Resistance measurement

The resistance of a consuming device in a DC circuit can either be measured indirectly or directly.

• With indirect measurement, the current through the consuming device and the voltage drop across the consuming device are measured (Figure 3.19a). Both measurements can either be performed one after the other or at the same time. The resistance is then calculated using Ohm's law.

• With direct measurement, the consuming device is separated from the circuit (Figure 3.19b). The measuring device is switched to the "resistance measurement" operating mode and connected to the two terminals on the consuming device. The resistance value is read directly on the measuring device.

If the consuming device is defective (e.g. the solenoid coil of a valve is burnt out), the resistance measurement will either give an infinitely high value or the value zero (short circuit).