Formula for calculation of case depth measured using hardness traverse method.

Many of us dont know how to finalize the case depth measured using hardness traverse method.
Use given formula

                   (D2-D1)(H1-Hs)
CD= D1+     -------------------
                        (H1-H2)
For example
Here i calculate Case depth for your reference.
 distance from case          Hardness(HV)
 towards core
0.05 mm                                 887
0.10 mm                                 774
0.15 mm                                 654
0.20 mm                                 570
0.25 mm                                 521
 In above hardness measured using hardness traverse has exceeded cut off values (i.e 550 VPN)
Take the distance and hardness value above cut off and below cut off value
D1 =0.20 mm
D2 =0.25 mm
H1 =570 HV
H2 =521 HV
Hs =550 HV( always remains constant)
 and apply to formula mentioned above and get effective case depth. for above case it is 0.22 mm.