Units of measurement of illuminance and conditions of use
Units for illuminance meters
Many customers will say, I want to buy a light meter, and they will naturally ask what the unit of the light meter is! Now let’s briefly introduce illuminance. Illuminance is a unit that reflects the intensity of light. Its physical meaning is the luminous flux illuminated on a unit area. The unit of illuminance is the number of lumens (Lm) per square meter, also called Lux: 1Lux=1Lm/m2. As can be seen from the above formula, Lm is the unit of luminous flux, which is defined as the amount of light radiated by a surface area of 1/60 square meters of pure platinum within a solid angle of 1 steradian at the melting temperature (about 1770°C).
The above explanation of illumination units seems very theoretical and generally difficult to understand. In order to have a more perceptual understanding of the amount of illumination, for example, a 100W incandescent lamp emits a total luminous flux of about 1200Lm. If it is assumed that the luminous flux is evenly distributed on a hemisphere, then the distance from the light source The illuminance values at 1m and 5m can be obtained according to the following steps: The area of a hemisphere with a radius of 1m is 2π×12=6.28 m2, and the illuminance value at 1m from the light source is: 1200Lm/6.28 m2=191Lux. In the same way, the area of a hemisphere with a radius of 5m is: 2π×52=157 m2, and the illumination value at a distance of 5m from the light source is: 1200Lm/157 m2=7.64Lux.
General conditions: In summer, the illuminance is about 100000LUX in the sun; the outdoor illuminance on a cloudy day is 10000LUX; the indoor daylight illuminance is 100LUX; the illuminance on our desktop 60cm away from the 60W desk lamp is 300LUX; the illuminance in the TV live broadcast room is 1000LUX; in the room at dusk The illuminance is 10LUX; the illuminance of street lights at night is 0.1LUX; the illuminance of candlelight (at a distance of 20cm) is 10~15LUX.
