Which one has better anti-interference, digital multimeter or analog multimeter?
Let me talk about my experience in using it. I first used an analog multimeter. When using it, for example, the resistance setting sometimes needs to be adjusted to zero. When measuring voltage, start measuring from the high setting first to prevent the meter from burning. In addition, you need to keep it steady when measuring. When numeric values are set, the line of sight should be perpendicular to the dial surface. It is subject to greater human and environmental interference.
On the other hand, digital multimeters do not have the above shortcomings, and their input impedance is large, so there is no need to worry about meter burnout.
However, an analog multimeter has the advantage of being intuitive when measuring parameters.
Digital multimeters have relatively low requirements for the use environment, have a wide range of applications, strong anti-interference capabilities, and intuitive parameters.
Analog multimeters are large in size, inconvenient to carry, have high requirements on the use environment, have poor anti-interference ability, and are inconvenient to read readings, but they have high accuracy.
Of course, the analog multimeter has better anti-interference ability. When measuring some electrical parameters, such as the voltage at certain points inside the frequency converter, the readings of the digital multimeter will jump randomly and cannot be read. The analog multimeter does not have this problem, but it is accurate and easy to use. The degree is worse than the digital meter. In short, both have their advantages and disadvantages.
There are two types of analog watches: internal magnetism and external magnetism. The error is too large due to the influence of static electricity. If you don’t believe it, if you rub your hand on the dial glass, the hands will not return. Digital watches are easier to use, but each has its own advantages and disadvantages.
Use a multimeter to determine the first and last ends of the 6 connectors of the motor
If the shorting strips are connected to three terminals on one side, it is a star connection of the motor, as shown on the left side of the figure above; if three shorting strips are connected in parallel, it is a delta connection of the motor, as shown on the right side of the figure above.
But it is a little more troublesome to judge the first and last ends of the six connectors of the motor. A commonly used method is introduced below.
1. Adjust the multimeter to the buzzing position and measure the 6 connectors of the motor. The two connected connectors form a group and can be divided into 3 groups. These are the 3 windings of the three-phase motor.
2. Then define three windings as U1', U2', V1', V2', W1', W2', and connect U1', V1', W1' in parallel, and U2', V2', W2 'Together in parallel.
3. Adjust the multimeter to the milliamp (mA) range, and connect the two test leads to the parallel terminals of U1’, V1’, and W1’ and the parallel terminals of U2’, V2’, and W2’ respectively.
4. Rotate the motor rotor, not too fast, just normal turning speed.
5. Then observe the multimeter pointer. If the pointer does not move, it means that the winding definition is correct, because the sum of the rotor residual magnetism and the appropriate amount of induced electromotive force in the three-phase motor winding is zero.
6. If the multimeter pointer moves, it means that the beginning and end of one group of windings are wrong. You need to replace the winding joints one by one and test until the multimeter pointer does not move.
