1. Measuring principle:>
Photoelectric cells are photoelectric components that directly convert light energy into electrical energy . When the light hits the surface of the selenium photovoltaic cell, the incident light passes through the metal thin film 4 and reaches the interface between the semiconductor selenium layer 2 and the metal thin film 4, generating a photoelectric effect on the interface. The magnitude of the generated photocurrent has a certain proportional relationship with the illuminance on the light-receiving surface of the photocell. At this time, if an external circuit is connected, a current will flow, and the current value will be indicated on the microammeter with lux (Lx) as the scale. The magnitude of the photocurrent depends on the intensity of the incident light. The Illuminance Meter> has a shifting device, so it can measure both high and low illuminance.
1. Visual inspection< >Illuminance meter>: Inconvenient to use, low precision, rarely used
2. Photoelectric Illuminance meter>: Selenium photocell illuminance meter and silicon photocell illuminance meter are commonly used
The composition and use requirements of the photocell illuminance meter:
1. Composition: Microammeter, shift knob, zero point adjustment, terminal, photocell, V(λ) correction filter, etc.
Commonly used selenium (Se) photocell or silicon (Si) photocell illuminance meter, also known as lux meter
2. Requirements for use: The probe of the illuminance meter is made of glass, which is easy to break and damage, and at the same time, the waterproof effect is very good when used Poor
① Photocells should use selenium (Se) photocells or silicon (Si) photocells with good linearity; they can still maintain good stability and high sensitivity after working for a long time; Low sensitivity and good linearity, not easy to be damaged by light
② There is a V(λ) correction filter inside, which is suitable for the illumination of light sources with different color temperatures, and the error is small
③ Add a cosine in front of the photocell The reason for angle compensator (opalescent glass or white plastic) is that when the incident angle is large, the photocell deviates from the cosine law
④The illuminance meter should work at room temperature or close to room temperature (photocell drift changes with temperature)
3. Illumination calibration:>
1. Calibration principle:
Make Ls irradiate the photocell vertically → E=I/r2, change r to get the photocurrent value under different illuminance, from the corresponding relationship between E and i Convert current scale to illuminance scale.
2. Calibration method:
Use the light intensity standard lamp, under the working distance of the approximate point light source, change the distance l between the photocell and the standard lamp, record the readings of the galvanometer at each distance, by The law of inverse square distance E=I/r2 calculates the illuminance E, from which a series of photocurrent values i with different illuminance can be obtained, and the change curve between photocurrent i and illuminance E can be obtained, which is the illuminance meter> The calibration curve can thus be divided into the dial of the illuminance meter, which is the calibration of the illuminance meter
3. Factors affecting the calibration curve:
The photocell and galvanometer need to be re-calibrated when they are replaced; the illuminance meter After using for a period of time, the illuminance meter should be calibrated again (generally, it should be calibrated 1-2 times a year); the high-precision illuminance meter can be calibrated with the light intensity standard lamp; the distance r can be changed by expanding the calibration range of the illuminance meter, or Choose different standard lamps and choose a small-range galvanometer
Illuminance is closely related to people's lives. Sufficient light can prevent people from accidents. Conversely, too dark light can cause human fatigue far more than the eyes themselves. Uncomfortable or poor lighting conditions are therefore one of the leading causes of accidents and fatigue. Existing statistics show that about 30% of all occupational labor accidents are directly or indirectly caused by insufficient light. The lighting requirements for stadiums (stadiums) are very strict, too or too dark light will affect the effect of the game.
So, what are the hygienic requirements for the indoor contrast illumination where people live? Illuminance is a very important indicator in hygiene. Light refers to the electromagnetic radiation that can cause the human eye to feel bright. When the light enters the eye, the perception that can be produced is called vision. The light that people see refers to visible light, and its wavelength range is between 380nm and 760nm (nanometer).
Daylighting can be divided into two categories: natural lighting and artificial light sources. Natural lighting refers to the natural illuminance of indoors and regions, including direct sunlight scattered light and reflected light from surrounding objects, and is often expressed by daylighting coefficient and natural illuminance. The daylighting factor refers to the ratio of the effective area of the daylight opening to the indoor floor area. The daylight factor of a general residence is between 1/5 and 1/15, and the living area ratio is between 1/8 and 1/10 (window area/indoor floor area). The natural illuminance coefficient is used to evaluate the illuminance level of natural light. It reflects the relationship between indoor and outdoor light exposure. It also reflects the local light climate (the sum of the natural light energy and the sunlight illuminance index of the climate).
In order to ensure that people live under suitable light, our country has formulated health standards for indoor (including public places) illumination. as in publicSanitary standards for illuminance in shopping malls (stores) in public places ≥100Lx; hygienic standards for countertop illuminance in libraries, museums, art galleries, and exhibition halls ≥100Lx; hygienic standards for illuminance in public bathrooms ≥50Lx; bathrooms (showers, pools, tubs) ≥30Lx, Sauna bathroom ≥ 30Lx. Foreign standards for indoor illuminance, such as Germany recommends several rated light intensities. The office includes 300Lx for clerical work area, 750Lx for typing and drawing work; the illuminance requirement for visual work on the factory and production line is 1000Lx; 200Lx for hotels and public rooms; 200Lx for reception points and cashiers; 1500-2000Lx for shop windows; 150-200Lx for hospital wards, 500Lx for emergency treatment areas; 400-700Lx for schools and classrooms; 300Lx for canteens and indoor gyms wait.
For the measurement method of illuminance, it is generally measured with an illuminance meter. The illuminance meter can measure the intensity of different wavelengths (such as the measurement of visible light band and ultraviolet band), and can provide people with accurate measurement results.
In a word, illumination and human health, especially eye care, have extremely important hygienic significance.
5. Scope of application: >
1. Application in general public places
In order to ensure that people can live under suitable light, my country has formulated relevant indoor Including hygienic standards for illuminance in public places), use the illuminance meter> to measure the illuminance of each place.
2. Lighting production industry, photography industry, stage lighting layout, etc.
Illuminance meter> has been successfully applied to many programs, such as lighting production industry, photography industry, stage lighting layout etc. Different models of illuminance meters can meet different measurement requirements.
3. Application of factory production line
In factories, the illumination requirements on the production line are relatively strict, continuous work will cause visual fatigue, and work efficiency will be greatly reduced. Usually, the illumination requirements are ≥1000Lx, and the illumination requirements are relatively high A large range of illuminance meters can be selected for the most suitable places, and the ultra-large range can cope with the measurement of light illuminance.
4. Illuminance meters are widely used, including applications in our daily life, such as factories, warehouses, schools, offices, homes, street lighting construction, laboratories and so on.