The multimeter can use the diode file to detect the LED
LEDs also belong to diodes, which also have the characteristics of one-way conduction. Only current is allowed to flow from the positive pole of the LED to the negative pole, so we can use the diode gear of the multimeter to measure the quality of the LED. The red and black test pens are directional. First You can first exchange the test leads to measure, so as to avoid wrong judgment, but LED is different from ordinary diode, its forward voltage drop is relatively high, and the forward voltage drop of LEDs of different colors is also different. When the voltage is lower than the forward voltage drop of the LED, the LED can only light up slightly or even not light up.
Multimeter diode gear measurement principle
The diode gear will provide a constant current, generally 1mA (some multimeters are 2mA). When the diode is connected, the voltage drop of the PN junction of the diode can be measured to judge the quality of the diode. Since the current provided by the diode gear is very small, when measuring the LED, if the current required by the LED is large, the brightness will be relatively low.
A multimeter powered by a 9V battery can generally light up the LED. Some multimeters powered by a 3V battery may not be able to light an LED with a high operating voltage drop.
Multimeter resistance gear can also measure light-emitting diodes
We can also use the resistor R100 to measure whether the LED emits light. If the working voltage drop of the LED is high, we can also consider connecting a 1.5V battery in series to increase the measurement voltage of the multimeter, thereby increasing the brightness of the LED so that we can better Determine whether the LED is damaged.
