Use a digital multimeter in AC-enabled ammeter mode to read the RMS current value directly from the electrical circuit. Alternatively, determine the RMS current value by dividing the peak value of the alternating current by the square root of 2. The peak value is the maximum value or the amplitude of the sinusoidal current function, where the function describes how the current changes with time. AC current functions can be visualized as waveforms using an oscilloscope fitted with an AC current probe. Peak current is obtained by examining the pattern on the oscilloscope monitor and finding the value at which the curve reaches its maximum value.
Use a digital multimeter in AC-enabled voltage mode to read the RMS voltage value directly from the electrical circuit. Alternatively, determine the RMS voltage value by dividing the peak AC voltage value by the square root of 2. The peak value is the maximum value of the sinusoidal voltage function. AC voltage functions can be visualized as waveforms using an oscilloscope. No special attachments are required for taking voltage measurements. Peak voltage may be read directly from the waveform on the oscilloscope monitor.
Calculate the RMS wattage or the direct current (DC) equivalent of the AC power by multiplying the RMS voltage and the RMS current. The unit for the product is the watt.