The digital multimeter is mainly based on the pointer multimeter. The digital multimeter is a device with a digital voltmeter as the core, which changes the internal analog circuit into a digital circuit and replaces the meter head with a liquid crystal screen.
Digital multimeter can measure DC current (A-), DC voltage (V-), AC current (A~), AC voltage (V~), (Ω), (buzzer file), current amplification factor (HFE), Gear (F), gear (H) can also identify live wire, square wave gear, TTL logic level measurement gear, duty cycle measurement, frequency (Hz) measurement, conductance nS and so on. .
Measure DC voltage, AC voltage, resistance, etc., insert the red test lead into the VΩ hole and the black test lead into the COM hole.
To measure the mA-level current, insert the red test lead into the mA hole, and the black test lead into the COM hole. The mA hole has a 200mA fuse.
To measure the current higher than mA level, insert the red test lead into the dedicated socket for 20A or 10A current, and insert the black test lead into the COM hole.
The COM port is also called the common port which is specially used for inserting the black test lead.
According to the measurement object, select the gear and range correctly.
Pay attention to the polarity of the test leads and try not to reverse the connection.
Before measuring resistance, short-circuit the two test leads and adjust to 0. Digital multimeters are popular among radio enthusiasts because they have the advantages of accurate measurement, convenient value acquisition, and complete functions. The most common digital square meters generally have resistance measurement, on-off sound detection, and diode forward voltage measurement. AC and DC voltage and current measurement, transistor magnification and performance measurement, etc. Some digital multimeters have added functions such as capacitance measurement, frequency measurement, temperature measurement, data memory and voice reporting, which bring great convenience to the actual inspection work. However, due to improper use of digital square meters, it is easy to cause damage to the components in the meter and cause malfunctions during actual testing.
In most cases, the damage of the digital multimeter is caused by the wrong measurement gear. For example, when measuring AC mains, the measurement gear is selected to be blocked. In this case, once the pen touches the mains, it can instantly cause the internal components of the multimeter. damage. Therefore, be sure to check whether the measurement gear is correct before using the multimeter to measure. After use, set the measurement option to AC 750V or DC 1000V, so that no matter what parameter is mis-measured during the next measurement, it will not cause damage to the digital multimeter.
Some digital multimeters are damaged because the measured voltage and current exceed the range. If the mains is measured in the AC 20V gear, it is easy to cause damage to the AC amplifier circuit of the digital multimeter, and the multimeter loses the AC measurement function. When measuring DC voltage, the measured voltage exceeds the measurement range, which is also likely to cause circuit failure in the meter. When measuring current, if the actual current value exceeds the range, it will generally only cause the fuse in the multimeter to blow, and no other damage will be caused. Therefore, when measuring voltage parameters, if you do not know the approximate range of the measured voltage, you should first set the measurement gear to the highest gear, measure its value and then change gears to obtain a more accurate value. If the voltage value to be measured far exceeds the maximum range that the multimeter can measure, a high-resistance measurement probe should be equipped. Such as detecting the second anode high voltage and focus high voltage of black and white color TV.
The upper limit of the DC voltage range of most digital multimeters is 1000V. Therefore, when measuring DC voltage, the highest voltage value is below 1000V, which will generally not damage the multimeter. If it exceeds 1000V, it is likely to cause damage to the multimeter. However, the upper limit value of the measurable voltage of different digital multimeters may be different. If the measured voltage exceeds the range, the resistance step-down method can be used to measure it. In addition, when measuring the DC high voltage of 40O～1000V, the test leads must be in good contact with the measuring place without any jitter. Otherwise, in addition to the damage of the multimeter and the inaccuracy of the measurement, the multimeter can also be used in severe cases. display.