The Use of Multimeters in ATX Power Supply Maintenance
A multimeter is a necessary measuring instrument for maintenance. Although any multimeter can be used for maintenance of switching power supplies such as ATX, digital ones are better than pointer ones, and automatic ones are better than non automatic ones.
The multimeter has the following uses in ATX power supply maintenance:
1. Measure the voltage and resistance to ground at the test point
2. Determine the straightness between test points
3. Measure the resistance value of the resistance
4. Measure the capacity of capacitance within the range of measurement
5. Measure a certain current
The function of the digital multimeter diode block:
The diode block of an automatic range digital multimeter generally has three functional options: resistance, resistance beep, and diode voltage drop beep
1. Resistance option: The dimension is resistance, used to measure the true resistance value between red and black probes.
2. Resistance buzzer option: The dimension is resistance, which is used to determine whether the buzzer is beeping based on the set buzzer resistance. If the true resistance value between the red and black probes exceeds the buzzer resistance, the multimeter will not emit a beep, and if it is small, it will beep.
3. Diode voltage drop beep option: When the multimeter is in the diode beep option, the red pen of the multimeter has voltage. When the voltage drop between the red and black pens is small and the beep is low, the multimeter will beep, otherwise it will not beep.
Conclusion: When the reading is small, the indication of a non automatic range digital multimeter is the same as the true resistance value between the two points being measured. As the true resistance value increases, the multimeter's indication gradually deviates from the true resistance value between the two points. However, regardless of whether its dimension is resistance ohms or voltage volts, it will not affect the measurement process and the judgments made based on the measurement value.
In the maintenance of ATX power supply, it is often necessary to use a multimeter to measure the ground resistance value of the test point. For one side of the AC high voltage input side, select the diode block of the multimeter, connect the red lead to the negative pole of the full bridge, and connect the black lead to the test point. At this time, the multimeter will have a reading, which is used to measure the ground resistance value; For the DC low-voltage output side, select the diode block, with the red pen connected to the ground in the output terminal and the black pen connected to the test point. At this time, there will also be a reading, which is called the ground resistance value on the low-voltage side of the power supply. Depending on the selected reference point, the ground resistance value of the ATX power supply is defined as the "ground resistance value on the high-voltage side" and "ground resistance value on the low-voltage side"!
