An apparatus for measuring an impedance produces an alternating current from digital codes representative of a sine wave, and converts an ac voltage due to an alternating current flowing into an object to a digital signal; a multiplier successively multiplies the binary values of the digital signal by...http://www.google.com/patents/US6581016?utm_source=gb-gplus-sharePatent US6581016 - Apparatus for accurately measuring impedance and method used therein
