Difference between revisions of "Best practices"
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(Consistency pass 2: airflow range via Configuration, multi-wavelength as in-development, ESP32/Pi CSV filename split, legacy sensor wording) |
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* Keep the device '''away from direct sunlight''', radiators, and fireplaces — it is sensitive to temperature and lighting changes. | * Keep the device '''away from direct sunlight''', radiators, and fireplaces — it is sensitive to temperature and lighting changes. | ||
* Position the inlet away from localized | * Position the inlet away from localized pollution sources so readings represent the surrounding air. | ||
* For indoor use, avoid placement near HVAC vents or drafts. | * For indoor use, avoid placement near HVAC vents or drafts. | ||
=== Sampling Configuration === | === Sampling Configuration === | ||
* '''Sample frequency:''' | * '''Sample frequency:''' For ambient monitoring, use '''180–600 seconds''' (3–10 min). Shorter intervals can increase noise. | ||
* '''Airflow:''' | * '''Airflow:''' | ||
Latest revision as of 01:45, 1 August 2026
Best Practices
Environment
- Keep the device away from direct sunlight, radiators, and fireplaces — it is sensitive to temperature and lighting changes.
- Position the inlet away from localized pollution sources so readings represent the surrounding air.
- For indoor use, avoid placement near HVAC vents or drafts.
Sampling Configuration
- Sample frequency: For ambient monitoring, use 180–600 seconds (3–10 min). Shorter intervals can increase noise.
- Airflow:
- Default 300 mL/min, adjustable (see Configuration for the range). Higher flow improves signal but loads the filter faster; the usable range narrows as the filter loads. With Auto Flow Control the device sets the rate automatically from the measured BC concentration.
- Higher airflow improves signal strength but loads the filter faster.
| Pollution Level | Daily Avg BC | Recommended Airflow |
|---|---|---|
| Heavy pollution | >2000 ng/m³ | 50 mL/min |
| Typical urban | ~500 ng/m³ | 100–250 mL/min |
| Low pollution | <500 ng/m³ | 300–400 mL/min |
When Auto Flow Control is enabled, the device adjusts airflow automatically based on measured BC concentration — reducing flow when BC is high (to extend filter life) and increasing flow when BC is low (for better signal).
Signal Quality
Signal-to-noise ratio improves with:
- Higher BC loads
- Higher air volume per sample
- Smaller sample spot diameter
Filtering: Apply median/average filtering (denoise slider) to reduce noise. The rolling average is closer to the "real" value than individual data points.
Calibration: Always calibrate after every filter change for reliable filter status indication and accurate measurement.
Filter Management
- At the default airflow in a typical urban environment (~500 ng/m³), a filter lasts approximately 3–5 days.
- In heavily polluted areas, a filter may saturate in 6–12 hours.
- Filter status is derived from attenuation (ATN): measurements are fully quantitative up to about ATN 75 and degrade at higher loading; the device flags the filter for replacement around ATN 120. (The ATN value is not a simple percentage of light loss.)
- The Airflow Reference table in Settings helps estimate filter lifetime for your conditions.
Supported Filter Papers
| Filter Paper | Scattering Correction Factor |
|---|---|
| Pall T60A20 | 1.0 |
| AE33 Filter | 0.75 |
| AE51 Filter | 1.0 |
Other filter papers can be supported by determining their scattering factor. Send a sample to jd@bcmeter.org for calibration.