Welcome to the SAIEE Historical Section Museum

The Historical Section of the SAIEE has many artifacts of historical interest in its collection and has an association with Eskoms historical collection.

Further detailed information on each artifact can be viewed by clicking on the image of the selected items shown below,

More antique electric exhibits can be viewed by visiting the museums at:

http://www.edisonian.com/edisonian001.htm 
http://www.ieee-virtual-museum.org
http://www.awasa.org.za/



Ionospheric recorder Wadley receiver Wire recorder
Ionospheric recorder Wadley receiver Wire recorder
Current balance Crystal set Marconiphone
Current balance Crystal set Marconiphone
Lightning recorder The first integrated circuit? The beginnings of electronics
Lightning recorder The first integrated circuit? The beginnings of electronics
Electrical power frequency control The prototype tellurometer Early x-ray tube
Electrical power frequency control The prototype tellurometer Early x-ray tube
Steam turbine driven DC generator Turbine used at Sabie Hydro Station Compressed air meter
Steam turbine driven
DC generator
Turbine used at Sabie Hydro Station
Portable voltmeter Portable laboratory ohmmeter
Portable voltmeter Portable laboratory ohmmeter Compressed air meter
Portable temperature indicator Portable current transformer Portable wattmeter
Portable temperature indicator Portable current transformer Portable wattmeter
Voltage ratio box Portable low resistance ohmmeter Phase splitting resistance box
Voltage ratio box Portable low resistance ohmmeter Phase splitting resistance box
Portable wattmeter Phase angle meter Mine telephone
Portable wattmeter Phase angle meter Mine telephone
Portable millivoltmeter Portable voltmeter Wheatstone bridge
Portable millivoltmeter Portable voltmeter Wheatstone bridge
Conductivity meter Universal galvanometer Wheatstone bridge
Conductivity meter Universal galvanometer Wheatstone bridge
Electrodynamometer Mercury Arc Rectifier DC Galvanometer
Electrodynamometer Mercury Arc Rectifier DC Galvanometer
AC Galvanometer Demand meter Time lag relay
AC Galvanometer Demand meter Time lag relay
Single element instantaneous relay Three element instantaneous relay Time lag relay
Single element instantaneous relay Three element instantaneous relay Time lag relay
Universal Potentiometer Current transformer Current transformer
   
Current transformer    



Lightning recorder

JOHANNESBURG OBSERVATORY LIGHTNING RECORDER
Manufactured in Budapest 1905

This remarkable lightning recorder is the only surviving instrument from the Transvaal Meteorological Station at the Johannesburg Observatory.

The coherer
THE COHERER

Its operation was based on the Marconi coherer wireless telegraphy receiver. The coherer is mounted between the two perforated brass posts to the left of centre of the instrument. Lightning impulses induced in an external antenna caused the coherer to conduct and operate the telegraph relay situated on the right hand side of the instrument. The relay activated the armature of the central assembly having a striker that de-cohered the coherer. The vertical arm attached to the armature held a pen which wrote on the helical chart rotated by the clock on the extreme left and a gong warned the operators that an event had been recorded.

Dimensions: 630 mm wide x 350 mm deep x 285 mm high

As far as we have been able to determine this is the sole surviving instrument of this type.

For further details see Vermeulen, DJ. 2000. The Historical Interest Group re-discovers Popov. Elektron 17(6), June:13.

The instrument is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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The first integrated circuit?
THE FIRST INTEGRATED CIRCUIT?

In the 1920s the German manufacture Loewe Radio produced a series of receivers in which several valves and their coupling components were assembled in a common envelope. The only additional items required were the tuning inductance/reaction coils and the tuning capacitor seen in the illustration. This amplifier integration was not easily achieved as each resistor and capacitor had to be individually encapsulated to ensure that they would not contaminate the vacuum.

The main reason for this surprising innovation was to minimise the German licence fee that was based on the number of valves used in a set.

Dimensions: 186 mm wide x 150 mm deep x 190 mm high

The instrument is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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The beginnings of electronics
THE BEGINNINGS OF ELECTRONICS
The Contribution of the South African Dr HJ van der Bijl

Electronics started in 1907 when the American entrepreneur, Lee De Forest, invented the first electronic amplifying device. He named it the Audion and it was subsequently known as the triode vacuum tube (valve).

De Forest promoted his invention extensively and made a special version for telephone repeater service (right hand side illustration). He persuaded the Western Electric Company (WE) to pay him $50 000 for the exclusive rights to use the Audion in the telephone industry. His original crude device was not suitable for industrial application and WE assembled a team of scientists to develop it into a practical unit.

In 1914 The South African, Dr Hendrik van der Bijl, analysed its performance mathematically and designed practical tubes for use on the first transcontinental telephone circuit linking New York and San Francisco (centre and right hand illustrations).

Dimensions: 50 mm diameter, 75 mm high & 55 mm diameter, 90 mm high

For more information see Vermeulen, DJ. 1998. The remarkable Dr Hendrik van der Bijl. Proc IEEE 86(12), December: 2445-2454.

All three of these unique valves form part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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Electric power frequency control
ELECTRICAL POWER FREQUENCY CONTROL

Electrical power suppliers were legally required to maintain mains frequency within close limits. Over 24 hours the total number of cycles generated had to be controlled to ensure that synchronous time keeping devices would remain accurate.

From the mid-1920s until they were linked with Eskom the equipment illustrated was used to monitor the Johannesburg supply frequency. The accurate pendulum clock was kept in step with standard South African time by regular corrections. The mains frequency drove a synchronous clock motor and a comparison between this and the clock time was made every 15 seconds and any discrepancy showed as a deviation between the two pointers of the main dial.

The two smaller clock faces showed mains time and clock time respectively and were useful when the deviation exceeded 3 minutes.

Dimensions: 485 mm wide x 335 mm deep x 1690 mm high

For further information see Vermeulen, DJ. 2001. Mains frequency control. Elektron 18(11), November:29.

The clock is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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The prototype tellurometer
THE PROTOTYPE TELLUROMETER
with its inventor Dr TL Wadley (1950)

The Tellurometer measured distances between 3 and 50 km with an accuracy of 3 parts in 106. Instruments were set up at each of the two required points and the distance between them was calculated from the time taken for a radio signal to travel from one end to the other and back again. Once the terminal stations were established the distance could be measured in less than half an hour where previously, using hand methods, it had taken a team several months to complete the same operation.

The Tellurometer was invented and developed by Dr Trevor Wadley working at the CSIR Telecommunications Research Laboratories and was subsequently manufactured in South Africa.

Dimensions: Dish 440 mm diameter, 360 mm front to back, 470 mm high

By 1971 it had earned over R12 million in foreign exchange. This instrument revolutionised land surveying as it became possible to measure distance as quickly and accurately as measuring angles.

The satellite based Global Positioning System has subsequently produced a second revolution in surveying technology.

The Tellurometer is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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Early x-ray tube
EARLY X-RAY TUBE Circa 1900

X-rays were discovered by the German Wilhelm Röntgen in 1895. In 1896 primitive equipment was already in use in South Africa. By the end of the Anglo-Boer war there were probably as many as 20 X-ray units in operation.

This tube is typical of early units that depended on a rather poor vacuum of about 10 mPa to produce cathode rays (electrons). The cathode lies on the right hand side of tube with the anode mounted at an angle in the centre of the tube. X-rays were produced when the electrons collided with the anode. Such early tubes produced rather low intensities requiring photographic exposures of several minutes.

Dimensions: 360 mm x 100 mm wide x 320 mm high.

A British supplier, Newton & Co, sold this tube but the manufacturer is unknown.

For further details see Vermeulen, DJ. 2002. Early X-ray equipment: a view from the south. Engineering Science & Education Journ, December 11(6): 231-242. The tube is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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STEAM TURBINE DRIVEN DC GENERATOR
STEAM TURBINE DRIVEN DC GENERATOR manufactured by Greenwood and Batley Limited at Albion Works in Leeds, England. It is believed to have been built circa 1900.

Greenwood and Batley Limited donated this DC generator to the University of the Witwatersrand in Johannesburg.
The university donated it to the enthusiasts of the Rand Society of Model Engineers.
In exchange for spare parts for another DC generator, the Rand Society of Model Engineers gave Greenwood and Batley’s DC generator to ESKOM.
This steam turbine driven DC generator is currently on display at Gold Reef City in Johannesburg.

TECHNICAL DESCRIPTION
DC Generator No. 2535 110 Volts 40 Amps 3 000rpm 4 kW
Steam turbine No. G258 3 000rpm Steam pressure 100 psi 7 BHP
Curtis wheel type

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TURBINE USED AT SABIE RIVER GORGE HYDRO STATION

TURBINE USED AT SABIE RIVER GORGE HYDRO STATION

This is the remaining turbine of three used at Sabie River Gorge Hydro Power Station. This power station was the first power station designed by engineers employed by the Electricity Supply Commission (ESCOM). The power station was established to supply electrical power to the gold mines in the Sabie district of Mpumalanga (or Eastern Transvaal as it was then known.)

Sabie River Gorge power station operated from 1 April 1928 until it was decommissioned on 5 November 1964.
James Gordon & Company Limited of London manufactured the three turbines in 1925.

TECHNICAL DESCRIPTION
A Francis type turbine and alternator, 450kW 600kVA 750rpm, three-phase, 50 cycles, 3300 volts. The turbine and alternator operated under 64 metres static head of water.

The turbine is on loan to Gold Reef City, Johannesburg. It can be viewed at the mine-shaft in this theme park.

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A COMPRESSED AIR METER
A COMPRESSED AIR METER used in conjunction with a Venturi in the airline.

Compressors at Rosherville Power Station supplied air to a compressed air grid. This grid supplied air to the Central District Gold mines. This meter was located at Rose Deep gold mine.

The meter has a unique air-driven clock.

The meter is on loan to Gold Reef City, Johannesburg. It can be viewed at the entrance to the mine-shaft in this museum and theme park.

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A PORTABLE DC VOLTMETER
A PORTABLE DC VOLTMETER manufactured in England by Cambridge and Paul Instrument Company. Circa 1920 - 1924.

TECHNICAL DESCRIPTION
Portable, dual range, moving coil instrument for voltage measurement up to 25 millivolts DC.
Scaled 0 - 2,5 Mirror scale Direct connected Ranges 2,5 and 25 mV
Range selection by terminal connection Resistance 10 and 20 ohms at 20°C
The instrument is housed in a wooden case
Approximate dimensions 185mm x 180mm x 95mm
The voltmeter is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A PORTABLE MULTI-RANGE LABORATORY OHMMETER
A PORTABLE MULTI-RANGE LABORATORY OHMMETER believed to have been used in 1900. It measured resistance up to 1250 ohms. The manufacturer is unknown.

Scaled 0 – 125 (black) and 125 – 250 (red) Mirror scale
Ranges 0 – 125 ohms, 125 – 250 ohms, 0 – 250 ohms, 250 – 500 ohms, 0 – 625 ohms, 625 – 1250 ohms. Range selection by switches
External power supply 5 x 2V storage cells
A portable instrument in wooden case with carrying handle
Approximate overall dimensions 245mm x 150mm x 260mm
Operating instructions inside lid:-
Crank set on - 1: black figures or 2: red figures 1 Division = 5 Ohms
Crank set on - 3: black figures or 4: red figures 1 Division = 2 Ohms
Crank set on - 5: black figures or 6: red figures 1 Division = 1 Ohm

"After having selected the proper sensitiveness, before making the measurement, the crank is to be set either on button 1, 3, or 5, corresponding to the sensitiveness which has been chosen, whereupon the key on the left hand side should be depressed and the button on top turned until the pointer indicates zero. The resistance, to be measured, is then inserted between the terminals on the right, with the crank set on the button, corresponding to the sensitiveness, and with the key in the middle depressed. The resistance is then read from the scale. The storage batteries are to be connected with the terminals on top of the apparatus before taking the measurement, in accordance with the accompanying sketch.

O-------6volts-------O-------2volts-------O-------2volts-------O"

The ohmmeter is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A "RESILIA" PORTABLE TEMPERATURE INDICATOR
A "RESILIA" PORTABLE TEMPERATURE INDICATOR manufactured by Foster Instrument Company, England. Circa 1945. Using a thermocouple as a sensor, it measured temperature.

Scaled 0 - 7 x 100°C and 0 - 12,9 x 100°F Mirror scale.
Type no. 751 YX/6
Provision is made for the simultaneous connection of 6 thermocouples, any one of which may be selected by key switch.
A portable instrument in a wooden case.
Approximate overall dimensions 300 mm x 80 mm x 290 mm.
The indicator is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A PORTABLE CURRENT TRANSFORMER
A PORTABLE CURRENT TRANSFORMER made by Ferranti Limited at Hollinwood, Lancashire, England. Circa 1910. The Victoria Falls and Transvaal Power Company Limited (VFP) was the original owner of the instrument.

Ratio 400/5A 7,5VA 50Hz Class AL Tested at 2000V With secondary shorting switch.
A portable instrument in wooden case with leather carrying handle.
It is labelled "VF & TP Co., Ltd. Test Dept."
Approximate overall dimensions 225 mm x 220 mm x 270 mm.
The current transformer is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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AN AC/DC PORTABLE WATTMETER
AN AC/DC PORTABLE WATTMETER manufactured in the USA by Weston Electrical Instrument Company, Newark, New Jersey in 1920. It was standardized at Weston Laboratory, Audry House, Ely Place, London.

It is a portable, laboratory type, sub-standard, dynamometer instrument for measuring power in AC or DC circuits.

TECHNICAL DESCRIPTION
Scaled 0 – 120 watts AC/DC Mirror scale
Ranges: Current 2,5 and 5,0 A Potential 50 and 100 V
Power 0 – 120/240/480 W
Range selection by terminals and links Model 310
Portable instrument in wooden case with hinged removable cover
Approximate overall dimensions 210 mm x 270 mm x 150 mm
The wattmeter is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A VOLTAGE RATIO BOX

A VOLTAGE RATIO BOX manufactured by H Tinsley and Company, London. Circa 1930.

The 'volt box' or 'ratio box' is used in conjunction with a potentiometer if the voltage to be measured is above about 2V. It consists of a high resistance having a number of accurately placed tappings and performs the function of a potential divider.

TECHNICAL DESCRIPTION
Input resistance 10 000 ohms Multiplication factors 10/20/50/100/200/500
Approximate overall dimensions 250 mm x 190 mm x 180 mm
The voltage ratio box is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.s

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A PORTABLE LOW RESISTANCE OHMMETER

A PORTABLE LOW RESISTANCE OHMMETER. Circa 1940. ESCOM’s Test Department is thought to have made the instrument.

The instrument was used to measure low resistance up to 1,8 ohms.
Range 0,1 – 1,8 ohms Detailed operating instructions are shown on the inside lid.
Approximate overall dimensions 295 mm x 240 mm x 170 mm
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A PHASE SPLITTING RESISTANCE BOX
A PHASE SPLITTING RESISTANCE BOX made by H Tinsley and Company, London. Circa 1930.

The Tinsley Phase Splitting Resistance consists of a variable number of non-inductively wound resistance coils. It is used in series with a variable capacitance to produce the quadrature phase of a 2-phase Drysdale phase-shifter when the available supply is single phase. The Drysdale phase-shifter is an essential component of the Drysdale-Tinsley AC potentiometer used for the accurate measurement of alternating currents and voltages.

Range 100 ohms - 1000 ohms in steps of 100 ohms
0,1 ohms - 111 ohms in steps of 0,1 ohm
Max. current 0,25A
Approximate overall dimensions 295 mm x 165 mm x 190 mm
5 plugs are missing.
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.s

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A PORTABLE AC/DC WATTMETER

A PORTABLE AC/DC WATTMETER made by Elliot Instruments, United Kingdom. Circa 1940.

It is a portable laboratory type, precision, dynamometer wattmeter, for measuring power in AC or DC circuits.

TECHNICAL DESCRIPTION
Scaled 0 – 110 Mirror scale
Ranges: 0 - 55W and 0 - 110W Range selection by terminals and links.
Max. voltage 110V Max. current 5A
Type PL
Correct at 68°F Accuracy % not readable
For use on a bench, the instrument has levelling screws and crossed spirit levels. It is mounted in a wooden case with a lid and carrying handle.
Approximate overall dimensions 215 mm x 280 mm x 240 mm
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A PHASE ANGLE METER
A PHASE ANGLE METER manufactured in the USA by Weston Electrical Instrument Corporation, Newark, New Jersey.

The instrument measures the angle between the current and the voltage in an AC circuit when these quantities are represented by vectors.

TECHNICAL DESCRIPTION
Scaled 0 - 90° 180 - 90° 180 - 270° 360 - 270°
Max. Voltage 260/130/75/17,5V Rated Voltage 220/110/65/15
Max. Current 6/3A Rated Current 2,5/1,25A Frequency 50Hz
Range selection by selector switch.
Voltage selection by terminal. Current selection by terminal and link.
Model 480
It is a portable instrument in a wooden case with cover and leather carrying handle.
Approximate overall dimensions 220 mm x 280 mm x 210 mm
One terminal top is missing.
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A FLAME-PROOF MINE TELEPHONE

A FLAME-PROOF MINE TELEPHONE manufactured by Siemens Brothers and Company Limited, London. Circa 1946. This type of telephone was used in fiery mines and industrial situations with high ambient noise levels.

This particular phone is mounted on a wooden baseboard with an inscribed plaque. The inscription reads "Presented to Mr. H P Alexander as a memento of his association with Colenso Power Station." Mr. Alexander was ESCOM’s Regional Manager in Natal.

Approximate overall dimensions 320 mm x 190 mm x 610 mm
The telephone is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A PORTABLE MILLIVOLTMETER

A PORTABLE MILLIVOLTMETER manufactured by Siemens and Halske, Germany. It is believed it was built circa 1900.
It is a portable, moving coil type that was used with external 60 millivolt shunts.
5 amp shunt multiply the reading by 0,1
20 amp shunt multiply the reading by 0,4
60 amp shunt multiply the reading by 1,0
Approximate overall dimensions 200 mm x 100 mm x 220 mm
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A PORTABLE AC/DC VOLTMETER

A PORTABLE AC/DC VOLTMETER believed to have been manufactured by Hartmann and Braun, Germany in 1897.

It is believed that this instrument was first used by the General Electric Power Co., Ltd., Germiston and was later taken over by the Victoria Falls and Transvaal Power Co., Ltd. (VFP).

It is a portable moving iron type for measuring voltage in AC or DC circuits.
Scaled 0 – 200V
It is housed in a wooden case with a lockable front flap and brass-carrying handle.
Approximate overall dimension 220 mm x 110 mm x 215 mm
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A PORTABLE WHEATSTONE BRIDGE

A PORTABLE WHEATSTONE BRIDGE made by H. Tinsley and Co., London. Circa 1940.

This is a portable, laboratory type used for the measurement of medium range resistance.
Ratio arms (by plug setting) 10, 100 or 1000 ohms
Reference standard (4 decades) 0 - 11'110 ohms in steps of 1ohm
The instrument has both Battery and Galvanometer keys, each with provision for locking in the "on" position.
Contained in a Teak case without lid.
Approximate overall dimensions 395 mm x 215 mm x 150 mm

N.B. This portable version of the Wheatstone Bridge was, at one time, commonly known as a "Post Office Box"
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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The Wheatstone Bridge circuit is one which is used extensively for the measurement of medium range resistance (typically 1,0 to 100 000 ohms), both as a precision method in the laboratory, and in a modified form, as a portable test set generally known as the "Post Office Box." It also forms the basis from which many other "bridge" networks have been developed for both AC and DC measurements.

The general arrangement is shown in the diagram. R1 and R2 are known as the ratio arms and are generally adjustable to one of four values, such as 1,0, 10, 100 and 1000 ohms. R3 is the reference standard and is variable typically between 1,0 and 1 000 ohms in steps of 1,0 ohm. Rx is the unknown resistance. G is a sensitive galvanometer.

The bridge is balanced (i.e. Zero deflection of the galvanometer) by adjusting R3. At balance the value of the unknown resistance is given by Rx = (R2/R1) x R3. The extreme sensitivity of the circuit makes it particularly suited to strain measurement in conjunction with a resistive transducer.

Modified versions of the Wheatstone Bridge are used for the measurement of inductance and capacitance.

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A CONDUCTIVITY METER

A CONDUCTIVITY METER made by Evershed and Vignoles, London.

Circa 1935. This instrument was supplied by British Agencies Limited, Johannesburg.

The conductivity meter is essentially a resistance-measuring device arranged to display the reciprocal of the resistance i.e. the conductivity. It has a moving coil movement without control springs but with two moving coils so connected that their resultant torques are in opposition. The one coil carries the current (I), or a definite portion of the current, flowing through the test piece. The other, a current proportional to the voltage applied (V). The displacement of the movement at balance is proportional to the ratio of the two torques i.e. V/I which, by Ohm's Law, is proportional to the resistance or inversely proportional to the conductivity.

A hand driven generator built into the instrument case provides power.
The instrument is a portable type used to measure the conductivity of earthing systems, electrolytes, etc.
Scaled 0 – 3000 Ranges 0 - 3000/300/30 Patented 1907
The instrument is housed in a wooden case with levelling screws.
Approximate overall dimensions 200 mm x 340 mm x 220 mm
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A UNIVERSAL GALVANOMETER

A UNIVERSAL GALVANOMETER made by Siemens and Halske, Germany in 1897.
Siemens and Halske supplied this instrument to the Rand Central Electric Works (RCEW) after the construction of Brakpan Power Station in 1897.

Approximate overall dimensions 200 mm diameter x 100 mm
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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A WHEATSTONE BRIDGE

A WHEATSTONE BRIDGE made by Siemens and Halske, Germany in 1887.
Approximate overall dimensions 100 mm diameter x 150 mm

The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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AN ASTATIC ELECTRODYNAMOMETER

AN ASTATIC ELECTRODYNAMOMETER believed to have been made by Siemens and Halske, Germany in 1887.
Approximate overall dimensions 100 mm diameter x 150 mm
The instrument is now part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.

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MERCURY ARC RECTIFIER

The function of the mercury arc rectifier is to convert alternating current into direct current. Peter Cooper Hewitt invented it in 1902.

It was generally more economical to obtain DC power by conversion from AC than to generate it as DC power.

A mercury arc rectifier consists of a glass or metal evacuated vessel containing a mercury pool cathode and two or more anodes. A bright dancing spot on the mercury surface is the source of electrons that move toward any positively charged anodes.

THE CATHODE SPOT
Electrons are emitted from the cathode spot and proceed into space where they strike neutral vapour molecules and ionise them by removing an electron. The new electron joins the old in conducting the current. The remainder of the molecule has a net positive charge and is a positive ion. It is attracted to the cathode. As the positive ions approach the cathode, they produce a high space charge potential gradient which removes electrons from the relatively cold mercury surface. At the same time, the positive ions striking the surface heat it and cause a violent evolution of mercury vapour. As the ions are also mercury vapour, a pressure of mercury vapour is built up which enables the electrons to strike molecules after a very short distance.

The entire process can thus take place very close to the mercury surface. This enables very few volts to produce a gradient of millions of volts per centimetre at the surface.

The exhibit is a three-phase, glass bulb mercury arc rectifier made in the United Kingdom by the Electric Construction Company Limited. (ECC) It has type/serial number 5/13068. It is mounted in a metal stand complete with all components to make a working exhibit.

The instrument is currently on display at Palmiet Power Station.

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A DC GALVANOMETER made in the United Kingdom by H. Tinsley and Company. Circa 1925.

This instrument is a sensitive mirror type. It is approximately 150mm in diameter and measures 250mm high. Serial number 1284.

The instrument is currently on display at Palmiet Power Station.

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AN AC GALVANOMETER made in the United Kingdom by H. Tinsley and Company. Circa 1925.

This instrument is a sensitive vibration type 432. It is approximately 150mm in diameter and measures 300mm high. Serial number 13385

The instrument is currently on display at Palmiet Power Station.

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PRINTING DEMAND METER

Printing demand meter (maximum demand printometer) manufactured in USA by General Electric. Circa 1950.

Type PD-5. Serial number 626103. Operating voltage 18V DC.

Enclosed in a cast-iron case with approximate overall dimensions 300mm wide x 330 high x 205mm deep.

The instrument is currently on display at Palmiet Power Station.

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TIME LAG RELAY

An electromechanical constant definite time delay relay made in the United Kingdom by Reyrolle.

Time delay is fixed at 5 seconds. Operating voltage is 15V DC.

Type T.D. Article number 415C98. Serial number BQTTD67.

Enclosed in a cast-iron case with approximate overall dimensions 240mm wide x 180 high x 110mm deep.

The instrument is currently on display at Palmiet Power Station.

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SINGLE ELEMENT INSTANTANEOUS RELAY

A single pole, attracted armature, non-directional, instantaneous over current relay. Manufacturer was possibly the Victoria Falls and Transvaal Power Company Limited or Escom.

Enclosed in a cast-iron case with approximate overall dimensions 230mm diameter x 100mm deep.

The instrument is currently on display at Palmiet Power Station.

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THREE ELEMENT INSTANTANEOUS RELAY

A three pole, balanced beam, non-directional, instantaneous over current relay. Manufacturer was possibly the Victoria Falls and Transvaal Power Company Limited or Escom.

Type instantaneous over current. Serial number 8995. Setting range 2 – 10A 50Hz. Trip circuit 24V DC.

Enclosed in a cast-iron case with approximate overall dimensions 370mm x 200mm high x 110msm deep.

The instrument is currently on display at Palmiet Power Station.

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TIME LAG RELAY

An electromechanical definite time delay relay, made in the United Kingdom by Metropolitan Vickers. Circa 1950.

Type AKA. Serial number 788073.

Time delay range 0 – 5 seconds. Operating voltage 110V DC. Hand reset flag indicator.

Enclosed in a cast-iron case with approximate overall dimensions 185mm x 220mm high x 120mm deep.

The instrument is currently on display at Palmiet Power Station.

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UNIVERSAL POTENTIOMETER

A potentiometer is used to measure alternating and direct current. It was made in the United Kingdom by H. Tinsley and Company. Circa 1930.

Serial number 1278.

Approximate overall dimensions 850mm long x 420mm wide x 90mm high.

The instrument is currently on display at Palmiet Power Station.

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CURRENT TRANSFORMER

A dry type switchboard current transformer made in the United kingdom by Switchgear and Equipment Company Limited.

Reference number W.O. 88T/1. Ratio 15/5. 50Hz. 15VA maximum. Class C. Maximum voltage 11 000V.

Approximate overall dimensions 150mm wide x 200mm high x 100mm deep.

The instrument is currently on display at Palmiet Power Station.

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CURRENT TRANSFORMER

A through type portable current transformer manufactured in the United Kingdom by Ferranti Company Limited.

Reference number 219095. Ratio 800/5. 50Hz. 7,5VA. Class AL. Tested at 2000V.

It is labelled "VF & TP Co. Ltd. Test Dept."

Enclosed in a wooden case with approximate overall dimensions 200mm wide x 200mm high x 140mm deep.

The instrument is currently on display at Palmiet Power Station.

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CURRENT TRANSFORMER

A through type portable current transformer manufactured in the United Kingdom by English Electric Company Limited.

Reference number PPS 29645. Ratio 500/5. 26 - 100Hz. 15VA. Maximum voltage 6600V.

Approximate overall dimensions 320mm wide x 130mm high.

The instrument is currently on display at Palmiet Power Station.

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THE IONOSPHERIC RECORDER circa 1948

Before submarine cables and satellites for transmitting telephone signals became available in the mid 1970s voice communication with overseas countries depended on short-wave radio. This form of transmission exploited the reflection of radio waves by the Ionosphere located hundreds of kilometres above the surface of the earth. The behaviour of this phenomenon was poorly understood and after WWII an international effort was launched to learn more about the technique.

TECHNICAL INFORMATION

It became essential to understand the variations in height of the Ionosphere and the range of frequencies reflected by these layers. Trevor Wadley, employed by the South African Council for Scientific and Industrial Research's (CSIR) Telecommunications Research Laboratory, was given the task of developing a suitable instrument for determining these parameters. The height was measured using Radar in the frequency range from 100 kHz to 20 MHz. Wadley devised unique equipment which generated bursts of radio signals over the full frequency range without band switching. Likewise his receiver tuned over the full band in a single smooth sweep. This achievement was unique and proved to be very successful. The results were recorded one frame at time on a 16 mm cinè camera and were shared internationally. Other countries developed similar equipment but the range of frequencies was covered in several steps and could not achieve the same elegant results.

Approximate dimensions 1m x 1m x 1m

The Ionospheric Recorder is part of the South African Institute of Electrical Engineers historical collection.
http://www.saiee.org.za
Tel: +2711 487 3003

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THE WADLEY RECEIVER circa 1952

Following the success of his Ionosphere Recorder, Trevor Wadley realised that the technique could be extended to produce a radio receiver with continuous frequency coverage. In the early 1950s he produced the prototypes shown in the illustration.

TECHNICAL INFORMATION

Based on a stable 1 MHz crystal controlled oscillator the receiver covered all frequencies from 0 to 30 MHz without gaps. There were two frequency-selecting dials, the first chose the desired megahertz range and the second interpolated between successive megahertz steps. By clever design Wadley was able to achieve exceptional frequency stability combined with accurate tuning calibration. It was possible to set the desired frequency on a cold receiver and when the power was switched on the selected frequency would be available to within 5 kHz - such performance had never been achieved previously.

The Royal Navy chose to standardise on this receiver and a small (at that time) British electronics company, Racal, took on the manufacture. It was used all over the world and remained supreme until digital equipment took its place. A transistorised version was manufactured in South Africa, known as the Barlow-Wadley XCR-30, which was very popular with amateur radio enthusiasts all over the world. The Yaesu FRG-7 was produced under licence in Japan.

Approximate dimensions 400mm x 350mm x 250mm

The Wadley Receiver is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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WIRE RECORDER circa 1948

Manufactured by Webster, Chicago.

http://www.videointerchange.com/wire_recorder1.htm

Before the development of oxide based magnetic tape, "glorified" steel piano wire was the dominant media of choice.

The technology of magnetic recording dates back to 1878, when Oberlin Smith proposed the idea of recording telephone signals onto a length of steel piano wire. Over the next thirty years the technology evolved at a "snail's pace"; stalled by lack of adequate and cost effective electronic amplification. By 1930, advances in electronics allowed the first commercially successful wire recorders to be introduced as dictating machines and telephone recorders in Europe and North America. During WWII, the machines found their way into the BBC who employed banks of them for sending messages to the French underground. Germany broadcast pre-recorded speeches by Adolf Hitler in quick succession from widely separated transmitters to confuse the allies. The early machines used large reels of steel tape at a speed of 1metre/second. The US Army & Navy also employed them for similar purposes in their operations centers. Following the war from 1947 to 1952, wire recorders became popular in America and across Europe, and started showing up in many homes.

The advent of oxide based magnetic tape had many benefits over steel wire.... Mainly the ability to record and playback in stereo. Thus magnetic tape put an end to the wire recording era.

Signals recorded on steel wire recorders have held up quite well over the years and the sound quality was fairly good considering the limited technology of the day.

Approximate dimensions: 430mm long x 290mm wide x 180mm deep.

A Wire Recorder is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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KELVIN CURRENT BALANCE pre-1940

The two coils mounted at the extremities of the pivoted beam were connected in series with four co-axial fixed coils placed above and below the moving coils. The magnetic fields produced by the current interact so as to unbalance the beam and weights are provided to restore the beams to the neutral position. Both AC and DC measurements were possible. International current standards were maintained by similar instruments.

Before World War Two and the formation of the South African Bureau of Standards, the University of the Witwatersrand provided a standardisation service for electrical measurements. This particular instrument was one of the measuring standards.

Approximate dimensions: 1 000mm x 120mm x 350mm

The Kelvin Current Balance is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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BURNDEPT ETHOPHONE JUNIOR CRYSTAL SET circa 1925
(450kHz - 1200kHz 1925 price about £5)

Most listeners were using crystal sets to receive broadcasts in the early 1920s as they could not afford valve receivers. The Galena crystal and "Cats Whisker" diode detector required frequent readjustment. This, combined with the discomfort of wearing headphones, made listening to broadcasts a dedicated pastime. John Samuel Streeter's weekly broadcasts of selected gramophone recordings were transmitted from his Cape Town home from 1919 until September 1924.

Approximate dimensions: 150mm x 150mm x 250mm

The Burndept Ethophone Junior Crystal Set is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa.
http://www.saiee.org.za
Tel: +2711 487 3003

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MARCONIPHONE circa 1925

A 2-valve-reaction detector and audio amplifier capable of driving an external loudspeaker at distances up to 60km from the transmitter. It required is a 4V accumulator, a grid bias battery and an HT battery. Long, short and medium waves were selected by means of the plug-in coil which was tuned by the rotating short circuited loop.

The Marconiphone is part of the South African Institute of Electrical Engineers historical collection and can be viewed in Observatory, Johannesburg, South Africa. It was donated to the SAIEE by the late G D Walker.
http://www.saiee.org.za
Tel: +2711 487 3003

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