General classification
There are several variables in dial indicators:
• Analog versus digital/electronic readout (most are analog)
• Dial size. Typically referred to be American Gauge Design Specification (AGD):
AGD Diameter range (in) Diameter range (mm)
0 1 > 1-⅜ 25 > 35
1 1-⅜ > 2 35 > 50
2 2 > 2-⅜ 50 > 60
3 2-⅜ > 3 60 > 75
4 3 > 3-¾ 76 > 95
• Accuracy
• Range of travel
• Number of dial revolutions
• Dial style: balanced (e.g., -15 to 0 to +15) or continuous (e.g., 0 to 30)
• Graduation style: positive numbers (clockwise) or negative numbers (counterclockwise)
• Revolution counters, which show the number of revolutions of the principal needle.