Can the diode gear of the multimeter light up the diode?
There is a diode gear on the multimeter, which can be used to detect diodes and light them up. But the lighting is not absolute, there are two main reasons: 1) The voltage of the diode gear of the multimeter is low; 2) The working voltage of the light-emitting diode is high.
The voltage of the diode gear of the multimeter is generally about 3V. This voltage can light up the ordinary light-emitting diode. When measuring the quality of the diode, you can use the red test lead to touch the positive pole of the LED, and the black test lead to the negative pole of the LED. You can judge when the LED is on. LEDs are fine. However, the output voltage of some meters is low, so the LED cannot be lit or can only be lighted slightly. I have used a cheaper multimeter from Unilever before, but the LED cannot be turned on, and the diode position is basically useless, which is very inconvenient.
Can the diode gear of the multimeter light up the diode?
LED is a special kind of diode with forward conduction voltage drop, and this parameter varies greatly. Light-emitting diodes of different colors have different conduction voltage drops. Generally speaking, the conduction voltage drop of the red light-emitting diode is the smallest, in the range of (1.5-2) V; the green is next, at about (1.8-2.5) V; and the blue voltage drop is the highest, at (2) -3.5) V or so. Therefore, when the same watch measures LEDs of different colors, its brightness is different. Generally, red is the brightest and blue is the darkest. Even some colors cannot be lit.
Use a multimeter to measure the motor with four wires, is it normal that two of the motors have buzzing sounds?
The four-wire motor refers to a 220V single-phase motor, two of which are starting windings and the other two are running windings.
How to judge which two wires are start winding or run winding?
The method of judging the main and auxiliary windings of a single-phase motor is mainly to use the resistance file of the multimeter to test. The auxiliary winding (starting winding) has a thinner coil with many turns, so the resistance must be large, usually tens of ohms to tens of ohms; the main winding (running winding) needs to run for a long time, so the wire diameter of the coil is thick and the turns If the number is small, the resistance value must be small, generally only a few ohms
Use a multimeter to measure four wires, is it normal for two wires to have buzzing sounds?
When the resistance level of the multimeter is set to the low rate buzzer level, if there is a long "beep" buzzer alarm sound, it means that it is in a short-circuit through state.
It is not normal to say that there are two wires buzzing, because even a running winding with a low resistance value will have a resistance value of several ohms, and the buzzing sound should not occur. Therefore, it is judged that there should be a short circuit fault in the winding.
