The difference (Δ I; Δ IL1 Δ IL2, Δ IL3) between the measured actual values is evaluated to detect the operability of the incandescent lamp.

These statements are used to check whether i and j gives remainder as 0 (zero) or not.

Substituting Δ I L O n {\displaystyle \Delta I_{L_{On}}} and Δ I L O f f {\displaystyle \Delta I_{L_{Off}}} by their expressions yields:

The ratio between the protrusion length (L) in a normal cross-section and the projection (D) thereof ranges from 1.05 to 1+δ, wherein δ is the membrane material plasticity.