Patent ID: 6255842
Filing Date: 2001-07-03
Classification: G01R

Abstract:
An applied-voltage-based current measuring method that comprises:applying the output voltage of an operational amplifier to a voltage sensing point via a current detecting resistor;supplying a load with the voltage applied to the voltage sensing point;feeding back the voltage at the voltage sensing point to an inverting input terminal of said operational amplifier;supplying said load with a voltage identical with that fed to an non-inverting input terminal of said operational amplifier; andmeasuring current flowing to said load by a voltage which is developed across said current measuring resistor;wherein:a plurality of current detecting resistors are prepared in correspondence to current measuring ranges;the plurality of current measuring resistors are connected in series between an output terminal of said operational amplifier and the voltage sensing point;voltages which are developed at respective ends of the plurality of current detecting resistors are measured;the measured voltages are subjected to arithmetic processing to compute voltages which are created across the respective current detecting resistors;one of the computed voltages is selected according to its value as compared to a threshold value; andthe selected voltage is used to calculate the value of current flowing to the load.