Quick Guide to Precision Measuring Instruments

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PG32Dial Indicators and Digital IndicatorsAlways minimize the angle between movement directions during use.θL1L2Workpiece movement directionWorkpiece movement directionStylus movement directionStylus movement directionL1: Result of measurementL2: Indicated valueL1=L2×Cos測移Dial Test Indicators and the Cosine EffectThe reading of any indicator will not represent an accurate measurement if its measuring direction is misaligned with the intended direction of measurement (cosine effect). Because the measuring direction of a dial test indicator is at right angles to a line drawn through the contact point and the stylus pivot, this effect can be minimized by setting the stylus to minimize angle (as shown in the gures). If necessary, the dial reading can be compensated for the actual value by using the table below to give the resulut of measurement.Result of measurement = indicated value x compensation valueExamplesIf a 0.200mm measurement is indicated on the dial at various values of , the result of measurements are: For = 10˚, 0.200mm×.98 = 0.196mmFor = 20˚, 0.200mm×.94 = 0.188mmFor = 30˚, 0.200mm×.86 = 0.172mmCompensating for a non-zero angleAngleCompensation value10˚0.9820˚0.9430˚0.8640˚0.7650˚0.6460˚0.50Note: A special contact point of involute form can be used to apply compensation automatically and allow measurement to be performed without manual compensation for any angle from 0 to 30˚. (This type of contact point is custom-made.)