Patent ID: 8988063
Filing Date: 2015-03-24
Classification: G01R

Abstract:
1. A method for measuring an electrical current flowing in a load comprising: providing a measurement resistor, said resistor having a first connecting terminal and a second connecting terminal, said load being electrically coupled to said second connecting terminal of said measurement resistor, said electrical current flowing through said measurement resistor; providing a first network resistor, said first network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said first network resistor being electrically coupled to said first connecting terminal of said measurement resistor; providing a second network resistor, said second network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said second network resistor being electrically coupled to said second connecting terminal of said measurement resistor; providing a third network resistor, said third network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said third network resistor being electrically coupled to said second connecting terminal of said first network resistor; providing a fourth network resistor, said fourth network resistor having a first connecting terminal and a second connecting terminal, said first connecting terminal of said fourth network resistor being electrically coupled to said second connecting terminal of said second network resistor, said second connecting terminal of said fourth network resistor being electrically coupled to said second connecting terminal of said third network resistor; providing a first amplifier, said first amplifier having an inverting input terminal, a non-inverting input terminal, and an output terminal, said non-inverting input terminal of said first amplifier being electrically coupled to said second connecting terminal of said first network resistor, said inverting input terminal of said first amplifier being electrically coupled to said second connecting terminal of said second network resistor; measuring a common mode voltage at said second connecting terminal of said measurement resistor; creating a compensating voltage equal in magnitude to said common mode voltage, said compensating voltage being 180 degrees out of phase with said common mode voltage; applying said compensating voltage to said second connecting terminal of said third and said fourth network resistors; measuring an output voltage from said output terminal of said first amplifier; generating an error correcting voltage from said common mode voltage and said compensating voltage; and summing said error correcting voltage with said output voltage from said first amplifier; wherein generating said error correcting voltage comprises providing a third amplifier, said third amplifier having a first input, a second input, and an output, said first input of said third amplifier being electrically coupled to said first connecting terminal of said second network resistor, said second input of said third amplifier being electrically coupled to said second connecting terminals of said third and said fourth network resistors, said error correcting voltage being generated at said output of said third amplifier.