Inline refractometers, especially for determining the water content of a liquid, especially a coolant

Description

[0001] The invention relates to an inline refractive index measurement, in particular an inline concentration measurement for determining the water content of a liquid, especially cooling lubricants used in the machining industry.

[0002] Concentration measurements of liquids, especially cooling lubricants, are important in the machining industry because the concentration of the oil component of a cooling lubricant depends on the material being machined, the tool being used, or the machining process. Refractometers are used to measure these concentrations. Refractometers can determine the properties of liquids based on the angle of refraction of light. This optical measuring device uses light refraction to indicate the respective concentration of solid or liquid substances. Such refractometers are known from FR 2 626 075 A1, FR 2 548 370 A1, and DE 10 2010 028319 A1.

[0003] There are three types of refractometers: handheld refractometers, digital refractometers, and inline refractometers. A handheld refractometer can be used to determine the water content of emulsions such as drilling emulsions, cutting oils, or cooling lubricants, for example, in CNC machining, as well as the sugar content of fruits, grapes, vegetables, soft drinks, and translucent fruit juices. Thanks to its integrated temperature compensation system, the handheld refractometer provides more accurate results, as the measurement can change with increasing temperature. Before taking a measurement, the prism and prism cap must be carefully cleaned and dried. Then, using a pipette, one or two drops of the sample should be placed onto the prism, and the prism cap closed. This ensures the sample is evenly distributed between the cap and the prism. Care must be taken to avoid the formation of air bubbles, as these would negatively affect the measurement.By gently moving the hinged lid, the sample liquid can be evenly distributed. The refractometer is then held up to daylight to view the scale through the eyepiece. The desired value can then be read directly. Since deposits can form on the prism and the lid, the instrument must be carefully cleaned and dried after each measurement to prevent inaccuracies in the next measurement. However, it is very easy to use.

[0004] A digital refractometer is a waterproof handheld measuring device used to determine concentrations within a measuring range of 0 to 90%. The measurement is not taken using a scale, but rather via sensors, specifically CCD sensors. The measurement result and the temperature of the medium being measured are displayed digitally. The sample is dripped into a measuring well; the lens does not need to be covered.

[0005] Inline process refractometers continuously measure the refractive index of liquids and determine the concentration and mixing ratio of two mass fractions. The measurement is performed in real time, allowing for continuous process monitoring. The measurement is independent of turbidity, color, and viscosity, thus ensuring constant process monitoring. Inline process refractometers can be installed in pipelines, mixing tanks, and storage containers using a variety of connection types, making them suitable for use in the manufacturing industry.

[0006] Handheld and digital refractometers must be loaded with a sample by the operator. The accuracy of the measurements and the samples is always dependent on the quality of the operation. For example, immersing a pipette in an emulsion, as often happens with cooling lubricants, is problematic because the floating foreign oil can adhere to the pipette and distort the measurement. Therefore, a measurement with a handheld refractometer is only suitable as a control measurement. These instruments cannot be used in process control systems.

[0007] Handheld refractometers are usually equipped with a resolution of 0-10% and a division of 0.1%. This concentration value is comparable in accuracy to the inline process refractometer.

[0008] Measurements are usually given in Brix. A liquid has a Brix value of 1 degree (= 1% Brix) if it has the same density as a solution of 1 g of sucrose in 100 g of sucrose / water; it has a Brix value of 10 (= 10% Brix) if its density is that of a solution of 10 g of sucrose in 100 g of sucrose / water (corresponding to a 10% solution). The sucrose solution is only the reference substance; the liquid being tested does not necessarily have to contain sucrose.

[0009] An analog handheld refractometer is about 100 times cheaper than an inline refractometer.

[0010] The invention is based on the technical problem of proposing an inline refractometer that is more favorable in terms of design, operation and cost than the known inline refractometers.

[0011] The aim is to reduce the formation of deposits on the refractometer, particularly during inline measurement of water content in cooling lubricants, so that measurements can be carried out over a longer period and / or more accurately.

[0012] This technical problem is solved by using an analog handheld refractometer as an inline refractometer. With this solution according to the invention, the analog handheld refractometer is installed in a pipeline.

[0013] The invention relates to an inline refractometer unit according to claim 1.

[0014] According to the invention, the hand refractometer is installed in a cross-section of a pipeline.

[0015] In the embodiment according to the invention, using a cross-piece, the two openings can be provided with an inlet and an outlet via a 1" internal thread. The liquid to be measured can then be pumped through the cross-piece. The liquid flows around the refractometer prism, so that the refractometer reading can be taken by looking through the eyepiece with the rubber eyecup. Since daylight only penetrates the interior of the cross-piece insufficiently, the dividing line cannot be seen. Therefore, additional illumination of the interior of the cross-piece and the prism is preferable.

[0016] The prism is preferably placed upright in the vertical position in the tube or cross piece, so that the flowing liquid advantageously surrounds the prism.

[0017] In the embodiment of the invention, a light source is mounted directly onto the sight glass. The light can then shine through the plug-like sight glass directly onto the prism of the refractometer facing it. The concentration value can thus be read through the eyepiece.

[0018] Preferably, the illumination is implemented as an LED lamp, which has the advantage that the sight glass heats up only minimally. To allow the amount and brightness of light in the measuring range to be adjusted to the medium, the light output is preferably adjustable via a dimmer, in particular continuously. Furthermore, the light color, e.g., yellow, green, blue, red, or white, or a mixed color, can improve the detection of the dividing line in the refractometer prism.

[0019] In a further advantageous enhancement of the invention, the refractometer can be viewed through the eyepiece using a camera. The image can be displayed on a screen, so that the operator sees the current concentration value. This image preferably shows a column of light with two different color ranges exhibiting different light intensities. The color differences result from the type of LED lamp and the selected light color.

[0020] At a suitable angle of attack, the prism can advantageously clean itself. If there is no flow through the coolant, deposits can form that impair the measurement. Preferably, a lotus-effect solution can be applied to the prism, which allows water to run off more easily onto the discs, thus keeping the prism clean for longer.

[0021] The use of a refractometer with a resolution of 0 to 18 Brix is ​​preferred, as it performs better in specific applications than one with a resolution of 0-10%. This may be related to the corresponding internal mirror.

[0022] In another advantageous embodiment of the light source, the intensity of the light and the associated lux value can be increased when the prism and / or the sight glass becomes dirty, thereby delaying the need for cleaning.

[0023] A preferred configuration of the invention is one in which the cross-piece is oriented horizontally and vertically. The inlet is vertical, flowing from below, away from the force of gravity. The outlet is offset by 90°, preferably horizontally. The prism of the refractometer can be positioned horizontally or vertically from above within the cross-piece. The sight glass is always opposite the prism. It is important that air is expelled with the liquid flow, as this can impair the light incidence and the measurement.

[0024] The present invention therefore relates in particular to: The present invention relates in particular to an inline refractometer comprising a prism, an eyepiece and a scale according to claim 1.

[0025] Preferably, the refractometer does not integrate a CCD sensor.

[0026] According to the invention, the inline refractometer is assigned to a cross-section of a pipeline.

[0027] Preferably, an inline refractometer is associated with a camera for reading the measured value displayed on the scale.

[0028] According to the invention, an inline refractometer is associated with a light source, in particular an LED lamp. Preferably, a light source, in particular an LED lamp, is integrated into the cross-section of the pipe.

[0029] Preferably, the inline refractometer is part of a machine, in particular with a pipeline.

[0030] Preferably, the inline refractometer is a component of a cooling lubricant line, in particular a cooling lubricant line of a machine tool.

[0031] The present invention also relates to the use of a hand-held refractometer as an inline refractometer in an inline refractometer unit according to the invention.

[0032] The present invention also relates to a machine comprising a piping system, in particular a pipeline system, wherein the piping system comprises an inline refractometer unit according to the invention.

[0033] The present invention also relates to a machining machine comprising a piping system for the removal and supply of a cooling lubricant, wherein the piping system comprises an inline refractometer unit according to the invention.

[0034] The present invention also relates to a method for metering a component of a mixture of at least two liquids in a piping system, comprising the steps of: a) Measuring the Brix value of the mixture of at least two liquids in the piping system with an inline refractometer unit according to the invention, and b) adding a specific proportion of one component when a threshold Brix value is reached.

[0035] The present invention also relates to a method for metering the water content or the oil content of a mixture in a piping system, comprising the steps of: a) Measuring the Brix value of the mixture in the piping system with an inline refractometer unit according to the invention, and b) Adding a specific quantity of water or oil when a threshold Brix value is reached.

[0036] The present invention also relates to a method for metering a cooling lubricant in a machining machine, comprising the steps of: a) Measuring the Brix value of the cooling lubricant in the piping circuit of the machining machine with an inline refractometer unit according to the invention, and b) Adding additional cooling lubricant or water when a threshold Brix value is reached.

[0037] In a preferred embodiment of the methods according to the invention, the measurement in step a) is carried out using a camera located on the eyepiece of the refractometer and the evaluation of the measured value is carried out using a computer connected to the camera, wherein the addition of the additional component, the water, the oil or the additional cooling lubricant in step b) is particularly preferably controlled by the computer. Commercial applicability

[0038] Concentration measurements are used in numerous applications, but inline measurement technology is very expensive and therefore only implemented in a few processes. Cost-effective concentration measurement can be used in many process plants in the machining industry because closed-loop systems are in place. This offers a significant advantage for the operator, as water evaporates during machining, causing the concentration to rise steadily. Automatic concentration monitoring enables automatic concentration control.

[0039] Further preferred embodiments are set out in the dependent claims. Examples

[0040] Fig. 1 shows a side view of the inline refractometer according to the invention and its components in a side view configuration. Fig. 2The figure framed and dashed under point 1 shows a sectional view of the inline refractometer unit according to the invention as a manual design in sectional view, and the figure framed and dashed under point 2 shows a sectional view of the inline refractometer unit according to the invention with an optical camera in sectional view. Fig. 3 shows the flow pattern in the upward flow of the inline refractometer unit according to the invention with optical camera and computer evaluation in the sectional view of the refractometer unit.

[0041] The invention will now be further explained and described with reference to the exemplary embodiments shown in the drawings, without these being to be understood as limiting.

[0042] In the Figure 1 , 2 and 3A refractometer unit 1 according to the invention is shown, which together with a camera 5 can form a refractometer unit with camera 2. A section of a piping system for transporting a cooling lubricant of a machine tool is shown. A cross-piece 3 and optionally ( Figure 3 ) a T-piece 3.1 is integrated. Thus, an inlet of the cooling lubricant through a pipe connection 3.4 and an outlet of the cooling lubricant through a pipe connection 3.5 result, i.e., a flow direction of the liquid 3.6 from the liquid inlet 3.7 through the cross piece 3 and the optional T-piece 3.1 to the outlet direction 3.8, resulting in the flow pattern 3.9 shown.

[0043] A hand refractometer 2.1 is screwed into the cross piece 3 via a threaded connection 2.2, so that the prism 2.4 of the hand refractometer 2.1 extends into the cross piece 3. Adjustment can be made via the adjusting ring (adjusting screw) 2.3a. The prism cover 2.3b was removed to allow the hand refractometer 2.1 to be screwed into the cross piece 3. The hand refractometer 2.1 can also be installed in the cross piece 3, for example, using a suitable threaded adapter 2.6.

[0044] A sight glass 4 is screwed into the opening of the cross piece 3, which is offset by 90°, via a thread 4.3, and the opening is sealed with a gasket 4.2. Light 4.7 can enter the prism 2.4 through the sight glass-prism distance 4.4 via the light incidence point 4.1 of the foam glass and enter the prism 2.4. The light can originate from a light source 4.5, in this case an LED light source 4.6. Advantageously, the power connection 4.9 of the light source 4.5 has a dimmer switch 4.8 to adjust the desired light intensity.

[0045] A camera 5 with a camera lens 5.1 can be assigned to the handheld refractometer 2.1. The refractometer image 5.3 captured by the camera lens 5.1 can be transmitted to a computer 5.2, where image data analysis 5.4 is performed.

[0046] In Figure 3An optional T-piece 3.1 is shown, which is connected to the inlet of the cross piece 3 via a threaded nipple 3.2. This T-piece 3.1 advantageously provides a prism cleaning access 2.5, which can be closed with a blind plug 3.3.

[0047] In an advantageous embodiment of the invention, a T-piece 3.1 (same DIN standard as the cross piece 3) is connected upstream of the inlet or outlet by means of a threaded nipple 3.2. The port-side connection of the T-piece is used as the inlet 3.7 or outlet 3.8. The through-flow side of the T-piece is used for cleaning the prism 2.4 and the sight glass 4. Deposits on the prism 2.4 and the sight glass 4 can be removed from the outside using a cleaning rod or cleaning nozzle, etc. During operation, a plug 3.3 or a ball valve, etc., then closes the T-piece inlet.

[0048] In an advantageous embodiment of the sight glass 4, the distance 4.4 between the prism 2.4 and the sight glass 4 can be adjusted. This involves lengthening the length of the sight glass 4 (as described) from, for example, 20 mm to, for example, 23 mm, or shortening it to, for example, 17 mm. This, in turn, allows the use of different products that may have different light transmittances.

[0049] The prism 2.4 is preferably positioned vertically in the tube or cross piece 3, so that the flowing liquid 3.6 flows around the prism 2.4. No flow shadow should form, as this would create a concentration gradient between the flowing and stagnant liquid.

[0050] An example shown is a line for transporting a liquid cooling lubricant 3.6 in a machining tool. However, the present invention can of course also be used for other lines that transport different types of liquids (Liquid 3.6).

[0051] In a resulting advantageous invention, the image-light column 5.3 can also be measured using computer-aided software 5.4, so that, for example, the zero point 0 and 10 are measured as the maximum value. If the total image to be measured is 100 mm high or long, a concentration increase of 0.1% can be assumed for every 1 mm. The displayed image shows a light-color change, usually from light to dark. Starting from the zero point (0), the light or color image changes, for example, at 66 mm, at which point the concentration value can be specified as 6.6%. Another measurement method is an area comparison measurement, in which a rectangular area, starting at the zero point and ending at the maximum value of, for example, 10, with a width of, for example, 40 mm, is placed over the image, resulting in a surface area of ​​100 mm x 40 mm = 4,000 m².Comparing the areas of 2640 m² (light) and 1360 m² (dark or other colors), we obtain an area comparison value of 66 to 34%, resulting in a concentration of 6.6%.

[0052] The resulting measurements enable PLC-controlled concentration regulation. For example, if a concentration value of cooling lubricants or emulsions, such as those commonly used in the machining industry, is monitored and adjusted, a lower concentration can be added if the target value of 6% exceeds the lighter area during subsequent dosing. Conversely, if the lighter area falls below 6%, a higher concentration can be added during subsequent dosing to compensate. Pure water and concentrate can also be used if they are added to the emulsion stream and emulsified.

[0053] It was found that a freshly prepared emulsion is still clear and transparent, and only when used in the machining machine did it become increasingly whiter; presumably, particles also play a role in the reflection and refractive index of the light.

[0054] An LED lamp proved effective, as its heat emission was also low. Furthermore, the image color and the separation colors could be influenced by the light source color (two different image colors). A warm light source (warm white) worked best, with a light output of approximately 5 watts at 12 volts. Light with a red component also worked very well.

[0055] The following experimental setup was tested: In an advantageous embodiment of the invention, the prism cover 2.3b, held by a type of "ring-eyelet clamp," is removed. The mounting point of the ring-eyelet clamp is cylindrical. This point is located between the prism 2.4 and the adjusting screw 2.3a, which is used for zero-value adjustment using water. The cylindrical mounting point between the prism 2.4 and the adjusting screw 2.3a is typically about 5–10 mm long. The diameter is approximately 24 mm, which allows for the cutting of a preferred metric ISO fine thread DIN 13 using a die M24 x 1.5 fine thread HSS DIN ISO 13.

[0056] In the resulting advantageous threaded design, a threaded adapter can be screwed onto the refractometer and sealed with a sealant. The threaded adapter is a standard reducer 2.6 according to DIN 2999, reducing from a 1" male thread to a 1 / 2" female thread. The 1 / 2" thread is drilled out, and a metric ISO fine thread is cut using an M24 x 1.5 HSS DIN ISO 13 tap. The type, dimensions, and size of the threaded adapter are adapted to the process and are independent of the inventive implementation. The refractometer 2.1, with the sealed threaded adapter 2.2 having a 1" male thread, is screwed into a cross fitting 3 (preferably the same DIN 2999) and sealed. The preferred sealant is a liquid thread sealant, e.g., Loctite type 572. However, another sealant approved for use with the respective fluid can also be used.

[0057] In a further advantageous embodiment of the invention, a sight glass 4 is manufactured from a round bar, e.g., DN 40 made of acrylic or the like, made of a transparent material; glass is also possible. The sight glass 4 is manufactured with a length of approximately 30 mm. The diameter (DN) 40 mm is turned down to DN 33 mm over a length of 20 mm and then provided with a 1" external thread (same as the internal thread of a cross fitting according to DIN 2999). The thread can also be cut using a tap. The sight glass then resembles a 1" sanitary plug, with the property of allowing a light source 4.5, 4.6, 4.7 to pass through it. This sight glass-like plug is screwed into the cross fitting 3 at a 90° angle to the refractometer 1. A flat or O-ring seal 4.2 is used as a sealing medium, since if the 1" threaded end becomes contaminated, the sight glass 4 can / must be unscrewed and cleaned.The 10 mm long and DN 40 outer of the sight glass 4 (can also have a different dimension) can be manually screwed onto the cross piece 3 so that the connection in the cross piece 3 is sealed.

[0058] The use of a glass vial as a sight glass was also implemented, glued into a 1" metal threaded sleeve. The standard glass vial had an outer diameter of 28 mm and protruded 15 mm from the threaded sleeve into the cross-shaped piece. It had been observed with the whitish emulsion of the cooling lubricant that the red light color facilitated the detection of the refractive index in the refractometer. However, this could change with a different fluid color. To address this, the inside of the glass vial was sprayed with transparent red glass paint. For this, the glass vial was first heated to 60°C and then clamped horizontally (with the vial upright) using a motorized drive. This resulted in a uniform, transparent film of paint. A cable gland was installed in the cap of the glass vial, sealing the interior where an LED lamp emitting warm white light was used.Because the LED lamp was positioned directly against the bottom of the glass vial, the light was distributed throughout the interior of the cross-shaped piece, extending over a 15 mm circumference. This created a homogeneous light source on the prism. Since the liquid's light absorption can vary depending on its composition and particle concentration, the light intensity could be adjusted. This was done manually or automatically after image analysis.

[0059] The optical image formed in the refractometer and on the lens was captured using a camera. The camera was positioned so that the image captured the entire prism area within the refractometer. The image resolution and focus were fixed at the eyepiece. The camera was preferably not positioned parallel to the eyepiece axis, but rather tilted slightly. A tilt of approximately 1° improved the view of the refraction.

[0060] Cameras use different light points to recognize the image, capturing, for example, 2-10 million image pixels in different colors of light. It is also possible to create a black and white image. Cameras also have a preset image format that is projected onto a surface. In the present experimental setup, the preset image area had a resolution of, for example, up to 8 megapixels (3280 x 2464 pixels). This image area shows the illuminated prism in the foreground, as well as the dark area around the prism. Since the pixel distribution was across the entire image area, only the prism area was needed for image analysis.

[0061] The overall image was approximately 10 x 10 cm and contained about 8 million image pixels, with the prism image to be analyzed occupying a 5 x 2 cm portion of the image. The prism section was elliptical and displayed a scale from 0 to 18 Brix. The resulting area was reduced to 640,000 image pixels. A light-dark boundary emerges during image refraction, increasing from 0% to 18%. For example, a value of 6% results in a ratio of 6% bright pixels to 12% dark pixels, which translates to a ratio of 33.33% to 66.66% across the area, or 213,333 bright pixels to 426,666 dark pixels. This ratio was then converted to the 0-18% display.

[0062] This percentage ratio was then converted in a further program step and sent to the PLC (programmable logic controller) as a signal of 0-10 volts, preferably 4-20 mA. 0% corresponded to 4 mA and 18% to 20 mA. At 6%, there was therefore a signal current of 9.33 mA, which was read by the PLC.

[0063] A Raspberry Pi was used as a simple computer for image recognition. The image area was cropped to represent 0-18% of the image and then converted into a measurement of 0-18%. This allowed for the calculation of the light points, the evaluation of color differences, and thus the determination of the dividing line. This was then converted into a signal of 4-20 mA; for example, 4 mA = 0% and 20 mA = 18%.

[0064] A hand refractometer with a scale of 0-18 worked better than a hand refractometer with a scale of 0-10, because it probably had a different prism and the dividing line was easier to see, which led to a better evaluation.

[0065] The online image was displayed on the control panel of the emulsion preparation plant. A Siemens Comfort Panel was used for this purpose, initially serving the operator solely for visual monitoring. The image was then displayed via an interface on any computer, enabling online monitoring directly at the workstation.

[0066] A control unit was set using an analog value, and this was used to regulate the concentration of the cooling lubricant. Water or cooling lubricant concentrate could be added. The value could also be used for documentation purposes, as operators are often required to monitor it continuously.

[0067] For dosing, 1,000 liters of coolant lubricant were monitored in a container assigned to one or more machining machines. The container's volume was measured, and a level sensor continuously measured the fill level. When the fill level fell below a certain threshold, for example, 2 cm, approximately 22 liters were added. If this caused the measured concentration to rise to 6.1%, water was added as well.

[0068] The fluid, especially the coolant lubricant, should have a free-flowing consistency to prevent it from adhering to the surface, the inner tube, the light source, or the prism. The fluid should be homogeneously mixed; otherwise, the refractive index on the prism and the detection element can change continuously, resulting in unstable measurements. If the prism becomes coated with grease or has gas bubbles adhering to it, it should be cleaned. This can be done manually or automatically at intervals. Cleaning can be done manually, for example, with a cleaning cloth or brush, or automatically with a wiper mechanism that moves up and down or back and forth across the prism using a pneumatic cylinder.

[0069] In the present invention, the terms liquid and fluid are used synonymously.

[0070] The present invention is therefore an advantageous alternative to expensive conventional online measuring devices, since the lens of these, usually no larger than 5 x 10 mm, becomes very dirty very quickly, thus reducing the amount of light passing through and causing the electronics to signal an excessively high concentration value. Automatic cleaning also works rather poorly with conventional measuring devices because they are made of graphite and grease.

[0071] In contrast, the alternative according to the invention can have a large prism area of ​​about 20 x 45 mm, so that the refractive index of light is easily measurable in both a loaded cooling lubricant and a clean cooling lubricant. Reference symbol list

[0072] 1. Manual refractometer unit 2. Refractometer unit with camera 2.1 Handheld refractometer 2.2 Threaded connection 2.3a Diopter adjustment ring 2.3b Prism cover 2.4 Prism 2.5 Prism cleaning access 2.6 Threaded adapter 3. Cross fitting 3.1 T-fitting 3.2 Threaded nipple 3.3 Blanking plug 3.4 Inlet pipe connection 3.5 Outlet pipe connection 3.6 Liquid 3.7 Liquid inlet 3.8 Liquid outlet 3.9 Flow pattern 4. Sight glass 4.1 Sight glass light incidence 4.2 Sight glass seal 4.3 Sight glass thread 4.4 Sight glass prism distance 4.5 Illumination 4.6 LED light source 4.7 Light waves 4.8 Aperture control 4.9 Power connection 5. Camera 5.1 Camera lens 5.2 Computer 5.3 Refractometer image 5.4 Image data analysis

Claims

1. An inline-refractometer unit (1) with a crosspiece (3), a pipeline and a refractometer (2.1), which has a prism (2.4), an eyepiece and a scale and is installed in the crosspiece such that the prism extends into the crosspiece, wherein an opening of the crosspiece has a sight glass (4) and a light source (4.5) is mounted immediately on the sight glass, such that light from the light source shines through the sight glass directly onto the facing prism, or wherein an LED lamp associated with the refractometer is integrated into the crosspiece.

2. The inline-refractometer unit of claim 1 with a camera (5) for reading the measurement value indicated on the scale.

3. The inline-refractometer unit of any one of the preceding claims, wherein the crosspiece is part of a coolant line, in particular a coolant line of a machining machine.

4. A use of a hand-held refractometer as the refractometer in an inline-refractometer unit of any one of claims 1 to 3.

5. A machine having a line system, wherein the line system has an inline-refractometer unit of any one of claims 1 to 3.

6. The machine of claim 5, wherein the machine is a machining machine having a line system for discharging and supplying a coolant, wherein the line system for discharging and supplying a coolant has an inline-refractometer unit of any one of claims 1 to 3.

7. A method for dosing a component of a mixture of at least two liquids in a line system, having the steps of: a) measuring the Brix value of the mixture of at least two liquids in the line system with an inline-refractometer unit of any one of claims 1 to 3, b) adding a specified quantity proportion of the one component when a threshold Brix value is reached.

8. The method of claim 7, wherein the one component is the water proportion or the oil proportion of the mixture.

9. The method of claim 7, wherein the mixture is a coolant in a machining machine and wherein, in step b), additional coolant or additional water is added.

10. The method of any one of claims 7 to 9, wherein the measurement in step a) is performed via a camera located at the eyepiece of the refractometer and the evaluation of the measurement value is performed via a computer connected to the camera, wherein the addition of the additional component, the water, the oil or the additional coolant in step b) is controlled via the computer.