Liquid sampling accessory with adjustable optical path and near infrared spectrum analysis device

Abstract

The utility model belongs to the field of testing by means of near-infrared light, and particularly relates to a liquid sampling accessory with an adjustable optical path and a near-infrared spectrum analysis device. In order to solve the technical problem that the accuracy of a detection result is poor due to the fact that bubbles exist in liquid, the utility model provides a liquid sampling accessory with an adjustable optical path. The liquid sampling accessory comprises a testing cavity and an adjusting cavity which form a communicating vessel of which two ends are communicated with the atmosphere, and further comprises a light reflecting cover which is used for forming a corresponding optical path with the light transmitting sheet and a lifting mechanism which is used for driving the light reflecting cover to move up and down so as to adjust the optical path; and the reflective cover is provided with a measuring station which is in sealing fit with the testing cavity and forms a corresponding optical path and a liquid adding station which is positioned outside the testing cavity. The utility model further provides a near infrared spectrum analysis device comprising the liquid sampling accessory. As the testing cavity and the adjusting cavity form the communicating vessel of which the two ends are communicated with the atmosphere, no bubble exists in the liquid when the liquid is added.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of testing by near infrared light, especially relates to a liquid sampling accessory with adjustable optical path and near infrared spectrum analysis device. BACKGROUND

[0002] Near infrared spectrum technology is a simple, efficient, low-cost green analysis technology, and near infrared spectrum technology can realize rapid, non-destructive detection and online analysis of a large number of samples, therefore, at present, near infrared spectrum technology is used to detect liquid samples.

[0003] The basic principle of using near infrared spectrum technology to detect liquid is Beer's law, that is, absorbance = absorption coefficient * optical path * concentration, therefore, the optical path is one of the parameters that must be controlled during detection.

[0004] When detecting, a near infrared spectrometer and corresponding detection accessories are needed, and the Chinese utility model patent with the authorization announcement number CN212364065U and the authorization announcement date of 2021.01.15 discloses a detection accessory of a miniature near infrared spectrometer, which is matched with the miniature infrared spectrometer.

[0005] The detection accessory includes a cylindrical container with a light-transmitting sheet at the bottom, the inner wall of the container is processed with internal threads, the carrying object is processed with external threads, and the lower end of the carrying object is connected with a reflection plate, the distance between the reflection plate and the bottom of the container can be adjusted by screwing the carrying object, so as to adjust the height of the liquid surface (that is, adjust the optical path). The cavity surrounded by the container, the reflection plate and the light-transmitting sheet is a test cavity for containing the liquid to be detected.

[0006] The bottom of the container is connected with a liquid inlet pipe and a liquid outlet pipe, when using, first, screw the carrying object to adjust the appropriate optical path; then, inject liquid from the liquid inlet pipe; then, the spectrometer detects the liquid; finally, the liquid is discharged through the liquid outlet pipe.

[0007] As can be understood by those skilled in the art, the light-transmitting sheet is arranged at the bottom of the container, instead of the whole container being made of light-transmitting material, because the material of the container must be light-proof material to prevent the spectrometer from receiving the reflected optical signal, and to prevent the external natural light from penetrating the container to the spectrometer, so as to avoid detection failure.

[0008] In the actual use of the above-mentioned detection accessory, when injecting liquid from the liquid inlet pipe (especially when injecting viscous liquid), because there is gas in the container, the liquid inlet pipe not only bears the function of liquid injection, but also bears the function of gas discharge, which leads to that the gas cannot be smoothly discharged from the container, and the gas is squeezed by the liquid, so that there are bubbles in the liquid, which affects the accuracy of the detection result.

[0009] At the same time, the threads on the inner wall of the container also affect the light propagation path, affecting the accuracy of the detection result. Utility model content

[0010] The utility model discloses a liquid sampling accessory with adjustable optical path, which aims to solve the technical problem of poor accuracy of detection results due to the existence of bubbles in the liquid when using existing detection accessories.

[0011] The utility model discloses a near-infrared spectrum analysis device, which aims to solve the technical problem of poor accuracy of detection results due to the existence of bubbles in the liquid when using existing near-infrared spectrum analysis devices.

[0012] To achieve the above-mentioned purpose, the technical scheme of the liquid sampling accessory with adjustable optical path provided by the utility model is as follows:

[0013] A liquid sampling accessory with adjustable optical path, comprising a test cavity and an adjusting cavity constituting a communicating vessel with both ends communicating with the atmosphere, the bottom of the test cavity is provided with a light transmission sheet, the liquid sampling accessory with adjustable optical path further comprises a reflective cover for forming a corresponding optical path with the light transmission sheet and a lifting mechanism for driving the reflective cover to move up and down to adjust the optical path.

[0014] The reflective cover has a measurement station for sealing cooperation with the test cavity and forming a corresponding optical path, and a liquid adding station for being located outside the test cavity to communicate the test cavity with the atmosphere when adding liquid.

[0015] Further, the adjusting cavity is provided with an indication mark corresponding to the corresponding optical path, to ensure that the height of the added liquid is not less than the corresponding optical path when the reflective cover is in the liquid adding station.

[0016] Further, the indication mark is an indication scale provided on the cavity wall of the adjusting cavity.

[0017] Further, the cavity wall of the adjusting cavity is provided with an overflow mark for indicating the maximum height of liquid addition when adding liquid, to avoid liquid overflow from the adjusting cavity when the reflective cover is in the measurement station.

[0018] Further, the adjusting cavity is provided with a monitoring device for monitoring the liquid level in the adjusting cavity, to ensure that the height of the added liquid is not less than the corresponding optical path when the reflective cover is in the liquid adding station.

[0019] Further, the cavity wall of the test cavity is a mirror surface reflection cavity wall.

[0020] Further, the adjusting cavity has a liquid adding port for adding liquid.

[0021] Further, the reflective cover comprises a cover body and a mirror surface reflection layer on the lower surface of the cover body.

[0022] Further, the communicating device comprises a partition plate for separating one chamber into a testing chamber and an adjusting chamber, and the partition plate is provided with a communicating hole for communicating the testing chamber and the adjusting chamber.

[0023] The liquid sampling accessory with adjustable optical path has the following beneficial effects: the liquid sampling accessory with adjustable optical path is an exploratory invention.

[0024] In the utility model, according to the communicating device principle, when the reflecting cover is in the liquid adding station, since the testing chamber and the adjusting chamber constitute the communicating device with both ends communicated with the atmosphere, the liquid adding station does not exist the condition that gas is extruded by liquid, and the liquid does not exist the bubble, and the detection result accuracy is improved.

[0025] After liquid adding is completed, the reflecting cover is switched to the measurement station by the lifting mechanism, at this time, the reflecting cover is just in contact with the liquid level (corresponding to the added liquid height equal to the corresponding optical path), or the reflecting cover presses part of the liquid into the adjusting chamber (corresponding to the added liquid height higher than the corresponding optical path).

[0026] When the reflecting cover is in the measurement station, testing can be carried out by using the spectrometer, the near-infrared light emitted by the spectrometer reaches the liquid through the light transmission sheet, and is reflected by the reflecting cover and then reaches the spectrometer again through the light transmission sheet.

[0027] To achieve the above-mentioned purpose, the technical scheme of the near-infrared spectrum analysis device provided by the utility model is as follows:

[0028] A near-infrared spectrum analysis device, comprising a spectrometer and a liquid sampling accessory, the liquid sampling accessory comprising a testing chamber and an adjusting chamber constituting a communicating device with both ends communicated with the atmosphere, the bottom of the testing chamber being provided with a light transmission sheet, the liquid sampling accessory further comprising a reflecting cover for forming a corresponding optical path with the light transmission sheet and a lifting mechanism for driving the reflecting cover to move up and down to adjust the optical path.

[0029] The reflecting cover has a measurement station for sealingly cooperating with the testing chamber and forming a corresponding optical path, and a liquid adding station for being located outside the testing chamber to communicate the testing chamber with the atmosphere when liquid is added.

[0030] Further, the adjusting chamber is provided with an indication mark corresponding to the corresponding optical path, so as to ensure that the added liquid height is not less than the corresponding optical path when the reflecting cover is in the liquid adding station.

[0031] Further, the indication mark is an indication scale provided on the chamber wall of the adjusting chamber.

[0032] Further, an overflow mark is arranged on the cavity wall of the adjusting cavity for indicating the highest liquid level during liquid adding, so as to avoid liquid overflow from the adjusting cavity when the light-reflecting cover is in the measuring position.

[0033] Further, the adjusting cavity is provided with a monitoring device for monitoring the liquid level in the adjusting cavity, so as to ensure that the added liquid level is not less than the corresponding optical path when the light-reflecting cover is in the liquid adding position.

[0034] Further, the cavity wall of the testing cavity is a mirror surface reflecting cavity wall.

[0035] Further, the adjusting cavity is provided with a liquid adding port for liquid adding.

[0036] Further, the light-reflecting cover comprises a cover body and a mirror surface reflecting layer arranged on the lower surface of the cover body.

[0037] Further, the communicating device comprises a partition plate for separating one chamber into the testing cavity and the adjusting cavity, and the partition plate is provided with a communicating hole for communicating the testing cavity and the adjusting cavity.

[0038] The near-infrared spectrum analysis device has the following beneficial effects: the near-infrared spectrum analysis device is an improved invention.

[0039] In the near-infrared spectrum analysis device, according to the communicating device principle, when the light-reflecting cover is in the liquid adding position, the testing cavity and the adjusting cavity constitute a communicating device with both ends communicating with the atmosphere, so that there is no gas being squeezed by liquid during liquid adding, and no bubbles exist in the liquid, which is beneficial to improving the accuracy of the detection result.

[0040] After liquid adding is completed, the light-reflecting cover is switched to the measuring position by the lifting mechanism, at this time, the light-reflecting cover is in contact with the liquid surface (corresponding to the added liquid level being equal to the corresponding optical path), or the light-reflecting cover presses part of the liquid into the adjusting cavity (corresponding to the added liquid level being higher than the corresponding optical path).

[0041] When the light-reflecting cover is in the measuring position, the testing can be performed by using the spectrometer, the near-infrared light emitted by the spectrometer passes through the light transmission sheet to the liquid, and then passes through the light transmission sheet again to the spectrometer under the reflection of the light-reflecting cover. BRIEF DESCRIPTION OF DRAWINGS

[0042] Figure 1 FIG. 2 is a structural schematic view of the adjustable optical path liquid sampling accessory of the present application when the light-reflecting cover is in the liquid adding position;

[0043] Figure 2This is a frontal view of the adjustable optical path liquid sampling accessory of this utility model when the reflective cover is in the liquid filling position;

[0044] Figure 3 This is a schematic diagram of the adjustable optical path liquid sampling accessory of this utility model when the reflective cover is in the measurement position;

[0045] Figure 4 This is a frontal view of the adjustable optical path liquid sampling accessory of this utility model when the reflective cover is in the measuring position;

[0046] Figure 5 for Figure 1 Schematic diagram of the cross section of the communicating vessel;

[0047] Figure 6 for Figure 1 A schematic diagram of the structure of a communicating vessel.

[0048] Explanation of reference numerals in the attached figures:

[0049] 1. Lifting mechanism; 2. Connecting arm; 3. Reflector cover; 4. Communicating vessel; 41. Test chamber; 42. Adjustment chamber; 43. Light-transmitting sheet; 44. Communicating hole; 45. Indicating scale; 46. Overflow mark; 5. Support base. Detailed Implementation

[0050] To address the problems in the background technology, the core inventive concept of this utility model is: to set up an adjustment cavity connected to the test cavity using the principle of communicating vessels, and to reflect the liquid level in the test cavity by adjusting the liquid level in the adjustment cavity, thereby avoiding the presence of air bubbles in the liquid and improving the accuracy of the test results.

[0051] The present invention will be further described in detail below with reference to the embodiments.

[0052] Specific embodiments of the adjustable optical path liquid sampling accessory provided by this utility model:

[0053] Reference Figures 1-6 As shown, as a basic specific implementation, the adjustable optical path liquid sampling accessory includes a test chamber 41 and an adjustment chamber 42 that constitute a communicating vessel 4 with both ends connected to the atmosphere. The bottom of the test chamber 41 is provided with a light-transmitting sheet 43. The adjustable optical path liquid sampling accessory also includes a reflective cover 3 for forming a corresponding optical path with the light-transmitting sheet 43 and a lifting mechanism 1 for driving the reflective cover 3 to move up and down to adjust the optical path.

[0054] The reflective cover 3 has a measurement station for sealing and fitting with the test chamber 41 to form a corresponding optical path and a liquid filling station located outside the test chamber 41 to allow the test chamber 41 to communicate with the atmosphere.

[0055] exist Figures 1-6In the preferred embodiment shown, the regulating cavity 42 is equipped with an indicator mark corresponding to the corresponding optical path or a monitoring device for monitoring the liquid level in the regulating cavity 42, so as to ensure that the liquid level added when the reflector cover 3 is in the liquid filling position is not less than the corresponding optical path.

[0056] The above scheme includes concepts such as communicating vessel 4, light-transmitting sheet 43, reflective cover 3, lifting mechanism 1, indicator mark and detection device, which are introduced below.

[0057] The following describes how the 4-connecting-unit system is constructed.

[0058] like Figures 1-6 As shown, the communicating vessel 4 can be composed of a single container made of a non-transparent material, with a partition dividing one chamber of the single container into a test chamber 41 and an adjustment chamber 42, and the partition having a connecting hole 44 connecting the test chamber 41 and the adjustment chamber 42; or, the communicating vessel 4 can be composed of two containers connected by a connecting pipe, with the container constituting the test chamber 41 being made of a non-transparent material, and the container constituting the adjustment chamber 42 being made of either a transparent or non-transparent material. Similarly, the connecting pipe can be made of either a transparent or non-transparent material.

[0059] The following is a description of the light-transmitting sheet 43.

[0060] The light-transmitting plate 43 is used to allow near-infrared light to pass through. Specifically, the light-transmitting plate 43 can be connected to the communicating vessel 4 by means of embedding or other methods. Since various existing liquid sampling accessories include the light-transmitting plate 43, and the light-transmitting plate 43 in this utility model does not have a special design, it will not be described in detail.

[0061] The following describes the liquid addition method without setting indicator marks and monitoring devices.

[0062] After the communicating vessel 4 is made, since the shape of the communicating vessel 4 is fixed, the corresponding liquid volume is also fixed when the liquid level is constant. The staff can use a measuring cup to measure out a liquid volume that is larger than the required volume, then pour all the liquid into the communicating vessel 4, and finally use a reflector to press the excess liquid into the regulating cavity 42.

[0063] Of course, there is usually a maximum optical path during testing. If the liquid volume corresponding to the maximum optical path is defined as the maximum liquid volume, then the staff can measure the liquid volume that is greater than the maximum liquid volume each time.

[0064] The following is an introduction to the indicator markers and monitoring devices.

[0065] Those skilled in the art will understand that the indicator mark can be an indicator scale of 45, an indicator protrusion, a colored indicator line, etc., as long as the operator can determine whether the liquid level has reached the indicator mark; the monitoring device can be any device that can monitor the liquid level height, such as a liquid level sensor or a liquid level gauge, so that the operator can determine whether the liquid level height is greater than the corresponding optical path, which will not be elaborated here.

[0066] Preferably, the indicator mark is an indicator scale 45 set on the cavity wall of the regulating cavity 42, which has a simple structure. At the same time, regardless of whether the part constituting the regulating cavity 42 is made of transparent or non-transparent material, the operator can determine whether the liquid level has exceeded the indicator scale 45.

[0067] Of course, when the part constituting the adjustment cavity 42 is made of transparent material, the indicator scale 45 can also be set on the outer surface of the corresponding part. In this case, the part constituting the adjustment cavity 42 is equivalent to a measuring cup.

[0068] When setting up indicator markers or monitoring devices, it is possible to effectively save liquid usage and reduce costs.

[0069] The following is a description of the lifting mechanism 1.

[0070] exist Figures 1-6 In the specific embodiment shown, the lifting mechanism 1 is an externally purchased electric slide table from Misumi, specifically model C-ZMBS420-L. The electric slide table is connected to the reflector cover 3 via a connecting arm 2. Specifically, the reflector cover 3 can be integrally formed with the connecting arm 2 or fixed by means of bonding or bolting. The connecting arm 2 is connected to the electric slide table by bolts.

[0071] In other specific embodiments, the lifting mechanism 1 can also be a screw jack, linear motor, or other direct-drive mechanism, and the output end of the direct-drive mechanism can be directly connected to the connecting arm 2 by bolts; alternatively, the output end of the direct-drive mechanism can be directly and fixedly connected to the reflector cover 3 by bolts or adhesive. It should be noted that the threaded hole on the reflector cover 3 must be machined on the upper surface of the reflector cover 3, and the threaded hole cannot be a through hole.

[0072] The following is a detailed introduction to reflective cover 3.

[0073] Preferably, as a specific embodiment, the reflective cover 3 includes a cover body and a mirror reflective layer located on the lower surface of the cover body. The mirror reflective layer can be applied to the cover body by means of coating or other methods, thereby saving mirror reflective material and allowing for more freedom in the selection of materials for the cover body, which is beneficial for reducing costs.

[0074] Of course, in other specific embodiments, the reflective cover 3 can also be made entirely of a mirror-reflective material.

[0075] The beneficial effects of this utility model will be described below.

[0076] Figures 1-6 The main difference between the specific implementation shown and the prior art is that the prior art only has a test chamber 41. Since near-infrared light needs to propagate in the test chamber 41 and the container is made of non-transparent material, it is impossible to set an indicator mark for indicating the liquid level or a monitoring device (such as a liquid level sensor) for monitoring the liquid level in the test chamber 41. Therefore, the optical path must be determined first, and then liquid is added through the liquid inlet pipe.

[0077] This utility model also includes an adjustment cavity 42. According to the principle of communicating vessels, when the reflective cover 3 is in the liquid filling position, since the test cavity 41 and the adjustment cavity 42 constitute a communicating vessel 4 with both ends connected to the atmosphere, the liquid level in the test cavity 41 and the adjustment cavity 42 is the same. Since the adjustment cavity 42 does not need to transmit near-infrared light, the adjustment cavity 42 can be equipped with an indicator mark for indicating the liquid level or a monitoring device (such as a liquid level sensor) for monitoring the liquid level, so as to ensure that the liquid level added is not less than the corresponding optical path when adding liquid.

[0078] During liquid addition, preferably, the regulating chamber 42 has a liquid addition port for adding liquid. Figures 1-6 The middle part is the opening for the reflector cover 3 to enter and exit. Liquid is added directly into the test chamber 41 through the liquid filling port. The liquid level in the regulating chamber 42 rises steadily, making it easy to observe the changes in the liquid in the regulating chamber 42. At the same time, the cross-section of the regulating chamber 42 can be set to be small to reduce the volume of liquid in the regulating chamber 42 and save liquid. Of course, liquid can also be added from the regulating chamber 42. In this case, the regulating chamber 42 must have a sufficiently large cross-sectional area to facilitate liquid addition.

[0079] Meanwhile, since both the test chamber 41 and the adjustment chamber 42 are connected to the atmosphere during liquid addition, there is no situation where gas is squeezed by liquid, and there are no air bubbles in the liquid, which helps to improve the accuracy of the test results.

[0080] It should be noted that when the regulating chamber 42 is not equipped with an indicator mark and a monitoring device, a pre-measured amount of liquid needs to be added.

[0081] After the liquid is added, the lifting mechanism 1 drives the reflector 3 to switch to the measurement position. At this time, the reflector 3 is in contact with the liquid surface (the height of the added liquid is equal to the corresponding optical path), or the reflector 3 presses a part of the liquid into the adjustment chamber 42 (the height of the added liquid is higher than the corresponding optical path).

[0082] When the reflective cover 3 is in the measurement position, the test can be performed using a spectrometer. The near-infrared light emitted by the spectrometer reaches the liquid through the light-transmitting sheet 43, and returns to the spectrometer again through the light-transmitting sheet 43 under the reflection of the reflective cover 3.

[0083] Need special explanation, based on the difference in structure, the liquid sampling assembly with adjustable optical path in the utility model has a unique use method, specific statement as follows.

[0084] When the results of the same liquid under multiple different optical paths are to be detected, the control variable method needs to be used, and the variable is the optical path. During detection, the liquid with a height not lower than the highest test optical path can be added to the test cavity 41 first, then the reflector cover 3 is moved up and down to switch to the position corresponding to the different optical path and test. When the reflector cover 3 moves downward, the excess liquid in the test cavity 41 is pressed into the adjusting cavity 42, and when the reflector cover 3 moves upward, the liquid in the adjusting cavity 42 is supplemented into the test cavity 41.

[0085] Among them, preferably, the reflector cover 3 is always moved downward, at this time, the reflector cover 3 does not reciprocate up and down, and the test efficiency is the highest.

[0086] In the utility model, in order to further improve the accuracy of the detection result, as a preferred specific embodiment, the cavity wall of the test cavity 41 is a mirror surface reflection cavity wall, which can be set on the container body used to constitute the test cavity 41 by coating, or the corresponding container is made of a mirror surface reflection material.

[0087] In other specific embodiments, referring to the Chinese utility model patent shown in the authorization announcement No. CN212364065U, the container body used to constitute the test cavity 41 can also be provided with an internal thread, and the reflector cover 3 is provided with an external thread. The lifting mechanism 1 drives the reflector cover 3 to rotate and lift at the same time.

[0088] Compared with the technical solution that the cavity wall of the test cavity 41 has a thread, when the cavity wall of the test cavity 41 is a mirror surface (i.e. a mirror surface reflection cavity wall), it is beneficial to reduce the interference of the thread on the light propagation and improve the accuracy of the detection result.

[0089] As a preferred specific embodiment, referring to the Figure 6 As shown, the cavity wall of the adjusting cavity 42 is provided with an overflow mark 46 for indicating the highest liquid adding height during liquid adding, so as to avoid liquid overflow from the adjusting cavity 42 when the reflector cover 3 is in the measuring station, and avoid liquid flowing everywhere, which is simple in structure.

[0090] In other specific embodiments, an overflow pipe can also be arranged at the adjusting cavity 42, and a waste liquid cup is placed at the outlet of the overflow pipe. When the liquid in the adjusting cavity 42 overflows, the liquid enters the waste liquid cup through the overflow pipe, thereby avoiding the liquid flowing everywhere.

[0091] In Figures 1-6In the specific embodiment shown, the support base 5 is further provided with a placing groove, and the groove bottom wall of the placing groove is provided with an avoidance hole for avoiding near-infrared light, and the cross-sectional area of the avoidance hole is smaller than the area of the groove bottom wall. During detection, the communicating vessel 4 is placed in the placing groove, the groove bottom wall of the placing groove is used to support the communicating vessel 4, and the groove side wall of the placing groove is used to limit the horizontal position of the communicating vessel 4, and the light emitted by the spectrometer can pass through the avoidance hole to reach the light-transmitting sheet 43.

[0092] At this time, after detecting one kind of liquid, the communicating vessel 4 can be taken down and the communicating vessel 4 is cleaned.

[0093] Of course, in other specific embodiments, as shown in the Chinese utility model patent with the authorization announcement number CN212364065U, a liquid discharge pipe directly communicating with the adjusting cavity 42 can also be arranged on the communicating vessel 4, and the liquid discharge pipe is configured with a corresponding plug, after detecting one kind of liquid, the plug is opened and the communicating vessel 4 is cleaned, and the waste liquid is discharged through the liquid discharge pipe.

[0094] The specific embodiment of the near-infrared spectrum analysis device provided by the utility model:

[0095] Referring to Figures 1-6 As shown, the near-infrared spectrum analysis device comprises a spectrometer and a liquid sampling accessory, and the liquid sampling accessory is any one of the specific embodiments of the adjustable optical path liquid sampling accessory of the utility model, which will not be repeated here.

[0096] Finally, it should be pointed out that the above is only the preferred embodiment of the utility model, and is not used to limit the utility model, although the utility model has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments without paying creative labor, or make equivalent replacement to part of the technical features, or organically combine different specific embodiments, so as to combine the specific embodiments given in the drawings, of course, those skilled in the art can also combine the specific embodiments not given in the drawings of the remaining specification. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the utility model should be included in the protection scope of the utility model.

Claims

1. A variable optical path liquid sampling accessory characterized by, The liquid sampling assembly comprises a test chamber and an adjusting chamber which constitute communicating vessels with both ends communicating with the atmosphere, and a light-transmitting sheet is arranged at the bottom of the test chamber; the liquid sampling assembly further comprises a light-reflecting cover for forming a corresponding optical path with the light-transmitting sheet and a lifting mechanism for driving the light-reflecting cover to move up and down to adjust the optical path; The light-reflecting cover has a measuring station for sealingly cooperating with the test chamber to form the corresponding optical path and a liquid-adding station for being located outside the test chamber to communicate the test chamber with the atmosphere when liquid is added.

2. The variable pathlength liquid sampling accessory of claim 1, wherein, The adjusting chamber is provided with an indicating mark corresponding to the corresponding optical path, so as to ensure that the height of the added liquid is not less than the corresponding optical path when the light-reflecting cover is at the liquid-adding station.

3. The variable pathlength liquid sampling accessory of claim 2, wherein, The indicating mark is an indicating scale arranged on the chamber wall of the adjusting chamber.

4. A variable pathlength liquid sampling accessory as claimed in any one of claims 1 to 3, wherein, An overflow mark for indicating the maximum height of the added liquid when liquid is added is arranged on the chamber wall of the adjusting chamber, so as to avoid liquid overflow from the adjusting chamber when the light-reflecting cover is at the measuring station.

5. The variable pathlength liquid sampling accessory of claim 1, wherein, The adjusting chamber is provided with a monitoring device for monitoring the height of the liquid in the adjusting chamber, so as to ensure that the height of the added liquid is not less than the corresponding optical path when the light-reflecting cover is at the liquid-adding station.

6. A variable pathlength liquid sampling accessory as claimed in any one of claims 1 to 3 and 5, wherein, The chamber walls of the test chamber are mirror surface reflecting chamber walls.

7. A variable pathlength liquid sampling accessory as claimed in any one of claims 1 to 3 and 5, wherein, The adjusting chamber has a liquid-adding port for adding liquid.

8. The variable pathlength liquid sampling accessory of any of claims 1-3 and 5, wherein, The light-reflecting cover comprises a cover body and a mirror surface reflecting layer arranged on the lower surface of the cover body.

9. The variable pathlength liquid sampling accessory of any of claims 1-3 and 5, wherein, The communicating vessel comprises a partition plate for separating one chamber into the test chamber and the adjusting chamber, and the partition plate is provided with a communicating hole for communicating the test chamber and the adjusting chamber.

10. A near infrared spectroscopic analysis apparatus comprising a spectrometer and a liquid sampling accessory, characterized in that, The liquid sampling assembly is the liquid sampling assembly with adjustable optical path as claimed in any one of claims 1 to 9.

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