Light Measurement
Light measurement turns perceived brightness or solar exposure into defined readings. Illuminance describes visible light reaching a surface and is expressed in lux. Solar irradiance describes solar power received per unit area in watts per square metre. They measure different quantities and answer different practical questions.
In buildings, readings support comparisons between positions, daylight reviews and checks following changes to lighting. Solar measurements record conditions around photovoltaic or solar thermal installations at a time and place. Within our Environmental Monitoring equipment, we supply Kimo instruments for both purposes, with the required quantity determining the appropriate sensor and unit.
Why Is Light Measurement Important?
Your eyes adjust quickly as lighting conditions change. Two desks, corridors or work areas often appear similarly bright even when the illuminance at each surface differs. Visual checks reveal glare, shadows and uneven lighting but cannot produce an objective value. Recorded measurements give you a consistent basis for comparing positions and checking changes.
Readings taken before and after fittings are replaced or layouts altered show how the illuminance has changed. Several positions across a room reveal variation that a single central measurement can miss. Recording the position, height and conditions makes later comparisons more meaningful.
Solar conditions vary throughout the day. Measurements across a roof or installation show differences caused by orientation, cloud cover, nearby structures or temporary shade. The result represents solar input at the sensor during the test. The recorded time, weather and position remain part of the interpretation; the result does not predict long-term energy production.
What Are the Main Light Measurements?
Illuminance is the visible light falling on a surface. One lux equals one lumen per square metre. A lux meter places a light-sensitive detector at the measurement plane and displays the result. Foot-candles are an alternative unit where supported. The terms illumination meter and digital lux meter describe the same type of equipment, although ranges and functions differ.
Illuminance is not the same as luminous flux, luminance, colour temperature, ultraviolet radiation or photographic exposure. Luminous flux describes visible light emitted by a source, while luminance relates to light travelling from or reflected by a surface in a particular direction. A lux reading describes light arriving at the detector.
Solar irradiance is solar power received per unit area at a particular moment. A solar irradiance meter, often called a solarimeter, displays it in watts per square metre. Some instruments also calculate accumulated solar energy over a defined period in watt-hours or kilowatt-hours per square metre. Illuminance, instantaneous irradiance and accumulated energy remain separate quantities.
Where Is Light Measurement Used?
Illuminance readings are taken in offices, educational buildings, healthcare settings, retail premises, public buildings, warehouses, production areas, sports facilities and outdoor work locations. They support comparisons between work surfaces, walkways, rooms and lighting layouts. Readings before and after a change show how illuminance has altered when the position and method remain consistent.
Lighting is only one part of the surrounding environment. Temperature measurements require their own sensors when thermal conditions are reviewed. Indoor Air Quality requires separate gas or particle measurements, while Sound Measurement records acoustic conditions. Keeping these quantities separate prevents a lighting result from being used to describe an unrelated condition.
Solar irradiance readings support site comparisons, panel orientation checks and reviews around photovoltaic or solar thermal installations. They record available solar input during the test and assist comparisons between positions or operating conditions. Electrical output also depends on system design, panel condition, temperature, shading and weather.
What Affects Light Measurement Results?
Where you place the detector affects the reading. Height, angle and distance from the source need to match the surface being assessed. Standing over the sensor can cast a shadow, while bright walls, polished finishes, glass and metal reflect extra light towards it. Even a small change in position often creates a noticeable difference.
Daylight varies with time, cloud cover, season and nearby structures. For solar readings, detector orientation is especially important because an angle change, passing cloud or temporary shadow alters the solar energy reaching its surface. Recording the position, time and weather makes comparisons easier to understand.
Detector cleanliness, calibration status, battery condition and stabilisation time influence performance. Comparable readings depend on retaining the same method across positions or periods. Instantaneous, minimum, maximum, average, relative, uniformity, mapping, memory and transfer functions vary by model. These features organise readings, but accurate comparison still depends on controlled positioning and conditions.
Order Light Measurement Equipment from Celtic Surveys
We supply Kimo equipment for illuminance and solar irradiance measurements in selected building, environmental and solar applications. The required quantity and unit determine the instrument type, followed by its range, resolution, stated accuracy, sensor arrangement, recording functions and operating conditions.
Our selection includes the Kimo LX 50, LX 100 and LX 200 luxmeters, together with the SL 100 and SL 200 solarimeters. Our team can help you compare their confirmed ranges, measurement modes, storage functions, accessories and calibration documentation for your work.
Need help choosing light measurement equipment for your work? Call 01 801 1335 or email sales@celticsurveys.ie for practical product advice before buying.