With the popularity of non-standard automation and the maturity of technology, more and more enterprises have adopted non-standard automation equipment. When the automation equipment suddenly fails to work, or the working sequence fails, fault diagnosis must be carried out.

　　The common problems of automation equipment are as follows:

　　1. Open circuit or open circuit: The disconnection or open circuit of the output of the instrumentation equipment and the input circuit of the feedback signal during the use of the machine is a general fixed fault.

　　2. Power failure: Power failure is a static failure. This fault is mostly caused by open circuit of the power line or ground wire, wrong wiring or poor contact. It may also be caused by the input voltage of the instrument equipment or the circuit board's own power supply component exceeding the allowable deviation, and the output of the power supply component's own circuit failure. The voltage exceeds the allowable deviation (such as abnormal increase or decrease of voltage).

　　3. Failure of passive components: loose end caps of resistors often lead to open circuits, open circuits or open circuits of capacitors, changes in capacitance or resistance values, and burnout of resistors. Changes in the resistance value cause failures such as fuzzy logic values, and changes in the capacitance value may cause failures such as poor decoupling, changes in the frequency of the oscillator, and failure to start equipment such as motors.

　　4. Poor power supply decoupling: This type of fault is mainly caused by the interference waveform (or signal) being superimposed on the normal waveform. This kind of interference can be suppressed by a large-capacity filter capacitor and a ceramic capacitor with good high-frequency performance.

　　5. Interference: The signal on one line is coupled to another line due to induction, which often causes interference in the product. The size of the crosstalk signal is proportional to the line spacing and signal frequency. If the strong current and the weak current are mixed in the same cable, the signal of the weak current will be bad or even burn the signal channel.

　　6. Unreliable auxiliary equipment or devices: Unreliable performance of nodes or contactors, mechanical failures and other equipment or devices will cause poor reliability.

　　7. PCB failure: PCB power supply short circuit or open circuit, jumper address error, especially highly integrated IC chips due to manufacturing defects, overheating and other reasons may interact and cause transient failure or permanent damage.

　　8. Poor contact: Poor contact occurs frequently, similar to an open circuit, but it is accidental, and it is extremely difficult to detect the fault at the initial stage. The common causes of poor contact are: loose plug-in, poor welding, oxidation of the contact surface, loose terminal wiring (sometimes caused by large environmental vibrations), and elastic degradation of the contact reed.

　　9. Poor insulation: Poor insulation is often ignored by the staff because of its small impact on the machine. Poor insulation caused by surface treatment and processing problems on the circuit board will further lead to signal cross-wiring and leakage, making the circuit board unstable or even unable to work normally.

　　10. Poor shielding: Poor shielding often causes related faults such as signal distortion or distortion.

　　11. Component aging and poor quality: equipment has a certain service life. When the equipment works longer than the service life, each component will enter the attenuation period. Therefore, the functional characteristics of the component will be greatly reduced, and the failure rate will increase. Poor quality of the component will also cause a high failure rate.