The measurement principle of the analytical illuminance meter
An illuminance meter is an instrument that specializes in measuring luminosity and brightness. It is to measure the light intensity (illuminance) is the degree to which the object is illuminated, that is, the ratio of the luminous flux obtained on the surface of the object to the illuminated area. An illuminance meter is usually composed of a selenium photocell or a silicon photocell and a microammeter.
Measuring principle of illuminance meter:
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 high illuminance or low illuminance.
The application of illuminance meters is very wide, including the applications in our daily life, such as factories, warehouses, schools, offices, homes, street lighting construction, laboratories and so on.
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 use 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 break, and the waterproof effect is poor when used
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; when E is high, choose photocells with high internal resistance, which have low sensitivity and good linearity , not easily damaged by strong 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
③Add 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 room temperature or close to room temperature (photocell drift changes with temperature)
