The use of a digital multimeter and measurement techniques
First, determine the line or device with or without electricity:
The AC voltage block of the digital multimeter is very sensitive, even if there is a very small induced voltage around the display. According to this feature, it can be used as a test pen. Usage is as follows: the multimeter to AC20V block, the black pen hanging empty, holding the red pen and the side of the line or device contact, then the multimeter will have a display, if the display figures in a few volts to dozens of volts (different multimeter will have different displays), indicating that the line or device with electricity, if the display is zero or very small, indicating that the line or device is not charged.
Second, distinguish the power supply line is fire or zero line:
The first method: you can use the above method to determine: show a larger number is the fire line, show a smaller number is the zero line. This method requires contact with the measured line or device.
The second method: do not need to contact with the measured line or device. Multimeter to AC2V block, the black pen hanging empty, holding the red pen so that the tip of the line along the road gently sliding, then the table if the display for a few volts, indicating that the line is the fire line. If the display is only a few volts or even smaller. The line is zero. This method of judgment is not in direct contact with the line. Not only safe and convenient.
Third, looking for cable breaks: When the cable line breaks, the traditional method is to use a multimeter resistor block a section of the cable looking for breaks, this is not only a waste of time, but also to a large extent, damage to the insulation of the cable. Using the inductive properties of the digital multimeter can quickly find the break point of the cable. First use the resistive block to determine which one cable core line breaks. Then one end of the core line disconnected to the AC220V power supply, and then the multimeter to AC2V block position, the black pen hanging empty, holding the red pen so that the tip of the pen along the line gently sliding, then the table if the display of a few volts or zero a few volts (due to different cables and different) of the voltage, if you move to a certain position when the table shows a sudden decrease in the position of a lot of, write down the position: general circumstances . The break point is somewhere between 10 and 20 cm in front of this position.
