Patent ID: 7642788

Claim:
A voltage measuring instrument, comprising: an analog-to-digital converter operable to generate a digital output signal indicative of the amplitude of a signal received by the analog-to-digital converter; an RMS circuit structured to generate an RMS output signal indicative of the RMS amplitude of a signal received by the RMS circuit; a capacitor; a display coupled structured to display a value corresponding to a digital input signal, the digital input signal being based on the digital output signal received from the analog-to-digital converter; and a switching circuit operable in an AC mode or an automatic mode, the switching circuit being operable in the AC mode to couple the input terminal to the RMS circuit through the capacitor and to couple the RMS output signal from the RMS circuit to the analog-to-digital converter, and being operable in the automatic mode to couple the input terminal to the RMS circuit without coupling the input terminal through the capacitor and to couple the RMS output signal from the RMS circuit to the analog-to-digital converter.