Electrical fault diagnosis methods

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1) Visual inspection method: Many electrical faults can be directly observed using the senses such as eyes, ears, and nose, or various parts of the human body. The intuitive method is often effective and the fastest approach; it is simple as well, making it the most economical diagnostic method. 2) Test pen inspection method: Although the visual inspection method is economical and simple, many faults cannot be detected directly; tools and instruments are required for that purpose. A voltage tester is another simple and commonly used tool, essential for maintenance workers. Things such as whether there is a power supply or if there is any leakage can be tested using a voltage tester. Testing each point systematically also allows for checking whether the circuit is correct. 3) Voltage, current, and resistance measurement methods: For faults in low-voltage circuits, voltage measurement is usually a suitable approach; however, for some faults, it is necessary to measure current or resistance in order to identify the fault location. Sometimes the voltage reading is normal, while the current reading is abnormal, making it easy to diagnose and identify the problem. Faults related to overheating are often closely associated with current. Sometimes, by measuring voltage and current simultaneously and checking the relevant components, faults in those components can be detected. Measuring the transistor current can determine whether the transistor is damaged, as well as whether the diode is broken or open-circuited ； It can be determined by measuring resistance. 4) Insulation resistance measurement method: Faults related to leakage current and poor insulation cannot often be detected using a multimeter; instead, a megohmmeter is needed to measure the insulation resistance in order to identify such faults. Sometimes the faults that arise due to low insulation resistance are subtle or peculiar, making them seem difficult to analyze. When the circuit is activated after being idle, in environments with a lot of dust, or in humid and oily conditions. In the event of a fault, it is advisable to measure the insulation resistance; once the insulation is in good condition, proceed with further diagnosis and repair. 5) Instrument measurement method: Sometimes, faults in control circuits cannot be easily detected by measuring voltage, current, and resistance; in such cases, instruments are needed. If the measured waveform allows for easy detection of faults in electronic circuits, an oscilloscope meeting the relevant requirements is commonly used for inspection. Sometimes, even standard instruments are not sufficient; specialized equipment such as digital frequency meters, digital voltmeters, signal generators, and distortion meters are required. This method requires significant investment, but it is also necessary for the electrical fault diagnosis of many control circuits. 6) Logic probe method: In transistor circuits and integrated circuits, using a logical probe, which is intuitive to use and easy to carry, is a good way to diagnose electrical faults. It can measure the level of voltage at a certain point, and it can also generate a square wave of a specific frequency as an analog signal. It can be used to detect faults in general electronic circuits, integrated circuits, logic circuits, and program-controlled circuits. 7) Replacement method: For many faults, it is difficult to make a judgment using tools, instruments, or meters, and the process is rather complicated. The replacement method involves substituting it with a new one to give it a try, and it is an effective and simple approach. When you suspect that a certain component or part is faulty and are not sure whether there is indeed a problem, try replacing it with a new one. Complex circuits, such as integrated circuits and even microcomputers, often use the substitution method. 8) Trace point tracking method: This is also a good way to diagnose faults, as after a fault occurs, it’s initially unclear where the fault lies – it’s like looking for a needle in a haystack. Especially for complex circuits, the trace-point tracing method allows for step-by-step exploration of each point, gradually narrowing down the area where the fault may lie. By tracking down suspicious points, it is possible to locate the fault location more quickly and accurately. 9) Elimination method: This is just one approach, but it is also a good way to diagnose faults. It involves eliminating those components and circuits that are known to be functioning properly, thereby allowing focus to be directed on checking the other components and circuits. This also narrows down the scope of the fault, thereby allowing the fault location to be identified more quickly and accurately. Of course, when using the elimination method to diagnose faults, it is also necessary to rely on various tools, instruments, and meters for assessment. 10) Comparison method: This method involves using the same circuit to compare parameters such as voltage, current, resistance, waveform, and frequency, in order to identify potential issues. Subsequent analysis and evaluation are then carried out to diagnose and locate the fault point. By taking advantage of the differences in temperature among transistors, especially in repetitive circuits or within parallel circuits that contain identical power transistors, comparisons can be made to identify the faulty transistor. Very cold transistors may not function or may be open-circuited, while very hot transistors could indicate problems with the transistors themselves or with the connected components and parameters. Therefore, the comparison method is also a commonly used approach for diagnosing electrical faults. 11) Reassembly method: For some faults, especially those involving components and units with complex structures, sometimes there is no problem at all other than poor contact, inflexible operation, or even jamming. Often, by disassembling them and then reassembling them according to the specified procedures, the fault can be resolved. Indeed, poor assembly quality can cause the circuit to malfunction; different levels of assembly quality indeed lead to different consequences. With the same components and parts, different assembly processes can result in vastly different circuit performance; in some cases, simply cleaning the components can eliminate faults. Therefore, the reassembly method is one of the good ways for control circuits to detect faults and carry out repairs. 12) Short-circuit and open-circuit methods: Without affecting signal transmission or causing other problems, a certain point can be short-circuited, and data such as the output current can be observed to determine whether a particular component is functioning properly. The open-circuit method involves breaking the connection between the output and the next-level input, and measuring the voltage or waveform of each separately in order to identify problems and diagnose the fault location. 13) Power-on operation test method: This method is often used in maintenance, as many faults do not become apparent when the device is at rest; they only occur when it is powered on and in operation. Therefore, it is necessary to run the device under power, then observe and measure it in order to locate the fault. However, when powered on, smoking, sparks, noises may occur, and there is even a risk of explosions and fires, so adequate preparation and preventive measures are necessary. The current application test method is commonly used during the commissioning of electrical boxes, cabinets, and panels. 14) Analysis method: This is a rational-based approach; many faults need to be diagnosed by analyzing the working principles of the components, as well as those of the control circuits. When performing a circuit check, one should keep the circuit diagram in mind; by analyzing the working principle of the circuit diagram, it is possible to locate the fault point accurately and quickly. When repairing more complex circuits, it is necessary to rely on diagrams and manuals. The manual can help maintenance personnel understand the principles and operation of specific control circuits; of course, they also need to have a clear understanding of the physical concepts behind various fault conditions. Many analyses based on this are highly useful for identifying faults, especially for diagnosing them accurately and quickly; therefore, analysis methods are an excellent approach for fault diagnosis.