Abstract: A method and apparatus for obtaining a voltage-isolated measurement channel in a measurement instrument is provided. An input signal is multiplied with a clock signal to obtain a modulated input signal that is coupled to an input winding of a balanced transformer. The modulated input signal is electromagnetically coupled from the input winding to an output winding. At the same time, the input winding and the output winding are voltage-isolated, meaning that the portion of the measurement channel coupled to the input winding is "floated" with the input signal whereas the remaining portion of the measurement channel is referenced to instrument ground. A sampling circuit coupled to the output winding samples the modulated input signal in the manner of a synchronous detector to extract the original input signal voltage which is provided to an analog to digital converter which generates the digital measurement values.