What Is a Lux Meter?
A lux meter is a device that measures illuminance (a measure of brightness) and outputs it as numerical data to a computer or other device.
When work is performed in a set area, the brightness of the surrounding area is important.
Human evaluation is not suitable for assessing brightness. This is because the human eye is accustomed to the environment, there are large individual differences, and numerical data cannot be obtained.
Since lux meters can measure brightness as objective and quantitative data called “illuminance,” they can solve the problem of human evaluation.
In addition, since lux meters have a function to send data to a PC, there is no need for a human to manually record the data.
Uses of Lux Meters
Lux meters are widely used in situations where the brightness of the environment is objectively evaluated.
Illuminance measurement is essential in environments such as factories and laboratories, where illuminance is more important for business than in general offices.
Since it is troublesome to manually input the measured illuminance into a personal computer for analysis, it is common to use lux meters so that they can be automatically transmitted to a personal computer.
Principle of Lux Meters
The unit of illuminance measured by lux meters is lux, also known as lx. It is calculated by dividing the luminous flux (in lm) by the area (in m2).
The definition of luminous flux is “the brightness of light passing through a surface”. However, since luminous flux is brighter when the area is larger, illuminance is calculated by dividing the luminous flux by the area of that surface.
Since the required brightness is the same in both large and small offices, it makes sense to use illuminance instead of luminous flux as a measure of brightness.
White light is a composite of light distributed over a wavelength of approximately 400 nm (blue-violet) to 700 nm (red). The human eye is sensitive to different wavelengths, with a peak distribution at about 555 nm (green).
A lux meter passes the incident light through a filter that mimics human sensitivity and receives the light with a photodiode. The photodiode is an element that converts the received light into an electrical signal.
The electrical signal converted from light by the photodiode is measured to obtain the illuminance. The obtained illuminance is sent to a PC with a log function, allowing analysis using software such as Excel.