A TDM wattmeter with 0.5 MHz carrier frequency

The operating principle and design of a TDM (time-division multiplexer) wattmeter with 0.5-MHz carrier frequency are described. At power frequency the meter was compared with the National Research Council´s current-comparator power bridge. The nonlinearity error of the meter was smaller than 100 ppm of full scale over the wide range of inputs and the whole range of power factor. Preliminary results have shown that the frequency dependent errors are below 100 ppm up to 2 kHz in the whole range of power factor. This accuracy is comparable with the accuracy of the standard thermal wattmeters. However, the meter itself is more compact, is relatively simple, and has a faster response time. The design described demonstrates that relatively simple corrections permit a considerable increase in the TDM wattmeter carrier frequency, thus decreasing its systematic frequency errors