Four wonderful ways to use the digital multimeter
1. Judging whether the circuit or device is charged or not
The digital AC voltage block is very sensitive, even if there is a small induced voltage around it, it can be displayed. According to this feature, it can be used as a test pencil.
The usage is as follows: turn the multimeter to AC20V gear, hang the black test lead in the air, hold the red test lead in contact with the measured route or device, then the multimeter will display, if the displayed number is between a few volts and more than ten volts (different multimeters will There are different displays), indicating that the line or device is charged, and if the display is zero or very small, it indicates that the line or device is not charged.
2. Distinguish whether the power supply line is live or neutral
the first method:
It can be judged by the above method: the larger number is the live line, and the smaller number is the zero line. This method requires contact with the line or device being measured.
The second method:
No contact with the line or device being measured is required. Turn the multimeter to the AC2V gear, hang the black test lead in the air, and hold the red test lead to slide the tip along the line gently. At this time, if the meter shows a few volts, it indicates that the line is live. If the display is only a few tenths of a volt or even less. It means that the line is the zero line. Such a judgment method is not in direct contact with the line. Not only safe but also convenient and fast.
3. Finding Breakpoints in Cables
When there is a breakpoint in the cable, the traditional method is to use a multimeter to block and find the breakpoint of the cable section by section. This will not only waste time, but also damage the insulation of the cable to a large extent. The disconnection point of the cable can be found quickly by using the inductive characteristic of the digital multimeter.
First use the electric barrier to determine which cable core wire is open circuited. Then connect one end of the broken core wire to AC220V, and then turn the multimeter to the position of AC2V gear, hang the black test lead in the air, hold the red test lead and slide the tip along the line gently, at this time, if there are several volts displayed on the meter Or a few tenths of volts (due to different cables), if the display on the meter suddenly drops a lot when moving to a certain position, write down this position: under normal circumstances. The breakpoint is between 10 and 20 cm in front of this position.
This method can also be used to find the breaking point of resistance wires such as faulty electric blankets.
4. Frequency of measurement
For UPS power supply. The stability of the voltage at its output terminal is an important parameter, and the frequency of its output is also very important. However, it cannot be measured directly with the frequency block of the digital multimeter, because the voltage that the frequency block can withstand is very low. Only a few volts.
At this time, a 220V/6V or 220V/4V step-down transformer can be connected to the output terminal of the UPS power supply to reduce the voltage without changing the frequency of the power supply, and then connect the frequency block to the output of the transformer to measure the UPS power supply. Frequency of.
