TITANIC-TITANIC.com | Titanic Articles: RMS Olympic Lord Kelvin's Patent Testing Set No.434
The instrument discussed below is a galvanometer and was used for the measuring the resistance of electrical insulation. It is likely to be capable of measuring voltage and amps, its modern day equivalent being an electrician's circuit tester (Avo meter, Multimeter) or similar.
This particular instrument was used on the White Star Line's Olympic and was most likely to have been used for testing the insulation on the ship's wiring. It is known to be a very sensitive instrument and is capable of detecting voltages as low as 10 -11 Volts, (0.0000000001 of a volt).
The number '434' is the number of the instrument and not the patent number, (indeed Kelvin did not invent the device but was intuitive enough to combine the technology of the day to produce an instrument for his needs). The number is also written in pencil inside the box beneath the post connectors.
The general appearance of the set is indicative of very little use, if any. Examination of the post connectors shows the lacquer protection to be essentially complete, indeed the lacquer would have hampered electrical contact further suggesting the set was probably little used.
The instrument has been in the ownership of an elderly gentleman, since the late 1930's who worked at Swan Hunter on Tyneside England all his working life, and believed to have retired in 1972. He acquired this and other White Star Line items at the final auction that took place at the time of the decommissioning of the ship at the Jarrow shipyards.
The "Asset Card"
Accompanying the instrument was a small card which I have termed "the asset card", and was probably used as a record card of the "asset" although it is not clear why the card number (in the top left) should be identical to the instrument number. Perhaps this was merely convenient for "A.E. Henderson CRO").
The "asset card" reads "please note this instrument not to be removed from 'Olympic'" and is signed A.E. Henderson CRO" and dated 13/2/1913.
It is uncertain what C.R.O is an abbreviation of - possible Chief Radio Officer although what we know today as radio operators were in 1913 known as wireless telegraphers, the capability for sending speech was not developed till some years later. The operators of the time were known as "Marconi Men", the term "radio" did not come into general use until much later, indeed "wireless" is still used as the generic term for radio.
C.R.O. could be Chief Records Officer or possibly Requisition Officer; research is ongoing to determine which is correct and any available background to A.E. Henderson.
The instrument would have possessed a tripod or levelling screws and possibly a brass-handled screwdriver used for zeroing the galvanometer. When not in use it is likely it would have fitted in the spring clips in the lid (one clip missing).
The lock on the box is a 2 lever lock made in Willenhall, Staffordshire, England, the home of British lock making, sadly the key is missing.
A leather carrying strap, now missing, was screwed to the side box using brass screws and washers.
Shunts (electrical resistors) are employed to enable the measurement to be read as Volts or Amps, (possibly Watts as well) and also probably to reduce large electrical inputs which may otherwise overload the instrument and produce an excess scale deflection. This dual functionality sometimes being acknowledged when the instrument is called a Dual (Tangent) Galvanometer.
The Galvanometer has a mirror back to enable the operator to ensure an accurate reading by removing parallax errors and is scaled with a centre zero moving left and right from 1 to 30 with large intervals of 10. The scale does not possess a legend,
The body of the instrument is compression moulded from Ebonite, also known as Vulcanite a very early vulcanised rubber (the first thermosetting compound) invented in 1843. A wiring diagram can be seen impressed into the moulding.
This type of instrument was probably used in many areas (not just maritime) where electricity was evident, for example in local D.C. power generating companies and electricity supply systems. Ocean liners of the day were floating towns and would have had powerful DC generators and electricity supply systems. In modern times, the instrument is rarely used outside teaching establishments as modern multipurpose equipment had superseded its technology. An incomplete instrument is on display in the Hunterian Museum & Art Gallery, University of Glasgow.
The instrument itself is of very simple construction, though very ornate instruments were produced by many companies, the basic components however, are the same.
A coil consisting of turns of copper wire over a cylinder of wood or bakelite up to about 10cms radius and approximately 2cms thick.
This 'cylinder' is fixed in a vertical plane to a base bearing three levelling screws although these are not present on this instrument.
A small magnetic (compass) needle (also known as a magnetomer) is balanced horizontally on a point or suspended on a fine fibre of silk at the centre of a vertical coil. Some instruments, possibly this one, were configured with a magnet at the centre of the coil to which the needle was attached.
The coil is adjusted to so that the plane of the coil is vertical and in line with the Earth's magnetic north and south plane.
In some instruments the turns of copper wire in the cylinder are so applied to provide a number of distinct separate coils, in the same plane, (although in this instrument there appears to be only one single coil.)
These coils are then joined to a series of terminals. Connections to these terminals determine the number of turns of wire through which the current will flow (usually 2, 50 and 500). When no current is present the needle should point to 0 on the scale and the vertical coil should be in the same plane. This is usually achieved by rotating the pointer housing. This instrument has a fixed pointer housing and therefore the whole instrument would need to be rotated.
When a current is present the pointer will be deflected to a position where a reading should be taken.
The calculation of the current passing through the coil is involved and requires calculation of factors such as 'the reduction factor of the Galvanometer' and the 'Earths Horizontal Field', amongst other things. These are generally applied as constants.
The two steel rods on the top of the coil are correcting magnets and are used to compensate for external magnetic influences.
Method of Operation
Maclean (1) lists the patents and provides illustrations and a description of some of the instruments designed by Kelvin; one of them (on pages 174 and 175) is undoubtedly the same test set.
TESTING SET FOR MEASUREMENT OF INSULATION RESISTANCE
The testing set (Fig. 13) consists of (1) a very sensitive galvanometer, whose deflections are directly proportional to the amount of current passing through its coil; (2) a magnet for controlling the sensibility of the galvanometer; (3) a set of shunts which reduce the indications of 1/10, 1/100, 1/500; (4) a set of compensating resistance controlled by shunt switch, keeping the resistance of the galvanometer circuit constant whether shunted or not; (5) a switch enabling deflection to be taken through the galvanometer alone for standardising, or through the galvanometer and unknown resistance when making test.
The main advantages of the instrument are :-
- Great sensibility (sensitivity)
Long range of measurement
It is simple to use, and with it rapid tests can be carried made
Can be used with a separate battery or with potential of lighting circuit whose insulation is under test
No plugs to get lost
All connections marked on Vulcanite base
The figures on the instrument 1/9, 1/99, 1/499 give the value of the various galvanometer shunt resistances as fractions of the resistance of the galvanometer coil and which reduce the sensitivity to 1/10, 1/100 and 1/500 of that of the unshunted galvanometer.
Further research could be undertaken to identify the actual patent(s) but this can be difficult as they all have uninformative titles such as 'Improvements in apparatus for measuring electric currents'; it would be a very long job to read through all the patents. In any event, parts of several patents might apply to this instrument.
The general appearance of the galvanometer coil, and the mention of magnets for controlling the sensibility (sensitivity in modern terminology) of the galvanometer makes it practically certain that it is a form of moving-magnet instrument. This was the most sensitive type available at the time. The magnets are the two bright steel rods.
Moving-magnet meters were influenced by the Earth's magnetic field and large iron / steel objects in the vicinity (such as the hull of a ship). Magnets placed in the correct orientation could cancel out most of these influences, thus increasing the sensitivity of the galvanometer. If it is a moving-magnet instrument, the deflection would not be exactly proportional to the current, but may have been near enough.
To use the instrument it was first connected directly to a battery or electricity supply, (see Fig,. of the connecting wires) and the current indication noted (using the shunts to give the least sensitive setting). The galvanometer and power source were connected in series with the insulator to be tested, and current indication was noted, using whatever shunt was appropriate.
The insulation resistance can then be calculated from resistance of the galvanometer, the ratio of the two current readings and the values of the attenuating shunts used.
It would be possible to measure resistances well in excess of 25 meg a ohms in this way.
Some were widely used in laboratories, but those intended for more general used tended to be to elaborate and expensive for the purpose
This type of instrument was often less commercially successful than technically inferior instruments. A different instrument invented by Evershed in 1889 became the standard type for measuring insulation resistance, especially in the form introduced in 1894 and known as the Megger.
WILLIAM THOMSON, LORD KELVIN (1824-1907)
One of the greatest of all nineteenth century physicists was William Thomson. Born in Belfast in 26th June 1824, of his numerous contributions to science and industry, he is particularly remembered as being the brains behind the first successful transatlantic telegraph cable of 1866.
He is as well know by physicists for inventing the Kelvin "absolute" scale of temperature which gives the freezing point of water on this scale as 273.15 degrees Kelvin (zero degrees Centigrade) and that all atomic motion (temperature) ceases at zero degrees Kelvin, i.e., "absolute zero".
William studied in Glasgow and then at Peterhouse College, Cambridge, where he graduated in 1845. At the incredibly young age of 22 William returned to Glasgow University as the professor of natural philosophy - the old name for physics. He retired from this position in 1899, 53 years later. He was knighted in 1866, and created a peer, Baron Kelvin of Largs, in 1892. (The Kelvin is a small river that flows along the edge of the Glasgow University grounds at Largs).
He was a practical scientist and recognised the opportunities of the developing world, pioneering developments in electric telegraphy to link Britain with America by carrying out a series of experiments to develop an insulated telegraph cable.
In 1858 Thomson was aboard the Great Eastern , the ship which laid the first transatlantic cable and which failed (after transmitting only 732 messages) principally due to poor insulation and the large voltages that were necessary to send the signal.
The cable ran 2000 miles from Valentia Island, offshore from off County Kerry to Trinity Bay, Newfoundland, in Canada. Queen Victoria, as a recognition of his achievements honoured William Thompson with a knighthood
An alternative instrument was required to replace the comparative insensitive land telegraph and Thomson responded by producing the mirror galvanometer patented in 1858. This was the essential element required for the cable laid in 1866, to function and succeed.
He also invented the siphon recorder in 1867 that produced accurate automatic recordings of telegraph messages.
William Thomson has other claims to maritime fame - a navigational sounding machine, a tide predictor and an improved compass for navigation, which was adopted by all British Navy vessels.
He formed a working relationship, and later a company, with the Glasgow instrument maker James White, and together they produced and sold a new generation of precise electrical and other instruments patented by Thomson. He accumulated great wealth through his patents and business interests.
After his retirement in 1899, Lord Kelvin of Largs, the title William Thomson adopted on being created a baron, became a major shareholder in the firm Kelvin & James White Ltd.
The advent of ships with iron and steel hulls caused major problems with navigation. The magnetic properties of the ship's hull markedly affected the ship's compass. Kelvin's responded by developing a compass that compensated for the magnetism of the hull and superstructure of the ship. His company, Kelvin & James White produced more than 10,000 of the mariner's compasses for ships all over the world..
In 1914, after Kelvin's death, the firm was renamed Kelvin, Bottomley & Baird Ltd In 1947 it merged with Henry Hughes & Son Ltd , becoming Kelvin & Hughes Ltd, and was acquired by Smith's Industries Ltd in 1964.
Lord Kelvin died in Glasgow in 1907, and is buried in Westminster Abbey.
A commemorative statue in the Botanic Gardens, Belfast, is inscribed
"He elucidated the laws of nature for the service of man".
Which is exactly what he did!
© D. R. Perks B.Sc., L.I.M., M.B.A. Kingswinford 2003
I do not object to any part of this paper being reproduced on the conditions that you contact me beforehand, that proper reference to the author is made and you will not do so for personal gain.
Many thanks to all those kind people around the world who have helped with facts, ideas and encouragement:
- Russ Upholster
- Bruce Beveridge
- Dave Gittins
- Neal McEwen K5RW
- Ray Minichiello
- John McPherson
- Eugene Rudd
- Tom Perera
- Parks Stephenson
- Brian Hawley
- Paul Adamthwaite, Ph.D.
The main body and breakthrough information came from:
Mike Jewkes Curator of Scientific Instruments at the Hunterian Museum & Art Gallery, University of Glasgow.
Neil Brown Senior Curator, Classical Physics, of the Science Museum, London, to which I am most grateful.
1. Dr. Magnus MacLean. 'Lord Kelvin's Patents' published by a 'Proceedings of the Philosophical Society of Glasgow', volume 19, 1897-98, pp 17
2. Numerous personal e-mails from those named above.
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