What is the difference between the resistance range and the beep range of a multimeter when measuring continuity
The resistance range of a multimeter can measure the specific size of the circuit resistance, and we can analyze and determine whether the circuit is normal or has any faults based on the resistance size.
The buzzing gear can only determine whether the resistance value of the circuit is large or small (usually around 30-50 Ω as the dividing point, and there may be some differences between different multimeters).
Assuming that the critical resistance value for the multimeter to emit a beep is 50 Ω, the beep will only sound when the resistance value of the circuit or load is less than 50 Ω, and the lower the resistance, the louder the beep. But when the resistance value of the circuit or load is greater than 50 Ω, the beep gear will not sound. So when the line resistance is greater than 50 Ω or ∞, we cannot distinguish it using a beep gear.
Single-phase motor quality judgment
From the question, we know that the motor has a total of 4 wires, so we can infer that the motor should be a single-phase motor (specific types of single-phase motors need to see the actual object to make a conclusion).
A single-phase motor has two coil windings, one is the starting winding and the other is the operating winding. Due to the thicker coil of the operating winding and the thinner coil of the starting winding, the resistance value of the starting winding is higher than that of the operating winding. The specific resistance value is related to the motor model and power, ranging from more than ten ohms to one or two hundred ohms. (The higher the motor power, the lower the resistance; the lower the power, the greater the resistance)
If the power of the motor is very small, its resistance value will be very high. If the resistance value is greater than 50 Ω, the result we measured using the buzzer gear is no noise. Similarly, if the motor winding is burnt out, then we will not make a sound using the buzzer gear.
If the motor has a high power, its resistance value will be very small. If the resistance value is less than 50 Ω, the result we measured with a beep gear is a beep sound. Similarly, if a short circuit occurs in the middle of the motor winding, the result we measured using the beep gear also shows a beep sound.
So, for the situation you mentioned, there is really no way to judge whether the motor is good or bad. To determine the quality of the motor, it is necessary to analyze it based on the combination of motor resistance and power.
For electricians who have just come into contact with a multimeter, I suggest that when using a multimeter to measure circuits or loads, try to use a resistance range instead of a beep range. This is very helpful for repairing and mastering the multimeter. Only after mastering the application of measuring resistance with a multimeter proficiently, can you use the beep gear to improve maintenance speed.
