Design of Instrument Dials for Maximum Legibility. Part 4. Dial Graudation, Scale Range and Dial Size as Factors Affecting the Speed and Accuracy of Scale Reading

摘要

The extent to which instrument-dial reading errors and reading times are influenced by the spacing of graduation marks, graduation-mark values, scale range, and dial size was investigated. The dials employed were scaled from 0 to 50, 0 to 100, 0 to 200, 0 to 400, and 0 to 600 units, and included graduation by tens, fives, twos, and units. Dial sizes were 2.8 in. and 1.4 in. The precision of scale reading varied with the distance on the scale allocated to each scale unit. Reading precision improved as this distance increases to about 0.05 in., a value which varied only slightly with graduation scheme but which appeared to vary with graduation mark thickness. For more expanded scales, reading precision remained reasonably uniform at a level which depends on graduation scheme.