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).
Calibration data for a Cambridge potentiometer instrument tested at 18 and 90 millivolt ranges.
| Identifier | ExFiles\Box 165\3\ img050 | |
| Date | 7th April 1924 guessed | |
| X975 86033 CAMBRIDGE MEASURING INSTRUMENT (POTENTIOMETER) (Mr. Hally). 18 millivolt range. True reading from 22407. | Reading on Galvan. scale. | Ratio. 2.80 | 2.86 | .980 - 9 5.37 | 5.48 | .980 - 9 7.94 | 7.96 | .984 - 5 10.69 | 10.74 | .994 + 5 12.98 | 13.10 | .990 + 1 15.70 | 15.90 | .987 - 2 17.85 | 17.98 | .993 + 4 Average ratio .989 Subtract 1.1% from all readings, result then correct to within ±.8% Scale proportionality V.fair. 90 millivolt range. True reading from 22407. | Reading on Galvan. scale. | Ratio. 6.95 | 7.0 | .993 0 12.98 | 13.1 | .990 - 3 20.8 | 21.0 | .990 - 3 33.5 | 33.7 | .994 + 1 45.5 | 45.9 | .992 - 1 56.0 | 56.3 | .995 + 2 71.4 | 71.9 | .994 + 1 Average ratio .993 Subtract .7% from all readings, result then correct to within ±.3% Scale proportionality good. | ||