In the state not in use, switch S must be opened so that the battery V not quickly becoming weaker. If the ohmmeter is used, then the switch S ditutup.Mula initially taken RX = infinity or AB in an open state, so as to obtain the current through M + IM. In these circumstances pontensiometer R2 is set to flow through M reaches the maximum price (full scale), so that:
Position R2 should not be changed again so that it always met Imaks above equation would thus obtained that scale with RX = infinity is located on the right. For RX = zero or AB shorted so no current through M or. So the scale of zero ohms is located on the left. What is the difference with ohmmeter series?
Calibration curves
When installed RX resistance in the circuit in Figure 5.60, it can be calculated current through M:
From the equation above can be made IM a calibration curve is a graph RX as the IM function. Here, it is shown an example of a calibration curve forms a parallel ohmmeter.
Figure 8.9 Calibration curve Parallel Ohmmeter