The DC Bias Current Source employs the property of positive temperature coefficient of a copper conductor (i.e., higher resistance at higher temperature), the formula is R2 = R1[1 + a(t2-t1)], where “a” represents 0.0039. Resistance R1 is measured prior to applying the current, followed by measuring the resistance alteration after the current application, the present temperature can then be deduced with the formula, thus getting the temperature rise.