The block diagram of a wattmeter based on a TDM is shown in Figure 3.10.
A square wave vm (Figure 3.11(a)) with constant period Tg, and duty cycle and amplitude determined by i(t) and v(t), respectively, is generated.
If Tg is much smaller than the period of measurands vx(t) and vy(t), these voltages can be considered as constant during this time interval.