CN203083902U - Magnetic force suspension density tester - Google Patents

Abstract

The utility model discloses a magnetic force suspension density tester which is characterized by comprising two vertical polar permanent magnets of which the polarities are opposite to each other, wherein a hollow glass column is arranged between the two permanent magnets; and a transparent magnetic liquid for measuring the density of a sample is filled into the glass column. As the density is measured according to the height that the sample is suspended in the magnetic liquid, the magnetic force suspension density tester has the characteristics of simplicity in structure and convenience in operation, the density of the sample can be conveniently and rapidly tested or the content of one component in the sample is estimated and tested, an extreme small amount of the sample is needed, the range of substances which can be analyzed is wide, the tester is applicable to solid, liquids, adhesives, gels, paste and the like, and samples of irregular shapes can also be tested. The magnetic force suspension density tester solves the problems that the conventional density testing is large in expense, the operation is complex or the precision is not high and the like, is high in measurement precision, convenient and rapid to measure, low in expense and worthy of wide popularization.

Description

Magnetic Levitation Density Meter

technical field

The utility model relates to the technical field of density measuring devices, in particular to a magnetic suspension density measurement device, which detects the density of a substance through the position or height of a sample suspended in a magnetic suspension device.

Background technique

At present, although there are many kinds of instruments for measuring the density of solids and liquids and measuring the concentration of solutions, such as: density gradient column, float hygrometer, oscillating tube density meter, suspended microresonator, etc., these detection technologies have their own shortcomings and limitations. Disadvantages, such as high cost, complicated operation, low precision, only specific samples can be measured, etc. Density gradient columns have high precision (10 ^-4 g/cm ³ ), but this method is expensive and complicated to operate, and requires professionally trained testers to measure accurate data in the laboratory; The basic modern equipment has high precision, convenient and quick, but the cost is very high. Generally, it costs several thousand yuan for testing, and it can only detect liquids within a certain viscosity range; the suspended microresonator is the instrument with the highest density measurement accuracy so far. However, this technology is limited to the analysis of substances smaller than 3-15 microns, and requires state-of-the-art equipment and careful optical detection; so there is an urgent need for a fast, accurate and low-cost detection equipment or instrument for detecting solid liquids density.

Contents of the invention

The technical problem to be solved by this utility model is to provide a magnetic levitation density measuring device with simple structure and convenient operation in view of the above-mentioned technical status, which can detect the density of a substance or estimate the content of a certain component in a substance conveniently and quickly. Moreover, the cost is low, the measurement accuracy is high, and the amount of sample required is extremely small.

The technical scheme adopted by the utility model to solve the above-mentioned technical problems is: a magnetic levitation density measuring device, which is characterized in that it includes two permanent magnets with opposite polarities on the upper and lower sides, and a hollow glass column is arranged between the two permanent magnets. The glass column is filled with a transparent magnetic liquid used to measure the density of the sample.

As an improvement, the lower end of the glass column is sealed and the upper end is open. The lower end of the glass column is fixed at the middle position of the upper end of the permanent magnet below, and the upper permanent magnet is sleeved on the upper end of the glass column. The joints of the two permanent magnets are respectively provided with rubber rings for sealing.

As an improvement, the permanent magnet is a cube with a length of 2.5 to 3.5 cm, a width of 2.5 to 3.5 cm, and a height of 0.8 to 1.2 cm. The distance between the two permanent magnets is 4.5 to 5.5 cm. The length of the glass column is 4.5-5.5 cm corresponding to the distance between two permanent magnets.

Further improvement, the length of the permanent magnet is 3cm, the width is 3cm, the height is 1cm, the distance between the two permanent magnets is 5cm, and the length of the glass column is 5cm corresponding to the distance between the two permanent magnets.

As a further improvement, the outer sides of the two permanent magnets are provided with a housing for supporting and fixing, and support plates are provided before and after the two permanent magnets in the housing for fixing, and the middle of the support plates is hollowed out corresponding to the position of the glass column , and the transparent glass used to protect the glass column is respectively installed in the hollow.

Finally, the clear glass is marked with graduations for easy reading.

Compared with the prior art, the utility model has the advantages that: the utility model measures the density by suspending the sample in the height of the magnetic liquid, has the characteristics of simple structure and convenient operation, and can detect the density or estimate the density of the substance conveniently and quickly To measure the content of a certain component in a substance, the amount of sample required is very small, and a wide range of substances can be analyzed. It is applicable to solids, liquids, colloids, gels, pastes, etc., and can also measure samples with irregular shapes. The utility model has high measurement precision (accurate to ±0.02-±0.0002g/cm3 according to different experimental conditions), convenient and quick measurement and low cost, and is worthy of mass promotion.

Description of drawings

Fig. 1 is the structural representation of the utility model;

Fig. 2 is a schematic diagram of the appearance structure of the utility model.

Detailed ways

The utility model is described in further detail below in conjunction with the accompanying drawings.

As shown in the figure, a magnetic levitation density measuring instrument includes two permanent magnets 1 and 7, a hollow glass column 2 arranged between the two permanent magnets 1 and 7, and two permanent magnets 1 and 7 The N poles and N poles are opposite, or the S poles and S poles are opposite to each other. The permanent magnets 1 and 7 are cubes, with a length of 3cm, a width of 3cm, and a height of 1cm. The distance between the two permanent magnets 1 and 7 The length of the glass column 2 is 5cm, the lower end of the glass column 2 is sealed, and the upper end is open. The transparent magnetic liquid 4 used to measure the density of the sample is filled in the glass column 2, and the lower end of the glass column 2 is fixed on the permanent below. At the middle position of the upper end of the magnet 7, the permanent magnet 1 above is sleeved on the upper end of the glass column 2, and rubber rings are respectively provided at the joints between the upper and lower ends of the glass column and the two permanent magnets 1 and 7 for sealing; The outer cover of magnet 1 and 7 is provided with a shell 3 for supporting and fixing, and shell 3 adopts plastics to make, is provided with support plate 5 before and after two permanent magnets 1 and 7 in shell 3 and fixes, and the middle of support plate 5 The position corresponding to the glass column 2 is hollowed out, and transparent glass 6 for protecting the glass column 2 is respectively installed in the hollowed out place, and a scale for easy reading is marked on the transparent glass 6 .

When in use, open the glass column 2 from the top, put the sample into the magnetic liquid 4, due to the magnetic force, the sample will be suspended in the magnetic liquid 4, observe its height h from the bottom of the glass column 2, and then according to the formula:

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; g</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; 4</span>}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

Calculate _ρs (i.e. the density of the sample):

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; =</span>\frac{{{\mathrm{<span\; class="notranslate">\; 4</span>}\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}{\mathrm{<span\; class="notranslate">\; g</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

Wherein h is the height of the sample in the magnetic liquid, ρ _m is the density of the magnetic liquid, g is the acceleration of gravity, μ ₀ is the vacuum permeability, d is the distance between the two magnets, B ₀ is the magnetic induction intensity on the surface of the magnet, χ _s is the magnetic susceptibility of the sample and χ _m is the magnetic susceptibility of the magnetic liquid.

The specific derivation process of the formula is:

Formula (1) can be deduced, and the magnetic force on the sample in the magnetic liquid can be expressed as:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{\mathrm{<span\; class="notranslate">\; mag</span>}}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{<span\; class="notranslate">\; \&dtri;</span>}<span\; class="notranslate">\; )</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The force exerted by the earth on the sample is:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; V</span>}\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

When the sample is balanced by force:

${\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{\mathrm{<span\; class="notranslate">\; mag</span>}}<span\; class="notranslate">\; +</span>{\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; f</span>}}}_{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; V</span>}\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; g</span>}}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}\mathrm{<span\; class="notranslate">\; V</span>}<span\; class="notranslate">\; (</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{<span\; class="notranslate">\; \&dtri;</span>}<span\; class="notranslate">\; )</span>\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 5</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; g</span>}<span\; class="notranslate">\; +</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>}{{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}\frac{<span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; x</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}\frac{<span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; the\; y</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}\frac{<span\; class="notranslate">\; \&PartialD;</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}}{<span\; class="notranslate">\; \&PartialD;</span>\mathrm{<span\; class="notranslate">\; z</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; 0</span>}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 6</span>}<span\; class="notranslate">\; )</span>$

$\stackrel{<span\; class="notranslate">\; \&Right\; Arrow;</span>}{\mathrm{<span\; class="notranslate">\; B</span>}}<span\; class="notranslate">\; \&equiv;</span>\left(\begin{array}{c}{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; x</span>}}\\ {\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; the\; y</span>}}\\ {\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; z</span>}}\end{array}\right)<span\; class="notranslate">\; =</span>\left(\begin{array}{c}\mathrm{<span\; class="notranslate">\; 0</span>}\\ \mathrm{<span\; class="notranslate">\; 0</span>}\\ <span\; class="notranslate">\; -</span>\frac{{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}{\mathrm{<span\; class="notranslate">\; d</span>}}\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right)<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

It is derived from formula (6) and formula (7):

$\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; =</span>\frac{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; g</span>}{\mathrm{<span\; class="notranslate">\; \&mu;</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}{<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; the\; s</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&chi;</span>}}_{\mathrm{<span\; class="notranslate">\; m</span>}}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; 4</span>}{{\mathrm{<span\; class="notranslate">\; B</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; d</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

Claims (6)

1. magnetic levitation dasymeter is characterized in that comprising two permanent magnets that polarity is oppositely arranged up and down, is provided with the glass column of a hollow between two permanent magnets, and filling completely is used for the transparent magnetic liquid of measuring samples density in the glass column.

2. magnetic levitation dasymeter according to claim 1, the following end closure that it is characterized in that described glass column, upper end open, the centre position, upper end of the permanent magnet of below is fixed in the lower end of glass column, the permanent magnet of top is nested with the upper end at glass column, and the two ends up and down of described glass column and the junction of two permanent magnets are respectively equipped with rubber band and seal.

3. magnetic levitation dasymeter according to claim 1, it is characterized in that described permanent magnet is cube, length is 2.5～3.5cm, wide is 2.5～3.5cm, height is 0.8～1.2cm, the spacing of two permanent magnets is 4.5～5.5cm, and the length of described glass column is and the corresponding 4.5～5.5cm of the spacing of two permanent magnets.

4. magnetic levitation dasymeter according to claim 3 is characterized in that the long 3cm of being of described permanent magnet, and wide is 3cm, and height is 1cm, and the spacing of two permanent magnets is 5cm, and the length of described glass column is and the corresponding 5cm of the spacing of two permanent magnets.

5. according to the described magnetic levitation dasymeter of the arbitrary claim of claim 1 to 3; the outside that it is characterized in that described two permanent magnets is arranged with a shell that is used for support fixation; the front and back of two permanent magnets are provided with back up pad and fix in the enclosure; the position hollow out of correspondence and glass column in the middle of the described back up pad, the hollow out place is equipped with the clear glass that is used for the cover glass post respectively.

6. according to the described magnetic levitation dasymeter of the arbitrary claim of claim 1 to 3, it is characterized in that described clear glass is marked with easy-to-read scale.

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