US Patent 7923985 Active autoranging current sensing circuit

A range-changing circuit for a measurement device having a desirable range includes an array of graduated impedances. And amplifier supplies an electrical voltage to at least one of the impedances of the array. A voltage sensing and limiting switch is provided in a feedback path of the amplifier. The switch limits said electrical voltage supplied to said at least one of the impedances in response to a sensed voltage that is sensed by the switch. An electrical voltage in the desirable range is developed across a different one of the impedances of the array based on an operation of the switch.