Determination of the rate at which energy is transmitted by microwave propagation. Power is one of the fundamental parameters measured at microwave frequencies. Since the physical dimensions of the microwave system are comparable with the wavelength, the voltage along a conductor is no longer constant. Further, for energy transmitted inside a hollow, uniconductor waveguide, the voltage difference between two points is not uniquely defined and varies as a function of the path taken to pass from one point to the other. Thus voltage standards, basic to low-frequency electrical measurements, give way to power standards at microwaves. Power meters are connected either temporarily, to measure all the power, in place of the normal termination, or permanently to measure a fixed portion of the power.