The adjustment of PM2.5 dust detectors is a comprehensive process that integrates precision calibration, environmental adaptation, and intelligent algorithm optimization. The following are systematic adjustment strategies summarized based on multidimensional practice:
1、 Basic calibration process
-Zero point calibration
-Principle: Place the device in clean air (PM2.5 concentration<1 μ g/m ³), remove particulate matter from the test chamber through an air purification system, stabilize sensor readings, and record raw data.
-Operation points: Continuous purification is required until the data is stable for 2 minutes to avoid residual particles interfering with the reference value.
-Span calibration
-Gas distribution control: Start the automatic gas distribution system, input standard concentration particulate matter (such as 30 μ g/m ³, 80 μ g/m ³), and record the sensor response value after the concentration stabilizes.
-Nonlinear compensation: Due to the approximate exponential relationship between concentration and signal, a "concentration particle size" comparison table needs to be generated through software and written into memory to achieve fast conversion using a lookup table.
2、 Hardware parameter tuning
-Optical system maintenance
-Lens cleaning: Use filters or instrument air to regularly blow the protective glass to prevent dust from weakening the light path intensity and causing signal attenuation.
-Laser power adjustment: Fine tune the power of the transmitting end through potentiometer L, and match the sensitivity of the receiving end with the span potentiometer S to ensure the linearity of the light scattering signal.
-Signal gain optimization
-Jumper configuration: Cutting specific gain jumpers can increase the output signal range, suitable for high concentration scenarios; Retaining jumper wires enhances the ability to capture weak signals.
-Angle calibration: It is generally not recommended to adjust the laser angle during on-site debugging. If it is necessary to operate, refer to the instruction manual and use specialized tools.
3、 Dynamic adaptation of key parameters
-K value setting
-Calculation formula: K=C/R, where C is the measured concentration of membrane sampling (mg/m ³) and R is the instrument counting rate (CPM).
-Application scenario: Industrial dust requires repeated calculation of K values for specific particle size distributions, while municipal monitoring can directly call preset values.
-Range segmentation management
-Threshold division: According to the national standard, a five level pollution response mechanism is set: ≤ 35 μ g/m ³ (excellent), 36-75 μ g/m ³ (good), 76-115 μ g/m ³ (mild pollution), 116-150 μ g/m ³ (moderate pollution), and>150 μ g/m ³ (severe pollution).
-Linkage control: When the concentration exceeds 75 μ g/m ³, the exhaust equipment is triggered. If it exceeds 115 μ g/m ³, the air purifier will automatically start. After recovering to below 35 μ g/m ³ for 30 seconds, the equipment will be turned off.
4、 Full cycle maintenance system
-Preventive maintenance
-Consumables replacement: Check the blockage of the intake filter element every quarter and replace it in a timely manner to prevent flow fluctuations from affecting sampling representativeness.
-Storage conditions: When idle for a long time, it should be placed in a dry and constant temperature environment (recommended temperature range 0~40 ℃) to avoid sensor drift caused by high humidity.
-Fault diagnosis tree
-Signal abnormality: prioritize troubleshooting lens contamination → check potentiometer contact → verify gain jumper status → ultimately consider laser aging.
-Data jump: Short circuit RS485 interface to test communication stability, combined with oscilloscope observation of pulse integrity.