During maintenance, it is suspected through troubleshooting that the diode or transistor in the circuit may be damaged. But use a digital meter diode range to measure its conduction voltage of about 0.6V, with infinite reverse direction. No problem, no fault found after checking the circuit. Why?

Solution: The test voltage emitted by most digital meter diodes is about 3-4. 5V. If the tested transistor has slight leakage or the characteristic curve has deteriorated, it cannot be displayed at such low voltage. At this point, we need to use a simulation table × In the 10K resistance range, the test voltage emitted by this range is 10V or 15V. At this test voltage, it will be found that the suspected transistor has leakage in the reverse direction. Similarly, when measuring the resistance of certain precision sensitive components with very low withstand voltage, using an analog meter can easily damage the sensitive components. At this point, you need to use a digital meter to measure.

3. Using a multimeter to measure the voltage value of the high-voltage probe after attenuation, it was found that the DCV test was more accurate, but the ACV error was significant. Even if a multimeter with high precision is used, what is the reason for this?

Solution: The vast majority of multimeters measure voltage in parallel, and for the entire testing circuit, the voltmeter itself is equivalent to a load being the input impedance. The larger the load impedance, the smaller the impact on the tested circuit, and the more accurate the test. But nothing can be perfect, as high impedance sacrifices the bandwidth of the test. At present, the input impedance of a multimeter with a frequency response of around 100KHz on the market is about 1.1M, so it will have a significant impact when testing the voltage at the two ends of a high resistance load, such as the high resistance value of the high-voltage probe itself. At this point, you need to choose a multimeter with high internal resistance, such as the ESCORT 170/172/176/178/179 handheld digital multimeter, which provides an input impedance of up to 10000 Ω when testing ACV, in order to avoid this problem.

4. What is traceability?

Solution: Traceability refers to the characteristic of connecting measurement results or standard values with specified reference standards, usually national or international measurement standards, through a continuous comparison chain with specified uncertainty. Namely, working measuring instruments ->measuring standard instruments ->measuring reference instruments. For example, the most commonly used unit of mass in daily life is the kilogram, which is based on the mass of a 1-kilogram platinum iridium alloy cylindrical weight stored in a three-layer lock safe in a castle in Sevre, Paris. All mass units in the world are based on this mass. Similarly, DCV 1V/10V is based on the Josephson quantum voltage array stored in the International Bureau of Metrology in Paris