Zero Adjustment

When the ohmmeter leads are open as shown in Figure 148, the meter is at a full scale deflection, indicating an infinite (∞) resistance or an open circuit. When the leads are shorted as shown in figure “zero adjust,” the pointer will be at the full right hand position, indicating a short circuit or zero resistance. The purpose of the variable resistor in this figure is to adjust the current so that the pointer is at exactly zero when the leads are shorted. This is used to compensate for changes in the internal battery voltage due to aging.