Instrumentation circuit for shunt-based metrology measurement

A method for measuring differences in voltage drop, comprising:

• coupling a current measurement component having first and second terminals in series with a voltage source and a load device, the voltage source operating at a first frequency;
• providing first and second voltage drop circuits each comprising a fixed value component and an adjustable value component coupled in series;
• coupling the first voltage drop circuit to the first terminal of the current measurement component;
• coupling the second voltage drop circuit to the second terminal of the current measurement component;
• superimposing a relatively high-frequency signal onto a control input of the adjustable value components;
• adjusting the values of the adjustable value components based on any difference in voltage drop values produced by the first and second voltage drop circuits due to measured variations in the voltage drops produced by the high-frequency signal;
• and
• measuring the difference in voltage drop produced by the difference in voltage drop values produced by the first and second voltage drop circuits at the first frequency.

Apparatus for measuring voltage drop at a first frequency through a load device, comprising:

• a current measurement component having first and second terminals;
• first and second voltage drop circuits coupled, respectively, to the first and second terminals of the current measurement component, each voltage drop circuit including a first fixed value component coupled in series with an adjustable value component;
• a tuning circuit configured to couple a high-frequency signal to a control input of the adjustable value components, to monitor voltage drops produced by said first and second voltage drop circuits from said high-frequency signal, and to provide signals to said adjustable value components based on any differences in the voltage drops;
• and
• a measurement device coupled to the first and second voltage drop circuits to measure voltage drop differences at said first frequency.

Apparatus for measuring voltage drop at a first frequency through a load device, comprising:

• a current measurement component having first and second terminals;
• first and second fixed value components connected, respectively, to said first and second terminals of the current measurement component;
• an adjustable value component;
• a switching device, the switching device configured to connect each fixed value device to said adjustable value component so that the first and second fixed value components are alternately coupled in series with said adjustable value component;
• a tuning circuit configured to couple a high-frequency signal to a control input of the adjustable value component, to monitor voltage drops produced by said first and second fixed value components when coupled in series with said adjustable value component from said high-frequency signal, and to a provide signals to said adjustable value component based on any differences in the voltage drops;
• and
• a measurement device coupled to the first and second fixed value components to measure voltage drop differences at said first frequency.