Switching Sampling Power Meter for Frequencies Up to 1 MHz

This paper describes a power measurement setup that is able to measure power up to the MHz region. The setup consists of a commercial digitizer together with a switch unit, and buffer amplifiers to alternately measure the voltage and current channel. A reference AC voltmeter provides an absolute reference by simultaneous measurement of the rms voltage of one channel, which significantly reduces the need for flat frequency response of the setup. The method described in this paper makes complex voltage ratio measurements possible in the range of 50 Hz up to 1 MHz with an uncertainty of a few parts in 10⁶ and in addition can be applied in wideband power measurements. Using our new method, the frequency response of cables and several other components is no longer a limiting factor for power measurements up to 1 MHz.