Table 5.

Length measurement uncertainties associated with different degrees of temperature measurement and control attainable in principle at temperatures near but not exactly at the standard temperature t₀ of 20 °C

	Engine piston	Lead screw	Tertiary laboratory	Secondary laboratory	Primary laboratory	R&D device
L	100 mm	1000 mm	1000 mm	1000 m	1000 mm	70 mm
Material	Aluminum	Steel	Steel	Steel	Steel	Si
α (10−6/°C)	23.4	11.8	11.8	11.8	11.8	2.6
u(t)	10 °C	1 °C	0.1 °C	0.01 °C	0.001 °C	0.001 °C
u (α) (10−6/°C)	0.7	0.7	0.035	0.035	0.035
t–t0	3 °C	3 °C	1 °C	0.1 °C	0.01 °C	0.000 °C
u(L)/L	2.3×10−4	1.2×10−5	1.2×10−6	1.2×10−7	1.2×10−8	2.6×10−9
u(L)	23 μm	12 μm	1.2 μm	0.12 μm	12 nm	0.2 nm