What separates the multimeter resistance file from the buzzer file for testing on-off
Many friends like to use the buzzer gear to judge whether the line is on or off or whether the equipment is good or bad, and many friends like to use the resistance gear to judge whether the line is on or off or whether the equipment is good or bad. So here comes the question, what is the difference between the multimeter resistance gear and the buzzer gear when measuring on-off?
The buzzer can only judge whether the line resistance is large or small (generally around 30-50Ω is the cut-off point, and different multimeters are slightly different).
Assuming that the critical resistance value of the beeping sound of the multimeter's beeping gear is 50Ω, the beeping gear will only sound when the resistance of the line or load is less than 50Ω, and the smaller the resistance, the louder the beeping sound. But when the line or load resistance is more than 50Ω, the buzzer will not sound. So when the line resistance is greater than 50Ω or ∞, we can't tell it with the buzzer.
Good or bad judgment of single-phase motor
The motor has a total of 4 wires, so we can speculate that the motor should be a single-phase motor (the specific type of single-phase motor can only be concluded by seeing the real thing).
If the power of the motor is small, then its resistance will be very large. If the resistance is greater than 50Ω, the result we measured with the buzzer file is that there is no sound. Similarly, if the motor winding is blown, it will not sound when we use the buzzer to test.
If the power of the motor is large, its resistance will be very small. If the resistance is less than 50Ω, the result we measured with the buzzer file is a buzzing sound. Similarly, if there is a short circuit in the middle of the motor winding, then we will also have a buzzing sound when we use the buzzer file to measure the result.
