Automatic testing device for detecting induction capability of magnetic field induction element

Abstract

The utility model provides an automatic testing device for detecting the sensing capability of a magnetic field sensing element, which comprises a rotating cylinder for driving magnets to rotate to generate a gradient magnetic field with a constant peak value or generating a uniform parallel magnetic field with the same magnetic induction line direction and equal magnetic induction intensity everywhere through magnets arranged according to a specific direction, the to-be-detected magnetic field induction component outputs analog quantity signals in one-to-one correspondence through induction of the gradient magnetic field with the constant peak value or induction of the magnetic field with the constant direction and size, and whether the induction capacity of the to-be-detected component is within a qualified range or not is judged according to the signals. The chip magnetic field induction capability automatic detection device is simple in structure, rapid, reliable and automatic in test, and realizes stable, reliable and accurate automatic detection of the chip magnetic field induction capability through reasonable positioning design.

Description

Technical Field

[0001] This utility model relates to the technical field of magnetic induction testing devices, specifically to an automatic testing device for detecting the sensing capability of magnetic field sensing elements. Background Technology

[0002] A magnetic sensor is a device that converts changes in the magnetic properties of a sensitive element caused by external factors such as magnetic fields, current, stress, strain, temperature, and light into electrical signals, thereby detecting corresponding physical quantities. Magnetic sensors are widely used in modern industry and electronic products to measure physical parameters such as current, position, and direction by sensing the strength of magnetic fields.

[0003] Existing invention patent CN107229022B discloses a magnetic sensor comprising: a magnetoresistive element located on a first surface, which is a side of a substrate, and having a sensitivity axis along a first direction, which is one of the in-plane directions of the first surface; a positioning soft magnetic body disposed non-contactly relative to the magnetoresistive element; and a pair of soft magnetic bodies disposed side-by-side along the first direction and extending respectively in a direction away from the first surface, the pair of soft magnetic bodies being magnetically connected to the positioning soft magnetic body, wherein the magnetoresistive element comprises a first magnetoresistive element proximate to one of the pair of soft magnetic bodies and a first magnetoresistive element proximate to the other of the pair of soft magnetic bodies. The second magnetoresistive element, the positioning soft magnetic body having a first nearest portion defined relative to the first magnetoresistive element and a second nearest portion defined relative to the second magnetoresistive element, the first nearest portion and the second nearest portion being formed by a straight surface erected along the normal direction of the first surface, the straight surface being arranged opposite each other, the two soft magnetic bodies constituting the pair of soft magnetic bodies being formed as one unit via a connecting portion, the width of the positioning soft magnetic body being greater than the width of the connecting portion extending along the first direction, the first magnetoresistive element and the second magnetoresistive element being located below the positioning soft magnetic body.

[0004] As can be seen from existing related technologies, the current detection of the sensing capability of magnetic induction elements typically uses a complex and precise instrument that can generate a stable magnetic field. Such equipment is expensive to manufacture, has high maintenance costs, is slow to test, and requires professional technical personnel to operate. In actual production, its cost and efficiency are relatively poor. Utility Model Content

[0005] In view of the deficiencies in the prior art, this utility model provides an automatic testing device for detecting the sensing capability of magnetic field sensing elements.

[0006] According to the present invention, an automatic testing device for detecting the sensing capability of a magnetic field sensing element is provided, the device comprising: a fixing device, a magnetic field assembly, and a signal processing unit;

[0007] The fixing device fixes the component to be tested for testing purposes;

[0008] The magnetic field component generates a gradually changing magnetic field with a constant peak value or a parallel magnetic field with equal magnetic induction intensity everywhere; after the device under test senses the magnetic field, it generates a corresponding analog signal.

[0009] The signal processing unit is connected to the device under test to collect and analyze the generated signals to complete the test.

[0010] Preferably, the fixing device includes: a fixing base, a fixing plate support, a clamping mechanism, and a component detection assembly;

[0011] The clamping mechanism is installed on the fixed plate support base, and the component detection assembly and the component to be tested are fixed together on the fixed plate support base by the clamping mechanism;

[0012] The fixed disk support is mounted on the fixed base, and the fixed base is mounted on the magnetic field component.

[0013] Preferably, the clamping mechanism includes: an elastic compression plunger and an elbow clamp;

[0014] The elastic compression plunger is fixed to the elbow clamp by fasteners;

[0015] The clamping mechanism includes: multiple clamping mechanisms are configured.

[0016] Preferably, the component detection assembly includes: a magnetic sensing element fixing block and a component fixing disk to be detected;

[0017] The magnetic sensing element fixing block is set on the component under test. Multiple sets of components under test are fixed together on the component fixing plate, and are fixed as a whole by the clamping mechanism for testing.

[0018] Preferably, the mounting plate of the element to be tested is provided with an opening corresponding to the position of the magnetic sensing element mounting block, and the elastic compression plunger passes through the opening and presses against the magnetic sensing element mounting block.

[0019] Preferably, the magnetic field assembly includes: a first magnet, a magnet fixing base, and a rotary cylinder;

[0020] The first magnet is fixedly mounted on a magnet mounting base, which is then fixed to a rotary cylinder by fasteners. The rotary cylinder drives the magnet mounting base to rotate, generating a gradual magnetic field with a constant peak value.

[0021] Preferably, the magnet fixing base is provided with a slot adapted to the size of the first magnet;

[0022] The first magnet is pressed into the slot of the magnet fixing base by interference fit.

[0023] Preferably, the magnetic field assembly includes: a second magnet and a parallel magnetic field base;

[0024] Multiple second magnets are fixed on a parallel magnetic field base according to the set direction of the magnetic field lines or the trend of that direction, so that a stable parallel magnetic field with the same direction of magnetic field lines and equal magnetic induction intensity is generated here.

[0025] Preferably, the arrangement of the magnetic field lines of the magnets is as follows:

[0026] Multiple second magnets are evenly distributed around the center on a parallel magnetic field base, and their magnetization directions are symmetrical from left to right.

[0027] The second magnets, which are symmetrically positioned vertically, are magnetized downwards, while the second magnets, which are symmetrically positioned horizontally, are magnetized upwards. From top to bottom and then to the left half-circle, the magnetization direction forms a clockwise loop on the left half-circle. From top to bottom and then to the right half-circle, the magnetization direction forms a counterclockwise loop on the right half-circle. The magnets arranged in this way form a uniform parallel magnetic field with the N-pole pointing downwards in the central region of the loop.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. For general components under test, the factors that have the greatest impact on the test results are, firstly, their own sensing capability; secondly, the distance between the sensing element and the stable magnetic field; and thirdly, the stable and consistent test environment. In this invention, a magnetic field with a stable peak value and a gradual change is generated through a magnet and a rotating structure, which facilitates the generation of an electronic signal with a corresponding peak value by the magnetic field sensing element under test.

[0030] 2. This utility model generates a stable parallel magnetic field by arranging magnets in a set magnetic field line direction, which makes the magnetic field sensing element under test generate a stable corresponding electronic signal. Furthermore, since the magnetic induction intensity is equal everywhere in the magnetic field, the influence of distance variables on the test results can be avoided.

[0031] 3. This utility model uses the design concept of minimizing cumulative tolerance to directly position the magnetic field sensing element to be tested on the fixed disk support base of this test structure, thereby minimizing cumulative tolerance and avoiding the accumulation of processing errors of different magnetic sensing element fixing blocks and the fixing disk of the element to be tested, which would lead to inaccurate test results.

[0032] 4. This utility model uses an elastic compression plunger to ensure that the component under test can be stably and flexibly attached to the support surface, avoiding uncontrollable unexpected factors caused by external environmental vibrations, and improving test stability and repeatability.

[0033] 5. This utility model uses a rotary cylinder in conjunction with a sensor in the electronic control system to detect the position of the sensor, enabling one-button start-up and automatic data processing and result generation. This allows for rapid, reliable, consistent, and highly accurate automated testing of the sensing capability of magnetic field sensing elements in actual production, as well as quantification and recording of the test results.

[0034] Other beneficial effects of this utility model will be explained in detail through the introduction of specific technical features and technical solutions in the specific embodiments. Those skilled in the art should be able to understand the beneficial technical effects brought about by the technical features and technical solutions through the introduction of these technical features and technical solutions. Attached Figure Description

[0035] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0036] Figure 1 This is a complete schematic diagram of the device of this utility model;

[0037] Figure 2 This is a schematic diagram showing the disassembled state of the device of this utility model;

[0038] Figure 3 This is a cross-sectional view of the device of this utility model;

[0039] Figure 4 This is a schematic diagram of the magnetic field component in Example 2.

[0040] Reference numerals: 1. Rotary cylinder; 2. First magnet; 3. Magnetic element fixing block; 4. Component under test; 5. Elastic clamping plunger; 6. Elbow clamp; 7. Fixed base; 8. Component under test fixing plate; 9. Magnet fixing base; 10. Fixing plate support; 11. Parallel magnetic field base; 12. Second magnet; 13. Direction of magnet magnetic field lines. Detailed Implementation

[0041] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the present invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0042] This utility model provides an automatic testing device for detecting the sensing capability of a magnetic field sensing element. A rotary cylinder 1 drives a magnet to rotate, generating a gradually changing magnetic field with a constant peak value, or, through magnets arranged in a specific direction, generating a uniform parallel magnetic field with the same magnetic field lines and equal magnetic induction intensity everywhere. The magnetic field sensing element under test senses the gradually changing magnetic field with a constant peak value or a magnetic field with a constant direction and magnitude, outputting a corresponding analog signal. By analyzing and processing the signals, it is determined whether the sensing capability of the tested element 4 is within the acceptable range. (Refer to...) Figure 1 and Figure 2 As shown, it specifically includes the following:

[0043] Example 1:

[0044] This embodiment provides an automatic testing device for detecting the sensing capability of magnetic field sensing elements, comprising: a fixed base 7, a fixed disk support 10, a magnetic field assembly, a clamping mechanism, a component detection assembly, and a signal processing unit.

[0045] The clamping mechanism is mounted on the fixed plate support 10, which is in turn mounted on the fixed base 7. The clamping mechanism secures the component testing assembly and the component under test (DUT) 4 together on the fixed plate support 10. The fixed plate support 10 is entirely mounted on the fixed base 7, which is mounted on the magnetic field assembly. The signal processing unit connects to the DUT to acquire and analyze the generated signals, completing the test.

[0046] The clamping mechanism includes: an elastic pressing plunger 5 and an elbow clamp 6; the elastic pressing plunger 5 is fixed to the elbow clamp 6 by fasteners and is used to elastically press the component under test 4. Multiple clamping mechanisms are provided.

[0047] The component testing assembly includes: a magnetic element fixing block 3 and a component fixing disk 8.

[0048] The magnetic element fixing block 3 is fixedly mounted on the component under test 4. Multiple sets of components under test 4 are fixed together on the test transition part test component fixing plate 8, and are fixed as a whole by a clamping mechanism for testing. The test component fixing plate 8 is provided with an opening corresponding to the position of the magnetic element fixing block 3. The elastic pressing plunger 5 passes through the opening and presses against the magnetic element fixing block 3. The opening acts as a limit, which can realize the accurate positioning of the elastic pressing plunger 5 on the magnetic element fixing block 3 and prevent the pressing from deviating.

[0049] The magnetic field assembly includes: a first magnet 2, a magnet fixing base 9, and a rotary cylinder 1; the first magnet 2 is pressed into the slot of the magnet fixing base 9 by interference fit, and the magnet fixing base 9 is then fixed to the rotary cylinder 1 by fasteners. In use, the rotary cylinder 1 drives the magnet fixing base 9 to rotate, generating a gradual magnetic field with a constant peak value.

[0050] The specific application of the detection device in this embodiment includes using this device to detect the sensing capability of a magnetic field sensing element, i.e., an automatic testing method for detecting the sensing capability of a magnetic field sensing element, including:

[0051] Step S1: Place the component detection assembly onto the support surface of the fixed plate support 10, and use the elbow clamp 6 to press and fix the component detection assembly with the elastically pressing plunger 5.

[0052] Step S2: Start the rotary cylinder 1. The rotating part of the rotary cylinder 1 drives the magnet fixing base 9, which is equipped with the first magnet 2, to rotate, thereby generating a rotating magnetic field.

[0053] Step S3: The component under test 4 senses the changing magnetic field and generates a corresponding analog signal. The signal is collected by the signal processing unit, which automatically analyzes the collected signal, records the test results, realizes automatic processing and storage of the test results, and judges whether the results are qualified, thus completing the test.

[0054] Signal acquisition and analysis: Analog signals are converted into digital signals via digital-to-analog conversion (DAC). Software then collects these digital signals at a specific sampling frequency and generates a CSV file. Python code is used to read this file and perform numerical calculations.

[0055] The calculation method is: (maximum value - minimum value) / 2. Check if the result is within the set threshold. Simultaneously, determine if the magnet's installation orientation is correct. The judgment method is to observe whether the curve first decreases and then increases, and whether the output direction is 1 or 0. If the direction is 1, the test result is passed. Store the test results and test files in the factory production system for easy viewing and traceability of the test results later.

[0056] Example 2:

[0057] This embodiment provides an automatic testing device for detecting the sensing capability of magnetic field sensing elements, referring to... Figure 3 and Figure 4 As shown, it includes: a fixed base 7, a fixed disk support 10, a magnetic field assembly, a clamping mechanism, a component detection assembly, and a signal processing unit.

[0058] The clamping mechanism is mounted on the fixed plate support 10, which is mounted on the fixed base 7. The component detection assembly is placed on the fixed plate support 10. The component detection assembly is set on the support surface of the fixed plate support 10. The signal processing unit is connected to the magnetic field assembly to collect and analyze the generated signals to complete the test.

[0059] The clamping mechanism includes: an elastic pressing plunger 5 and an elbow clamp 6; the elastic pressing plunger 5 is fixed to the elbow clamp 6 by fasteners and is used to elastically press the component under test 4. Multiple clamping mechanisms are provided.

[0060] The component testing assembly includes: a magnetic element fixing block 3 and a component fixing disk 8;

[0061] The magnetic element fixing block 3 is fixedly mounted on the component under test 4. Multiple sets of components under test 4 are fixed together on the test transition part test component fixing plate 8 for testing. The test component fixing plate 8 is provided with an opening corresponding to the position of the magnetic element fixing block 3. The elastic pressing plunger 5 passes through the opening and presses against the magnetic element fixing block 3. The opening acts as a limit, which can realize the accurate positioning of the elastic pressing plunger 5 on the magnetic element fixing block 3 and prevent the pressing from deviating.

[0062] The magnetic field assembly includes a second magnet 12 and a parallel magnetic field base 11. Multiple second magnets 12 are fixed to the parallel magnetic field base 11 according to a predetermined magnetic field line direction 13 or the trend of that direction, so that a stable parallel magnetic field with the same magnetic field line direction and equal magnetic induction intensity is generated there.

[0063] Reference Figure 4 As shown, the magnetic direction 13 set in this embodiment is specifically as follows:

[0064] From a top-down view, defining counter-clockwise as positive and the direction from 12 o'clock to 6 o'clock as 0 degrees, the magnetization directions are arranged as follows: 0 degrees between 12 o'clock and 6 o'clock, 180 degrees between 3 o'clock and 9 o'clock, 90 degrees between 1:30 and 7:30, and 270 degrees between 4:30 and 10:30. In this example, using eight magnets evenly distributed around the center, their magnetization directions are symmetrical. The magnets at the top and bottom have their magnetization directions downwards, the bottom left magnet has its magnetization direction pointing to the left, the left magnet has its magnetization direction pointing upwards, and the top left magnet has its magnetization direction pointing to the right. From top to bottom and then to the left half-circle, the magnetization directions form a loop resembling a left half-circle. The right half is symmetrical to the left, with the bottom right magnet having its magnetization direction pointing to the right, the right magnet having its magnetization direction pointing upwards, and the top right magnet having its magnetization direction pointing to the left, forming a loop on the right half-circle. This arrangement of magnets creates a uniform, parallel magnetic field with the N pole pointing downwards in the central region of the loop.

[0065] The specific application of the detection device in this embodiment includes using this device to detect the sensing capability of a magnetic field sensing element, i.e., an automatic testing method for detecting the sensing capability of a magnetic field sensing element, including:

[0066] Step S1: Place the component detection assembly onto the support surface of the fixed plate support 10, and use the elbow clamp 6 to press and fix the component detection assembly with the elastically pressing plunger 5.

[0067] Step S2: Fix multiple second magnets 12 to the parallel magnetic field base 11 according to the set magnetic field line direction 13 or the trend of that direction, so that a stable parallel magnetic field with the same magnetic field line direction and equal magnetic induction intensity is generated here.

[0068] Step S3: The component under test 4 senses the changing magnetic field and generates a static and stable induction signal. The signal is collected by the signal processing unit. The signal processing unit automatically analyzes the collected data, records the test results, realizes automatic processing and storage of test results, and judges whether the results are qualified, thus completing the test.

[0069] The present invention will now be described in more detail.

[0070] This utility model provides an automatic testing device for detecting the sensing capability of magnetic field sensing elements. The device is mainly divided into three parts: the first part is an elastic clamping plunger 5 fixed to the elbow clamp 6 by a nut, which plays the role of elastically clamping the object to be tested. There is a set of elbow clamps 6 on each side, which are installed on the fixed plate support 10. Then the fixed plate support 10 is fixed to the fixed base 7 of the whole structure. The fixed plate support 10 is both the fixing block of the elbow clamp 6 and the placement platform of the component to be tested. Finally, the fixed base 7 is installed on the rotary cylinder 1. During use, the first part of the components is fixed.

[0071] The second part is that the first magnet 2 is pressed into the slot of the magnet fixing base 9 by interference fit, and the magnet fixing base 9 is then fixed to the rotary cylinder 1 by screws. In use, the magnet fixing base 9 can be rotated by the rotary cylinder 1.

[0072] The last part is the frequently replaced component testing assembly. The magnetic element fixing block 3 is fixed to the component under test 4 with glue. The two sets of components under test 4 on the left and right are fixed together on the test transition part component fixing plate 8. Together they form the component testing assembly, which is placed in this structure for testing.

[0073] During testing, the component detection assembly, which includes a magnetic induction element fixing block 3, the component under test 4, and the component fixing disk 8, is first placed on the support surface of the fixing disk support base 10. The elbow clamp 6 is used to press and fix the component detection assembly with the elastic compression plunger 5. The start button is pressed, and the rotary cylinder 1 is started. The rotating part of the rotary cylinder 1 drives the magnet fixing base 9, which is equipped with the first magnet 2, to rotate, generating a rotating magnetic field. The magnetic induction element fixing block 3 in the component under test senses the changing magnetic field and generates a one-to-one corresponding analog signal. The signal is collected by the software (i.e., the signal processing unit). The software automatically analyzes the collected data, records the test results, realizes the automatic processing and storage of the test results, and judges whether the results are qualified, thus completing the test.

[0074] It is worth noting that: Add 8 second magnets (12 or more) according to... Figure 4 The magnetic field lines of the magnet shown are fixed in the direction 13 or similar direction on the parallel magnetic field base 11, so that a stable parallel magnetic field with the same magnetic field line direction and equal magnetic induction intensity is generated here. This component is replaced in the structure composed of the first magnet 2, the magnet fixing base 9 and the rotating cylinder 1, so that the magnetic element fixing block 3 of the component to be tested generates a static and stable induction signal, which can also realize the testing of the component to be tested.

[0075] This utility model provides an automatic testing device for detecting the sensing capability of magnetic field sensing elements. It has a simple structure, and the testing is fast, reliable, and automated. Through reasonable positioning design, it can achieve stable, reliable, and accurate automatic detection of the magnetic field sensing capability of chips.

[0076] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0077] The specific embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the substantive content of this utility model. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. An automatic test apparatus for detecting the sensing capability of a magnetic field sensing element, characterized by comprising: The utility model relates to a kind of test device for electronic component, including: Fixing device, magnetic field assembly and signal processing unit; The fixing device fixes the component to be tested (4) for detection; The magnetic field assembly generates a constant peak gradual magnetic field or parallel magnetic field with equal magnetic induction intensity everywhere;After the component to be tested (4) is inducted to magnetic field, it generates a corresponding analog signal; The signal processing unit is connected to the component to be tested (4) to collect and analyze the generated signal, complete test.

2. The automatic test apparatus for detecting the sensing ability of a magnetic field sensing element according to claim 1, characterized by, The fixing device includes: fixed base (7), fixed disc support seat (10), clamping mechanism and component detection assembly; The clamping mechanism is installed on the fixed disc support seat (10), and the component detection assembly is fixed on the fixed disc support seat (10) together with the component to be tested (4) through the clamping mechanism; The fixed disc support seat (10) is integrally installed on the fixed base (7), and the fixed base (7) is installed on the magnetic field assembly.

3. The automatic test apparatus for magnetic field sensing element sensing capability detection according to claim 2, wherein, The clamping mechanism includes: elastic compression plunger (5) and elbow clamp (6); The elastic compression plunger (5) is fixed on the elbow clamp (6) by fastener.

4. The automatic test apparatus for detecting the sensing ability of a magnetic field sensing element according to claim 3, characterized by The clamping mechanism is provided with multiple.

5. The automatic test apparatus for detecting the sensing ability of a magnetic field sensing element according to claim 3, wherein The component detection assembly includes: magnetic sensing element fixing block (3) and detected component fixing disc (8); The magnetic sensing element fixing block (3) is arranged on the component to be tested (4), and multiple sets of components to be tested (4) are fixed on the detected component fixing disc (8) as a whole, which is fixed and detected by the clamping mechanism.

6. The automatic test apparatus for magnetic field induction element sensing capability detection according to claim 5, wherein The detected component fixing disc (8) is provided with an opening corresponding to the position of the magnetic sensing element fixing block (3), and the elastic compression plunger (5) presses on the magnetic sensing element fixing block (3) through the opening.

7. The automatic test apparatus for detecting the sensing ability of a magnetic field sensing element according to any one of claims 1 to 6, characterized by, The magnetic field assembly includes: first magnet (2), magnet fixed base (9) and rotary air cylinder (1); The first magnet (2) is fixedly arranged on the magnet fixed base (9), and the magnet fixed base (9) is fixed on the rotary air cylinder (1) by fastener, the rotary air cylinder (1) drives the magnet fixed base (9) to rotate, and generates a constant peak gradual magnetic field.

8. The automatic test apparatus for magnetic field induction element sensing capability detection according to claim 7, wherein The magnet fixed base (9) is provided with a slot opening corresponding in size to the first magnet (2); The first magnet (2) is assembled by interference, and is pressed into the slot opening of the magnet fixed base (9).

9. The automatic test apparatus for detecting the sensing ability of a magnetic field sensing element according to any one of claims 1 to 6, characterized by, The magnetic field assembly includes: second magnet (12) and parallel magnetic field base (11); Multiple second magnets (12) are fixed on the parallel magnetic field base (11) according to the set magnet magnetic induction line direction (13) or the trend of the direction, so that a stable parallel magnetic field with the same magnetic induction line direction and equal magnetic induction intensity is generated here.

10. The automatic test apparatus for magnetic field induction element sensing capability detection according to claim 9, wherein, The set magnet magnetic induction line direction (13) arrangement mode is: Multiple second magnets (12) are evenly distributed around the center on the parallel magnetic field base (11), and the magnetizing direction is left-right symmetrical. The second magnet (12) in the upper and lower symmetrical position is magnetized downward, and the second magnet (12) in the left and right symmetrical position is magnetized upward; from top to bottom to the left half circle, the magnetization direction forms a left half circle clockwise annular loop; from top to bottom to the right half circle, the magnetization direction forms a right half circle counterclockwise annular loop; the magnet arranged in this way forms an N-level uniform parallel magnetic field pointing downward in the annular central region.

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