Platinum and Nickel which are not used in the pure form are listed for comparison purposes only. However, the strain sensitivity factor S itself ranges from -12.1 in Nickel up to 6.1 in Platinum. This wide variation indicates that the change in electric resistivity r , the so called piezo-resistance effect, can be quite large in some materials. Although the sensitivity factor S is usually provided by the strain gage vendors, engineers still need to choose the right gage wire materials for their applications. It has almost constant sensitivity across a wide range of strain.
Isoelastic alloy is suitable for dynamic strain measurement in vibration and impact.
It has better fatigue properties among strain gage materials. Karma alloy has similar overall properties to Constantan. But, - It is more difficult to solder. The mismatch of thermal expansion coefficients between gage wire, backing, and specimen induces so called apparent strain which contributes errors to the strain measurements. Constantan and Karma alloy are two most common gage wire material which have self-compensation property.