Machinery's Handbook, 31st Edition
786 CALIPERS, VERNIER AND DIAL distinguished. The 0 (zero) index and each major division shall be clearly marked with the numerical incremental value. Dial Caliper.— The dial caliper uses a precise rack and pinion movement that drives an indicating hand to provide a direct reading on a circular dial. This precision movement eliminates the necessity to visually read the vernier scale and negates the effects of subjective observation.
Inside Jaws
Gib Slide Screws
Depth Rod
Lock Screw
Beam
0
90 10
70 80
20 30
Fine Adjusting Roll
Metric Range 150 mm. Bar Graduations 2mm Dial Indicator 0.02 mm Graduations 2 mm Range per Revolution English Range 6 ”. Bar Graduatons 0.100 ” Dial Indicator 0.001 ” Graduations 0.100 ” Range per Revolution
60 50
40
Dial Indicator
Bezel Clamp
Outside Jaws
0
90 10
70 80
20 30
0
90 10
70 80
20 30
60 50
40
60 50
40
Inside Measurement
Depth Measurement
Outside Measurement
Fig. 20. Dial Caliper – Fine Adjust Wheel and Gib Slide Screws for Accuracy Adjustment The movement, when adjusted properly and calibrated will provide a measurement with a higher level of confidence than the vernier scale. Typically the indicating hand rotates once every 0.100 in or 1 mm and provides a resolution of 0.001 inch or 0.02 millimeter. The main scale still indicates the major divisions that are added to the reading taken from the dial indication. An additional feature of the dial caliper is that the dial is designed to be rotatable beneath the pointer allowing the operator to “set” the caliper at a known value and zero the indicator and make “differential measurements” from the known value. This function was not possible with the original vernier caliper. Digital Caliper.— The most current refinement in the instrument is in the replacement of the dial movement or vernier scale with a digital display. The dial rack and pinion movement or vernier scale has been replaced with the application of a linear encoder that allows switching between millimeters and inches on demand, zeroing the scale at any point along the scale for differential measurements and electronically “holding” a measurement possibly taken in an awkward position where the digital display may not be visible. Many digital calipers offer a serial data output function that allows the operator to capture collected data in a spreadsheet or dedicated controller for analysis and more accurate records collection.
Inside Measurement Jaws
Step Measurement Land
Lock Screw In/mm Conversion Button
Digital Display
IEEE Output Connector
inch/mm
18.80
mm
OFF
ON ZERO
Thumb Roller/Fine Adjustment
Battery Compartment
Power ON/ZERO Button
Depth Measurement Rod
Power OFF Button
Slider Outside Measurement Jaws
Fig. 21. Digital Caliper – Average Feature Configuration
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