CaloCalc
Film thickness from ball-crater ring diameters. Type the rings, press Enter: the coupon is logged and the next one is ready.
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Reading the crater
Under the microscope each interface is a ring. Measure each ring's full diameter, inner to outer.
The formula
Spherical-cap geometry, with R the ball radius. Valid while the film is far thinner than the ball.
1 layer t = (b² − a²) / 8R 2 layers t₁ = (b² − a²) / 8R t₂ = (c² − b²) / 8R
The log
Each row keeps the rings as typed, the ball, the unit and the time. Spec limits apply to total thickness. Copy table pastes straight into a spreadsheet; Print gives a one-page record.
Nothing is sent anywhere. No warranty: check results against your own method.