Electric power measuring system

An electric power measuring system wherein a current signal initially in analog format is to be multiplied with a voltage signal to provide a measure of power;

• said system including, for converting said analog-format current signal to a digital signal prior to its multiplication with said voltage signal, an A-to-D converter of the successive-approximation type comprising:
• a comparator to receive said current signal together with an analog feedback signal;
• search algorithm means responsive to the output of said comparator and operable in accordance with a search algorithm to produce a programmed sequence of digital signals;
• and
• D-to-A converter means receiving said sequence of digital signals and producing corresponding analog feedback signals for comparison with said current signal so as to control the operation of said search algorithm means;
• said D-to-A converter means comprising means to produce said analog feedback signals in accordance with a non-linear relationship with respect to said digital signals from said search algorithm means thereby producing a digital output signal from said search algorithm means having said non-linear relationship with respect to said current signal.