AC ammeter circuit

Figure 5-18 shows the AC ammeter circuit . Following the analysis method in Figure 5-17,
    IAV= (l+R1/R2)li<Aw
meter reading is determined by the full-wave rectified average value h^v of the measured AC current
L].     If the measured current L is a sinusoidal current, that is, Ii=-√iEsinOJt, then the above formula can be written as
    IAv=0. 9(l_[-R1/Rz)11.
Then the meter can be scaled according to the effective value.