The core function of a dust detector is to measure the concentration of suspended particulate matter in the air through optical scattering or beta ray absorption methods. Before debugging, it is necessary to clarify the equipment type: laser scattering type is suitable for real-time monitoring, while beta ray method is suitable for long-term continuous sampling. Regardless of the principle, the core goal of debugging is to ensure data accuracy and stability.
1、 The key preparation work includes:
1. Environmental investigation: Confirm the temperature and humidity range of the testing scene, and whether there are corrosive gases or electromagnetic interference sources. For example, explosion-proof equipment should be used in chemical facilities, and dehumidification devices should be installed in high humidity environments.
2. Accessory inspection: After opening the packaging, check the integrity of accessories such as sampling rods, filters, calibration membranes, etc. Pay special attention to whether the sampling head is equipped with a dedicated cutter to achieve particle size separation of PM2.5/PM10.
3. Basic settings: The first startup requires language selection, time synchronization, unit switching (mg/m ³ or μ g/m ³), and checking whether the battery level meets the continuous working requirements for more than 4 hours.
2、 Key points for installation and positioning
The correct spatial layout directly affects the reliability of the detection results. Fixed equipment should be installed at a breathing zone height of 1.5-2 meters above the ground, avoiding areas with airflow disturbances such as air conditioning vents, doors, and windows. Mobile instruments should pay attention to three principles:
-Representative sampling: Workers' operating positions should be arranged in areas with frequent personnel activities, and large spaces such as warehouses should adopt grid based multi-point layout.
-Avoid obstruction: Leave at least 30 centimeters of unobstructed space in front of the sampling port to prevent eddy currents from affecting the intake efficiency.
-Direction correction: For handheld devices, keep the sampling port vertically upward to avoid tilting and gravity settling interference.
3、 Core debugging steps
1. Zero point calibration
Press and hold the 'zero' button in a clean environment to enter calibration mode. At this time, use the matching zero calibration sheath gas (HEPA filtered air) to continuously flush the sensor for 3-5 minutes. If the displayed value cannot be reset to zero, it may be due to contamination of the optical components. Use a dust-free cloth dipped in alcohol to wipe the emission/reception window.
2. Span calibration
Generate known concentration aerosols using standard dust generation equipment. Taking KCl solution atomization as an example, gradually adjust the concentration to 80% of the full range and observe the indication error. When the deviation between the actual value and the theoretical value exceeds ± 5%, enter the engineering menu for multi-point linear correction. Special attention: Cross sensitivity must be rechecked after each calibration, as water vapor may cause false alarms in infrared instruments.
3. Flow calibration
Measure the actual flow rate of the sampling pump using a soap film flowmeter. Inject soap solution into a glass tube and measure the time it takes for a single soap film to pass through the upper and lower scale lines. The calculation formula is Q=V/t. If the difference between the measured value and the set value is greater than ± 3%, the pump speed needs to be adjusted or the aging pipeline needs to be replaced. It is recommended to perform traffic verification once a month.
4、 Data collection optimization
1. Sampling mode selection
-Instantaneous monitoring: used to capture sudden pollution such as welding fumes, with a 1-second interval to capture peak concentrations.
-Periodic sampling: For fixed sources such as waste incineration plants, it is recommended to use a dual time cycle of 'working days+rest days', with 45 minutes of sampling and 15 minutes of downtime in each stage.
-Cumulative sampling: When using the filter membrane weighing method, set the sampling time to 8 hours and control the volumetric flow rate at 16.7L/min.
2. Application of intelligent algorithms
Enabling dynamic compensation function can effectively reduce environmental interference. For example, for every 10 ℃ increase in temperature, the laser scattering intensity will increase by about 2%, and the instrument will automatically deduct the temperature drift effect. Some models also have vibration self diagnosis function, which can identify optical path deviation caused by transportation.
5、 Troubleshooting Guide
When encountering data jumps or crashes, troubleshoot in the following order:
1. Physical layer inspection: Check whether the sampling tube is flattened, whether the filter is saturated and blackened, and promptly clean the condensed water in the water cup.
2. Electrical connection test: Use a multimeter to measure the output voltage of the power adapter and check if the RS485 communication terminal is loose.
3. Software reset: Press and hold the power button for 10 seconds to force a restart, restore the factory settings, and then recalibrate. If it still doesn't work properly, contact the manufacturer to upgrade the firmware program.
6、 Periodic maintenance standards
Establish a three-level maintenance system:
-Daily inspection: visually inspect the dust accumulation of the sampling head and clean the fingerprint stains on the display screen.
-Quarterly maintenance: Replace the pre filter element and add lubricating grease to the fan bearings.
-Annual calibration: Send to provincial metrology institutes for traceability verification and obtain CMA certification reports.
Special reminder: Equipment involving radioactive sources (such as beta radiation type) must be operated by certified personnel, and it is strictly prohibited to dismantle the radioactive source without authorization when scrapped.
7、 Special scenario response strategies
In high temperature and high humidity environments, a cyclone separator and Nafion drying tube should be installed at the front end of the sampling tube to reduce the dew point of the sample gas to below -20 ℃. Explosion prone dust environments must use ATEX certified intrinsic safety equipment, and sealed joints should be used during wiring to prevent dust infiltration. For nanoscale ultrafine particles, it is recommended to use a static eliminator to reduce the adsorption loss of particles on the inner wall of the pipeline.
8、 Acceptance and delivery standards
After the final debugging is completed, it is necessary to run continuously for 24 hours to verify stability. The qualification criteria include:
-Zero drift not exceeding ± 2% FS
-Repetitive error less than ± 5%
-Response time T90<20 seconds
-All alarm thresholds are accurately triggered
Simultaneously provide a complete debugging report, including raw data records, parameter modification logs, and on-site operating condition explanations. The user training session should demonstrate daily maintenance skills, emphasizing the prohibition of directly rinsing optical windows with water and other precautions.