Fig. 1.13 The principle of vectors.

If current is flowing towards the positive electrode a positive deflection will be seen on the voltmeter (EcG). If the vector is directed away from the positive electrode a negative

deflection is recorded. If the same voltage current flows along an axis which is oblique to the positive electrode but towards it, a smaller positive deflection is detected. If the vector of depolarisation is perpendicular to the axis of the electrodes there will be no net depolarisation.