Multimeter troubleshooting circuit board short circuit fault
Both the diode and resistance files of the multimeter can test the circuit board fault. If the diode file is used, use the test pen to test the points to be tested separately. If the circuit board is short-circuited, it will beep. If there is an indicator light on the multimeter, or If it is a resistance file, if it is a short circuit, the display of the multimeter will be zero.
1. Multimeters, also known as multimeters, multimeters, three-meters, multimeters, etc., are indispensable measuring instruments in power electronics and other departments. Generally, the main purpose is to measure voltage, current and resistance. The multimeter is a multi-functional, multi-range measuring instrument. Generally, the multimeter can measure DC current, DC voltage, AC current, AC voltage, resistance and audio level, etc., and some can also measure AC current, capacitance, inductance and semiconductor some parameters etc. Multimeters are divided into pointer multimeters and digital multimeters according to the display method.
2. Measurement of DC voltage: First, insert the black test lead into the "com" hole, and the red test lead into "V Ω". The value can be read directly from the display screen, if it is displayed as "1.", it indicates that the measuring range is too small, then it is necessary to increase the measuring range before measuring industrial electrical appliances. Select the knob to a range larger than the estimated value (note: the values on the dial are the maximum range, "V-" indicates the DC voltage range, "V～" indicates the AC voltage range, and "A" is the current range), and then turn the The test lead is connected to the power supply or both ends of the power supply; keep the contact stable. If "-" appears on the left side of the value, it means that the polarity of the test lead is opposite to that of the actual power supply. At this time, the red test lead is connected to the negative pole.
3. Measurement of AC voltage: The test lead jack is the same as the measurement of DC voltage, but the knob should be turned to the required range at the AC gear "V~". There is no difference between positive and negative AC voltage, and the measurement method is the same as before. Regardless of measuring AC or DC voltage, pay attention to personal safety, and do not touch the metal part of the test lead with your hands.
4. Resistance measurement: Turn the range switch to the appropriate range of Ω, insert the red test lead into the V/Ω hole, and insert the black test lead into the COM hole. If the measured resistance value exceeds the maximum value of the selected range, the multimeter will display .1. At this time, a higher range should be selected. When measuring resistance, the red test lead is positive and the black test lead is negative, which is just the opposite of the pointer multimeter. Therefore, when measuring polar components such as transistors and electrolytic capacitors, you must pay attention to the polarity of the test leads.
5. Use a multimeter to measure the current: first select the range. The DC current range of the multimeter is marked with "mA", and there are three ranges: 1mA, 1omA, and 100mA. The range should be selected according to the current in the circuit. The multimeter should then be in series with the circuit under test. After disconnecting the corresponding part of the circuit, connect the multimeter leads to both ends of the breakpoint. The last correct reading, the scale line of the DC current range is still the second line, if you choose the 100mA range, you can use the third line of numbers, and multiply by 10 after the reading.
6. Use a multimeter to measure capacitance: Some digital multimeters have the function of measuring capacitance, and their ranges are divided into five levels: 2000p, 20n, 200n, 2μ and 20μ. When measuring, the two pins of the discharged capacitor can be directly inserted into the Cx jack on the panel, and the displayed data can be read after selecting an appropriate range.
