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).
Comparison report of an N. & Z. instrument against a Vapour pressure instrument across various performance tests.
| Identifier | ExFiles\Box 40\1\ Scan070 | |
| Date | 11th October 1926 | |
| -2- N.& Z. Inst. No. E/1617 Vapour pressure Inst. No.29386 Actual. reads. up. down. reads. up down. 70° C. 70° C. 70° C. 70.8° C. 71.3° C. 80 80 80 80.2 80.8 90 90 90 89.9 90.3 98 98 98 98 98 The above readings are to nearest 0.1° C. From these figures it is apparent the N.& Z. type is of greater accuracy, but in fairness to the other type, it should be pointed out that the N.& Z. type was a calibrated dial and not a fitted dial. The up and down or hysteresis error of the vapour pressure type is, however, very marked, also owing to the small vapour pressure below 50° the scale becomes very constricted and reading at 0° can not be obtained. This is rather a disadvantage with the vapour pressure type. (3) Barometer. The N.& Z. Thermometer has been subjected to a change of barometer equivalent to 25,000 feet with no perceptible alteration in the readings. In the case of the vapour pressure type, the errors are considerable, and amount to between 5 & 14° at 20,000 ft. (4) Position of Bulb. Errors due to the relative position of the bulb in height in relation to the indicator are negligible in the N.& Z. type, and of a small order in the vapour pressure type. (5) Thermometric Lag. The thermometric lag of the N.& Z. type is considerably less than the vapour pressure type. Over a given change of temperature, the N.& Z. type indicated the correct temperature in 17 secs. against 35 seconds for the vapour pressure type. (6) Vibration. The N.& Z. type is very steady under vibration, due to the movement being completely balanced, and due to the large control force on the pointer. The control force is probably 10 times that of the vapour pressure type. (7) Test on Car. From actual tests on a car, it is apparent that the N.& Z. type has the advantage that all temperatures of the engine water can be observed from freezing point to boiling point, the pointer is particularly steady, and there is apparently no sluggishness in the readings. The movement of the pointer is perfectly smooth without any jerks, and there is no oscillation. The instrument should stand a certain amount of rough handling as the parts are not | ||