Hioki 3227 - Page 26

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1.3 Measurements and Working Systems
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Diameter [mm]
Annealed copper
wire
Tin-plated annealed
copper wire
Hard drawn coppe
r
wire
0.10 to 0.26
(excluding 0.26
)
0.98 0.93
0.26 to 0.50
(excluding 0.50
)
0.993 0.94 0.96
0.50 to 2.00
(excluding 2.00
)
1.00 0.96 0.96
2.00 to 8.00
(excluding 8.00
)
1.00 0.97 0.97
α
Ct
=
1
α
20
× C
+(t 20
)
1
α
20
=
1
0.00393 × 0.9
3
+ (20 20
)
1
≒ 3650 (ppm
)
(1) Properties of metal and alloy conductive materials
(2) Conductivity of copper wire
The temperature coefficient changes in relation to temperature and
conductivity. Assume the temperature coefficient is α
20
at 20℃ and that the
temperature coefficient is α
Ct
at t (℃) with a conductivity of C. Then Ct at
around room temperature is represented as follows:
The temperature coefficient of international standard annealed copper is 3930
ppm at 20℃. For tin-plated annealed copper wire (not less than 0.10 but
below 0.26 in diameter), the temperature coefficient α
20
at 20℃ can be
calculated using the following formula: