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).
The causes of noise from sliding electrical contacts and a proposed test for the microphonic effect.
| Identifier | WestWitteringFiles\K\June1923\ Scan44 | |
| Date | 11th June 1923 | |
| Contd. -2- EFC2/T11.6.23. according to its degree of goodness. A poor contact will cause noise due to quite small vibrations existing from any cause, without other disturbance. Noises are caused by the sliding contacts of switches (without actually breaking circuit) though the contacts are apparently quite good, but we have proved experimentally that such sliding contacts if properly cleaned and vaselined, can be moved relative to one another without causing the least noise. Experimenting upon one of our standard Goshawk ignition condensers in this manner, we showed that the application and removal of pressure by means of the thumb and the finger to the sides of the case will cause an appreciable noise. In oscillatory circuits for radio, and also we think, in those of ignition, this would be the test for the goodness of switch and other contacts, that they may be moved about relative to one another without producing any suggestion of this microphonic effect. EFC. | ||