Be familiar with the dial before using a multimeter correctly. Two zero regulators, gently rotate to adjust the zero position. Correct selection of terminals, red and black pen insertion hole. Switch to shift, the gear selection should be correct. Reasonable choice of range, the measurement reading is accurate. Look at the range scale line, vertical surface reading. After measuring the dial pen, the switch rotates in high pressure. The battery in the table is often checked, deterioration will leak electrolytic solution. Good instrument environment, no vibration, damp and weak magnetic field.
The resistance must be adjusted to zero each time the ratio file is changed. Nib measuring point contact good, measuring object pen hand does not touch. Measuring the electrical route, should be more than 1000 ohm range file.
When measuring voltage with a multimeter. Clear table resistance size, must be monitored. The measured circuit table is in parallel, and the range cannot be changed when it is live.
When measuring DC voltage, identify the positive and negative terminals of the circuit. Measure the inductive voltage of the circuit, during which the power supply cannot be cut off. Test kV high voltage, must use a special marker line. Induced electric voltage to earth, range different values of large difference.
Use a multimeter to measure the current, switch to milliampere, determine the positive and negative poles of the circuit, the meter is in series circuit. Select a larger range to reduce the impact on the circuit.
Judgment of three - phase motor winding head - tail DC method. Multimeter dial milliampere, DC power dry battery. One phase winding is connected to the instrument and the other phase winding is connected to the battery. Power instantaneously watch hand turn, reverse the positive pole is the first. If the conversion connection is not reversed, the cophase winding is judged in the same way.
Running motor, head and tail remanence method. Three phase winding outlet head, after marking parallel. Multimeter dial milliampere, cross parallel common points. Slowly turn the motor shaft while watching the instrument needle. The pointer does not swing obviously, and the three heads and three tails are connected. The pointer swings to the left and right, two ends and one end. A phase winding replacement head, and then use the same method to detect. Until the watch hand does not swing, the end and end respectively.
The running motor head and tail circulation method. The three - phase winding outlet head is connected into a triangle. Multimeter dial milliampere, series-connected three-phase winding. Evenly dial the motor shaft while watching the instrument needle. The pointer basically does not swing, and the end of the winding is connected. Pointer swing amplitude is large, a phase winding head upside down. Two connecting points and two wire heads, both of which are head and tail ends.