I. Preparation before calibration
1. Environmental verification: Ensure the calibration environment meets explosion-proof requirements (e.g., IP65 protection level is required in underground coal mines), avoiding interference from flammable and explosive gases or dust.
2. Tools and standards: Use explosion-proof tools and standard calibration equipment (e.g., pressure testing machine, standard gases), ensuring the power supply voltage matches the sensor nameplate.
II. Calibration process
1. Static calibration
Zero point and range adjustment: Apply known pressure using a standard instrument (e.g., pressure testing machine) and adjust the sensor output signal to match the standard value. For example, the GAD10 tension sensor requires the output current to be set to (current tension value × 1.6 + 4) mA.
Nonlinear correction: Use a lookup table method or intelligent algorithm (e.g., piecewise linear interpolation) to correct the sensor's input-output characteristics, ensuring the linearity error is within the allowable range.
2. Dynamic Calibration
Frequency Response Test: For dynamic devices such as accelerometers, use a turntable-type gravity field calibration method to record output values at different frequencies to verify dynamic sensitivity.
Interference Suppression: In environments with strong electromagnetic interference, a shielding layer or fiber optic sensor should be installed, and the signal waveform stability should be tested using an oscilloscope.
III. Post-Calibration Verification
1. Repeatability Test: Apply the same standard quantity multiple times and check if the output deviation exceeds the allowable range (e.g., ±2%).
2. Sealing Check: For explosion-proof sensors, verify the sealing of the housing to prevent the intrusion of corrosive gases or liquids.
IV. Precautions
1. Cycle: It is recommended to calibrate every six months or one year; the cycle should be shortened in harsh environments.
2. Record Management: Establish a calibration history archive and analyze performance trends through statistical process control (SPC) to provide early warning of potential faults.
