Accurate measurement method for density of irregular object

Abstract

The invention relates to the field of mechanical measurement, in particular to a method for accurately measuring the density of an irregular object, which can also be used for measuring the volume of the irregular object. From the perspective of operation and calculation processes, the measurement method has low requirements on measurement objects, and is simple and convenient to operate and simple in calculation in the measurement process. From the aspect of measurement results, the reading precision of the measurement results is high; based on the cosecant relation in the triangle, the transparent spiral ruler is innovatively used to subdivide the length of a certain unit in the measurement process; the winding spiral angle of the transparent spiral ruler is as small as possible, and the smaller the spiral angle is, the higher the reading precision is. The device is reasonable in design, adopts a measurement mode of winding the transparent spiral ruler, performs length subdivision on liquid level height change by utilizing a trigonometric relationship, realizes accurate, efficient, multi-field and multifunctional measurement on the density of irregular objects, and has a very good practical application value.

Description

Technical Field

[0001] The invention relates to the field of mechanical metrology, in particular to a method for accurately measuring the density of an irregular object, and can also be used for measuring the volume of the irregular object. Background Art

[0002] Density is a basic property of matter, and its measurement method is widely used in scientific experiments, industrial production, musical instrument making and other fields. For example, in scientific experiments, many physical and chemical studies rely on the precise value of the density of materials; in industrial production, factories need to judge the quality of raw materials based on the density; in musical instrument making, manufacturers can choose materials of different densities according to demand to adjust the sound quality of the instrument. The importance of material density measurement is far higher than volume measurement. Importantly, in the above fields, the density measurement of irregular objects still has problems that need to be solved, such as high cost, difficult operation, and low precision.

[0003] When measuring the density of irregular objects, the measurer usually develops different measurement plans, adopts different measurement methods, and selects different measurement tools according to the characteristics of the measured object. There are two common methods for measuring the density of irregular objects, one is to use liquid as a medium, and the other is to use solid as a medium. Specifically, the liquid medium measurement method is based on the Archimedes principle and can be divided into five types: drainage method, counterweight / pressing method, overflow method, and buoyancy method; the second is to use solid as a medium for measurement. This measurement method is mostly used to measure the density of solids that are easily soluble in water, and small particles such as fine sand are often used for measurement. However, the above two methods can only determine the approximate data of the density of irregular objects, and neither can accurately measure their density.

[0004] There are 6 patent applications for density measurement of existing general objects, namely: CN201410146255.9 "Rock density measurement method and rock density measurement device", CN201480072718.X "Density measurement equipment", CN201580061229.9 "Density measurement system and method", CN201610591000.2 "A density measurement method based on the magnetic Archimedean principle", CN202010779626.2 "A physical teaching experiment display system"; CN202111677185.6 "A double weighing volume and density measurement method". There is 1 patent application for measuring the density of irregular objects, namely CN201420624644.3 "Device for indirect determination of the density of irregular objects". Comprehensively analyzing the specific contents of the above patents, it is not difficult to find that the above patents related to object density measurement have problems such as high cost, inconvenient operation or many interference factors, and the measurement of the density of irregular objects mostly focuses on the exploration of measurement methods, and rarely pays attention to the improvement of measurement accuracy.

[0005] In summary, the density measurement of irregular objects is of great significance in basic scientific research or practical applications, but the previous methods are complicated in operation and cannot guarantee the accuracy of the experimental results, so it is difficult to accurately measure the density of irregular objects. It is urgent to invent a more efficient and accurate method for measuring the density of irregular objects. Summary of the invention

[0006] The purpose of the present invention is to make up for the shortcomings of the existing detection technology and provide a method for accurately measuring the density of irregular objects. The method of the present invention can accurately measure the density of irregular objects while reducing interference factors.

[0007] The present invention is achieved by adopting the following technical solutions:

[0008] The invention discloses an accurate density measurement method for irregular objects, which mainly includes four parts: mass measurement, waterproof treatment, volume calculation and density derivation of the irregular objects.

[0009] Among them, mass measurement is to place the irregular object to be measured on the mass measuring instrument, measure and record its mass.

[0010] To ensure the accuracy of the measurement results, waterproofing is to waterproof the irregular objects that are not waterproof. Specifically, rosin powder and alcohol are mixed in a certain proportion and stirred until viscous, and then evenly brushed on the surface of the irregular object to be measured and dried in the shade.

[0011] Volume calculation includes two parts: data collection and data processing. First, collect the required data: First, stick the vertical scale and transparent spiral ruler on the outer wall of the container respectively. In order to improve the accuracy, the spiral angle between the transparent spiral ruler and the bottom of the container should be as small as possible when sticking the transparent spiral ruler. Then observe and record the vertical height of the container and the length of the transparent spiral ruler; secondly, inject a certain amount of liquid into the container, observe and record the length of the transparent spiral ruler at the lowest point of the concave liquid surface; thirdly, if the density of the irregular object to be measured is less than that of water, a solid with a density greater than that of water is required to make the object to be measured sink in the water. Therefore, a solid with a density greater than that of water is first placed in the container. After the liquid surface is still, record the length of the transparent spiral ruler at the lowest point of the concave liquid surface after the change; finally, empty the container and dry it, re-inject the same volume of liquid as before, fix the irregular object to be measured and the solid with a density greater than that of water together and put them into the container. After the liquid surface is balanced, record the length of the transparent spiral ruler at the lowest point of the concave liquid surface after the change. Second, the collected data is calculated and processed: first, the vertical height and volume of the quantitative liquid in the container are observed, and then the radius of the container is calculated; second, the ratio constant C of the spiral ruler length and vertical height is calculated; finally, the volume of the irregular object must be measured before measuring its density.

[0012] Density derivation, calculate the density of irregular objects through formula.

[0013] The specific accurate measurement method is as follows:

[0014] Step 1. Measure

[0015] (1) Place the object b on the mass measuring instrument and measure and record its mass m b ;

[0016] (2) a non-retractable transparent scale c is attached to the outer wall of a container a having a volume scale in a spiral manner with a winding angle of θ; the angle θ between the transparent spiral scale and the bottom surface of the container is such that the smaller the spiral angle, the higher the reading accuracy;

[0017] (3) Observe and record the vertical height h from the low scale to the high scale of container a. a and the length of the transparent spiral ruler l a ;

[0018] (4) Pour a certain amount of liquid into container a, observe and record the lowest mark of the transparent spiral ruler at the concave liquid surface as l 1 ;

[0019] (5) When the density of the irregular object b is greater than that of the liquid, place the irregular object b into container a. After the liquid is still, record the lowest mark of the spiral ruler at the concave liquid surface after the change as l. 4 ;

[0020] (6) When the density of the irregular object b is less than that of the liquid, a solid d with a density greater than that of the liquid is required to make the irregular object sink in the liquid. Therefore, solid d is measured first. Solid d is placed in container a. After the liquid is still, the lowest mark of the spiral ruler at the concave liquid surface after the change is recorded as l. 2 ;

[0021] After container a is emptied and dried, refill it with the same volume of liquid as before;

[0022] Fix the irregular object b and solid d together and put them into container a. After the liquid is still, record the lowest point of the concave liquid surface after the change as l. 3 .

[0023] Step 2: Calculation

[0024] Assume that the radius of the experimental container is r a , it is known that the vertical height from the low scale to the high scale in container a is h a , the volume is V a ;

[0025] Volume Va = πr a 2 ×h a

[0026] Then the radius of container a is

[0027] Since the length of the transparent spiral ruler from the low scale to the high scale of container a is l a and vertical height h a The ratio is a constant, denoted by C;

[0028]

[0029] For the irregular object b whose density is greater than that of the liquid, the vertical height change of the irregular object b after it sinks into the liquid is Δh, and the corresponding length of the spiral ruler is Δl, and Δl=l 4 -l 1 ;

[0030] For the irregular object b whose density is less than that of the liquid, after being placed in the container a, the change in vertical height of the irregular object b and the solid d after sinking into the liquid is Δh, and the corresponding change in the length of the spiral ruler is Δl, and Δl = l 3 -l 2 ;

[0031]

[0032] V b =πr 2 ×Δh

[0033]

[0034] Further preferably, the low-order scale is a minimum integer scale, and the high-order scale is a maximum range scale.

[0035] Further preferably, the angle θ is in the range of 5° to 15°.

[0036] The principle of this measurement method is:

[0037] First, under the condition that the diameter of the cylinder remains unchanged, the volume change caused by putting the measured object into the measuring cylinder is simplified to the expression of the height change of the volume inside the measuring cylinder, V = πr 2 Δh.

[0038] Second, the bottom area (radius) of the cylinder remains unchanged, and the sensitivity relationship between the change in liquid level and volume change is:

[0039] Third, the sensitivity relationship between the change in the bottom area (radius) of the cylinder, the change in the liquid level and the change in radius: The smaller the radius of the measuring cylinder, the more sensitive the liquid level is to volume changes.

[0040] Fourth, the unit liquid level change height (D) is used as the lead of the spiral line around the measuring cylinder to improve the reading sensitivity from the indication value, and the reading sensitivity is increased by cscθ times, 1 螺旋 =Dcscθ, the helix angle is θ.

[0041] The technical solution provided by the present invention has the following advantages compared with the prior art:

[0042] (1) From the perspective of operation and calculation process, this measurement method has low requirements on the measurement object, and the operation and calculation are simple during the measurement process.

[0043] (2) The measurement results show that the reading accuracy is high. There are two key points: ① Based on the cosecant relationship in a triangle, a transparent spiral ruler is innovatively used to subdivide a certain unit of length during the measurement process; ② The winding angle of the transparent spiral ruler is as small as possible. The smaller the spiral angle, the higher the reading accuracy.

[0044] The present invention is reasonably designed and adopts a transparent spiral ruler winding measurement method to subdivide the length of the liquid level change using trigonometric relationships, thereby achieving accurate, efficient, multi-field and multi-functional measurement of the density of irregular objects, and has good practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 A schematic diagram showing the experimental flow of the method of the present invention.

[0048] Figure 2 A schematic diagram showing the angle (helix angle) between the transparent spiral ruler and the bottom surface of the container in the method of the present invention. DETAILED DESCRIPTION

[0049] In order to more clearly understand the above-mentioned objectives, features and advantages of the present invention, the scheme of the present invention will be further described below. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0050] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present invention, rather than all of the embodiments.

[0051] The specific embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0052] An accurate method for measuring the density of irregular objects is as follows:

[0053] Step 1. Measure

[0054] (1) Place the object b on the mass measuring instrument and measure and record its mass m b .

[0055] (2) If the object to be tested is not waterproof, it needs to be waterproofed with alcohol and rosin.

[0056] (3) A non-retractable transparent scale c is attached to the outer wall of a container a having a volume scale in a spiral manner with a winding angle of θ; when attaching the transparent spiral scale, the angle θ (helix angle) between the transparent spiral scale and the bottom surface of the container should be as small as possible. The smaller the helix angle, the higher the reading accuracy.

[0057] (4) Observe and record the vertical height h from the low scale to the high scale of container a. a and the length of the transparent spiral ruler l a ;

[0058] Here, the low scale is generally the smallest integer scale of container a, and the high scale is generally the maximum range scale.

[0059] (5) Pour a certain amount of liquid into container a with a transparent spiral ruler attached, observe horizontally and record the lowest point of the concave liquid surface as l. 1 .

[0060] (6) When the density of the irregular object b is greater than that of the liquid, place the irregular object b into container a. After the liquid is still, record the lowest mark of the spiral ruler at the concave liquid surface after the change as l. 4 ;

[0061] (7) When the density of the irregular object b is less than that of the liquid, a solid d with a density greater than that of the liquid is required to make the irregular object sink in the liquid. Therefore, solid d is measured first. Solid d is placed in container a. After the liquid is still, the lowest mark of the spiral ruler at the concave liquid surface after the change is recorded as l. 2 ;

[0062] After container a is emptied and dried, refill it with the same volume of liquid as before;

[0063] Fix the irregular object b and solid d together and put them into container a. After the liquid is still, record the lowest point of the concave liquid surface after the change as l. 3 .

[0064] Step 2: Calculation

[0065] Assume that the radius of the experimental container is r a , it is known that the vertical height from the low scale to the high scale in container a is h a , volume V a ;

[0066] Container volume Va = πr a 2 ×h a

[0067] Then the radius of container a is

[0068] Assume that the winding angle of the transparent scale c in this experiment is θ. When the volume of liquid in the container is constant, the ratio of the length of the spiral scale at the lowest point of the concave liquid surface to the vertical height is a constant. This constant is also the minimum multiple by which the method of the present invention can improve the measurement accuracy of density ρ. This method is recorded as C.

[0069] In this method, the vertical height from the low scale to the high scale of container a is h a , the length of the transparent spiral ruler is l a ;

[0070]

[0071] For the irregular object b whose density is greater than that of the liquid, the vertical height change of the irregular object b after it sinks into the liquid is Δh, and the corresponding length of the spiral ruler is Δl, and Δl=l 4 -l 1 ;

[0072] For the irregular object b whose density is less than that of the liquid, after being placed in the container a, the change in vertical height of the irregular object b and the solid d after sinking into the liquid is Δh, and the corresponding change in the length of the spiral ruler is Δl, and Δl = l 3 -l 2 ;

[0073]

[0074] V b =πr 2 ×Δh

[0075]

[0076] Example 1

[0077] An accurate method for measuring the density of an irregular object (bridge) is as follows:

[0078] Step 1. Measure

[0079] (1) The object to be tested in this embodiment is a 1 / 4 wooden violin bridge (also known as the "bridge"), which is 34 mm long, 24 mm wide, and 4.5 mm thick, with a through hole. The function of the violin bridge is to transmit the vibration of the strings to the body of the violin, causing it to resonate and produce sound. It is known as the "heart" of the violin. The length, width, thickness, wood density, etc. of the bridge will affect the overtone frequency, volume, and timbre of the violin.

[0080] (2) In this embodiment, a 100±0.5ml measuring cylinder is selected for measurement, and the graduation value of the measuring cylinder is 1ml. The measuring cylinder produced by Syntheware is used for this measurement, and its accuracy can meet the requirements of relevant measurement accuracy of international standards such as GB, ISO, ASTM, and DIN.

[0081] (3) Use an electronic scale to measure the weight of the bridge: Place the bridge on the electronic scale, weigh it and record the reading m b It is 1.17g.

[0082] (4) Waterproof the bridge to prevent it from being soaked in water and affecting the experimental results. Mix rosin powder and 98% industrial alcohol in a ratio of 3:2 and stir thoroughly until it becomes viscous. Use a brush to evenly brush it onto the bridge surface and let it dry naturally.

[0083] (5) A non-retractable transparent scale is attached to the outer wall of the measuring cylinder in a spiral upward manner. When attaching the transparent scale, the spiral angle is as small as possible. The smaller the spiral angle, the higher the reading accuracy. The transparent scale selected in this embodiment is 250 cm long and 1 cm wide. When attached, the angle between the transparent scale and the bottom surface of the measuring cylinder is 10°. Because the bottom wall of the measuring cylinder is curved, in order to reduce experimental errors, the 0 cm scale line of the spiral scale is attached starting from the 10 ml scale of the measuring cylinder.

[0084] (6) Observe and record the length l of the spiral ruler from 10ml to 100ml scale of the measuring cylinder 90ml It is 166.9cm.

[0085] (7) Observe and record the vertical height h from the 10 ml to 100 ml mark of the measuring cylinder 90ml It is 17.22cm.

[0086] (8) Pour water into the measuring cylinder until the 20 ml mark is reached (the line of sight is level with the lowest point of the concave liquid surface). After the liquid surface is still, record the length of the spiral ruler at the lowest point of the concave liquid surface, l. 20ml is 18.5cm.

[0087] (9) Use a waterproof thin wire (to prevent water splashing and affecting the experimental results) to slowly place the magnet into 20 ml of water. Observe and record the changes in the liquid level. It is found that the horizontal surface becomes 22 ml, and the length of the spiral ruler at the lowest point of the concave liquid surface is l 2 It is 22.2cm.

[0088] (10) Pour out the water and magnet in the measuring cylinder and refill it with 20 ml of water.

[0089] (11) To prevent the bridge from floating on the liquid surface, place the bridge between the magnets and slowly place it in 20 ml of water using a thin wire. After the liquid surface is still, observe and record the changes in the liquid surface. It is found that the water level increases to the 24 ml mark on the measuring cylinder, and the lowest mark on the spiral ruler is l 3 It is 25.9cm.

[0090] Step 2: Calculation

[0091] (1) In this experiment, since the radius of the measuring cylinder is fixed, πr 2 is a constant.

[0092] The vertical height h from the 10ml to 100ml mark of the measuring cylinder 90ml It is 17.22cm.

[0093] V=πr 2 ×h

[0094]

[0095] The radius of the cylinder is approximately 1.2898 cm

[0096] πr 2 =3.14159×1.2898 2 ≈5.226

[0097] (2) In this embodiment, the winding angle of the transparent spiral ruler is θ = 10°. When the volume of liquid in the measuring cylinder is constant, the ratio of the length of the spiral ruler to the vertical height is a constant, which is also the multiple by which the method can improve the accuracy of density measurement.

[0098] h 90ml =17.22cm

[0099] l 90ml =166.9cm

[0100]

[0101] l 3 =25.9cm

[0102] l 2=22.2cm

[0103] Δl=l 3 -l 2 =25.9-22.2=3.7cm=37mm

[0104]

[0105] Δh≈3.818mm

[0106] V b =πr 2 ×Δh

[0107] =522.6×3.818

[0108] ≈1995.29mm 3

[0109] ≈1.995cm 3

[0110]

[0111] Therefore, the density of 1 / 4 violin wooden bridge is 0.586g / cm 3 .

[0112] Two additional points need to be explained here. First, the present invention measures the average density of irregular objects. Second, the accuracy of the electronic scale used to measure the mass (m) affects the measurement result.

[0113] The above is only a specific implementation of the present invention, which enables those skilled in the art to understand or implement the present invention. Although detailed descriptions are given with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments, and they should all be covered by the protection scope of the claims.

Claims

1. A method for accurately measuring the density of an irregular object, characterized in that: The steps include: Step 1: Measure (1) Place the object b on the mass measuring instrument and measure and record its mass m b ; (2) a non-retractable transparent scale c is attached to the outer wall of a container a having a volume scale in a spiral manner with a winding angle of θ; the angle θ between the transparent spiral scale and the bottom surface of the container is such that the smaller the spiral angle, the higher the reading accuracy; (3) Observe and record the vertical height h from the low scale to the high scale of container a. a and the length of the transparent spiral ruler l a ; (4) Pour a certain amount of liquid into container a, observe horizontally and record the transparent spiral ruler scale at the lowest point of the concave liquid surface as l1; (5) When the density of the irregular object b is greater than that of the liquid, place the irregular object b into the container a. After the liquid is still, record the lowest mark of the spiral ruler at the concave liquid surface after the change as l4; (6) When the density of the irregular object b is less than that of the liquid, a solid d with a density greater than that of the liquid is required to make the irregular object sink in the liquid. Therefore, solid d is measured first. Solid d is placed in container a. After the liquid is still, the lowest mark of the spiral ruler at the concave liquid surface after the change is recorded as l2. After container a is emptied and dried, refill it with the same volume of liquid as before; Fix the irregular object b and solid d together and put them into container a. After the liquid is still, record the lowest scale of the spiral ruler at the concave liquid surface after the change as l3; Step 2: Calculation Assume that the radius of the experimental container is r a , it is known that the vertical height from the low scale to the high scale in container a is h a , the volume is V a ; Volume Va = πr a 2 ×h a Then the radius of container a is Since the length of the transparent spiral ruler from the low scale to the high scale of container a is l a and vertical height h a The ratio is a constant, denoted by C For the irregular object b to be measured whose density is greater than that of the liquid, the change in vertical height of the irregular object b after it sinks into the liquid is Δh, and the corresponding change in the spiral ruler length is Δl, and Δl=l4-l1; For the irregular object b whose density is less than that of the liquid, after being placed in the container a, the change in vertical height of the irregular object b and the solid d after sinking into the liquid is Δh, and the corresponding change in the length of the spiral ruler is Δl, and Δl = l3-l2; V b =πr 2 ×Δh 2. The method for accurately measuring the density of an irregular object according to claim 1, characterized in that: If the irregular object b being tested is not waterproof, waterproof treatment should be performed.

3. The method for accurately measuring the density of an irregular object according to claim 2, characterized in that: Mix rosin powder and alcohol in proportion and stir thoroughly until viscous. Brush it evenly and lightly onto the surface of the irregular object b to be measured, and then dry the irregular object b in the shade.

4. The method for accurately measuring the density of an irregular object according to claim 1, characterized in that: In step (3), the low-order scale is the smallest integer scale, and the high-order scale is the maximum range scale.

5. The method for accurately measuring the density of an irregular object according to claim 1, characterized in that: The angle θ is in the range of 5° to 15°.

Images