Electrical Engineering ⇒ Topic : Loading Effects Due to Shunt Connected Instruments

Loading Effects Due to Shunt Connected Instruments

Let V be the generator voltage, Z be the output impedance, V_L be the load voltage, I_L be the load

current, and Z_L be the load impedance. [See Figure (1)]

Here                                      V_L = /_L Z_L

and                                        V_L = V -  I_LZ                                                                       .......... (1)

                                               V = V_L + I_LZ = I_LZ_L + I_LZ = I_L(Z + Z_L)

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

From Eq. (2) it is clear that if Z_L, >> Z, V_L = V. So the impedance of the voltmeter must be very large.

                                                            FIGURE (1)  Loading effect due to voltmeter