61 the measuring unit 60 is connected to measure the capacitance of capacitor 52 in the third position of switch 61 the common terminal of the capacitors 62 and 63 is connected through conductors 67 and 75 and contact 61 1 to conductor 71 and thence to the measuring unit 60 the shield 68 is connected through contact 61 3 to the shield 74 the lower terminal of the simulating capacitor 63 is connected through conductors 77 and 82 and contact 61 2 to conductor 73 and thence to the measuring unit 60 the upper terminal of capacitor 62 is grounded through contact 61 4 the measuring unit is now connected to measure the capacitance of simulating capacitor 63 in the fourth position of switch 61 the upper terminal of simulating capacitor 62 is connected through conductors 76 and 78 and switch contact 61 2 to conductor 73 the connections through contacts 61 1 and 61 3 remain as in the third position the lower terminal of capacitor 63 is grounded through contact 61 4 the measuring unit 60 is now connected to measure the capacitance of simulating capacitor 62 in the fifth position of switch 61 only contacts 61 5 to 61 8 are employed the common terminal of the simulating capacitors 62 and 63 is connected through conductors 67 and 75 contact 61 7 and conductor 54a to the operating means 56 for indicator 57 the lower terminal of capacitor 63 is connected through conductors 77 and 82 contact 61 6 and conductor 53a to the operating means 56 the upper terminal of simulating capacitor 62 is connected through conductors 76 and 78 switch contact 61 8 and conductor 55a to the indicator operating means 56 the shield 68 is connected through contact 61 5 to shield 66.