What it measures

A lux meter or illuminance meter measures light falling on a surface and expresses illuminance in lux. It is a tool for assessing workplace lighting, but one reading does not describe its overall quality. Glare, reflections and temporal variation in light require additional consideration.

Preparing measurements

First identify the visual task and the plane on which it takes place. Measuring a desk does not necessarily represent vertical shelving or a circulation area. Record the time, daylight contribution, lights switched on and room conditions. This allows the result to be interpreted and repeated without confusing changed conditions with genuine improvement.

Avoiding observer error

The person measuring must not introduce shadows or reflections unrelated to normal operation. Orient the sensor to the plane being assessed and use it according to its instructions. Check the reading scale too. A photograph of the instrument beside a number does not replace records of position, conditions and the method used at each point.

A suitable, traceable instrument

Range, spectral response and angular response must suit the application. Calibration and checks help establish performance. A phone app should not automatically be equated with an assessment instrument: its sensor and signal processing may not be characterised for that purpose or for the installed light sources.

A warehouse example

In a hypothetical warehouse, a midday measurement near the entrance appears adequate. However, order picking also takes place at night in internal aisles. A representative plan includes these scenarios and the labels that must be read. The solution may require redistributing luminaires, maintaining them or changing the work layout.

From a number to a decision

Compare results with criteria applicable to the task and country, considering uniformity and conditions of use. Minimum values are not universal across all jobs. After intervention, repeat assessment and record limitations; the aim is safe, comfortable vision rather than one favourable reading.