Abstract: A vector voltmeter for measuring the amplitude and phase difference between two signals. A first signal is fed to a power divider in which one of its outputs is measured with a power detector and the other output is fed to a second divider, each output thereof being fed one each to a third and fourth power divider. The second signal is fed to a fifth power divider in which one of its outputs is measured by a second power detector and the other output of the fifth divider is fed to a hybrid circuit having quadrature outputs, one of which is fed to the third power divider whose output is measured by a third power detector and the other quadrature output is fed to the fourth power divider whose output is measured by a fourth power detector. The four power detectors are connected to two differential amplifiers which drive the X and Y axis of an oscilloscope.