A simple VFC based wattmeter suitable for application at industrial frequency

In this paper, the design of a simple AC wattmeter is presented. Its main features are that it uses a multiplier built with two voltage-to-frequency converters (VFC), and that it can be easily connected to a digital instrument, without further analogue conditioning. The design process is described in detail, and two design approaches are presented. Tests performed in a prototype validate the suitability of the meter. A limitation is that it can only be used with null-average signals, such as those usually those found in AC metering applications.