Several tips for making good use of digital multimeters
1. Determine whether the circuit or device is charged or not
The AC voltage block of the digital multimeter is very sensitive and can display even a small induced voltage around it.
According to this feature, it can be used as a test pen.
The usage is as follows: turn the multimeter to AC20V, leave the black test lead in the air, hold the red test lead in contact with the circuit or device on the side, 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. 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 the live wire or the neutral wire
The first method: You can use the above method to judge: the larger number is the live wire, and the smaller number is the neutral wire. This method requires contact with the line or device being measured.
The second method: no contact with the circuit or device being measured is required. Set the multimeter to AC2V, leave the black test pen hanging in the air, hold the red test pen and gently slide the pen tip along the line. If the meter shows a few volts, it means that the line is a live wire.
If it shows only a few tenths of a volt or even less. This means that the line is the zero line. This judgment method does not have direct contact with the line. Not only safe but also convenient and fast.
3． Find breakpoints in cables
When a breakpoint occurs in a cable, the traditional method is to use a multimeter to electrically block the cable section by section to find the breakpoint. This not only wastes time, but also damages the cable insulation to a great extent. Using the sensing characteristics of a digital multimeter, you can quickly find the disconnection point of the cable.
First use electrical blocking to determine which cable core wire is open. Then connect one end of the open core wire to the AC220V power supply, and then set the multimeter to the AC2V position. The black test pen is suspended in the air. Hold the red test pen and gently slide the pen tip along the line. At this time, if the meter shows how many Voltage or a few tenths of a volt (different depending on the cable). If the display on the meter suddenly drops a lot when moving to a certain position, note this position: Under normal circumstances. The break point is between 10 and 20cm in front of this position.
This method can also be used to find the break point of a faulty electric blanket or other resistance wire.
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 important.
However, you cannot directly use the frequency block of a digital multimeter to measure because the voltage that the frequency block can withstand is very low. Only a few volts.
You can connect a 220V/6V or 220V/4V step-down transformer to the output end of the UPS power supply to reduce the voltage without changing the frequency of the power supply. Then connect the frequency block to the output of the transformer to measure the frequency of the UPS power supply. .
