Electrical Engineering ⇒ Topic : Loading Effect Due to Series Connected Instruments

Loading Effect Due to Series Connected Instruments

Let V be source voltage, Z be output impedance, and Z_L be input impedance of the ammeter.

From Figure 1 (a),

                                                    ............. (1)

From Figure 1 (b),

                                                                               ............ (2)

Using Eqs. (1) and (2), we get

                                                 ............. (3)

From Eq. (3) it is clear that I_L will be equal to I if and only if Z>> Z_L, i.e., the input impedance of the ammeter should be very small.

                                                                  Figure (1) Loading effect due to ammeter.