Luxmeter & luminance meter calibration
Luxmeters and luminance meters are general purpose devices to measure light, collectively they are known as lightmeters. Typically they are hand held or tripod mounted devices however they can be fixed in place and used to adjust illumination in workplaces or at tunnel entrances. Light meters are used in a number of industries, including: photography, occupational health and safety, non-destructive testing, lighting laboratories, and by 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 used to determine camera exposure.
Lightmeters typically comprise a detector, an amplifier circuit and a display. The detector is now almost invariably silicon and, for luxmeters, located behind an opal diffuser to yield a cosine response. Luminance meters are used to measure surfaces through a series of focussing lenses and a baffle to reduce the field of view to a spot.In both cases there are an assembly of coloured filters to match the spectral response to that of the eye.
Lightmeters typically comprise a detector, an amplifier circuit and a display. The detector is now almost invariably silicon and, for luxmeters, located behind an opal diffuser to yield a cosine response. Luminance meters are used to measure surfaces through a series of focussing lenses and a baffle to reduce the field of view to a spot.In both cases there are an assembly of coloured filters to match the spectral response to that of the eye.
Calibration
As for any electronic measuring device, for accurate and repeatable results a lightmeter benefits from calibration for primary attributes affecting measurement and from characterisation of secondary attributes. The three primary attributes of a luxmeter are the illuminance, visible spectral and cosine responsivities. Secondary attributes include response of the meter to flicker and response to out-of-band radiation in the UV and infrared. For a luminance meter the primary are illuminance and visible spectral, the secondary are: flicker, UV & infrared, out-of-field and in-field non-uniformity responsivities.
LightLab Illuminance Calibration
For illuminance responsivity, a luxmeter is calibrated against a reference illuminance detector to determine its accuracy by using a transfer standard such as an incandescent illuminant A or an LED LV41 source. The device under test and the reference source are mounted on an optical rail at a known distance from the reference to establish a reference illuminance. Linearity of illuminance response is measured separately using a variable illuminance source. The spectral response is calibrated using a monochromator at 5 nm intervals across the visible spectrum. Additional information includes the meter response ratio to a set of RGB and IR filters, the and (optionally) the cosine response. The results of the measurements are written into an accredited report (the illuminance responsivity & linearity and cosine response are covered by the laboratory accreditation).
LightLab Luminance Calibration
A calibrated uniform luminance source is used as reference for calibrating luminance meters for luminance responsivity and linearity. Meter response ratio is calibrated using a set of RGB & IR filters. An optional spectral response calibration can be performed. Luminance & luminance linearity is covered by the laboratory accreditation.
LightLab Illuminance Calibration
For illuminance responsivity, a luxmeter is calibrated against a reference illuminance detector to determine its accuracy by using a transfer standard such as an incandescent illuminant A or an LED LV41 source. The device under test and the reference source are mounted on an optical rail at a known distance from the reference to establish a reference illuminance. Linearity of illuminance response is measured separately using a variable illuminance source. The spectral response is calibrated using a monochromator at 5 nm intervals across the visible spectrum. Additional information includes the meter response ratio to a set of RGB and IR filters, the and (optionally) the cosine response. The results of the measurements are written into an accredited report (the illuminance responsivity & linearity and cosine response are covered by the laboratory accreditation).
LightLab Luminance Calibration
A calibrated uniform luminance source is used as reference for calibrating luminance meters for luminance responsivity and linearity. Meter response ratio is calibrated using a set of RGB & IR filters. An optional spectral response calibration can be performed. Luminance & luminance linearity is covered by the laboratory accreditation.
