Patent ID: 6466026
Filing Date: 2002-10-15
Classification: G01R

Abstract:
Apparatus for passing a periodic time-varying current at a particular measurement frequency through an electrochemical cell or battery during measurement of at least one component of complex immittance comprising:an auxiliary dc power supply contacting a first terminal of said cell or battery and adapted to inject current into said cell or battery in the charging direction; a resistor contacting a second terminal of said cell or battery and adapted to conduct current through said cell or battery in either the charging direction or the discharging direction; a pair of complementary transistors connected in series across said dc power supply and arranged to conduct current through said resistor in either the charging direction or the discharging direction; an operational amplifier arranged to sense the voltage across said resistor and to control conduction of said complementary transistors in such manner as to cause the voltage drop across said resistor to emulate a control signal applied to an input of said operational amplifier; and, a signal source delivering a periodic control signal at said measurement frequency to said input of said operational amplifier.