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 electric pen. The usage is as follows: turn the multimeter to AC20V, hang the black test pen in the air, hold the red test pen in contact with the measured line or device, then the multimeter will display, if the display number is between several volts to 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.
The above method can be used to judge: 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.
There is no need to contact the line or device being measured. Set the multimeter to the AC2V block, hang the black test pen in the air, and hold the red test pen to gently slide the pen tip along the line. At this time, if the meter shows a few volts, it indicates that the line is a live line. If the display is only a few tenths of a volt or even smaller. It means that the line is the zero line. Such a judgment method does not directly contact the circuit. Not only safe but also convenient and fast.
When a breakpoint occurs in the cable, the traditional method is to use a multimeter to block the breakpoint of the cable piece by piece. This not only wastes time, but also damages the insulation of the cable to a large extent. The inductive characteristic of the digital multimeter can quickly find the disconnection point of the cable. First, use an electric block to determine which cable core wire is broken. Then connect one end of the broken core wire to the AC220V, and then turn the multimeter to the AC2V block position, the black test pen is suspended, and the red test pen is held in hand to gently slide the pen tip along the line. At this time, if there are several volts displayed on the meter Or a voltage of 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, write down this position: under normal circumstances. The breakpoint is between 10 and 20 cm in front of this position.
In this way, it is also possible to find the breaking point of resistance wires such as faulty electric blankets.
For UPS power supply. The stability of its output voltage is an important parameter, and its output frequency is also very important. But it is not possible to directly use the frequency block of the digital multimeter to measure, 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 end 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.
