From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Specification sheet for a miniature current transformer and ammeter portable testing outfit.
| Identifier | ExFiles\Box 168\5\ img291 | |
| Date | 20th June 1934 guessed | |
| SHEET G 40. MEASURING INSTRUMENTS. SECTION G.{Mr Griffiths - Chief Accountant / Mr Gnapp} MINIATURE CURRENT TRANSFORMER AND AMMETER. A PORTABLE TESTING OUTFIT FOR USE WITH ALTERNATING CURRENT. (FIRST GRADE ACCURACY TO BRITISH STANDARD SPECIFICATION No. 89) DESCRIPTION—continued. The transformer is mounted in a neat case of moulded insulation material, and it is very compact and light in weight. The diameter of the central aperture is 1·375 inches. Ammeter.—The ammeter, which is normally supplied for use with the transformer, is a portable miniature sector pattern instrument, working on the moving iron principle. It has a scale-length of 2·375 inches and an angular deflection of 100 degrees, and gives full scale deflection for 0·5 ampere when used without the transformer. Accurate readings can be obtained from 1/10 of full scale deflection and upwards, i.e., from 50 milliamperes, with this range. The figures for this range are rendered in black on the scale. In addition to alternating current measurements, the ammeter, when used alone with a range of 0·5 ampere, will give direct current readings with a reasonable degree of accuracy. When the ammeter is used in conjunction with the transformer, the red scale figures must be adopted. Figures in red are given for two ranges, viz., 10 and 25 amperes, and indication of other ranges for which the outfit is available, can be accommodated on these two scales. By means of appropriate wording, rendered in red on the scale plate, the ranges obtainable with the transformer are clearly indicated. The movement works on the principle of the mutual repulsion between a fixed and a movable iron, located in the magnetic field at the centre of a coil through which the current is flowing. It is spring controlled and accurately balanced and the moving element is pivoted in sapphire jewels, thus reducing friction to a minimum, whilst an efficient air damping device renders the instrument dead-beat. The design is such that the instrument is extremely robust, without sacrifice of accuracy or sensitivity. The moving and fixed irons are made of a special iron alloy which is treated to avoid hysteresis errors, etc., and thus enables the instrument to be used on direct current, if required. An external zero adjusting device is provided on all instruments, and a knife-edge pointer ensures greater accuracy of reading. The ammeter is mounted in a case of pressed steel with dull black enamel finish, and with a black moulded bakelite base. Two terminals, with non-removable insulated heads, are mounted on the base. Outfit.—The complete outfit, comprising Transformer, Ammeter and connecting leads, can be supplied in a leather transport case at a small extra cost, thus providing an exceedingly light, accurate and convenient portable test set. | Description. | Catalogue No. | Price. £ s. d.{John DeLooze - Company Secretary} | | :--- | :--- | :--- | | Complete Outfit, comprising : Miniature Current Transformer, Moving Iron Ammeter and connecting leads— Suitable for the following seven ranges :—0·5, 2·5, 10, 25, 50, 100 and 200 amperes ... ... ... ... ... | 53121 | 4 10 0 | | Leather Transport Case for outfit above ... ... ... ... | 53123 | 0 13 6 | | Miniature Current Transformer only ... ... ... ... ... | 53125 | 4 0 0 | ELLIOTT BROTHERS (LONDON) LTD in association with SIEMENS BROTHERS & CO. LTD | ||