Instrument and equipment three defense four is a method of management and protection of instruments and equipment. Dustproof, moistureproof, shockproof is to protect instruments and equipment from dust, moisture and vibration to ensure its normal operation and extend the service life. Fixed-person custody means designating a person to be responsible for the custody and use of instruments and equipment to ensure their safety and proper use. Fixed person maintenance means appointing a person to carry out the daily maintenance and repair work of the instrument and equipment, including cleaning, calibration, etc., in order to ensure its performance and accuracy. Fixed-room storage is to store instruments and equipment in a specific room or area, providing appropriate environmental conditions, such as temperature, humidity, etc., to prevent damage and deformation. Periodic calibration is the periodic inspection and calibration of instrumentation to ensure its accuracy and reliability. By taking these measures, instrumentation can be effectively managed and protected to improve efficiency and quality.