Precautions for the maintenance of instruments and meters

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In the work of repairing instruments and meters, it is first necessary to understand their basic principles and acquire knowledge and skills related to electronics. Additionally, technical documents such as manuals and diagrams for all instruments and meters should be readily available. It is also important to develop good working habits in order to improve efficiency and reduce errors in the repair process. 　　1. During maintenance, do not strike or touch things randomly to avoid exacerbating the fault and making it worse. 　　II. When removing or adjusting instruments, their original positions should be recorded so that they can be restored. III. When using the ohm meter function of a multimeter, be sure not to take measurements on live circuits. 　　IV. When using a logic probe or oscilloscope to detect signals, care must be taken to ensure that the probes do not touch two measurement pins at the same time, as this essentially creates a short circuit while power is applied. 　　V. When testing the filter capacitors in the power supply, it is necessary to first short-circuit the positive and negative terminals of the electrolytic capacitor. When performing this short-circuiting, do not use the test lead wires as a substitute for wires to discharge the capacitor, as this can easily cause the core wire to burn out. A 220V, 60–100W lamp with a bulb lead can be used, connected across the capacitor; the bulb will flash at the moment of discharge. 　　VI. When troubleshooting instrument faults in humid environments, it is essential to use a multimeter to check whether the various points on the printed circuit are conductive, as the main issue in such situations is copper foil corrosion. 　　VII. When repairing the internal circuits of instruments, if the contacts of the components and the circuit board are coated with insulating varnish, a regular sewing needle can be soldered to the probes of a multimeter in order to measure the parameters at various points; this allows the multimeter to penetrate the varnish layer and take measurements directly, without the need to remove large areas of the varnish. 　　VIII. Do not plug or unplug various control boards and plugs while they are powered on. Because when the power is on, plugging in or removing the control board generates a strong induced electromotive force; the resulting reverse voltage at that moment is very high, which can easily damage the corresponding control board and plug. 　　9. When repairing precision instruments, if small parts are accidentally sent flying, one should first determine the possible locations where they might have fallen; there’s no need to search around randomly. Magnet scanning and visual scanning can be used to locate them.