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Constantan® Strip and Foil

Constantan® is a copper-nickel alloy that contains specific minor amounts of additional elements to achieve precise values for the temperature coefficient of resistivity. Careful control of melting and conversion practices results in a very low level of pinholes at ultra-thin thicknesses. The alloy is used extensively for foil resistors and strain gauges.

The TCR can be adjusted from the furnished cold rolled values by using a low temperature heat treatment to achieve compensation for all types of spring elements. The foil is normally supplied with 90% cold reduction and a smooth bright surface. The foil is reasonably flat at 4” wide and nearly free of pinholes. The cold rolled foil can be produced with a TCR between +10 to –35 PPM/°C. The heat treatment will shift the foil TCR to the desired value. A typical heat-treat curve for Constantan® shows decreasing resistivity but increasing TCR with increased heat-treating temperature.

Constantan® is available from Hamilton Precision Metals as foil and strip product in thicknesses from 0.0005” to 0.050” (0.0127 mm to 1.27 mm) and in widths up to 12” (304.8 mm). It is also available as thin as 0.000100” (0.00254 mm) and in widths up to 4” (101.6 mm) maximum.

Nominal Composition
Nickel 44.2%
Manganese 1.5%
Iron 0.50
Copper Balance
Typical Mechanical Properties of Constantan® Alloy
Ultimate Tensile Strength 60,000 PSI. 120,000 PSI
Elongation in 2” * 25% 2%
Modulus of Elasticity (Tension) 24 x 106 PSI
Physical Properties of Constantan® Alloy
Density 0.321 lbs/
Melting Point (Approx.) 1210°C
Electrical Resistivity @ R.T 50.8 Microhm·cm
Temperature Coefficient of Resistivity (TCR) (25° to 105°C) ± 30 PPM/°C
Thermal Expansion Coefficient (20°C to 100°C) 14.9 x 10-6/°C
Thermal EMF vs. Copper (0°C to 100°C)  -0.043 Millivolts/°C
Thermal Conductivity R.T. 21.2W/m·K
Magnetic Attraction None
Specific Heat 0.094 gram·cal./°C
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