LightLab International

Lightmeter and luxmeter calibration

What is a lightmeter?

A lightmeter is, quite simply, a device used to measure illuminance, or the amount of light. Lightmeters are also known as luxmeters or illuminance meters. A lightmeter comprises a detector, an amplifier circuit and a display. The detector is typically made of silicon and located behind one or more coloured filters to match its response to that of the eye.

Light meters are used in a number of industries, including: photography, occupational health and safety, lighting laboratories, lighting designers. In lighting design and OH&S a lightmeter is used to measure the illuminance levels in workplaces. In photography, a light meter is often used to determine the proper exposure.

LightLab offers a number of calibrated light meters, refer here for details.

Why calibrate a luxmeter?

As for any electronic measurement device, a luxmeter needs to be calibrated against a known reference to ensure it is reading accurately. The meter is adjusted at the factory to read true. From time to time after that the luxmeter must be checked to ensure it has not drifted from the reference. A calibrated luxmeter yields accurate and consistent measurements over many years.

The two important characteristics of the meter that require calibration are the illuminance and spectral responsivities. The illuminance responsitity determines how accurately the meter responds to the illuminance level. The spectral responsivity determines how accurately the colour response of the meter matches that of the eye.

What is in a LightLab calibration?

LightLab operates a NATA accredited photometric calibration laboratory. Calibration capability includes responsivity of light meters*, luminance meters*, UVA detectors*, phototherapy meters including bilirubin meters. The laboratory maintains a number of reference detectors that are traceable to the SI system of units to enable the capability.

For example, a luxmeter is calibrated against a reference illuminance detector to determine its performance. To determine the spectral responsivity of the meter, light from an illuminant A source is passed through four filters in turn: a red, green, blue and an infrared filter and the meter reponse against a reference detrmined. The results of the calibration are recorded in a NATA endorsed report. LightLab can optionally determine the cosine response of the lux meter sensor.