An iron–constantan thermocouple is to be used to measure temperatures between 0 and 400°C. What will be the non-linearity error as a percentage of the full-scale reading at 100°C if a linear relationship is assumed between e.m.f. and temperature? e.m.f. at 100°C = 5.268 mV, e.m.f. at 400°C = 21.846 mV