WO2000025133A1 - An apparatus for measuring opacity - Google Patents

An apparatus for measuring opacity Download PDF

Info

Publication number
WO2000025133A1
WO2000025133A1 PCT/GB1999/003561 GB9903561W WO0025133A1 WO 2000025133 A1 WO2000025133 A1 WO 2000025133A1 GB 9903561 W GB9903561 W GB 9903561W WO 0025133 A1 WO0025133 A1 WO 0025133A1
Authority
WO
WIPO (PCT)
Prior art keywords
sample
plate
plates
test plate
depth
Prior art date
Application number
PCT/GB1999/003561
Other languages
French (fr)
Inventor
Barry Ingham
Neil Thatcher
Original Assignee
Rhopoint Instrumentation Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Rhopoint Instrumentation Limited filed Critical Rhopoint Instrumentation Limited
Publication of WO2000025133A1 publication Critical patent/WO2000025133A1/en

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/26—Oils; Viscous liquids; Paints; Inks
    • G01N33/32—Paints; Inks
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
    • G01N21/47—Scattering, i.e. diffuse reflection
    • G01N21/4738—Diffuse reflection, e.g. also for testing fluids, fibrous materials

Definitions

  • opacity In the field of coatings, for example paints, an important consideration is the opacity of a product.
  • one parameter indicative of opacity is the wet film hiding power. This is a measure (m 2 /kg) of how good the paint is at hiding the surface on which is has been applied. For paints, a higher hiding power means less paint needs to be applied to cover a surface successfully. Opacity is also important in the field of cosmetics.
  • opacity as a function of coating thickness.
  • Pfund black and white precision cryptometer which is designed to allow measurement of hiding power of wet paint.
  • a photo-electric device is used to measure the reflectance of a wet film of paint constrained as a wedge shaped layer of uniformly increasing depth on a glass substrate along the length of a black and white boundary of the substrate.
  • the photo-electric device moves in a direction parallel to the black and white boundary line until a position is found where the reflectance of paint over the black area is no longer the same as that of the white area.
  • the film thickness at this position is determined with reference to a graduated scale provided to one side of the substrate. This is the thickness where the paint has 98 % opacity with the known concentration of trioxide.
  • the problem with this instrument is that it is difficult to establish the wedge of paint in a truly repeatable manner.
  • the film thickness does not always vary along the length of the black and white boundary of the glass substrate in the expected manner indicated by the scale so that the determination of the film thickness is not reliable.
  • parameter representing the opacity of a sample comprises the steps of compressing a sample between two parallel plates, one of the plates consisting of a first portion having a first optical reflectivity and a second portion having a second, different, optical reflectivity, and, at a number of measuring instants, detecting the intensity of light reflected from each of the first and second portions of the one plate and measuring the depth of the sample between the two plates.
  • the parameter is the wet film hiding power.
  • the plates are driven together at a first predetermined speed whilst measuring the depth of the sample at a number of measuring instances until a difference is detected between the intensity of light reflected from the first and second portions of the one plate.
  • the relative motion of the plates is reversed and the plates driven apart at a second predetermined speed, the second predetermined speed being slower than the first predetermined speed, whilst continuing to detect the intensity of light reflected from each of the first and second portions of the one plate at a number of measuring instants and comparing these measurements with earlier measurements to determine the depth at which said difference is first detectable and thereby the wet film niJing power of the sample.
  • the method further comprises the step of determining a force with which the plates are driven together. More preferably, the lorce is determined from a measurement of current drawn by an electrical motor used to drive the plates together.
  • an apparatus for determining a parameter representing the opacity of a sample in accordance with the method of the first aspect of the present invention comprises: a test plate which consists of a first portion having a first optical reflectivity and a second portion having a second, different, optical reflectivity;
  • an optical unit which includes an optical detector for detecting the intensity of light reflected from the first and second portions of the test plate, the optical unit being mounted opposite the test plate for relative movement in a direction perpendicular to the plane of the test plate and having a sample contact plate which lies in a plane parallel to the plane of the test plate;
  • a sample depth sensor for measuring automatically the depth of a sample between the test plate and the sample contact plate of the optical unit as one plate is moved relative to the other.
  • the optical detector is linear array sensor and ⁇ test plate comprises a biochromatic plate having a boundary line aligned with the linear array sensor. More preferably, the first portion of the plate is black and the second portion is
  • test plate is mounted within a sample receiving well opposite the optical unit and the sample contact plate is shaped to at least partially fit within and extend into the sample receiving well.
  • the sample depth sensor comprises a needle proble which is arranged to pass through an aperture provided in one of the test plate and the contact plate, and so co-operate with the other of the contact plate and the test plate, respectively, as the plates move relative to each other.
  • the sample depth sensor further comprises a linear voltage differential transducer.
  • one of the test plate and the contact plate is fixed and the other is
  • the apparatus further comprises an electrical motor to drive the support arms and so cause the plates to be moved relative to each other.
  • the apparatus further comprises a memory device encoded with computer executable instructions for carrying out the method in accordance with the first aspec, of the present invention.
  • the present invention provides an automatic method for measuring wet film hiding power in which reflectance measurements and film thickness measurement are made simultaneously without the need to establish and constrain a wedge of the sample.
  • Figure 1 is a simplified partially sectioned view of an example of an apparatus for determining wet film hiding power in accordance with the present invention
  • Figure 2 is a simplified perspective view of the apparatus of Figure 1 with an optical unit removed
  • Figure 3 is a block diagram showing the functional elements of the apparatus of Figures 1 and 2;
  • Figures 4 to 7 show the results of a test sequence for a paint sample
  • Figure 8 shows a graph of film thickness against concentration of pigment for 98 % opacity
  • Figures 9 to 11 show a flow diagram for a computer program used to control a teest sequence.
  • Figures 1 and 2 show an example of an apparatus for determining wet film hiding power in accordance with the present invention.
  • the apparatus comprises an opaque back anc w.iite glass plate 1 mounted within a cavity 2 machined in a base member 3.
  • the exposed surface of the glass plate 3 defines the base of a shaped sample receiving well 4.
  • An optical unit 5 having a correspondingly shaped transparent glass plate 6 is mounted immediately above the sample well 4 for movement in a direction perpendicular to the plane of the black and white glass plate 3 and is sized
  • the optical unit 5 houses a light source 7 arranged to illuminate the black and white glass plate 1.
  • the light source 7 is mounted at an angle of 45 degrees to a 128 element linear optical array sensor 8 which directly faces the black and white glass plate 1.
  • the optical array 8 extends transversely to the boundary 9 between the black and white areas 10 and 11 so that one portion of the array detects the intensity of light reflected from the black side 10 of the glass whilst another portion detects the intensity of light reflected from the white side 11 of the glass.
  • a linear voltage differential transducer 12 having a fine needle probe 13 which passes through a narrow passage 14 in the base member 3 into the sample well 4 provides a means of determining a depth measurement, as will be described below.
  • the needle probe 13 is free to slide within the passage 14 and any displacement of the probe is detected by the transducer 12 which generates an output signal.
  • the optical u t 5 is held by a pair of support arms 15.
  • the optical urn. 5 is hinged to the support arms 15 about a first pair of pins 16.
  • the support arms 15 are in turn mounted for rotation about a second pair of pins 17 relative to a support block 18 which ii upstanding relative to the base member 3.
  • This doubly pivoted mounting system allows the optical unit 5 to be raised or lowered relative to the base member 3 whilst ensuring that the two plates 1 and 6 remain parallel to each other.
  • An electrical motor 20 (see Figure 3) is provided to control the displacement of the support arms 15 and hence the vertical height of the optical unit 5.
  • FIG. 3 shows a block diagram of the entire system.
  • a microprocessor 18 having a memory 19 is shown connected to the light source 7, the optical sensor 8, a DC motor 20, the linear voltage differential transducer 12, a command keyboard 21 and a display /printer 22.
  • the microprocessor 18 controls the operation of the light source 7 and the DC motor 20 and receives inputs from the optical sensor 8 and transducer 12 which are used to determine a measure of wet film hiding power for a sample, as will be described in detail below.
  • the memory 19 stores a computer program for controlling the test procedure and the determination of hiding power.
  • the operation of the apparatus is as follows: a sample of paint 23, for example, containing a known concentration of an off-white pigment is placed within the sample well 4. With the light source 7 switched on, the electrical motor 20 is actuated to drive the optical unit 5 vertically downwards in a continuous manner so that the glass plate 6 contacts the upper surface of the sample 23. Further vertical movement compresses the sample, causing it to spread out and so reducing the thickness or dep cf the sample. The depth of the sample is measured by t ⁇ critiqueeedle probe 13 which contacts the moving glass plate 6 directly and is thus pushed away as the plate 6 descends. This causes the transducer 12 to generate a signal from the transducer 12 which is fed to the microprocessor 18 for subsequent data manipulation.
  • the sensor array 8 outputs signals corresponding to the detected intensity of light reflected from the two halves 10 and 11 of the black and white plate, respectively, which is also fed to the microprocessor 18.
  • the magnitude of these two signals from the sensor array are the same.
  • a point will be reached where a difference can be detected due to a difference in reflectance between the black and white surfaces of the glass plate. This is shown in Figure 5. This occurs just as the black surface 10 becomes visible under the film of the paint sample, whereupon the difference in reflectivity between the two surfaces takes effect. This point corresponds to a value of 98% opacity and the depth is the hiding power.
  • Figure 6 as the depth continues to decrease and the difference between these two signals becomes greater the measured opacity decreases.
  • Figure 7 shows the results for a different sample of paint which contains a lower concentration of trioxide.
  • the depth at which 98% opacity occurs is, as expected, greater than that shown in Figure 6.
  • a graph such as that shown in Figure 8 can be constructed to allow interpolation of the required concentration of the pigment for any arbitrary coating thickness to be determined with accuracy.
  • the apparatus can also be used to measure the opacity of any compressible substance.
  • further uses of the apparatus could be to measure the opacity of oils or cosmetics.
  • the tests sequence implemented in software is illustrated in the form of a flow diagram in Figures 9 to 11.
  • the computer program stored in the memory 19 has the ability to issue commands via a serial port (not shown) to the various connected hardware components of the apparatus.
  • the computer program starts the test sequence by prompting the user to apply a sample on the centre of the black and white glass plate 1. A depth reading is then taken and stored as an "open plates" depth reading. Subsequently, a command is given to the position motor 20 to start moving the glass plate 6 towards the glass plate 1 at full speed (0.01 mms ).
  • the CPU 18 continues to read the sample depth until the measured depth is less than the open plates depth, at which point the CPU 18 issues a command to decrease the plate closing speed by half.
  • the electric motor 20 that drives the glass plates together has an additional circuit (not shown) that measures the motor current.
  • the current consumed (as determined by a current sensing differential amplifier) reaches a predetermined level the plates have a known force applied. If this force is too excessive it is possible to determine that the plates are static and a stall condition has happened. In this event the user is notihc accordingly so that the test sequence can be restarted.
  • the CPU 18 takes readings from the sensor array 8 and stores the reflectance readings in a corresponding "software array ' in memory, whereby a sensor array position corresponds to the stored location in the software array.
  • the test sequence then continues by taking a further depth reading and comparing the current software array readings against any earlier readings to determine whether or not the ratio of black reflectance S 1 to white reflectance S2 has changed across the sensor array 8. If it has not, the electric motor 20 continues to drive the two glass plates together and further readings are made. As soon as the ratio changes the plates are stopped and subsequently moved apart at low speed. Further readings are then taken from the sensor array 8 and the reflectance values stored in the software array. These are then compared with the earlier software array readings stored in memory to determine the point where a difference in reflectance is first discemable. The plates are then stopped and a final depth reading taken and displayed as the hiding power of the test sample.

Landscapes

  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Analytical Chemistry (AREA)
  • Biochemistry (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • Food Science & Technology (AREA)
  • Medicinal Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Investigating Or Analysing Materials By Optical Means (AREA)

Abstract

The present invention provides an apparatus for determining a parameter representing the opacity of a sample such as, the wet film hiding power, including a test plate (1) having a first portion with a first optical reflectivity and a second portion having a second, different optical reflectivity; an unit (5) which includes an optical detector (8) for detecting intensity of light reflected from the first and second portions of the test plate (1), wherein the optical unit is mounted opposite the test plate for relative movement perpendicular to the plane of the test plate and having a sample contact plate (6) which lies in a plane parallel to that of the test plate. A sample depth sensor (12, 13) is also provided for measuring automatically the depth of a sample between the test plate (1) and the sample contact plate (6) of the optical unit as the plates move relative to each other.

Description

An Apparatus for Measuring Opacity
Background to the Invention
In the field of coatings, for example paints, an important consideration is the opacity of a product. In the case of paints, one parameter indicative of opacity is the wet film hiding power. This is a measure (m2/kg) of how good the paint is at hiding the surface on which is has been applied. For paints, a higher hiding power means less paint needs to be applied to cover a surface successfully. Opacity is also important in the field of cosmetics.
A further consideration is that of the cost of raw materials. In the paints industry trioxide (TiO2) is used as a white additive, but it is a very expensive chemical. Accordingly, paints manufacturers need Lo del 're the optimal amount of trioxide to add to a paint such that at some predetermined average thickness of application of paint, 98% opacity will be achieved. This is the degree of opacity which is accepted as an industry standard as providin a satisfactory covering of a surface. Using more than this optimal amount of trioxide is an expensive waste of material and using less will adversely affect the hiding powder of the paint.
Instruments already exist that can measure opacity as a function of coating thickness. One such example is the Pfund black and white precision cryptometer, which is designed to allow measurement of hiding power of wet paint. In this instrument, a photo-electric device is used to measure the reflectance of a wet film of paint constrained as a wedge shaped layer of uniformly increasing depth on a glass substrate along the length of a black and white boundary of the substrate. The photo-electric device moves in a direction parallel to the black and white boundary line until a position is found where the reflectance of paint over the black area is no longer the same as that of the white area. The film thickness at this position is determined with reference to a graduated scale provided to one side of the substrate. This is the thickness where the paint has 98 % opacity with the known concentration of trioxide.
The problem with this instrument is that it is difficult to establish the wedge of paint in a truly repeatable manner. In particular, the film thickness does not always vary along the length of the black and white boundary of the glass substrate in the expected manner indicated by the scale so that the determination of the film thickness is not reliable.
Summary of the Invention
According to a first aspect of the present invention, a method for determining a
parameter representing the opacity of a sample comprises the steps of compressing a sample between two parallel plates, one of the plates consisting of a first portion having a first optical reflectivity and a second portion having a second, different, optical reflectivity, and, at a number of measuring instants, detecting the intensity of light reflected from each of the first and second portions of the one plate and measuring the depth of the sample between the two plates. Preferably, the parameter is the wet film hiding power.
Preferably, the plates are driven together at a first predetermined speed whilst measuring the depth of the sample at a number of measuring instances until a difference is detected between the intensity of light reflected from the first and second portions of the one plate.
Preferably, after said difference is detected the relative motion of the plates is reversed and the plates driven apart at a second predetermined speed, the second predetermined speed being slower than the first predetermined speed, whilst continuing to detect the intensity of light reflected from each of the first and second portions of the one plate at a number of measuring instants and comparing these measurements with earlier measurements to determine the depth at which said difference is first detectable and thereby the wet film niJing power of the sample.
Preferably, the method further comprises the step of determining a force with which the plates are driven together. More preferably, the lorce is determined from a measurement of current drawn by an electrical motor used to drive the plates together.
According to a second aspect of the present invention, an apparatus for determining a parameter representing the opacity of a sample in accordance with the method of the first aspect of the present invention, comprises: a test plate which consists of a first portion having a first optical reflectivity and a second portion having a second, different, optical reflectivity;
an optical unit which includes an optical detector for detecting the intensity of light reflected from the first and second portions of the test plate, the optical unit being mounted opposite the test plate for relative movement in a direction perpendicular to the plane of the test plate and having a sample contact plate which lies in a plane parallel to the plane of the test plate; and,
a sample depth sensor for measuring automatically the depth of a sample between the test plate and the sample contact plate of the optical unit as one plate is moved relative to the other.
i-i, erably, the optical detector is linear array sensor and ά^ test plate comprises a biochromatic plate having a boundary line aligned with the linear array sensor. More preferably, the first portion of the plate is black and the second portion is
white.
Preferably, the test plate is mounted within a sample receiving well opposite the optical unit and the sample contact plate is shaped to at least partially fit within and extend into the sample receiving well.
Preferably, the sample depth sensor comprises a needle proble which is arranged to pass through an aperture provided in one of the test plate and the contact plate, and so co-operate with the other of the contact plate and the test plate, respectively, as the plates move relative to each other.
Preferably, the sample depth sensor further comprises a linear voltage differential transducer.
Preferably, one of the test plate and the contact plate is fixed and the other is
pivotally mounted between a pair of support arms which are themselves pivotally connected to a support block to ensure that at all times the plates remain parallel to each other whilst being driven together.
Preferably, the apparatus further comprises an electrical motor to drive the support arms and so cause the plates to be moved relative to each other.
Preferably, the apparatus further comprises a memory device encoded with computer executable instructions for carrying out the method in accordance with the first aspec, of the present invention.
The present invention provides an automatic method for measuring wet film hiding power in which reflectance measurements and film thickness measurement are made simultaneously without the need to establish and constrain a wedge of the sample.
Brief Description of the Drawings
An example of the present invention will now be described with reference to the accompanying drawings, in which:
Figure 1 is a simplified partially sectioned view of an example of an apparatus for determining wet film hiding power in accordance with the present invention; Figure 2 is a simplified perspective view of the apparatus of Figure 1 with an optical unit removed; Figure 3 is a block diagram showing the functional elements of the apparatus of Figures 1 and 2;
Figures 4 to 7 show the results of a test sequence for a paint sample; Figure 8 shows a graph of film thickness against concentration of pigment for 98 % opacity; and, Figures 9 to 11 show a flow diagram for a computer program used to control a teest sequence.
Detailed inscription
Figures 1 and 2 show an example of an apparatus for determining wet film hiding power in accordance with the present invention. The apparatus comprises an opaque back anc w.iite glass plate 1 mounted within a cavity 2 machined in a base member 3. The exposed surface of the glass plate 3 defines the base of a shaped sample receiving well 4. An optical unit 5 having a correspondingly shaped transparent glass plate 6 is mounted immediately above the sample well 4 for movement in a direction perpendicular to the plane of the black and white glass plate 3 and is sized
so that it can fit within the sample well 4.
The optical unit 5 houses a light source 7 arranged to illuminate the black and white glass plate 1. The light source 7 is mounted at an angle of 45 degrees to a 128 element linear optical array sensor 8 which directly faces the black and white glass plate 1. The optical array 8 extends transversely to the boundary 9 between the black and white areas 10 and 11 so that one portion of the array detects the intensity of light reflected from the black side 10 of the glass whilst another portion detects the intensity of light reflected from the white side 11 of the glass.
A linear voltage differential transducer 12 having a fine needle probe 13 which passes through a narrow passage 14 in the base member 3 into the sample well 4 provides a means of determining a depth measurement, as will be described below. The needle probe 13 is free to slide within the passage 14 and any displacement of the probe is detected by the transducer 12 which generates an output signal.
The optical u t 5 is held by a pair of support arms 15. The optical urn. 5 is hinged to the support arms 15 about a first pair of pins 16. The support arms 15 are in turn mounted for rotation about a second pair of pins 17 relative to a support block 18 which ii upstanding relative to the base member 3. This doubly pivoted mounting system allows the optical unit 5 to be raised or lowered relative to the base member 3 whilst ensuring that the two plates 1 and 6 remain parallel to each other. An electrical motor 20 (see Figure 3) is provided to control the displacement of the support arms 15 and hence the vertical height of the optical unit 5.
Figure 3 shows a block diagram of the entire system. A microprocessor 18 having a memory 19 is shown connected to the light source 7, the optical sensor 8, a DC motor 20, the linear voltage differential transducer 12, a command keyboard 21 and a display /printer 22. The microprocessor 18 controls the operation of the light source 7 and the DC motor 20 and receives inputs from the optical sensor 8 and transducer 12 which are used to determine a measure of wet film hiding power for a sample, as will be described in detail below. The memory 19 stores a computer program for controlling the test procedure and the determination of hiding power.
The operation of the apparatus is as follows: a sample of paint 23, for example, containing a known concentration of an off-white pigment is placed within the sample well 4. With the light source 7 switched on, the electrical motor 20 is actuated to drive the optical unit 5 vertically downwards in a continuous manner so that the glass plate 6 contacts the upper surface of the sample 23. Further vertical movement compresses the sample, causing it to spread out and so reducing the thickness or dep cf the sample. The depth of the sample is measured by t ^ „eedle probe 13 which contacts the moving glass plate 6 directly and is thus pushed away as the plate 6 descends. This causes the transducer 12 to generate a signal from the transducer 12 which is fed to the microprocessor 18 for subsequent data manipulation. At the same time the sensor array 8 outputs signals corresponding to the detected intensity of light reflected from the two halves 10 and 11 of the black and white plate, respectively, which is also fed to the microprocessor 18. As shown in Figure 4, initially, the magnitude of these two signals from the sensor array are the same. However, as the depth of the sample decreases a point will be reached where a difference can be detected due to a difference in reflectance between the black and white surfaces of the glass plate. This is shown in Figure 5. This occurs just as the black surface 10 becomes visible under the film of the paint sample, whereupon the difference in reflectivity between the two surfaces takes effect. This point corresponds to a value of 98% opacity and the depth is the hiding power. As shown in Figure 6, as the depth continues to decrease and the difference between these two signals becomes greater the measured opacity decreases.
Figure 7 shows the results for a different sample of paint which contains a lower concentration of trioxide. The depth at which 98% opacity occurs is, as expected, greater than that shown in Figure 6.
If a series of such tests are performed for a series of samples having different concentrations of trioxide then a graph such as that shown in Figure 8 can be constructed to allow interpolation of the required concentration of the pigment for any arbitrary coating thickness to be determined with accuracy.
The apparatus can also be used to measure the opacity of any compressible substance. For example, further uses of the apparatus could be to measure the opacity of oils or cosmetics.
The tests sequence implemented in software is illustrated in the form of a flow diagram in Figures 9 to 11. The computer program stored in the memory 19 has the ability to issue commands via a serial port (not shown) to the various connected hardware components of the apparatus. The computer program starts the test sequence by prompting the user to apply a sample on the centre of the black and white glass plate 1. A depth reading is then taken and stored as an "open plates" depth reading. Subsequently, a command is given to the position motor 20 to start moving the glass plate 6 towards the glass plate 1 at full speed (0.01 mms ). The CPU 18 continues to read the sample depth until the measured depth is less than the open plates depth, at which point the CPU 18 issues a command to decrease the plate closing speed by half.
The electric motor 20 that drives the glass plates together has an additional circuit (not shown) that measures the motor current. When the current consumed (as determined by a current sensing differential amplifier) reaches a predetermined level the plates have a known force applied. If this force is too excessive it is possible to determine that the plates are static and a stall condition has happened. In this event the user is notihc accordingly so that the test sequence can be restarted.
After decreasing the plate closing speed the CPU 18 takes readings from the sensor array 8 and stores the reflectance readings in a corresponding "software array ' in memory, whereby a sensor array position corresponds to the stored location in the software array.
Again, a further test for stall is made. If it is determined that a stalled condition has not been reached, the test sequence continues.
The test sequence then continues by taking a further depth reading and comparing the current software array readings against any earlier readings to determine whether or not the ratio of black reflectance S 1 to white reflectance S2 has changed across the sensor array 8. If it has not, the electric motor 20 continues to drive the two glass plates together and further readings are made. As soon as the ratio changes the plates are stopped and subsequently moved apart at low speed. Further readings are then taken from the sensor array 8 and the reflectance values stored in the software array. These are then compared with the earlier software array readings stored in memory to determine the point where a difference in reflectance is first discemable. The plates are then stopped and a final depth reading taken and displayed as the hiding power of the test sample.

Claims

Claims
1. A method for determining a parameter representing the opacity of a sample comprising the steps of:
compressing a sample between two parallel plates, one of the plates consisting of a first portion having a first optical reflectivity and a second portion having a second, different, optical reflectivity; and, at a number of measuring instants, detecting the intensity of light reflected from each of the first and second portions of the one plate and measuring the depth of the sample between the two plates.
2. A method according to claim 1, in which the parameter is the wet film hiding power.
3. A method according to claim 1 or 2, in whk .., 'he plates are driven together at a first predetermined speed whilst measuring the depth of the sample at a number of measuring instances until a difference is detected between the intensity of light reflected from the first and second portions of the om plate.
4. A method according to claim 3, in which after said difference is detected the relative motion of the plates is reversed and the plates driven apart at a second predetermined speed, the second predetermined speed being slower than the first predetermined speed, whilst continuing to detect the intensity of light reflected from each of the first and second portions of the one plate at a number of measuring instants and comparing these measurements with earlier measurements to determine the depth at which said difference is first detectable and thereby the wet film hiding power of the sample.
5. A method according to any preceding claim, further comprising the step of determining a force with which the plates are driven together.
6. A method according to claim 5, in which said force is determined from a measurement of current drawn by an electrical motor used to drive the plates together.
7. An apparatus for determining a parameter representing the opacity of a sample, comprising: a test plate (1) consisting of a first portion having a first optical reflectivity . "'d a second portion having a second, different, optical . ■. f ectivity; an optical unit (5) which includes an optical detector (8) for detecting the intensity of light reflected from the first and second portions of the test plate (1), tl e optical unit (5) being mounted opposite the test plate (Y, for relative movement in a direction perpendicular to the plane of the test plate (1) and having a sample contact plate (6) which lies in a plane parallel to the plane of the test plate (1); and. a sample depth sensor (12, 13) for measuring automatically the depth of a sample between the test plate (1) and the sample contact plate (6) of the optical unit
(5) as one plate is moved relative to the other.
8. An apparatus according to claim 7, in which the parameter is the wet film hiding power.
9. An apparatus according to claim 7 or 8, in which the optical detector (8) is a linear array sensor.
10. An apparatus according to any of claims 7 to 9, in which the test plate comprises a biochromatic plate having a boundary line (9) aligned with the linear array sensor (8).
11. An apparatus according to any of claims 7 to 10, in which said first portion of the plate (1) is black and said second portion is white.
12. An apparatus according to any of claims 7 to 11, in which the test plate (1) is ...junted within a sample receiving well (4) opposite the u -ical unit (5) and the sample contact plate (6) is shaped to at least partially fit within and extend into the sample receiving well (4).
13. An apparatus according to any of claims 7 to 12, in which the sample depth sensor comprises a needle probe (13) which is arranged to pass through an aperture (14) provided in one of the test plate (1) and the contact plate (6), and so co-operate with the other of the contact plate (6) and the test plate (1), respectively, as the plates move relative to each other.
14. An apparatus according to claim 13, in which the sample depth sensor further comprises a linear voltage differential transducer (12).
15. An apparatus according to any of claims 7 to 14, in which one of the test plate (1) and the contact plate (6) is fixed and the other is pivotally mounted between a pair of support arms (15) which are themselves pivotally connected to a support block (18) to ensure that at all times the plates remain parallel to each other whilst being driven together.
16. An apparatus according to claim 15, further comprising an electrical motor (20) to drive the support arms (15) and so cause the plates to be moved relative to each other.
17. An apparatus according to any of claims 7 to 16, further comprising a memo..' "evice encoded with computer executable instructions k arrying out the method of any of claims 1 to 6.
PCT/GB1999/003561 1998-10-28 1999-10-28 An apparatus for measuring opacity WO2000025133A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9823618.5 1998-10-28
GBGB9823618.5A GB9823618D0 (en) 1998-10-28 1998-10-28 An apparatus for measuring wet film hiding power

Publications (1)

Publication Number Publication Date
WO2000025133A1 true WO2000025133A1 (en) 2000-05-04

Family

ID=10841455

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/003561 WO2000025133A1 (en) 1998-10-28 1999-10-28 An apparatus for measuring opacity

Country Status (2)

Country Link
GB (1) GB9823618D0 (en)
WO (1) WO2000025133A1 (en)

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008070154A3 (en) * 2006-12-05 2008-11-20 Du Pont Method for characterizing hiding of coating compositions and apparatus used therefor
WO2010090912A1 (en) * 2009-02-03 2010-08-12 Peter Du-Hai Zuo Method and apparatus for measuring light absorption of liquid samples
CN102507505A (en) * 2011-11-10 2012-06-20 攀枝花鼎星钛业有限公司 Determination method for covering power of titanium dioxide
CN104345135A (en) * 2013-12-18 2015-02-11 浙江吉利控股集团有限公司 Paint covering power measuring device and paint covering power measuring method
WO2020172133A1 (en) * 2019-02-19 2020-08-27 The Chemours Company Fc, Llc Assessment of the applied hiding of a coating
CN111721742A (en) * 2020-06-29 2020-09-29 亚士漆(上海)有限公司 Auxiliary device for testing covering power of wet coating and method for testing covering power of wet coating
CN113125381A (en) * 2020-01-15 2021-07-16 日涂(上海)涂料研究开发有限公司 Detection method and comparison method for evaluating covering power of wet coating film and special pressing plate device thereof
CN114112930A (en) * 2020-08-26 2022-03-01 立邦涂料（中国）有限公司 Testing device and testing method for contrast ratio of paint wet film

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1468075A (en) * 1919-11-21 1923-09-18 Pfund August Herman Determining the hiding power of paints and pigments
GB1085595A (en) * 1965-08-09 1967-10-04 Polymark Int Ltd Testing or comparing the visual properties of spreadable materials
GB1404636A (en) * 1971-11-17 1975-09-03 Basf Farben & Fasern Method and apparatus for determining the hiding power of paints
WO1998016822A1 (en) * 1996-10-15 1998-04-23 Renner Herrmann S.A. Fluid analysis system and method, for analysing characteristic properties of a fluid

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1468075A (en) * 1919-11-21 1923-09-18 Pfund August Herman Determining the hiding power of paints and pigments
GB1085595A (en) * 1965-08-09 1967-10-04 Polymark Int Ltd Testing or comparing the visual properties of spreadable materials
GB1404636A (en) * 1971-11-17 1975-09-03 Basf Farben & Fasern Method and apparatus for determining the hiding power of paints
WO1998016822A1 (en) * 1996-10-15 1998-04-23 Renner Herrmann S.A. Fluid analysis system and method, for analysing characteristic properties of a fluid

Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2008070154A3 (en) * 2006-12-05 2008-11-20 Du Pont Method for characterizing hiding of coating compositions and apparatus used therefor
WO2010090912A1 (en) * 2009-02-03 2010-08-12 Peter Du-Hai Zuo Method and apparatus for measuring light absorption of liquid samples
US7969575B2 (en) 2009-02-03 2011-06-28 Quawell Technology, Inc. Method and apparatus for measuring light absorption of liquid samples
CN102507505A (en) * 2011-11-10 2012-06-20 攀枝花鼎星钛业有限公司 Determination method for covering power of titanium dioxide
CN102507505B (en) * 2011-11-10 2014-03-05 攀枝花鼎星钛业有限公司 Determination method for covering power of titanium dioxide
CN104345135B (en) * 2013-12-18 2016-04-27 浙江吉利控股集团有限公司 A kind of method utilizing paint covering power determinator to measure paint covering power
CN104345135A (en) * 2013-12-18 2015-02-11 浙江吉利控股集团有限公司 Paint covering power measuring device and paint covering power measuring method
WO2020172133A1 (en) * 2019-02-19 2020-08-27 The Chemours Company Fc, Llc Assessment of the applied hiding of a coating
CN113125381A (en) * 2020-01-15 2021-07-16 日涂(上海)涂料研究开发有限公司 Detection method and comparison method for evaluating covering power of wet coating film and special pressing plate device thereof
CN113125381B (en) * 2020-01-15 2023-04-11 日涂(上海)涂料研究开发有限公司 Detection method and comparison method for evaluating covering power of wet coating film and special pressing plate device thereof
CN111721742A (en) * 2020-06-29 2020-09-29 亚士漆(上海)有限公司 Auxiliary device for testing covering power of wet coating and method for testing covering power of wet coating
CN111721742B (en) * 2020-06-29 2023-11-17 亚士漆(上海)有限公司 Paint wet film hiding power test auxiliary device and paint wet film hiding power test method
CN114112930A (en) * 2020-08-26 2022-03-01 立邦涂料（中国）有限公司 Testing device and testing method for contrast ratio of paint wet film
CN114112930B (en) * 2020-08-26 2023-06-27 立邦涂料（中国）有限公司 Paint wet film contrast ratio testing device and testing method

Also Published As

Publication number Publication date
GB9823618D0 (en) 1998-12-23

Similar Documents

Publication Publication Date Title
US7943092B2 (en) Portable surface plasmon resonance biosensor
US3850526A (en) Optical method and system for measuring surface finish
EP0048346A1 (en) Automatic measurement of areas
CN104568781A (en) Method for automatically detecting and evaluating color of laser beam emitting paper and quality of laser beams
WO2000025133A1 (en) An apparatus for measuring opacity
JPS59208443A (en) Method and device for detecting and measuring flock
EP0321836A2 (en) Improved reflectance photometer
JP2001264294A (en) Toner characteristic analyzer
US4899102A (en) Electrode system for a parallel plate dielectric analyzer
EP0055914A2 (en) Fluorescence polarization analyzer
CN204373781U (en) A kind of light beam laser paper color and light beam quality automatic checkout system
KR0151703B1 (en) Liquid crystal device for calibration and testing of optical instruments
EP0347125A2 (en) Parallel plate dielectric analyzer
KR940004671B1 (en) Automatic apparatus for measuring density
JPH0614025B2 (en) Ultrasonic wave metal appraisal device
JP3203411B2 (en) Clinical testing device and method
JPH09178470A (en) Surface roughness test evaluation method and device thereof
RU2819268C1 (en) Method of detecting hidden defects and device for their detection
WO1989001152A1 (en) Fabric testing apparatus
CN212585658U (en) Food inspection instrument
TR200100892T2 (en) Test device for the detection and determination of substance inhomogeneities
JPH09292339A (en) Method and device for measuring reflective index without destruction
JPH0623757B2 (en) Measuring method and measuring device for measuring amount of oily substance
Rakhimov et al. Development of Optoelectronic Control Measurement System Based on Attenuated Total Reflectance Effect
US3428402A (en) Apparatus for determining the concentration of a substance in a solution

Legal Events

Date Code Title Description
AK Designated states

Kind code of ref document: A1

Designated state(s): JP US

AL Designated countries for regional patents

Kind code of ref document: A1

Designated state(s): AT BE CH CY DE DK ES FI FR GB GR IE IT LU MC NL PT SE

121 Ep: the epo has been informed by wipo that ep was designated in this application
DFPE Request for preliminary examination filed prior to expiration of 19th month from priority date (pct application filed before 20040101)
122 Ep: pct application non-entry in european phase