Table 1.

Overview of traditional coating thickness methodologies.

Methodology	A1	A2	A3	A4	A5	A6	A7
Thickness ranges	1 nm–50 µm	1–800 µm	1–10,000 µm	1–10,000 µm	0.5 nm–10 µm	1 nm–1 µm	10–7500 µm
Measurement accuracy (%)	0.1–0.5	0–5	0.1–0.7	1–3	0.2–0.5	0.33–0.65	0.53–0.7
Multi-layer	✓	✓	X	X	✓	✓	✓
Sampling rate	1–500 m	0.5–15 s	0.6–1 s	0.6–1 s	0.5–100 s	1 s–60 m	0.5–2.5 s
Detection area (ø)	1.5–3.2 mm	0.63–20 mm	5–8 mm	5–8 mm	0.1–15 mm	2 mm	5 mm
Commercial availability	[47]	[48,49]	[50]	[50]	[51]	[52]	[53]
Typical cost (GBP)	>3000	Unspecified	>1000	>1000	>35,000	>30,000	>1000
Non-contact	X	✓	✓	X	✓	✓	X
Non-destructive	X	✓	✓	✓	✓	✓	✓
Materials	✓	X	X	✓	✓	✓	X