Multimeter Buying Skills and Operation Methods
A multimeter can not only be used to measure the resistance of the object being measured, but also to measure AC and DC voltages. Even some multimeters can measure the main parameters of transistors and the capacitance of capacitors. Fully mastering the usage of a multimeter is one of the most fundamental skills in electronic technology. Common multimeters include pointer multimeters and digital multimeters.
A pointer type multimeter is a multifunctional measuring instrument with the meter head as the core component, and the measured values are read by the pointer on the meter head. The measured values of a digital multimeter are directly displayed in digital form on the LCD screen, making it easy to read. Some even have voice prompts. A multimeter is an instrument that uses a common meter head and integrates a
voltmeter, ammeter, and ohmmeter.
The DC current range of a multimeter is a multi range DC voltmeter. The parallel connection of a closed circuit voltage divider resistor in the meter head can expand its voltage range. The DC voltage range of a multimeter is a multi range DC voltmeter. Connecting a voltage divider resistor in series with the meter head can expand its voltage range. The corresponding range varies depending on the voltage divider resistor.
1. Offline detection
Measure the positive and negative resistance values between each pin of the IC chip and ground. Compare this with good IC chips to identify the fault point.
2. Online detection
The detection method for DC resistance is the same as offline detection. However, it should be noted that the power supply on the circuit board to be tested should be disconnected, and the internal voltage of the multimeter should not exceed 6V. When measuring, attention should be paid to the influence of the external environment.
3. AC working voltage testing method
Measure the approximate AC voltage of the IC using a multimeter with dB range. If there is no dB level, a 0.1-0.5 μ F isolated DC capacitor can be connected in series with the positive probe. This method is suitable for ICs with relatively low operating frequencies. However, it should be noted that these signals will be affected by their natural frequencies and waveforms, so the measured data is an approximate value.
4. Total current measurement method
By measuring the total current of the IC power supply, the quality of the IC can be determined. Due to the fact that most of the internal components of the IC are DC coupled, damage to the IC (such as PN junction breakdown or open circuit) can cause saturation and cutoff of the subsequent stage, resulting in a change in the total current. So measuring the total current can determine the quality of the IC. By measuring the voltage on the circuit resistance online, the current value can be calculated.
