Plain-language explanations of the measurements, sensors and numbers behind environmental monitoring.
An inspection camera carries its own light down a cable, reflects it off a surface a few centimetres away and converts the return into video on a small sensor behind a fixed lens.
Read Article→A borescope inspection camera is a lit camera head on a long thin cable with a screen at the other end, built to look inside spaces you cannot dismantle, and it measures nothing.
Read Article→A pinless meter reports the dielectric response of everything within about 19 mm of its pad, so a high reading on an exterior wall identifies a place to investigate and never identifies mould.
Read Article→Accuracy on a multi channel air quality monitor is never one number, because every channel uses a different sensing technology with its own error and its own meaning.
Read Article→In a normal house a carbon dioxide monitor works as a ventilation gauge, because the gas accumulates in proportion to the people in the room and leaves in proportion to the fresh air reaching it.
Read Article→A daily mean of 20 to 30 micrograms per cubic metre sits above the World Health Organization 24 hour guideline and below the United States 24 hour standard, which makes it a baseline problem rather than a one day emergency.
Read Article→Usually both are honest about different air. The purifier samples at its own intake while it is actively cleaning that air, and your monitor samples wherever it stands.
Read Article→A sensor, a converter, a clock, non volatile memory and a battery. The instrument wakes on a timer, converts, timestamps, writes and goes back to sleep.
Read Article→The percentage on a hygrometer is how close the air at the sensor is to saturating, at the sensor temperature. It is not a quantity of water.
Read Article→There is no single correct humidity. The right reading is set by what you are protecting, and by the coldest surface in the room.
Read Article→An accuracy specification is a promise with an expiry date on it. If the reading matters to anyone but you, the meter needs periodic comparison against a traceable reference.
Read Article→A handheld multimeter has no watts function, because power needs two quantities sampled at the same instant and a meter has one measuring path.
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