How to read Proving Ring Dial Gauge with least count calculation

Least Count is the ratio of smallest value of one division on the main scale to number of divisions on vernier scale.

Least Count for Dial Gauge = Smallest value of one division on the main scale (i.e. on small hand dial gauge)/ Total number of divisions on long hand dial gauge

In small dial gauge one division = 0.2 mm

Number of divisions on big dial gauge = 100 (can be seen in given image)

Hence, Least Count, L.C = 0.2 mm/100

= 0.002 mm

Strain reading in mm = small dial gauge reading + (outer dial reading x least count)

Suppose needle stops at  2 in short  dial and outer dial needle stops at 7 then,

Strain in mm= 2 + ( 35 x 0.002)

= 2.07 mm