Pointer multimeter measurement and judgment of diodes
Generally diodes have a direct indication of the positive and negative poles, when you see a white coil on the casing of the section, it is the negative pole. Or the side with the shorter pin is negative. But if there is no such characteristics how to do?
Multimeter is an electrician have tools on hand, the use of multimeter ohm file (resistance) to measure the diode's positive and negative resistance, due to the multimeter connected to the battery, it should be noted that the multimeter shell labeled "-" on the end of the wires connected to the black pen; case labeled "+" on the end of the wires red pen. " on the case is labeled "+" on the terminal red pen connected. The current is flowing out from the red pen and back from the black pen. In addition should be selected to measure the Rx1000 ohm file, because the Rx1 file current is too large, Rx10K file voltage is too high, are easy to damage the
Diode, so should not be selected.
Specific test method: the two pens of the multimeter were connected to the two pins of the diode. The forward resistance of the diode is very small, generally dozens of ohms to hundreds of ohms, while the reverse resistance is very large, generally tens of kilo-ohms to hundreds of kilo-ohms. If the two tests, the right side of the test shows a smaller resistance, the left side of the test shows a larger resistance, you can conclude that the right side of the red pen connected to the diode pin for the positive pole, the other pin is the negative pole.
Some modern digital multimeter may have a diode above the good and bad judgment of the gear (pass-break gear), the multimeter will be set in this gear for measurement if there are readings, the red pen for a section of the positive pole, if there is no readings or show "1", then the black pen for the positive pole.
Judgment diode method
Still above the use of multimeter resistance file measurement method to determine. If the measured positive and negative resistance difference is very large, the measurement shows that the diode's unidirectional conductivity is good; if the measurement of the two resistance values are very small or very large, the diode has lost the unidirectional conductivity, and in time there is a quality problem of the bad diode.
