Thread Content
Level sensors can convert changes in various level parameters into standard current signals, which are transmitted to the operation control room for centralized display, alarm generation, or automatic control by secondary instruments or computers. They feature a robust structure and convenient installation methods. It can be used for the continuous detection of liquid level, material level, or substance level under special conditions such as high temperature, high pressure, severe corrosion, easy crystallization, resistance to clogging and freezing, as well as with solid powdery or granular materials. It can be widely applied in the detection and control of various industrial processes. However, as level sensors are used more and more widely, and an increasing number of electrical devices incorporate them, there are also more and more instances of failures in photoelectric sensors. For example: How should we address the issues of misjudgment in photoelectric level sensors caused by infrared rays, water vapor, and so on? The editor from Gongcaiwang will tell you the solution. Sensor errors caused by water vapor, steam, or water droplets formed upon contact with liquid. A photoelectric level sensor contains a near-infrared LED and a photosensitive receiver. The light emitted by the light-emitting diode is directed into the lens at the top of the sensor. When the liquid submerges the lens of the photoelectric water level sensor, light is refracted into the liquid, resulting in the receiver receiving no light or only a small amount of it. (See the left side of the diagram) The photoelectric level sensor detects these changes in conditions; the receiver can then activate the internal electrical switch, thereby triggering an external alarm or control circuit. If there is no liquid, the light emitted by the LED is reflected directly from the lens back to the receiver. (See the right side of the image below.) Based on the working principle of photoelectric level sensors, water vapor or steam, or water droplets formed upon contact with liquid can cause errors in the sensor’s readings. When there are water droplets on the probe, some of the light is refracted into the liquid, and this affects the light that is received, thereby leading to incorrect readings by the sensor. As a result, it is possible for the sensor to indicate that water is present when in fact it is not, due to the influence of those water droplets. Solution: When the liquid being detected is water and the water level is below the critical level, water vapor or water droplets will accumulate on the surface of the sensor, resulting in a decrease in the signal output voltage. Therefore, taking into account the effects of water vapor, steam, or water droplets, Gongcai Network Technology recommends addressing this issue by adjusting the voltage setting of the level control valve. The issue of misjudgment caused by liquid surface fluctuations contacting the water level sensor: When the surface of the liquid fluctuates, it continuously comes into contact with the sensor, which may lead to misjudgments by the sensor. So how can we avoid this problem? Adding debouncing logic to the program can prevent this phenomenon from occurring. The problem of incorrect readings by the water level sensor caused by direct sunlight: Photoelectric water level sensors utilize the principle of optical reflection of infrared light to measure water levels, and the infrared rays in sunlight can interfere with the detection function of these photoelectric water level sensors. According to Gongcai.com’s technical recommendations, this issue can be resolved by using light shields or changing the installation method. In addition to the issues mentioned above, in many industrial applications related to level detection, not only is high accuracy in level measurement required, but the measuring instruments also need to be able to function well in the special conditions of industrial environments, such as those with high temperatures, high pressures, strong corrosive effects, or high radiation levels. They must also be suitable for use over long distances or inside sealed pressure vessels. For such applications, Gongcai Network recommends the British SST photoelectric level sensor/photoelectric level switch – LLC200D3SH. This level sensor provides single-point level detection and a TTL-compatible push-pull output. The designed sensor consists of an infrared emitter and a detector, which are mounted in precise positions to ensure good optical coupling between them in the air. When the tapered end of the sensor is immersed in a liquid, infrared light passes through the tapered surface, resulting in a reduced intensity of light reaching the detector. The LLC series of photoelectric level sensors (industrial-grade type, photoelectric submersion sensors) are designed specifically for industrial applications. It can handle heavy-duty environments in industrial applications. This series of products is suitable for power supply environments with a wide voltage range, and the drive current can reach 250mA. Therefore, this series of sensors can directly drive alarms and other devices. Electrical specifications of the photoelectric level sensor/photoelectric level switch LLC200D3SH (industrial grade):