated is only one of many possible interpretations as a specialist stockist of components, test of the circuit. instruments and records and provided an No provision is made in this tester for the measurementV to (turnover of voltage). installation and maintenance service onA more comprehensive transistor tester, capable of determining this parameter, was industrial electronic equipment. Prior to described in Outlook, Vol. 1, No. 4. 1948, Mr. Pearce spent 15 years on the Laboratory Staff of a leading electronics manufacturer and thus has an enthusiastic IF YOU CHANGE YOUR ADDRESS: understanding of our goods and the atten­1. Notify Mullard-Australia Pty. Ltd. immediately. dant application techniques. Mr. Pearce is President of the Queens­ 2. If possible, let us know in advance. Thirty days’ notice will enable our mailing land Section of the Royal Flying Doctor system to operate more efficiently. Service, Chairman of the Radio Sub-Com­ 3. Notify us in writing and include the address label from one of the recent issues mittee and a Committee member of the showing your old address and code line. Brisbane Division of the Institution of Radio Engineers, Australia. THANK YOU. 58 I Milliard I

LUMINANCE — LIGHT UNITS — ILLUMINATION

One often finds some confusion, among The candela is evaluated in terms of the The metric unit of illumination is thelux electronics people, about photometric units. luminous intensity of a ‘black body’ at the (Ix), which is the illumination produced by Many engineers are familiar with a small temperature of solidification of platinum. one lumen falling on an area of one square number of units (some of them, perhaps, A full definition is given by Kaye and Laby metre. It follows that an illumination of obsolete), but are uncertain about the rest. (12th edition, page 71), and the practical 1 lux is produced on an area of 1 square Discussions, therefore, tend to be at cross­ setting-up and observation of this primary metre at a distance of 1 metre from a point purposes and to be complicated by attempts standard is fully discussed in J. W. T. source of 1 candela. at conversion; and data sheets are readilyW alsh’s Photometry and in the recent An alternative (but not preferred) metric understood by only a proportion of their Stationery Office publication Photometric unit is the phot, which is one lumen per users. Standards and the Unit of Light by J. S. square centimetre. One phot is equivalent This state of affairs is not surprising, Preston. to 10,000 lux. It will be noticed that, as the since the basic concepts of photometry A number of national laboratories have area is smaller, the illumination produced have similar names; and a great number evaluated the candela in this way, and they by one lumen is greater. of units have been devised from time to have set up secondary standards in the form Illumination can, of course, be defined time—some metric and some English—with of tungsten lamps, of special design, cali­ inconvenient and unmemorable conversion in terms of any unit of area. Thus the brated against the primary standard. There English unit is the foot-candle (a term factors which are often ruthlessly rounded are slight experimental discrepancies be­ deprecated by the British Standards Insti­ off to ‘about 10’. tween the standard candelas maintained intution) or lumen per square foot, which There are so many units, and such a various countries, but these are too small to is approximately equal to 10 lux. There variety of usage, often extending to the affect practical photometry. are also the sea-mile candle and thenox. employment of units taken haphazardly The only real difficulty about the candela from metric and English systems, that any is that lamps blacken with use, and their attempt to sort out the confusion must take filaments undergo changes which alter the LUMINANCE the form of specific recommendations. This light output. It is therefore essential to A surface, which is either illuminated or article will therefore discuss the preferred reserve one or two of one’s ‘substandard’self-luminous, will appear to an observer units for the main photometric quantities, lamps strictly for the purpose of calibrating to be more or less bright. Brightness, and then provide conversion tables coveringthe ‘working standards’ which are used for however, is a subjective concept, and the all the units which are likely to be still in routine measurements. The substandards term luminance is used for the definable use. should be sent back to the standardising quantity. laboratory for recalibration when any doubt Luminance is expressed in terms of PREFERRED UNITS arises. luminous intensity (‘candle power’) per unit area. The metric unit is the nit (n t), In Mullard data sheets and technical LUMINOUS FLUX which is a luminance of 1 candela per publications we have employed what have square metre. Occasionally the stilb (1 seemed to be the most practical, useful, and A point source of light, with a luminous candela per square centimetre) is used. The convenient units for the devices and appli­intensity measured in candelas, will emit stilb is not a preferred British Standard (it cations concerned. This practice, though it light in all directions. If one visualises a is deprecated in BS233), but it is a practical is defensible, has led to inconsistency andsphere with the point source at its centre, and convenient unit for some purposes. the possibility of confusion. We therefore then the luminous flux can be conveniently propose to go over to the four photometric specified in terms of the flow of light in a There are two other metric units of units of the metric system (candela, lumen, defined section of the sphere. luminance, the apostilb (with a submultiple, lux, and nit) and to discontinue the use of The unit of luminous flux, in both the the skot), and the lambert, which are de­ English units. This decision appears to be metric and English systems, is the lumen fined in terms of luminous flux per unit in line with the tendency of British Standard(lm). This is the luminous flux from a area. They are deprecated by the British practice, since BS1991:1954 gives abbrevia­point source of one candela within a solid Standards Institution. Their relationships to tions for these four units and no others; angle of one steradian. the preferred units are shown in the table. The foot-lambert (with the deprecated and, moreover, these units have been The steradian is defined in the following adopted by the C.I.E. synonym equivalent foot-candle) and the manner. If the radius of a sphere isr, and candela per square foot are the English The units relate to the four quantities an area equal to r is marked on the surface units of luminance. which have to be defined and measured inof the sphere, then the solid angle sub­ photometry. These are, briefly: tended by this area is one steradian. It is METRIC UNITS (C.I.E.) Luminous intensity:the ‘candle power’ of clear that the definition is independent of a light source (which is assumed to be a the actual magnitude of r. The radius may The preferred units, which are taken point source, although, of course, this is be a foot or a metre; the solid angle re­ from the metric system, are, therefore, as not realisable in practice). mains the same. It is also seen that the follows: complete sphere comprises An steradians— Unit Abbreviation Luminous flux:the flow of light from the that is, 12.57. Thus the total luminous flux Luminous source, related to the solid angle over from a point source of one candela is 12.57 intensity candela cd which measurement is made. lumens. Luminous Illumination: the luminous flux falling on flux lumen lm a surface, expressed as luminous flux per ILLUMINATION Illumination lux (lm /m 2) lx unit area. Luminance nit (cd/m2) nt When the luminous flux falls on the inner Luminance: the luminous intensity of an surface of the sphere, the surface is illumin­ These metric units, with the customary illuminated surface, usually expressed as ated. Illumination is defined in terms ofmultiples and submultiples, will be generally luminous intensity per unit area. luminous flux and the area of the surface. used in Mullard data sheets and technical Much photometry, of course, is concerned publications. However, in many laboratories, other units of illumination and luminance LUMINOUS INTENSITY with luminous flux falling on flat surfaces. The error entailed in ignoring the differencehave become well established; therefore There is no confusion of units here. On between a flat surface and a spherical sur­ conversion tables are given for these units, 1 lanuary, 1948, a multiplicity of ‘candles’ face can often be ignored; but if the angle the preferred (metric) unit being shown in and lamps (English, German, Pentane, which the surface subtends is large, then the heavy type. Methven, Carcel, Vernon-Harcourt, Inter­ necessary correction factor should be used. national, and Hefner-Alteneck, to say Tables are available in H. A. E. Keitz’s THE BACKGROUND OF nothing of the Bougie Decimale), were Light Calculations and Measurements. The PHOTOMETRY superseded by the ‘new candle’ orcandela error is 0.4% when the half-apex angle of (cd), which has won international recogni­ the cone of light is 4°, and 2.3% when it Photometry is a sufficiently, but not tion. is 10°. wholly, exact science. Its units are not

59 I Muliard I

Luminance nit stilb cd /ft2 apostilb lambert foot-lambert 1 nit (cd /m 2) = 1 10-4 9.29 x 10-2 n n x 10-4 0.292

1 stilb (cd/cm2) = 104 1 929 IT X 104 n 2920 1 cd/ft2 — 10.76 1.076 x 10-3 1 33.8 3.38 x 10-3 n 1 apostilb (lm/nr) = 1/n l/( n x l0 - 4 ) 2.96 x 10-2 1 10-4 9.29 x 10-2 1 lambert (lm /c m 2) = 1 /( jt x 10-4) 1/n 296 104 1 929 1 foot-lambert or 'equivalent foot- candle’ ( lm /ft2) = 3.43 3.43 x 10-4 1/n 10.76 1.076x10-3 1

absolute, since they are necessarily ex­ pressed in terms of light—that is, the part Illumination of the electromagnetic spectrum which excites the sensation of vision. The spectral lux phot foot-candle response of the eye is not equal throughout 1 lux (lm/m2) 1 10-4 9.29 x 10-2 this narrow frequency band, so that photo­ = metry cannot be directly based on absolute 1 phot (lm/cm2) = 104 1 929 units of energy. Further, the spectral re­ sponse curve of any particular eye differs 1 foot-candle( lm /ft2) = 10.76 10.76x10-4 1 from that of other eyes and is not even constant with time or with different levels of luminous flux. Finally, the eye is subject to fatigue, after-images, and the effect of Bibliography glare; and it is relatively slow to adapt to changed illumination. J. W. T. Walsh. Photometry(3rd edition). British Standard 1991: Part 1:1954.Letter Constable, 1958. (A standard text-book, Symbols, Signs and Abbreviations:Part 1, with useful tables and a comprehensive General. British Standards Institution, 1954, The dependence of photometry on the list of definitions.) characteristics of the eye is summed up on with amendments 1955, 1957, and 1960. page 82 of W alsh’s Photometry. ‘It is more H. A. E. Keitz. Light Calculations and Units and Standards of Measurement Em­ than likely that in many of the branches of Measurements. Philips Technical Library. ployed at the National Physical Laboratory: practical photometry there are unrecognised Cleaver-Hume Press, 1955. Part II, Light (Photometry, Colorimetry and sources of uncertainty which may, later on, Radiometry). HMSO, 1952. be traced to some at present unsuspected Kaye and Laby. Tables of Physical and phenomenon of vision’. Chemical Constants (12th edition). Long­ J. S. Preston. Photometric Standards and the mans, Green, 1959. Unit of Light (Notes on Applied Science, In present day photometry the tendency (Colour temperature—not dealt with in the No. 24). HMSO, 1961. is to use an artificial eye consisting of a present article— is defined on page 73.) suitable photocell combined with filters J. W. T. Walsh et al. Units and Standards of which produce a spectral response curve British Standard 233:1953. Glossary of Light Maintained at the National Physical which approximates to that of the inter­ Terms used in Illumination and Photo­ Laboratory, 1915-60.Proc. I.E.E., Vol. 108, nationally agreed ‘standard observer’. The metry. British Standards Institution, 1953. Part A, No. 39, June 1961, pp. 173 to 181. National Physical Laboratory is, however, Preston. ... investigating the possibility of placing the unit of light on a radiometric basis. An account of this work is given by J. S. Preston. Historical Notes Hertz, 1887—found that ultra-violet light on a spark gap lowered its breakdown It should be noted that the measurement voltage if polished terminals were used. of infra-red radiation isnot part of photo­ metry. Data on infra-red devices are given Hallwachs, 1888—found that ultra-violet light dispersed a negative charge on a polished in terms of ordinary physical units. zinc plate but not a positive charge, and neutral plates became positive. SUMMARY Stoletow, 1890—passed the first photoelectric current between a polished zinc plate exposed to ultra-violet light, and a grid nearby. No attempt has been made in this article to give either a rigorous or a complete Elster and Geitel, 1889—found that sodium, potassium and rubidium gave the photoelectric account of photometric principles. It is, effect with visible light. indeed, probably impossible to write a short and simple guide to photometry. The Lenard, 1900—showed that the current was carried by electrons (discovered by Knowledgeable reader will, therefore, be J. T. Thomson in 1897) and not by metal ions from the cathode. able to point out many inadequacies and silences. These are deliberate. Einstein, 1905—proposed the photoelectric equation that the energy of a photon is hv. Our object has been to disentangle the Richmyer, 1909 and—showed that the photoelectric current was linear with illumination confusion which tends to surround the main photometric units, and to recommend the Elster and Geitel, 1913 over the range 5 x 107 to 1. use of a coherent system. Readers who wish to go further will find the bibliography Millikan, 1916—showed the light energy absorbed equalled the energy to free the useful. electron plus the maximum observed energy of an ejected electron.

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