Before measuring the current strength, the measurement range corresponding to the expected value of the measured current is set on the device. If the current strength is unknown, then the highest limit must be set and, if the device does not show any current, the device must be successively switched to the measurement ranges of currents of lower strength.
To measure the current, the electrical circuit must be broken and the measuring device (ammeter) must be connected to the break in the circuit. For this, for example, the plug is disconnected and the red wire (+) of the ammeter is connected to the supply wire. The black wire (-) of the ammeter is connected to the contact to which the disconnected wire was connected. The ground contact (-) between the plug and the current consumer should be closed with an auxiliary wire.
Warning! Never measure the current on the starter wire with a regular ammeter (about 150 A) or to the glow plugs of a diesel engine (up to 60 A), because the ammeter may be damaged by the large currents flowing. In workshops, current clamps are used for such measurements. The clamps are connected to an insulated wire and the current is measured using the phenomenon of induction.