Film thickness: terms and measuring equipment
WMV: Weight measuring value
The WMV value is derived from the weight of the probe. From the area per square A and the mass m of the probe and the knowledge of the density ρ one can calculate the thickness by
d = m / ρ / A
This method is commonly applied for master rolls of raw film. It is also applicable for wound material like a capacitor element or a strip of film.
The calculation for metallized films needs to compensate the amount of metal. E.g. for OPP the literature value for ρ has to be increased by about 1-2%:
0,905 [g / cm³] unmetallized -> 0,92 [g / cm³] metallized.
Mechanical caliper system
Mechanical caliper system that facilitates a spot measurement.
Mechanical calipers and number of turns:
- 10 layer method (10 successive layers)
- 5 times folded (5 x folded -> 32 layers)
- Number of turns and diameter of a winding
Winding method
In the winding method, the layer thickness is determined by the number of turns and the measured diameter.