Low-error gate opening sensor

Abstract

The present invention relates to the technical field of opening sensors, and discloses a low-error gate opening sensor, which includes a rotary encoder. The rotary encoder is composed of an optical code disk and a detection element for detecting the rotation angle of the optical code disk. The optical code disk is composed of a rotating shaft, a first grating scale, and a second grating scale. The first grating scale and the second grating scale are coaxially arranged and have the same size. The circumferential arrays at the edges of the first grating scale and the second grating scale have light-shielding areas formed by strip-shaped light-shielding films. The detection element is composed of a control circuit base and a photoelectric sensor. The photoelectric sensor is provided with a light-emitting diode capable of emitting light. The light emitted by the light-emitting diode can pass through the first grating scale and the second grating scale and enter the photosensitive element, and the light emitted by the light-emitting diode will be absorbed by the light-shielding film. The light-shielding film on the second grating scale is spiral, and the shielding area formed by the light-shielding film on the first grating scale is sparser than the shielding area on the second grating scale.

Description

Technical Field

[0001] The present invention relates to the technical field of opening sensors, specifically a low-error gate opening sensor. Background Technique

[0002] The gate opening sensor determines the height of the water level or liquid level by measuring the opening of the gate. It can convert the position information of the gate into an electrical signal output, so as to achieve precise monitoring and control of the gate opening. Such sensors are widely used in fields such as water conservancy projects, power projects, and chemical engineering. The working principle of the gate opening sensor is mainly based on the synchronous movement of a rotary encoder and a coupler. When the gate makes a vertical movement or a rotational movement, the coupler connected to the rotating shaft of the gate hoist or directly connected to the gate will make a synchronous movement. The coupler then drives the main shaft of the encoder to rotate. The encoder outputs a gate position encoded electrical signal corresponding to the rotation position through an electrical socket. These electrical signals can be transmitted to a data acquisition system or a PLC controller to achieve automatic control and monitoring of the water level or liquid level.

[0003] The optoelectronic rotary encoder mainly consists of a light source, a code disk (grating sheet), and a photosensitive element (light reader), etc. The light source usually uses an infrared light source to emit a light beam to the rotating part on the encoder. The code disk rotates with the measured shaft and has a series of equally spaced transparent and opaque areas to form an optical code. The photosensitive element is used to detect the light beam reflected from the rotating part and convert it into an electrical signal. The light-shielding part on the code disk usually has radial stripes for easy processing. When detecting such radial stripes, if the only distance between two detections is the same as the stripe pitch, the accurate rotation angle cannot be recorded. At the same time, the traditional optoelectronic rotary encoder cannot detect the rotation direction and is prone to deviation. Summary of the Invention

[0004] (1) Technical problems to be solved: Aiming at the deficiencies of the prior art, the present invention provides a low-error gate opening sensor, which has the advantage of low-error detection and solves the problem of deviation in the detection of the opening sensor.

[0005] (2) Technical solution: To achieve the above object of low-error detection, the present invention provides the following technical solution: A low-error gate opening sensor, including a rotary encoder, the rotary encoder is composed of an optical code disk and a detection element for detecting the rotation angle of the optical code disk, the optical code disk is connected to the rotating shaft of the hoist in the gate, the optical code disk is composed of a rotating shaft, a first grating scale and a second grating scale, the first grating scale and the second grating scale are coaxially arranged and have the same size, the first grating scale and the second grating scale are in the shape of transparent disks, and the circumferential arrays at the edges of the first grating scale and the second grating scale have light-shielding areas formed by strip-shaped light-shielding films, the detection element is composed of a control circuit base and a photoelectric sensor, the photoelectric sensor is provided with a light-emitting diode capable of emitting light, the light emitted by the light-emitting diode can pass through the first grating scale and the second grating scale and enter the photosensitive element, and the light emitted by the light-emitting diode will be absorbed by the light-shielding film, the light-shielding film on the second grating scale is spiral, and the shielding area formed by the light-shielding film on the first grating scale is sparser than the shielding area on the second grating scale, and the light spot irradiated on the photosensitive element through the light-transmitting area of the second grating scale will generate displacement on the photosensitive element as the optical code disk rotates.

[0006] Preferably, the light-shielding film provided on the first grating scale is radial, and the light emitted by the light-emitting diode passes through the light-transmitting areas on the second grating scale and the first grating scale, and the light spot formed on the photosensitive element is in an arc-shaped strip.

[0007] Preferably, the light-shielding film provided on the first grating scale is spiral, and the inclination angle differs from that of the light-shielding film on the second grating scale by 180°, and the light emitted by the light-emitting diode passes through the light-transmitting areas on the second grating scale and the first grating scale, and the light spot formed on the photosensitive element is in a rhombus shape.

[0008] Preferably, the photoelectric sensor is arranged on the control circuit base, and the control circuit base and the optical code disk are arranged on the same plane of the rotary encoder and are detachably connected.

[0009] Preferably, the edge of the upper surface of the first grating scale is inclined downward, and the inclination angle is greater than 2° and less than 5°.

[0010] Preferably, the first grating scale and the second grating scale are made of glass, and the light-shielding film is a metal wire embedded in the first grating scale and the second grating scale.

[0011] Preferably, a light-shielding cover is provided outside the light-emitting diode and the photosensitive element.

[0012] Preferably, gaps are provided at intervals on the light-shielding cover.

[0013] (3) Beneficial effects: Compared with the prior art, the present invention provides a low-error gate opening sensor with the following beneficial effects: 1. For this low-error gate opening sensor, through the coaxial and same-size design of the first grating scale and the second grating scale, complementary light-shielding effects can be generated when the two rotate. This design not only improves the measurement accuracy but also enables the sensor to capture more subtle rotational angle changes, thereby improving the resolution. The spiral light-shielding film design on the second grating scale causes the light spots received by the photosensitive element to produce continuous displacement changes during rotation. This continuous displacement change provides richer measurement data for the sensor, which helps to calculate the rotational angle and the gate opening height more accurately. In the case of a traditional rotary encoder, misjudgment may occur at a specific rotational angle because the gap of the light-shielding film is consistent with the rotational angle. However, for the dual-grating-scale structure of this design, even in this situation, different light-shielding effects can be generated through the spiral light-shielding film of the second grating scale, thus avoiding misjudgment. The redundant design of the first grating scale and the second grating scale enables the sensor to maintain a high measurement accuracy in harsh environments (such as dust, water droplets, etc.). Even if one of the grating scales is interfered with, the other grating scale can still provide reliable measurement data, thereby improving the reliability of the sensor. Due to the spiral design of the second grating scale, when the optical code disk rotates, the light spots received by the photosensitive element will produce displacements. The direction of this displacement can indicate the direction of rotation. This design not only improves the measurement accuracy but also provides feedback on the rotation direction for the control system. By monitoring the displacement speed and frequency of the light spots on the photosensitive element, the rotation speed can be calculated. This design enables the sensor to measure the rotational angle, direction, and speed simultaneously, providing more comprehensive information for the control system.

[0014] 2. For this low-error gate opening sensor, when the light-shielding film on the first grating scale is radial, its design and manufacturing process are relatively simple because the radial pattern is easier to achieve through mechanical processing or lithography techniques. The radial light-shielding film can reduce measurement errors caused by uneven rotation or vibration because the light passes through fixed and evenly distributed light-transmitting areas. Therefore, even if the rotation speed changes, the position change of the light spots on the photosensitive element is relatively stable. Combined with the second grating scale with a spiral design, the first grating scale with a radial light-shielding film can provide additional measurement information. When the second grating scale cannot measure accurately due to certain reasons (such as contamination, damage), the first grating scale can still provide reliable measurement data. Due to the regularity of the radial light-shielding film, it is easier for the sensor to determine key parameters such as the zero point and full scale during calibration.

[0015] 3. For this low-error gate opening sensor, when the light-shielding films on both grating scales are spiral and the inclination angles differ by 180°, they can cancel out the measurement deviation caused by the rotation angle error. This design can further improve the measurement accuracy and stability. Since the light-shielding film designs of the two grating scales are different, their sensitivities to external interferences (such as dust, water droplets, etc.) are also different. Therefore, even if one grating scale is interfered with, the other grating scale can still provide reliable measurement data, thus enhancing the anti-interference ability of the sensor.

[0016] 4. For this low-error gate opening sensor, the first grating scale and the second grating scale are made of glass. This material has high light transmittance and good dimensional stability, which helps to ensure the clarity and accuracy of the grating signal. The glass material also has high hardness and corrosion resistance, and can resist the erosion of dust, dirt and other pollutants in the environment, thus extending the service life of the grating scale. The embedded metal wire light-shielding film, as part of the grating, can precisely control the transmission and blocking of light, forming clear Moiré fringes, improving the measurement resolution and accuracy. The stability and durability of the metal wire also ensure the reliability of long-term measurement. The light-shielding cover arranged outside the light-emitting diode and the photosensitive element, especially the gap design arranged at intervals thereon, effectively utilizes the dynamic characteristics of the air flow. When the air flow enters the inside of the light-shielding cover through these narrow gaps, the air flow will diverge and form eddy currents. This irregular movement helps to disperse the water vapor that may accumulate inside the light-shielding cover. By preventing the water vapor from condensing into water droplets, this design avoids the interference of water droplets on the light signal and ensures the stable operation of the grating scale measurement system in high-humidity or changing humidity environments, which is crucial for many industrial applications, especially for occasions that require high-precision measurement. Brief Description of the Drawings

[0017] Figure 1 Structural Schematic of the Present Invention Figure 1 。

[0018] Figure 2 Structural Schematic of the Present Invention Figure 2 。

[0019] Figure 3 Schematic of the Detection Element of the Present Invention Figure 1 。

[0020] Figure 4 Schematic of the Detection Element of the Present Invention Figure 2 。

[0021] Figure 5 Schematic of the Light-Shielding Film in Embodiment 1 of the Present Invention.

[0022] Figure 6 Schematic of the Light-Shielding Film in Embodiment 2 of the Present Invention.

[0023] In the figure: 1, rotary encoder; 2, optical code disk; 3, detection element; 21, first grating scale; 22, second grating scale; 31, control circuit base; 32, photoelectric sensor; 211, light-shielding film; 321, light-emitting diode; 322, photosensitive element; 323, light-shielding cover. Specific implementation mode

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Embodiment 1: Please refer to Figures 1 - 3 and Figure 5 , a low-error gate opening sensor, including a rotary encoder 1, the rotary encoder 1 is composed of an optical code disk 2 and a detection element 3 for detecting the rotation angle of the optical code disk 2, the optical code disk 2 is connected to the rotating shaft of the hoist in the gate, the optical code disk 2 is composed of a rotating shaft, a first grating scale 21 and a second grating scale 22, the first grating scale 21 and the second grating scale 22 are coaxially arranged and have the same size, the first grating scale 21 and the second grating scale 22 are transparent disk-shaped, and a light-shielding area formed by strip-shaped light-shielding films 211 is circumferentially arranged at the edges of the first grating scale 21 and the second grating scale 22, the detection element 3 is composed of a control circuit base 31 and a photoelectric sensor 32, the photoelectric sensor 32 is provided with a light-emitting diode 321 capable of emitting light, the light emitted by the light-emitting diode 321 can pass through the first grating scale 21 and the second grating scale 22 and enter the photosensitive element 322, and the light emitted by the light-emitting diode 321 will be absorbed by the light-shielding film 211, the light-shielding film 211 on the second grating scale 22 is spiral, and the shielding area formed by the light-shielding film 211 on the first grating scale 21 is sparser than the shielding area on the second grating scale 22, and the light spot irradiated on the photosensitive element 322 through the light-transmitting area of the second grating scale 22 will generate displacement on the photosensitive element 322 as the optical code disk 2 rotates.

[0026] When the gate moves vertically, the photoelectric code disk 2 is connected to the rotating shaft of the hoist in the gate to make it rotate synchronously. When the first grating scale 21 and the second grating scale 22 on the photoelectric code disk 2 rotate, the light-shielding film 211 on the upper surface rotates accordingly, so that the light emitted by the light-emitting diode 321 in the photoelectric sensor 32 is intermittently blocked by the light-shielding film 211. The photosensitive element 322 records the situation of the light emitted by the light-emitting diode 321 being blocked, and calculates the overall rotation of the photoelectric code disk 2 through the change of the output signal, and deduces the opening height of the gate. The light-shielding film 211 on the grating scale of the traditional rotary encoder 1 is in a radially uniform circular array. There may be a situation where the rotation angle is the same as the gap angle of the light-shielding film 211 during two acquisitions by the photosensitive element 322, resulting in the photosensitive element 322 misjudging that the rotation angle is zero. At the same time, it is also impossible to judge whether the rotation angle is positive or negative. In this application, a double-grating scale structure of the first grating scale 21 and the second grating scale 22 is used, and the first grating scale 21 and the second grating scale 22 are of the same size and coaxially arranged. The shielding area formed by the light-shielding film 211 on the first grating scale 21 is relatively sparse compared with the second grating scale 22, and the light-shielding film 211 on the second grating scale 22 is spiral, so that even if the rotation angle of the photoelectric code disk 2 is the same as the interval angle of the light-shielding film 211 on the first grating scale 21, the shielding areas on the second grating scale 22 between adjacent light-shielding films 211 on the first grating scale 21 will be different. And the light spot generated by the light emitted by the light-emitting diode 321 passing through the light-transmitting area on the light-shielding film 211 of the second grating scale 22 on the photosensitive element 322 will displace on the photosensitive element 322 as the rotation progresses, and can more accurately judge the change of the rotation angle. At the same time, because of the setting of the two grating scales, and the shielding area of the second grating scale 22 is denser than that of the first grating scale 21, the influence of the first grating scale 21 on the light is reduced. Even if there is water droplet refraction on the first grating scale 21, it can be corrected by the second grating scale 22.

[0027] Refer to Figure 5 , the dotted line in the figure represents the position of the light-shielding film 211 of the second grating scale 22. The light-shielding film 211 provided on the first grating scale 21 is radial. The light emitted by the light-emitting diode 321 passes through the light-transmitting areas on the second grating scale 22 and the first grating scale 21, and the light spot formed on the photosensitive element 322 is in an arc-shaped strip.

[0028] The photoelectric sensor 32 is arranged on the control circuit base 31, and the control circuit base 31 and the photoelectric code disk 2 are arranged on the same plane of the rotary encoder 1 and are detachably connected.

[0029] The edge of the upper surface of the first grating scale 21 is inclined downward, and the inclination angle is greater than 2° and less than 5°, so that when there are water droplets on the upper surface of the first grating scale 21, they can be quickly thrown off from its upper surface as it rotates.

[0030] The first grating scale 21 and the second grating scale 22 are made of glass, and the light-shielding film 211 is a metal wire embedded in the first grating scale 21 and the second grating scale 22.

[0031] Refer to Figure 4 , a light-shielding cover 323 is provided outside the light-emitting diode 321 and the photosensitive element 322. The light-shielding cover 323 is provided with gaps at intervals. When the air flow penetrates into the light-shielding cover 323 from the gaps, entering from the narrow gaps into a larger space will cause the air flow to diverge, forming vortices with irregular movements, blowing away the water vapor existing in the light-shielding cover 323, and avoiding condensation into water droplets to interfere with detection.

[0032] Embodiment 2: Please refer to Figures 1 - 3 and Figure 6 , a low-error gate opening sensor, including a rotary encoder 1. The rotary encoder 1 is composed of an optical code disk 2 and a detection element 3 for detecting the rotation angle of the optical code disk 2. The optical code disk 2 is connected to the rotating shaft of the hoist in the gate. The optical code disk 2 is composed of a rotating shaft, a first grating scale 21 and a second grating scale 22. The first grating scale 21 and the second grating scale 22 are coaxially arranged and of the same size. The first grating scale 21 and the second grating scale 22 are in the shape of transparent discs, and light-shielding areas formed by strip-shaped light-shielding films 211 are circumferentially arrayed at the edges of the first grating scale 21 and the second grating scale 22. The detection element 3 is composed of a control circuit base 31 and a photosensor 32. The photosensor 32 is provided with a light-emitting diode 321 capable of emitting light. The light emitted by the light-emitting diode 321 can pass through the first grating scale 21 and the second grating scale 22 and enter the photosensitive element 322, and the light emitted by the light-emitting diode 321 will be absorbed by the light-shielding film 211. The light-shielding film 211 on the second grating scale 22 is in a spiral shape, and the shielding area formed by the light-shielding film 211 on the first grating scale 21 is sparser than the shielding area on the second grating scale 22. The light spot passing through the light-transmitting area of the second grating scale 22 and irradiating on the photosensitive element 322 will generate displacement on the photosensitive element 322 as the optical code disk 2 rotates.

[0033] When the gate moves vertically, the photoelectric code disk 2 is connected to the rotating shaft of the hoist in the gate to make it rotate synchronously. When the first grating scale 21 and the second grating scale 22 on the photoelectric code disk 2 rotate, the light-shielding film 211 on the upper surface rotates accordingly, so that the light emitted by the light-emitting diode 321 in the photoelectric sensor 32 is intermittently blocked by the light-shielding film 211. The photosensitive element 322 records the situation of the light emitted by the light-emitting diode 321 being blocked, calculates the overall rotation of the photoelectric code disk 2 through the change of the output signal, and deduces the opening height of the gate. The light-shielding film 211 on the grating scale of the traditional rotary encoder 1 is in a radially uniform circular array. There may be a situation where the rotation angle is the same as the gap angle of the light-shielding film 211 during two acquisitions by the photosensitive element 322, resulting in the photosensitive element 322 misjudging that the rotation angle is zero. At the same time, it is also impossible to judge whether the rotation angle is positive or negative. In this application, a double-grating scale structure of the first grating scale 21 and the second grating scale 22 is used, and the first grating scale 21 and the second grating scale 22 are of the same size and coaxially arranged. The shielding area formed by the light-shielding film 211 on the first grating scale 21 is relatively sparse compared to the second grating scale 22, and the light-shielding film 211 on the second grating scale 22 is spiral. Even if the rotation angle of the photoelectric code disk 2 is the same as the interval angle of the light-shielding film 211 on the first grating scale 21, the shielding areas on the second grating scale 22 between adjacent light-shielding films 211 on the first grating scale 21 will be different. Moreover, the light spot generated by the light emitted by the light-emitting diode 321 passing through the light-transmitting area of the light-shielding film 211 on the second grating scale 22 on the photosensitive element 322 will displace on the photosensitive element 322 as the rotation progresses, enabling more accurate judgment of the change in the rotation angle. At the same time, due to the setting of the two grating scales, and the shielding area of the second grating scale 22 is more dense than that of the first grating scale 21, the influence of the first grating scale 21 on the light is reduced. Even if there is water droplet refraction on the first grating scale 21, it can be corrected by the second grating scale 22.

[0034] Refer to Figure 6 , the dotted line in the figure represents the position of the light-shielding film 211 of the second grating scale 22. The light-shielding film 211 provided on the first grating scale 21 is spiral, and the inclination angle is 180° different from that of the light-shielding film 211 on the second grating scale 22. The light emitted by the light-emitting diode 321 passes through the light-transmitting areas of the second grating scale 22 and the first grating scale 21, and the light spot formed on the photosensitive element 322 is rhombus-shaped.

[0035] The photoelectric sensor 32 is arranged on the control circuit base 31, and the control circuit base 31 and the photoelectric code disk 2 are arranged on the same plane of the rotary encoder 1 and are detachably connected.

[0036] The upper surface edge of the first grating scale 21 is inclined downward, and the inclination angle is greater than 2° and less than 5°. When there is water on the upper surface of the first grating scale 21, it can be quickly thrown off from its upper surface as it rotates.

[0037] The first grating scale 21 and the second grating scale 22 are made of glass, and the light-shielding film 211 is a metal wire embedded in the first grating scale 21 and the second grating scale 22.

[0038] Refer to Figure 4 , a light-shielding cover 323 is provided outside the light-emitting diode 321 and the photosensitive element 322. When air flows into the light-shielding cover 323 through gaps provided at intervals on the light-shielding cover 323, it enters from the narrow gaps into a larger space, which will cause the air flow to diverge and form eddies with irregular movements, blowing away the water vapor existing in the light-shielding cover 323 and preventing it from condensing into water droplets to interfere with detection.

[0039] Working principle: When the gate moves vertically, the optoelectronic code disk 2 is connected to the rotating shaft of the hoist in the gate to make it rotate synchronously. When the first grating scale 21 and the second grating scale 22 on the optoelectronic code disk 2 rotate, the light-shielding film 211 on the upper surface rotates accordingly, causing the light emitted by the light-emitting diode 321 in the optoelectronic sensor 32 to be intermittently blocked by the light-shielding film 211. The photosensitive element 322 records the situation of the light emitted by the light-emitting diode 321 being blocked, calculates the overall rotation of the optoelectronic code disk 2 through the change of the output signal, and deduces the opening height of the gate. The light-shielding film 211 on the grating scale of the traditional rotary encoder 1 is in a radially uniform circular array. There may be a situation where the rotation angle is the same as the gap angle of the light-shielding film 211 during two acquisitions by the photosensitive element 322, resulting in the photosensitive element 322 misjudging the rotation angle as zero. At the same time, it is also impossible to judge whether the rotation angle is positive or negative. In this application, a dual-grating scale structure of the first grating scale 21 and the second grating scale 22 is used, and the first grating scale 21 and the second grating scale 22 are of the same size and coaxially arranged. The occlusion area formed by the light-shielding film 211 on the first grating scale 21 is relatively sparse compared to the second grating scale 22, and the light-shielding film 211 on the second grating scale 22 is spiral. Even if the rotation angle of the optoelectronic code disk 2 is the same as the interval angle of the light-shielding film 211 on the first grating scale 21, the occlusion areas on the second grating scale 22 between adjacent light-shielding films 211 on the first grating scale 21 will be different. Moreover, the light spot generated by the light emitted by the light-emitting diode 321 passing through the light-transmitting area of the light-shielding film 211 on the second grating scale 22 on the photosensitive element 322 will displace on the photosensitive element 322 as the rotation progresses, enabling more accurate judgment of the change in the rotation angle. At the same time, due to the setting of the two grating scales, and the occlusion area of the second grating scale 22 is denser than that of the first grating scale 21, the influence of the first grating scale 21 on the light is reduced. Even if there is water droplet refraction on the first grating scale 21, it can be corrected by the second grating scale 22.

[0040] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0041] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-error gate opening sensor, comprising a rotary encoder (1), wherein the rotary encoder (1) is composed of a photoelectric encoder (2) and a detection element (3) for detecting the rotation angle of the photoelectric encoder (2), wherein the photoelectric encoder (2) is connected to a rotating shaft of a gate hoist in the gate, and wherein: The photoelectric code disk (2) is composed of a rotating shaft, a first grating scale (21) and a second grating scale (22); the first grating scale (21) and the second grating scale (22) are coaxially arranged and have the same size; the first grating scale (21) and the second grating scale (22) are transparent disc-shaped; and the circumferential array at the edge of the first grating scale (21) and the second grating scale (22) has a light shielding area formed by a strip-shaped light shielding film (211); the detection element (3) is capable of emitting light and passing through the first grating scale (21) and the second grating scale (22) to form a light spot on the detection element (3) located below the light spot code disk (2); and the light emitted by the detection element (3) Light is absorbed by the shading film (211); the shading film (211) on the second grating scale (22) is spiral-shaped; a light spot passing through a light-transmitting area of ​​the second grating scale (22) is displaced on the detection element (3) as the photoelectric code disk (2) rotates; the shading film (211) provided on the first grating scale (21) is radial or spiral-shaped; and when the shading film (211) is spiral-shaped, its inclination angle differs by 180° from that of the shading film (211) on the second grating scale (22); and the shielding area formed by the shading film (211) on the first grating scale (21) is sparser than the shielding area on the second grating scale (22).

2. The low error gate opening sensor according to claim 1, characterized in that: The detection element (3) is composed of a control circuit base (31) and a photoelectric sensor (32). The photoelectric sensor (32) is provided with a light-emitting diode (321) capable of emitting light. The photoelectric sensor (32) is arranged below the photoelectric code disk (2), and a photosensitive element (322) for detecting the movement of a light spot is provided on the photoelectric sensor (32).

3. The low error gate opening sensor according to claim 1, characterized in that: The shading film (211) provided on the first grating ruler (21) is radially shaped, and the light emitted by the light emitting diode (321) passes through the light-transmitting areas on the second grating ruler (22) and the first grating ruler (21), and the light spots formed on the photosensitive element (322) are in the shape of arc strips.

4. The low error gate opening sensor according to claim 1, characterized in that: The shading film (211) provided on the first grating scale (21) is spiral-shaped and has an inclination angle that is 180° different from that of the shading film (211) on the second grating scale (22). Light emitted by the light-emitting diode (321) passes through the light-transmitting areas on the second grating scale (22) and the first grating scale (21), and a light spot formed on the photosensitive element (322) is in a rhombus shape.

5. The low error gate opening sensor according to claim 4, characterized in that: The photoelectric sensor (32) is arranged on a control circuit base (31); the control circuit base (31) and the photoelectric code disk (2) are arranged on the same plane of the rotary encoder (1) and are detachably connected.

6. The low error gate opening sensor according to claim 1, characterized in that: The edge of the upper surface of the first grating scale (21) is inclined downward, and the inclination angle is greater than 2° and less than 5°.

7. The low error gate opening sensor according to any one of claims 3-4, characterized in that: The first grating scale (21) and the second grating scale (22) are made of glass, and the light shielding film (211) is a metal wire embedded in the first grating scale (21) and the second grating scale (22).

8. The low error gate opening sensor according to claim 2, characterized in that: A light shield (323) is provided outside the light emitting diode (321) and the photosensitive element (322).

9. The low error gate opening sensor according to claim 8, characterized in that: Gaps are arranged at intervals on the light shield (323).

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