Question:
Can the Photomicrosensors (photointerrupter) detect transparent liquid in a transparent tube?
Answer:
For the detection of transparent liquid in transparent tubes, consider using a transmissive type Photomicrosensors(photointerrupter) that utilizes the refraction of light.
Explanation:
For liquid detection in transparent tubes such as chemical analyzers, if the liquid is opaque, the S/N ratio is high between the absence or presence of liquid, so the presence of liquid can be detected stably, depending on the tube diameter and tube wall thickness. However, if the liquid is transparent, the S/N ratio is quite low, making it difficult to adjust the threshold. It may also become undetectable due to changes in light current caused by changes in temperature or LED strength over time. In such applications, an increase in the S/N ratio by the refraction of light by the liquid can be utilized. Install a horizontal slit type slot Photomicrosensors (e.g. EE-SX1096-W11) with its sensor beam shifted from the center of the tube as shown below. In this way, the direction of the light flux changes due to the refraction by the liquid, and the receiving light level of the sensor changes. As a result, the S/N ratio increases, making it much easier to adjust the threshold value. However, the S/N ratio varies depending on the position of the beam, the tube diameter and tube wall thickness, and the type of liquid (refractive index).
Quick tips
If the tube diameter is small, a horizontal slit type, such as EE-SX1096W11 (slot width: 3.4 mm), is effective for increasing the S/N ratio. However, if the tube diameter is larger, consider EE-SX1035 (slot width: 5 mm), EE-SX1160W11 (slot width: 9.5 mm), or EE-SX1140 (slot width: 14 mm).
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Optical Sensors | Digi-Key Electronics
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