Today, Wuxi Rihuan Sensing Technology Co., Ltd. will introduce to you the scale lines and arrows on the slot-type photoelectric sensor, and tell you what they are for?

The slot-type photoelectric sensor (U-shaped photoelectric switch) is almost used every day in automated equipment. However, many people only pay attention to the slot width and output type, but ignore the two unremarkable marks on the sensor's casing - the scale lines and arrows. They may seem simple, but they directly relate to the detection accuracy and anti-interference ability.

1. Scale lines: Position of the optical axis

On both sides of the slot of the slot-type photoelectric sensor, there is usually a fine scale line. This line indicates the center position of the optical axis - that is, the invisible straight line between the light beam emitted by the emitting end and the photo-sensitive window of the receiving end.

Why is it necessary to know the position of the optical axis? Because the detection area of the slot-type photoelectric sensor is not uniformly effective throughout the slot. The light beam is concentrated near the optical axis, and the farther it deviates from the optical axis, the weaker the light intensity. Only when the measured object falls within the range of the optical axis can the detection effect be the most stable and sensitive.

Therefore, during installation or debugging, the movement trajectory of the measured object should be aligned as much as possible with the scale lines. For applications requiring precise positioning (such as edge detection, counting of small parts), the scale lines are the benchmark for finding the "optimal detection point".

2. Arrow: Direction of light transmission

Next to the slot, there is usually an arrow mark. It represents the propagation direction of light from the emitting end to the receiving end.

This arrow seems irrelevant in ordinary situations, but it plays a significant role in two special cases:

1. When detecting small objects, the detection point should be close to the emitting end

The internal part of the slot-type photoelectric sensor uses an LED light source, and the emitted light beam is not completely parallel but has a certain divergence angle. After the light beam leaves the emitting end, it gradually spreads as it travels - the closer it is to the receiving end, the larger the light spot and the more dispersed the energy.

Therefore, when the measured object is very small (such as thin lines, small parts, or thin sheets), setting the detection point close to the emitting end makes the light spot more concentrated, the energy more dense, and the signal change more obvious, resulting in more accurate detection. If it is placed close to the receiving end, the light spot has already spread, and the small object may only block a small part of the light beam, resulting in a weak signal change and easy missed detection.

2. In strong light environments, use the arrow to adjust the installation direction

The receiving end of the slot-type photoelectric sensor is sensitive to strong light. If the installation direction happens to allow external strong light (such as sunlight, high-power lighting) to directly shine on the receiving end, it will cause the receiver to saturate or trigger incorrectly, resulting in unstable signals.

At this time, the arrow is a reference for adjusting the direction: according to the light path direction indicated by the arrow, rotate the sensor or add a shading structure to prevent the strong light from directly shining on the receiving end. For example, placing the receiving end facing away from the strong light source or making the arrow direction different from the incident direction of the strong light can effectively reduce interference.

3. Summary

Mark Meaning Actual Use

Scale lines Optical axis center position Align the movement trajectory of the measured object to find the optimal detection point

Arrow Direction of light transmission (emitting → receiving) Detect small objects when close to the emitting end; avoid direct exposure of the receiving end to strong light in strong light environments

Although the slot-type photoelectric sensor is small, these two marks are left by the designers for the on-site engineers as a "user manual". The scale lines tell you "which way to align", and the arrow tells you "where the light goes" - understanding them can improve the detection accuracy and stability by one level.

Rihuan Sensing provides various slot width specifications of slot-type photoelectric sensors. The product casings are clearly marked with the optical axis scale lines and the light transmission direction arrow, making it convenient for on-site quick alignment and installation and debugging. Welcome to follow Rihuan Sensing to get more product information and technical support.