Patent ID: 6307378
Filing Date: 2001-10-23
Classification: G01R

Abstract:
An apparatus for measuring impedance in an electrochemical cell comprising:a current generator for producing an input current signal I.sub.i along a current signal path in a current divider network;said current divider network having at least a sensing current path and a battery current path, said sensing and battery current paths being in parallel to each other, each of said sensing and battery current paths also being in series with said current signal path, said current signal, sensing, and battery paths interconnecting with each other at a current dividing connector and at a current converging connector;said sensing current path having a measurable sensing impedance Z.sub.s located along said sensing current path, a connector-wire impedance Z.sub.1 between said current dividing connector and said sensing impedance Z.sub.s, and a connector-wire impedance Z.sub.3 between said sensing impedance Z.sub.s and said current converging connector, wherein a portion I.sub.s of current signal I.sub.i flows through said sensing current path;said battery current path having a battery impedance Z.sub.b located along said battery current path, a connector-wire impedance Z.sub.2 between said current dividing connector and said battery impedance Z.sub.b, and a connector-wire-capacitor impedance Z.sub.4 between said battery impedance Z.sub.b and said current converging connector, wherein a portion I.sub.b of current signal I.sub.i flows through said battery path;a DC-blocking capacitor in series with said battery impedance Z.sub.b and located along said battery current path to prevent said battery from discharging current through said sensing impedance Z.sub.s ;said sensing current path also having a magnetic field sensor with a coupling attached thereto for measuring the magnitude and phase of I.sub.s, thereby permitting mathematical determination of the value of Z.sub.b.