1. Measuring principle:>
Photovoltaic 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 Illuminance Meter>: Inconvenient to use, low accuracy, rarely used
2. Photoelectric illuminance meter>: commonly used selenium photocell illuminance meter and silicon photocell illuminance meter
The composition and application requirements of the photoelectric 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 light meter probe is made of glass, which is easy to break and damage, and the waterproof effect is poor when used at the same time
① Photovoltaic cells use selenium (Se) photocells or silicon (Si) photocells with good linearity; they can maintain good stability and high sensitivity after working for a long time; when E is high, choose photocells with high internal resistance, which have low sensitivity and good linearity , not easily 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 angle compensator (opalescent glass or white plastic) in front of the photocell because when the incident angle is large, the photocell deviates from the cosine rule
④ The illuminance meter should work at or near room temperature (photoelectricCell drift changes with temperature)
3. Illuminance calibration:>
1. Calibration principle:
Let Ls irradiate the photocell vertically → E=I/r2, change r to get the photocurrent value under different illuminance, and convert the current scale into the illuminance scale according to the corresponding relationship between E and i.
2. Calibration method:
Using 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 ammeter at each distance, and calculate the illuminance E by the inverse square law of distance E=I/r2, and then calculate the illuminance E by In this way, a series of photocurrent values i with different illuminance can be obtained, and the change curve of photocurrent i and illuminance E can be obtained, which is the calibration curve of the illuminance meter>. Calibration for lux meters
3. Factors affecting the calibration curve:
The photocell and galvanometer need to be re-calibrated when they are replaced; the illuminance meter should be re-calibrated after a period of use (generally 1-2 times within a year); the high-precision illuminance meter can be calibrated with a light intensity standard lamp; The calibration range of the illuminance meter can change the distance r, or choose different standard lamps, and choose a small-range ammeter
Illumination 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).
Lighting 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).
to ensure that people areTo live under suitable light, our country has formulated health standards for indoor (including public places) illumination. For example, the sanitary standard of illuminance in shopping malls (stores) in public places is ≥100Lx; the sanitary standard of illuminance on the countertops of libraries, museums, art galleries, and exhibition halls is ≥100Lx; the sanitary standard of illuminance in public bathrooms is ≥50Lx; 30Lx, sauna ≥ 30Lx. Foreign standards for indoor illuminance, such as Germany recommends several rated light intensity, the office includes 300Lx for clerical work, 750Lx for typing and drawing work; the illuminance requirements for visual work on the factory and production line are 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; canteens and indoor gyms For 300Lx etc.
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 short, illumination and human health, especially eye care, have extremely important hygienic significance.
5. Application scope:>
1. Application in general public places
In order to ensure that people can live under suitable light, my country has formulated health standards for indoor (including public places) illuminance, and used illuminance meters> to measure the illuminance of various places.
2. Lighting production industry, photography industry, stage lighting layout, etc.
Illuminance meter> has been successfully applied to many projects, such as lighting production industry, photography industry, stage lighting layout, etc. Different models of illuminance meters can meet different measurement requirements.
3. Factory production line application
In the factory, 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 requirement is ≥1000Lx. For places with relatively high illumination requirements, a large-range illuminance meter can be selected, with a super-large range. Can deal with light illumination measurement.
4. The application of illuminance meters is very extensive, including the applications in our daily life, such as factories, warehouses, schools, offices, homes, street lamp construction, laboratories and so on.