Some Skills of Using Digital Multimeter Well
Regarding the skills of using the digital multimeter, it will be very helpful to use the digital multimeter correctly, including judging whether the circuit or device is charged or not, distinguishing whether the power supply line is live or neutral, finding the breakpoint of the cable with the digital multimeter, and measuring ups power frequency, etc.
1. Judging whether the circuit or device is charged or not
The AC voltage block of the digital multimeter 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 side line 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: You can use the above method to judge: the one with the larger number is the live line, and the one with 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 measured line or device is required. Turn the multimeter to the 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 the meter shows a few volts, it means 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 the AC220V power supply, and then turn the multimeter to the AC2V position, hang the black test lead in the air, hold the red test lead and slide the tip along the line gently, then if there are several Volts or a few tenths of volts (different 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. Measure the frequency of ups power supply
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.
A 220V/6V or 220V/4V step-down transformer can be connected to the output 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 frequency of the UPS power supply .
