Plain-language explanations of the measurements, sensors and numbers behind environmental monitoring.
Lux meters measure eye-weighted illuminance; PAR meters measure photosynthetic photon flux density over 400 to 700 nm. For plant decisions, PAR is the right unit, but a lux meter can still be useful for relative comparisons if you understand its limits.
Read Article→Cosine correction makes a light sensor respond to angled light the way a flat surface does, so readings stay honest as the sun moves or the sensor tilts.
Read Article→Extended band PAR includes photons outside the 400 to 700 nm waveband, so its micromole total is larger by construction and cannot be compared with a 400 to 700 nm reading.
Read Article→Lux, PAR and irradiance quantify different aspects of light; this article explains the physics, the instruments, and when each measurement is the right one.
Read Article→How a saturated salt solution produces a known humidity, how to run the test, and where it stops being useful.
Read Article→Factory calibration establishes a baseline, but sensor physics, environmental exposure and handling cause readings to change over time.
Read Article→A calibration certificate records a comparison against a reference, not a promise that the instrument will stay accurate or that your reading is fit for every purpose.
Read Article→A plain explanation of what NIST traceable, factory calibrated and pre calibrated each mean, what they do not mean, and how to read the claim on a listing.
Read Article→The vane needs a minimum airflow to overcome bearing friction and start turning; below that speed the display stays at zero by design.
Read Article→Multiply average duct velocity by duct cross sectional area to get volumetric airflow, and treat both inputs as measurements with their own errors.
Read Article→An anemometer measures local air velocity; volume flow in CFM requires velocity multiplied by cross sectional area, corrected for how uneven the flow is.
Read Article→Self heating is the rise in a sensor's own temperature caused by the power it and its neighbours dissipate, and it biases every reading upward unless it is designed out or corrected.
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