A Novel TDM-Based High-Precision Wattmeter

A novel high-precision wattmeter is developed based on a standard watt converter design using time-division multiplication. A commercial 22-b delta-sigma A/D converter is used for the measurement of the watt converter output dc voltage. The measurement results are presented on a local display. In addition to power, the instrument measures ac voltage and ac current and displays their measured values on separate displays. Two prototypes were tested and compared with an existing standard watt converter connected to a high-precision digital voltmeter. The measurement results are presented and analyzed. Achieved measurement uncertainties (k = 2) of the power measurement are better than 50 μ W/VA.