The diode has two electrodes called the anode and the cathode. It is capable to carry current from the anode to the cathode, but not on the contrary. The marking explaining purpose of conclusions is available not on all diodes.
Instruction
1. If marking is available, pay attention to its appearance and arrangement. It looks as the arrow resting against a plate. The direction of an arrow coincides with the direct direction of the current proceeding via the diode. In other words, to an arrow there corresponds an anode conclusion, and a plate - cathode.
2. Analog multipurpose measuring devices have various polarity of tension attached to probes in the ohmmeter mode. At some of them it same, as in the mode of the voltmeter or ampermeter, at others - opposite. If it is unknown to you, take the diode having marking, switch the device to the ohmmeter mode then connect to the diode at first in one, and then in other polarity. At option in which the arrow deviates, remember what electrode of the diode was connected to what of probes. Now, connecting probes in various polarity to other diodes, you will be able to define arrangement of their electrodes.
3. At digital devices in most cases the polarity of connection of probes in all modes coincides. Switch a multimeter to the mode of check of diodes - near the relevant provision of the switch there is a designation of this detail. The red probe corresponds to the anode, black - to the cathode. In the correct polarity the direct voltage drop on the diode will be shown, in wrong the infinity is displayed.
4. If near at hand there is no measuring device, take the battery from the motherboard, a light-emitting diode and the resistor on one kilohm. Connect them consistently, having connected a light-emitting diode in such polarity that the light-emitting diode shone. Now turn on the checked diode in a rupture of this chain, having experimentally picked up such polarity that the light-emitting diode was lit again. The diode conclusion turned to battery plus - anode.
5. If when checking it is found out that the diode is constantly open or constantly closed, and nothing depends on polarity, it means it is faulty. Replace it, previously having made sure that its failure is not caused by malfunction of other details. In this case at first replace also them.