What should I do if the photoelectric level sensor is misjudged?

- Sep 10, 2019-

As water level sensors are used more and more widely, there are some problems. For example, because the misjudgment of optical level detector caused by infrared rays, water vapor, etc., how should we solve these problems? EPT tells you the solution.


The misjudgment caused by steam, water vapor or water droplets


To solve the problem, we must know how the problem is generated. First, let's understand the working principle of the optical level detector.


The optical level detector internally includes a near-infrared light emitting diode and a photosensitive receiver. The light emitted by the LED is directed into the lens at the top of the sensor. When the liquid is immersed in the lens of the optical level detector, the light is refracted into the liquid, so that the receiver does not receive or can only receive a small amount of light. (See the left) The optical level detector senses this change and the receiver can drive an internal electrical switch to activate an external alarm or control circuit. If there is no liquid, the light from the LED is reflected directly from the lens back to the receiver. (see the right).

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Therefore, when there are water drops on the probe, then some of the light will be refracted into the liquid, and the final received light will affect the final detection result, which will lead to the sensor's judgment error,because the affect of water drop, when the water does not arrive the level, but the level sensor still judge to have a water state. So how do we solve the problem of water droplet?


When the detected liquid is water and the water level is lower than the critical liquid level, water droplets will accumulate on the surface of the sensor body, leading to a decrease in the signal output voltage. Therefore, considering the influence of water vapor or water droplets, EPT uses the adjustment of the liquid level threshold voltage to solve this problem.


Misjudgment caused by liquid level fluctuation


When the liuqid level fluctuates, the liuqid can not be in contact with the sensor all the time, which may cause the sensor to misjudge. So how to avoid this problem? Adding anti-shake logic to the program can circumvent this phenomenon.


Misjudgment of the water level sensor caused by direct sunlight


The optical level detector uses the optical reflection principle of infrared light to measure the liquid level, and the infrared light in the sunlight interferes with the detection of the photoelectric water level sensor. EPT Technology recommends using a hood or changing the installation angle.