Table 3.

Overview of potential in-line coating thickness methodologies.

Methodology	C1	C2	C3	C4	C5	C6	C7	C8	C9
Thickness ranges	1–200 µm	300–1400 µm	0.5 nm–3 mm	0.1 nm–10 µm	0.5 nm–1 mm	>1 µm	>1 µm	>1 µm	>1 µm
Measurement accuracy (%)	10	0.43	0.1–0.2	<1	0.1	Unspecified	Unspecified	<3%	Unspecified
Multi-layer	Unspecified	✓	✓	✓	✓	✓	✓	✓	✓
Sampling frequency	0.1–4 s	>50 ms	0.1–5 s	<3 s	0.1–300 s	Unspecified	Unspecified	<1 s	<1 s
Detection area (ø)	Unspecified	Unspecified	50 µm–1 mm	Unspecified	50 µm–1 mm	Unspecified	Unspecified	Unspecified	Unspecified
Commercial availability	Unspecified	[106]	[105]	[107]	[108]	Unspecified	Unspecified	[109]	[110]
Typical cost (GBP)	Unspecified	Unspecified	>13,000	>45,000	>40,000	Unspecified	Unspecified	>10,000	>10,000
Non-contact	✓	✓	✓	✓	✓	✓	✓	✓	✓
Non-destructive	✓	✓	✓	✓	✓	✓	✓	✓	✓
Materials	✓	✓	✓	✓	✓	X	X	✓	✓