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 to the Weston Electric Instrument Co. detailing the test results of a loaned moving iron chassis ammeter.
| Identifier | ExFiles\Box 168\5\ img228 | |
| Date | 14th December 1931 | |
| Hs{Lord Ernest Hives - Chair}/Wst.1/AD. December 14th, 1931. The Weston Electric Instrument Co. 15, Great Saffron Hill, London, E.C.1. Dear Sirs, Weston Moving Iron Chassis Ammeter. We have now received and tested the small polarised moving iron ammeter which you have kindly loaned us. We found on the bench tests that there was a tendency, after a heavy discharge through the instrument, for the needle to stick and for the accuracy of the instrument to be affected. Our test results read as follows :- "When first tested, the instrument was found to be correct in both directions. After passing a momentary discharge of 60 amperes through the instrument in both directions, the zero position had moved .5 amperes in the charge direction. On readjusting for accuracy, the readings were found to be inconsistent owing to a slight stickiness of the needle. After passing a current of 90 amperes through the instrument for 3 seconds in both directions, the readings obtained were .5 ampere high for over 5 amperes, for 10 ampere deflection the instrument showed 11 amperes, and for 15 amperes the instrument read 16.5." It will be understood that it is necessary for these instruments to stand a momentary heavy discharge as this will be the case should a short circuit occur on the c We have recently tested another moving iron ammeter of well-known British make which is usually fitted to British cars and we find that this ammeter will stand all our tests without the accuracy of the readings being affected. | ||