Multimeter to measure the positive and negative polarity of the diode and whether it is good or bad.
With the help of a multimeter to measure the resistance or on-off test gear, you can easily find out the polarity of the diode positive and negative polarity as well as a rough measurement of the diode is good or bad.
Diode positive and negative polarity
General diode is a direct representation of the positive and negative polarity, when you see a white coil on the shell of the section, is the negative pole. Or the shorter side of the line for the negative side. But what if there are no such characteristics?
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 case of the multimeter marked "-" on the end of the wires connected to the black pen; case marked "+" on the end of the wires red pen. " on the case of the red pen connected to the terminal end. The current is flowing out from the red pen and back from the black pen. In addition should be selected Rx1000 ohm file to measure, because Rx1 file current is too large, Rx10K file voltage is too high, are easy to damage the diode, so it is not suitable for selection.
Specific test method shown in the figure on the right, 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 dozens of kilo-ohms to hundreds of kilo-ohms. If the two tests in the figure, the right side of the test shows a smaller resistance, the left side of the test shows a larger resistance, it can be concluded that the right side of the red pen connected to the diode's positive pin, the other pin that is the negative pole.
Some modern digital multimeter may have a diode above the good and bad judgement of the gear (on and off gear), the multimeter will be set in this gear for measurement if there are readings, the red pen section for the positive pole, if there is no readings or show "1", then the black pen for the positive pole.
Diode good or bad judgement
Still above the use of multimeter resistance file measurement method to judge. If the measured positive and negative resistance difference is very large, measured that the diode's unidirectional conductivity is good; if the resistance value of the two measurements are very small or very large, it means that the diode has lost the unidirectional conductivity, and in time there is a quality problem of the bad diode.
