Photoelectric device composition
1.Photoresistor
The most commonly used photosensors are photosensitive resistors. The photoresistor has a relatively high resistance value in the absence of illumination. When it is exposed to light, the resistance decreases more and the conductivity is significantly enhanced. The main parameters of the photoresistor are Dark resistance, dark current, corresponding to the bright resistance, bright current. They are measured values in the presence of light and no light, respectively. The greater the difference between the bright resistance and the dark resistance, the better. In the selection of the photoresistor Also pay attention to its lighting characteristics, spectral characteristics. [2]
2. Photodiode
The photodiode operates in the off-state under the condition of no light, and has the same characteristics as the general diode. It has a single-conducting performance. When exposed to light, the carrier concentration in the PN region is greatly increased, and the carrier flows to form a photocurrent. .
3. Phototransistor
The difference between a phototransistor and an ordinary triode is that the size of the emitter is relatively small. When the light is illuminated, the photocurrent is almost equal to the base current of the ordinary triode. The phototransistor is more sensitive than the photodiode.
4. Photocell
In practice, the more used photocells are silicon photocells. It can convert light energy directly into electrical energy. An important feature of photocells is that the current in the short circuit is substantially linearly proportional to the illumination. In the application, the load resistance is generally small. The smaller the resistance, the better the linearity.
5. Photocell
Photocells are generally divided into vacuum photocells and gas-filled photocells. Inflatable phototubes are generally filled with argon or argon-helium mixed gases, which are all inert gases and have a relatively small atomic weight. The lack of aerated phototubes is that the sensitivity decays quickly.
6. Photomultiplier tube
The photomultiplier tube is mainly composed of a cathode chamber and a secondary emission multiplication system. The photoelectric characteristics of the photomultiplier tube are linear when the luminous flux is small. Due to the existence of the dark current of the photomultiplier tube, the minimum range of the measurement is limited.