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Evanohm® R Strip and Foil

Evanohm® R is a unique resistance alloy with high electrical resistivity and very low temperature coefficient of resistivity (TCR). The alloy is produced by melting and conditioning practices which result in a low level of pinholes at ultra-thin thicknesses. This combination of attributes with inherent corrosion resistance makes it suitable for a variety of strain gauge and foil resistor applications.

The alloy is supplied with 90% cold reduction which has a positive TCR of about 70 PPM/ºC. A stabilizing heat treatment (approximately 475ºC) during manufacture of finished parts adjusts the TCR to a desired value. The heat treatment virtually eliminates any drift tendency of the resistivity. A heat-treat curve for each melt is developed at Hamilton and is made available as a guide in regulating TCR.

Sizes
Evanohm® R is available from Hamilton Precision Metals as foil and strip product in thicknesses from 0.0005” to 0.010” (0.0127 mm to 0.254 mm) and in widths up to 12.0” (304.8 mm) maximum. It is available in foil as thin as 0.000100” (0.00254 mm) in widths of 4.0” (101.6 mm) maximum.

Nominal Composition
NOMINAL COMPOSITION
Chromium 20.0%
Aluminum 2.8%
Copper 2.0%
Silicon 1.0%
Manganese 0.90%
Zirconium 0.08%
Nickel Balance
Typical Mechanical Properties of Evanohm® R Alloy
ANNEALED COLD ROLLED HEAT TREATED
Ultimate Tensile Strength 120,000 PSI 200,000 PSI 240,000 PSI
Yield Strength (0.2% Offset) 70,000 PSI 195,000 PSI 235,000 PSI
Elongation in 2” * 30% 1% 1%
Physical Properties of Evanohm® R Alloy
PHYSICAL PROPERTIES
Density 0.293 lbs/cu.in. 
Melting Point (Approx.) 1350°C
Electrical Resistivity @ R.T 133 Microhm·cm
Temperature Coefficient of Resistivity (TCR)
(-55°C to 105°C) – Heat Treated
± 10 PPM/°C
Thermal Expansion Coefficient (20°C to 100°C) 13 x 10-6/°C
Thermal EMF vs. Copper (0°C to 100°C)  <1.0 Millivolts/°C
Thermal Conductivity R.T. 14.6 W/m·K
Magnetic Attraction None
Specific Heat 0.104 gram·cal./°C
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