Measured illuminance is a lux reading recorded at a named surface and condition.
Measured illuminance is the lux value read at a named plane under recorded operating conditions. It should not be mixed with estimates that use a different plane or condition.
Technical meaning
Measured illuminance is a recorded lux value at a surface such as a desk, bench, floor path, shelf face or wall.
The value depends on meter position, operating fittings, daylight condition, shadows, surface reflectance and maintenance condition.
Calculation use
Measured illuminance can be compared with a lumens-to-lux estimate when the area, plane and operating condition match.
A daylight-factor check can use measured indoor and outdoor lux readings from the same daylight condition.
Not the same as
Measured illuminance is not a room-wide result from one point unless the measurement note says how the area was sampled.
A measured value is not the same as maintained illuminance unless the maintenance basis and comparison method are clear.
Australian context
Australian room and workplace notes should keep measured lux readings beside the assessed plane, date, operating condition and comparison basis.
Examples
Example
Value
Planning note
Desk reading
420 lx
Read at the desktop with the normal fittings and daylight condition recorded.
Daylight check
180 lx indoor
Needs the same-condition outdoor reading before calculating daylight factor.
Warehouse shelf face
vertical reading
A shelf-face reading should not be compared with a floor-plane target.
Measured illuminance supports comparison notes. Formal workplace or public-space assessment needs the applicable method, sampling plan and project evidence.