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).
Letter investigating a hysteresis effect in a Weston ammeter, concluding the cause is residual magnetism and proposing air-cored poles as a solution.
| Identifier | ExFiles\Box 168\5\ img267 | |
| Date | 9th January 1934 guessed | |
| -2- We would say that this trouble was not experienced on the undamped ammeters of other manufacture which we previously fitted to our chassis. It was decided therefore to investigate the cause of the hysteresis effect and a Weston ammeter was accordingly dismantled and examined. We came to the conclusion that the cause of the trouble was the residual magnetism in the iron poles. If these main poles were air-cored and the inductor made larger the trouble should be non existent. We are aware of the inherent difficulties involved by a change of design of this description but we consider the air cored poles to be the solution to the zero hysteresis effect. Will you kindly give this matter your urgent attention and advise us accordingly. We should be quite willing to discuss the matter still further with one of your technical representatives at our Works if necessary. Yours faithfully, FOR ROLLS-ROYCE LIMITED. | ||