Several of the Most Practical Methods for Using a Multimeter to Troubleshoot Circuit Faults
Voltage Measurement Method
First, power on the control circuit. Adjust the range switch of the multimeter to the AC voltage range of 750V. Referring to the circuit schematic diagram, keep one probe of the multimeter on Line 9, and use the other probe to measure Lines 8, 7, 6, 5, 4, and 3 respectively. When the switch is not closed, if the two probes are of the same phase, the voltage is 0V. When measuring Lines 2 and 1, if the two probes are of different phases, the voltage is around 380V. This is the normal state of the circuit. If during the measurement process, the voltage value at any line or point does not match that in the circuit schematic diagram, then in most cases, the point with the incorrect voltage value is the fault point!
Resistance Measurement Method
First, the circuit needs to be powered off and the electricity should be checked. After confirming that there is no electricity, adjust the range switch of the multimeter to the buzzer range or the resistance range. Place the two probes of the multimeter on Line 1 and Line 9 respectively. Under normal circumstances, press Button SB1 or SB2 respectively, or directly press the springs of the two AC contactors manually (that is, manually close the normally open contacts of KM1 or KM2). At this time, Lines 1 and 9 are conducting, the circuit is connected, and the multimeter will show the resistance value of the corresponding coil. If there is no resistance value, it proves that the loop is not connected. It is necessary to measure and analyze the continuity of each point one by one according to the circuit schematic diagram. The measurement method is similar to that of the voltage measurement.
The resistance measurement method and the voltage measurement method of the multimeter are the two most commonly used methods in circuit fault troubleshooting. It can be said that each has its own advantages and conveniences. The key is which one you are accustomed to using. Use the method you are most familiar with to measure with the help of the multimeter.
