EP3574300A1 - Fluid sampling device - Google Patents

Fluid sampling device

Info

Publication number
EP3574300A1
EP3574300A1 EP17702155.7A EP17702155A EP3574300A1 EP 3574300 A1 EP3574300 A1 EP 3574300A1 EP 17702155 A EP17702155 A EP 17702155A EP 3574300 A1 EP3574300 A1 EP 3574300A1
Authority
EP
European Patent Office
Prior art keywords
culture media
inlet
point
distance
fluid
Prior art date
Legal status (The legal status 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 status listed.)
Withdrawn
Application number
EP17702155.7A
Other languages
German (de)
French (fr)
Inventor
Gethin Rhys Jones
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Pinpoint Scientific Ltd
Original Assignee
Pinpoint Scientific Ltd
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 Pinpoint Scientific Ltd filed Critical Pinpoint Scientific Ltd
Publication of EP3574300A1 publication Critical patent/EP3574300A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
    • G01N1/2208—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling with impactors
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2202—Devices for withdrawing samples in the gaseous state involving separation of sample components during sampling
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12M—APPARATUS FOR ENZYMOLOGY OR MICROBIOLOGY; APPARATUS FOR CULTURING MICROORGANISMS FOR PRODUCING BIOMASS, FOR GROWING CELLS OR FOR OBTAINING FERMENTATION OR METABOLIC PRODUCTS, i.e. BIOREACTORS OR FERMENTERS
    • C12M23/00—Constructional details, e.g. recesses, hinges
    • C12M23/50—Means for positioning or orientating the apparatus
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N1/00—Sampling; Preparing specimens for investigation
    • G01N1/02—Devices for withdrawing samples
    • G01N1/22—Devices for withdrawing samples in the gaseous state
    • G01N1/2273—Atmospheric sampling
    • 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
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0006—Calibrating gas analysers

Definitions

  • This invention relates to a fluid sampling device and more particularly but not solely to a device for sampling the quality of air.
  • Microbial air sampling devices are well known and comprise a sealed chamber in which a petri dish containing a culture media is placed. During testing, a known volume of air is then drawn into the chamber through a slit, where it is directed onto the culture media. The petri dish rotates on a turntable at a selected speed and any micro-organisms in the air are circumferentially spatially separated by the plate rotation. Because of their mass, the micro-organisms become impacted on the surface of the culture media and an analysis of microbial contamination over time can thus be achieved by cultivating the media.
  • the distance between the slit or other air inlet aperture needs to be fixed to ensure that the microorganisms are correctly impacted onto the cultural media and to ensure that each test is carried out under the same conditions. Since the distance is dependent on the fill level of the culture media in the petri dish, a problem exists because the distance between the surface of the culture media and the air inlet can vary between tests due to variances in the fill level.
  • some known air sampling devices are able to measure the distance between the air inlet and the surface of the culture media at the start of the test, so that the height of the turn table can then be adjusted to achieve the required distance of separation (typically 2.5mm).
  • the required distance of separation typically 2.5mm.
  • a motor raises or lowers the turntable until light reflected by the central region of the culture media is incident on a photodetector, at which point the top surface of the culture media is known to be at the required distance of separation.
  • a problem of this arrangement is that the surface of the culture media may be inclined across the diameter of the petri dish and thus it will be appreciated that the separation distance will vary as the dish is rotated. Also, there is a risk that the turntable may not rotate in a plane which is truly normal to its axis of rotation. Also, it is difficult for the device to determine whether the turntable needs to be raised or lowered.
  • a fluid sampling device comprising fluid inlet, a turntable having a major surface for supporting a container containing culture media onto which a fluid flow through the inlet is directed, means for rotating the turntable about an axis of rotation extending normal to said major surface, a laser arranged to direct a light beam onto a point on the surface of the culture media which is radially offset from the axis of rotation, an optical sensor array arranged to receive a portion of the beam reflected from said point, and a processor connected to the optical sensor array and arranged to output a control signal to an actuator to adjust the distance between the surface of the culture media and the inlet and to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point.
  • the predetermined point on the optical sensor array may be determined during a calibration procedure, for example by placing a reflective surface at the desired separation distance.
  • the processor comprises a memory which then stores the resultant point of incidence of the reflected beam on the optical sensor array.
  • the processor outputs a control signal to the actuator to adjust the distance between the surface of the culture media and the inlet and to bring the point of incidence of the reflected beam on the optical sensor array substantially back to the predetermined point.
  • the separation distance is maintained during sampling.
  • the turntable is not rotating in a plane which is truly normal to its axis of rotation.
  • the use of an optical sensor array allows the processor to determine whether the separation distance needs to be increased or decreased to bring the point of incidence of the reflected beam on the optical sensor array substantially back to the predetermined point.
  • the predetermined point may be a point disposed at or adjacent the centre of the array.
  • the use of a laser provides a simple, accurate and un-harmful way of controlling the distance between the upper surface of the culture media and the inlet.
  • the processor is arranged to continuously adjust the distance between the surface of the culture media and the inlet.
  • the processor is arranged adjust the distance between the surface of the culture media and the inlet at a set number of rotational positions of the turntable.
  • the turntable may be advanced in a plurality of rotational steps. For example, there may be 120,000 steps per 360° rotation.
  • the processor may be arranged adjust the distance between the surface of the culture media and the inlet at each or a set number of rotational steps.
  • the optical sensor array may be a unitary device or it may be a plurality of discrete devices.
  • the array may be elongate and may be arranged such that the longitudinal axis thereof extends in the direction in which the distance between the surface of the culture media and the inlet is adjusted.
  • the array may be 1 pixel wide and over 3 pixels long.
  • the point on the surface of the culture media at which the laser is directed may be at or adjacent a region on the surface of the culture media at which the fluid flow is directed through the inlet.
  • the laser may be directed onto the surface of the culture media at an angle of incidence which less than 45%, so that the reflected beam from the surface of the culture media is more spatially separated from beams which may be reflected from the bottom of the dish or the turntable.
  • the so-called D50 value is often used to describe the impact efficiency of an air sampling device.
  • the D50 value is the particle size at which 50% of the particles are collected, and 50% pass through the sampling device because they are too small to impact.
  • a sampling device with a D50 value of 1 is 50% efficient at collecting particles of 1 micron in diameter.
  • a test procedure will specify the D50 value of the sampling device to be used and this can lead to problems if different tests specify different D50 values, since users will need to keep a different sampling device for each test.
  • sampling devices Since the D50 value is partly dependant on the dimension of the air inlet, some sampling devices have inlets which can be interchanged according to the desired D50 value i.e. a wide inlet will have a higher flow rate with the result that a greater number of smaller particles will be impacted compared with a narrow inlet.
  • a fluid sampling device comprising fluid inlet, a turntable having a major surface for supporting a container containing culture media onto which a fluid flow through the inlet is directed, means for rotating the turntable about an axis of rotation extending normal to said major surface, an input for setting the desired impact efficiency of the device, a detector for detecting the distance between the surface of the culture media and the inlet, a processor connected to the detector and arranged to output a control signal to an actuator to adjust the distance between the surface of the culture media and the inlet according to the set desired impact efficiency.
  • a fluid sampling device in accordance with the first aspect invention can be used to perform tests over a range of desired impact efficiencies, such as D50 or another D value. This is achieved by varying the distance between the surface of the culture media and the inlet on the basis that a greater number of smaller particles will be impacted when the distance is small compared when the distance is great.
  • the detector may comprise a laser arranged to direct a light beam onto a point on the surface of the culture media which is radially offset from the axis of rotation and an optical sensor array arranged to receive a portion of the beam reflected from said point.
  • the processor may output a control signal to the actuator to adjust the distance between the surface of the culture media and the inlet to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point according to the desired impact efficiency.
  • the processor may output a further control signal to control the flow rate of the fluid entering the device, so that the range of impact efficiencies achievable by the device can be increased.
  • the input may comprise means for entering or selecting the percentage efficiency and/or particle size related to the efficiency. Also in accordance with the present invention, as seen from the first aspect, there is provided a method of sampling a fluid, the method comprising:
  • determining in a processor the position of the reflected beam on the sensor determining in a processor the position of the reflected beam on the sensor; and outputting a control signal from the processor to an actuator to adjust the distance between the surface of the culture media and a fluid inlet to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point.
  • the predetermined point may be a point disposed at or adjacent the centre of the array.
  • the predetermined point on the optical sensor array may be determined during a calibration procedure, for example by placing a reflective surface at the desired separation distance.
  • the resultant point of incidence of the reflected beam on the optical sensor array may then be stored in a memory to provide a point of reference for the control signal.
  • the processor may continuously adjust the distance between the surface of the culture media and the inlet during rotation of the turntable.
  • the processor may adjust the distance between the surface of the culture media and the inlet at a set number of rotational positions of the turntable.
  • the point on the surface of the culture media at which the laser is directed may be at or adjacent a region on the surface of the culture media at which the fluid flow is directed through the inlet.
  • a method of sampling a fluid comprising:
  • the distance may be adjusted by a control signal output by a processor to an actuator which varies the distance between the surface of the culture media and the fluid inlet.
  • the processor may determine the distance required for the set impact efficiency using an algorithm or a memory of stored values.
  • the processor may output a further control signal to control the flow rate of the fluid entering the device, so that the range of impact efficiencies achievable by the device can be increased.
  • Figure 1 is a schematic diagram of an upper portion of an air sampling apparatus in accordance with the present invention.
  • Figure 2 is a perspective view from below of the air inlet and height sensor portions of the air sampling apparatus of Figure 1 ;
  • Figure 3 is a perspective view illustrating the operation of the height sensor of the air sampling apparatus of Figure 1.
  • an upper portion of an air sampling apparatus comprises an external housing having a body portion 10 and a closure 1 1 for closing the open upper end of the body portion 10.
  • the housing defines an internal compartment 12 which is exposed when the closure 1 1 is opened.
  • a turntable 13 is mounted inside the compartment 12 for rotation about a vertical axis A, the turntable 13 having an upper surface which lies in a plane normal to the axis A of rotation.
  • a motor 14 or other type of actuator is arranged to raise and lower the turntable 13.
  • a motor and fan unit (not shown) is disposed inside the housing for drawing air into the compartment 12 through a tubular inlet 15 disposed in the closure 11.
  • the inlet 15 comprises a bottom wall 24 in which an elongate slit 16 is formed.
  • the bottom wall of the inlet 15 lies in the plane which is parallel to the plane of the upper surface of the turntable 13.
  • the inlet 15 is disposed directly above the turntable 13 in a position which is radially offset from the axis A of rotation and which is arranged such that the slit 16 extends radially of the axis A.
  • a petri dish 20 filled with culture media 21 is placed on upper surface of the turntable 13.
  • the upper surface of the culture media 21 lies in a plane which is inclined across the dish 20 relative to the upper surface of the turntable 13.
  • a height sensor 17 is disposed alongside the inlet 15.
  • the height sensor 17 comprises a laser 22 arranged to direct a light beam B at the upper surface of the culture media 21 at a shallow angle of approximately 35°.
  • the height sensor 17 also comprises an elongate photo sensor array 18 mounted on a circuit board 23.
  • the photo sensor array 18 comprises a 1 x 100 array of photo cells each having an 8-bit resolution.
  • the photo sensor array 18 is arranged to receive a portion RB of the beam B which is reflected by the upper surface of the culture media 21.
  • the photo sensor array 18 lies in plane substantially normal to the reflected beam RB and is oriented such that its elongate axis extends in the direction of upward and downward movement of the turntable 13.
  • a processor 19 is connected to the circuit board 23 of the photo-sensor array 18 and comprises an output which is connected to the motor 14 arranged to raise and lower the turntable 13.
  • the device Prior to use, the device is calibrated by placing a reflective surface at exactly 2.5mm below the bottom surface 24 of the inlet 15.
  • the laser 22 is then energised to produce a beam which reflects off the reflective surface onto the photo sensor array 18.
  • the photo sensor array 18 is preferably arranged such that the reflected beam is incident on a photo cell disposed intermediate opposite ends of the array. The point of incidence is then recorded and stored by the processor 19. Following calibration, the reflective surface is removed.
  • the motor and fan unit is energised to draw air into the internal compartment 12 where it is directed through the slit 16 onto a region of the culture media 21.
  • the petri dish 20 rotates on the turntable 13 at a selected speed and any micro-organisms in the air are circumferentially spatially separated by the dish rotation.
  • the height sensor 17 is energised to direct the laser B onto the upper surface of the culture media 21 at an adjacent point either lagging or leading the region on the surface of the culture media 21 at which the air flow is directed through the slit 16.
  • the processor 19 analyses the position of the reflected beam RB on the photo-sensor array 18 and outputs a control signal to the actuator 14 to raise or lower the turntable 13, thereby bringing the surface of the culture media 21 to the required distance of 2.5mm away from the slit 16.
  • the processor 19 senses that the reflected beam RB has moved away from the stored point of incidence on the photo- sensor array 18, perhaps because the surface of the media 21 is inclined or because the turntable 13 is rotating in an uneven plane, it outputs a control signal to the actuator 14 to raise or lower the turntable 13, thereby bringing the surface of the culture media 21 back to the required distance as the turntable rotates.
  • a keypad 50 is provided for optionally entering or selecting the percentage impact efficiency (e.g. D50) and/or particle size (e.g. 1 ⁇ ) related to the percentage impact efficiency.
  • the stored point of incidence on the photo-sensor array 18 is determined by the processor according to the set desired impact efficiency and the processor outputs a control signal to the actuator 14 to raise or lower the turntable 13, thereby bringing the surface of the culture media 21 to the required distance of away from the slit 16 to achieve the selected impact efficiency.
  • An air sensing apparatus in accordance with the present invention is able to maintain a set distance D1 between the inlet 15 and the culture media 15 even if the surface of the culture media 21 is inclined across the width of the petri dish 20. In this manner, the surface of the culture media 21 is exposed to substantially the same airflow conditions through the slit 16 throughout the rotational cycle of the turntable 13.
  • the apparatus also enables samples to be taken using a specified impact efficiency.

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Abstract

An air sampling device comprises an air inlet (15), a turntable (13) for supporting a petri dish (20) containing culture media (21) onto which an air flow through the inlet (15) is directed, a laser (22) arranged to direct a light beam B onto a point on the surface of the culture media (21) which is radially offset from the axis of rotation, an optical sensor array (18) arranged to receive a portion RB of the beam reflected from the point, and a processor (19) connected to the optical sensor array (18) and arranged to output a control signal to an actuator (14) to adjust the distance between the surface of the culture media (21) and the inlet (15) and to maintain the point of incidence of the reflected beam RB on the optical sensor array (18) substantially at a predetermined point.

Description

FLUID SAMPLING DEVICE
This invention relates to a fluid sampling device and more particularly but not solely to a device for sampling the quality of air.
There is often the requirement, for example in pharmaceutical clean rooms, to sample quality of air in order to determine microbial levels. Microbial air sampling devices are well known and comprise a sealed chamber in which a petri dish containing a culture media is placed. During testing, a known volume of air is then drawn into the chamber through a slit, where it is directed onto the culture media. The petri dish rotates on a turntable at a selected speed and any micro-organisms in the air are circumferentially spatially separated by the plate rotation. Because of their mass, the micro-organisms become impacted on the surface of the culture media and an analysis of microbial contamination over time can thus be achieved by cultivating the media. Whilst such sampling devices provide the benefit of time analysis, the distance between the slit or other air inlet aperture needs to be fixed to ensure that the microorganisms are correctly impacted onto the cultural media and to ensure that each test is carried out under the same conditions. Since the distance is dependent on the fill level of the culture media in the petri dish, a problem exists because the distance between the surface of the culture media and the air inlet can vary between tests due to variances in the fill level.
In order to overcome this problem some known air sampling devices are able to measure the distance between the air inlet and the surface of the culture media at the start of the test, so that the height of the turn table can then be adjusted to achieve the required distance of separation (typically 2.5mm). Once such device comprises an infrared light emitting diode which creates an angled conical beam of light that is directed towards a region in the centre of the top surface of the culture media. In use, prior to sampling, a motor raises or lowers the turntable until light reflected by the central region of the culture media is incident on a photodetector, at which point the top surface of the culture media is known to be at the required distance of separation.
A problem of this arrangement is that the surface of the culture media may be inclined across the diameter of the petri dish and thus it will be appreciated that the separation distance will vary as the dish is rotated. Also, there is a risk that the turntable may not rotate in a plane which is truly normal to its axis of rotation. Also, it is difficult for the device to determine whether the turntable needs to be raised or lowered.
With these problems in mind, we have now devised an improved sampling device.
In accordance with the present invention, as seen from a first aspect, there is provided a fluid sampling device comprising fluid inlet, a turntable having a major surface for supporting a container containing culture media onto which a fluid flow through the inlet is directed, means for rotating the turntable about an axis of rotation extending normal to said major surface, a laser arranged to direct a light beam onto a point on the surface of the culture media which is radially offset from the axis of rotation, an optical sensor array arranged to receive a portion of the beam reflected from said point, and a processor connected to the optical sensor array and arranged to output a control signal to an actuator to adjust the distance between the surface of the culture media and the inlet and to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point. The predetermined point on the optical sensor array may be determined during a calibration procedure, for example by placing a reflective surface at the desired separation distance. The processor comprises a memory which then stores the resultant point of incidence of the reflected beam on the optical sensor array. In use, because the laser is directed onto a point on the surface of the culture media which is radially offset from the axis of rotation, the point of incidence of the reflected beam on the optical sensor array will vary as the dish rotates if the surface of the culture media is inclined across the diameter of the dish. However, the processor outputs a control signal to the actuator to adjust the distance between the surface of the culture media and the inlet and to bring the point of incidence of the reflected beam on the optical sensor array substantially back to the predetermined point. In this manner, the separation distance is maintained during sampling. The same applies if the turntable is not rotating in a plane which is truly normal to its axis of rotation. Also, the use of an optical sensor array allows the processor to determine whether the separation distance needs to be increased or decreased to bring the point of incidence of the reflected beam on the optical sensor array substantially back to the predetermined point. In order to assist with this, the predetermined point may be a point disposed at or adjacent the centre of the array.
The use of a laser provides a simple, accurate and un-harmful way of controlling the distance between the upper surface of the culture media and the inlet. In a first embodiment, the processor is arranged to continuously adjust the distance between the surface of the culture media and the inlet.
In a second embodiment, the processor is arranged adjust the distance between the surface of the culture media and the inlet at a set number of rotational positions of the turntable. The turntable may be advanced in a plurality of rotational steps. For example, there may be 120,000 steps per 360° rotation. The processor may be arranged adjust the distance between the surface of the culture media and the inlet at each or a set number of rotational steps. The optical sensor array may be a unitary device or it may be a plurality of discrete devices.
The array may be elongate and may be arranged such that the longitudinal axis thereof extends in the direction in which the distance between the surface of the culture media and the inlet is adjusted. The array may be 1 pixel wide and over 3 pixels long.
The point on the surface of the culture media at which the laser is directed may be at or adjacent a region on the surface of the culture media at which the fluid flow is directed through the inlet.
The laser may be directed onto the surface of the culture media at an angle of incidence which less than 45%, so that the reflected beam from the surface of the culture media is more spatially separated from beams which may be reflected from the bottom of the dish or the turntable. The so-called D50 value is often used to describe the impact efficiency of an air sampling device. The D50 value is the particle size at which 50% of the particles are collected, and 50% pass through the sampling device because they are too small to impact. Hence a sampling device with a D50 value of 1 is 50% efficient at collecting particles of 1 micron in diameter. Often a test procedure will specify the D50 value of the sampling device to be used and this can lead to problems if different tests specify different D50 values, since users will need to keep a different sampling device for each test. Since the D50 value is partly dependant on the dimension of the air inlet, some sampling devices have inlets which can be interchanged according to the desired D50 value i.e. a wide inlet will have a higher flow rate with the result that a greater number of smaller particles will be impacted compared with a narrow inlet.
In accordance with the present invention, as seen from a second aspect, there is provided a fluid sampling device comprising fluid inlet, a turntable having a major surface for supporting a container containing culture media onto which a fluid flow through the inlet is directed, means for rotating the turntable about an axis of rotation extending normal to said major surface, an input for setting the desired impact efficiency of the device, a detector for detecting the distance between the surface of the culture media and the inlet, a processor connected to the detector and arranged to output a control signal to an actuator to adjust the distance between the surface of the culture media and the inlet according to the set desired impact efficiency.
We have realised that a fluid sampling device in accordance with the first aspect invention can be used to perform tests over a range of desired impact efficiencies, such as D50 or another D value. This is achieved by varying the distance between the surface of the culture media and the inlet on the basis that a greater number of smaller particles will be impacted when the distance is small compared when the distance is great. The detector may comprise a laser arranged to direct a light beam onto a point on the surface of the culture media which is radially offset from the axis of rotation and an optical sensor array arranged to receive a portion of the beam reflected from said point. In order to overcome the problem that the surface of the culture media may be inclined across the diameter of the container, the processor may output a control signal to the actuator to adjust the distance between the surface of the culture media and the inlet to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point according to the desired impact efficiency.
The processor may output a further control signal to control the flow rate of the fluid entering the device, so that the range of impact efficiencies achievable by the device can be increased.
The input may comprise means for entering or selecting the percentage efficiency and/or particle size related to the efficiency. Also in accordance with the present invention, as seen from the first aspect, there is provided a method of sampling a fluid, the method comprising:
placing a container containing a culture media onto a major surface of a turntable; rotating the turntable about an axis of rotation extending normal to said major surface;
directing a laser beam onto a point on the surface of the culture media which is radially offset from the axis of rotation;
receiving, in an optical sensor, a portion of the beam reflected from said point;
determining in a processor the position of the reflected beam on the sensor; and outputting a control signal from the processor to an actuator to adjust the distance between the surface of the culture media and a fluid inlet to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point.
The predetermined point may be a point disposed at or adjacent the centre of the array.
The predetermined point on the optical sensor array may be determined during a calibration procedure, for example by placing a reflective surface at the desired separation distance. The resultant point of incidence of the reflected beam on the optical sensor array may then be stored in a memory to provide a point of reference for the control signal.
The processor may continuously adjust the distance between the surface of the culture media and the inlet during rotation of the turntable.
The processor may adjust the distance between the surface of the culture media and the inlet at a set number of rotational positions of the turntable. The point on the surface of the culture media at which the laser is directed may be at or adjacent a region on the surface of the culture media at which the fluid flow is directed through the inlet.
Also in accordance with the present invention, as seen from the second aspect, there is provided a method of sampling a fluid, the method comprising:
placing a container containing a culture media onto a major surface of a turntable; setting the desired impact efficiency of the device;
detecting the distance between the surface of the culture media and a fluid inlet of the device and adjusting the distance according to the set desired impact efficiency; and
rotating the turntable about an axis of rotation extending normal to said major surface.
The distance may be adjusted by a control signal output by a processor to an actuator which varies the distance between the surface of the culture media and the fluid inlet. The processor may determine the distance required for the set impact efficiency using an algorithm or a memory of stored values.
The processor may output a further control signal to control the flow rate of the fluid entering the device, so that the range of impact efficiencies achievable by the device can be increased. An embodiment of the present invention will now be described by way of example only and with reference to the accompanying drawings, in which:
Figure 1 is a schematic diagram of an upper portion of an air sampling apparatus in accordance with the present invention;
Figure 2 is a perspective view from below of the air inlet and height sensor portions of the air sampling apparatus of Figure 1 ; and
Figure 3 is a perspective view illustrating the operation of the height sensor of the air sampling apparatus of Figure 1.
Referring to the drawings, an upper portion of an air sampling apparatus comprises an external housing having a body portion 10 and a closure 1 1 for closing the open upper end of the body portion 10. The housing defines an internal compartment 12 which is exposed when the closure 1 1 is opened. A turntable 13 is mounted inside the compartment 12 for rotation about a vertical axis A, the turntable 13 having an upper surface which lies in a plane normal to the axis A of rotation. A motor 14 or other type of actuator is arranged to raise and lower the turntable 13. A motor and fan unit (not shown) is disposed inside the housing for drawing air into the compartment 12 through a tubular inlet 15 disposed in the closure 11. The inlet 15 comprises a bottom wall 24 in which an elongate slit 16 is formed. The bottom wall of the inlet 15 lies in the plane which is parallel to the plane of the upper surface of the turntable 13. The inlet 15 is disposed directly above the turntable 13 in a position which is radially offset from the axis A of rotation and which is arranged such that the slit 16 extends radially of the axis A.
A petri dish 20 filled with culture media 21 is placed on upper surface of the turntable 13. In the example shown the upper surface of the culture media 21 lies in a plane which is inclined across the dish 20 relative to the upper surface of the turntable 13.
A height sensor 17 is disposed alongside the inlet 15. The height sensor 17 comprises a laser 22 arranged to direct a light beam B at the upper surface of the culture media 21 at a shallow angle of approximately 35°. The height sensor 17 also comprises an elongate photo sensor array 18 mounted on a circuit board 23. The photo sensor array 18 comprises a 1 x 100 array of photo cells each having an 8-bit resolution. The photo sensor array 18 is arranged to receive a portion RB of the beam B which is reflected by the upper surface of the culture media 21. The photo sensor array 18 lies in plane substantially normal to the reflected beam RB and is oriented such that its elongate axis extends in the direction of upward and downward movement of the turntable 13.
A processor 19 is connected to the circuit board 23 of the photo-sensor array 18 and comprises an output which is connected to the motor 14 arranged to raise and lower the turntable 13.
Prior to use, the device is calibrated by placing a reflective surface at exactly 2.5mm below the bottom surface 24 of the inlet 15. The laser 22 is then energised to produce a beam which reflects off the reflective surface onto the photo sensor array 18. The photo sensor array 18 is preferably arranged such that the reflected beam is incident on a photo cell disposed intermediate opposite ends of the array. The point of incidence is then recorded and stored by the processor 19. Following calibration, the reflective surface is removed. In use, once the petri dish 20 filled with culture media 21 is placed on upper surface of the turntable 13, the motor and fan unit is energised to draw air into the internal compartment 12 where it is directed through the slit 16 onto a region of the culture media 21. The petri dish 20 rotates on the turntable 13 at a selected speed and any micro-organisms in the air are circumferentially spatially separated by the dish rotation.
During sampling, the height sensor 17 is energised to direct the laser B onto the upper surface of the culture media 21 at an adjacent point either lagging or leading the region on the surface of the culture media 21 at which the air flow is directed through the slit 16. The processor 19 analyses the position of the reflected beam RB on the photo-sensor array 18 and outputs a control signal to the actuator 14 to raise or lower the turntable 13, thereby bringing the surface of the culture media 21 to the required distance of 2.5mm away from the slit 16. If the processor 19 senses that the reflected beam RB has moved away from the stored point of incidence on the photo- sensor array 18, perhaps because the surface of the media 21 is inclined or because the turntable 13 is rotating in an uneven plane, it outputs a control signal to the actuator 14 to raise or lower the turntable 13, thereby bringing the surface of the culture media 21 back to the required distance as the turntable rotates. A keypad 50 is provided for optionally entering or selecting the percentage impact efficiency (e.g. D50) and/or particle size (e.g. 1 μηι) related to the percentage impact efficiency. If the impact efficiency is selected, the stored point of incidence on the photo-sensor array 18 is determined by the processor according to the set desired impact efficiency and the processor outputs a control signal to the actuator 14 to raise or lower the turntable 13, thereby bringing the surface of the culture media 21 to the required distance of away from the slit 16 to achieve the selected impact efficiency.
An air sensing apparatus in accordance with the present invention is able to maintain a set distance D1 between the inlet 15 and the culture media 15 even if the surface of the culture media 21 is inclined across the width of the petri dish 20. In this manner, the surface of the culture media 21 is exposed to substantially the same airflow conditions through the slit 16 throughout the rotational cycle of the turntable 13. The apparatus also enables samples to be taken using a specified impact efficiency.

Claims

A fluid sampling device comprising fluid inlet, a turntable having a major surface for supporting a container containing culture media onto which a fluid flow through the inlet is directed, means for rotating the turntable about an axis of rotation extending normal to said major surface, a laser arranged to direct a light beam onto a point on the surface of the culture media which is radially offset from the axis of rotation, an optical sensor array arranged to receive a portion of the beam reflected from said point, and a processor connected to the optical sensor array and arranged to output a control signal to an actuator to adjust the distance between the surface of the culture media and the inlet and to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point.
A fluid sampling device as claimed in claim 1 , in which the processor comprises a memory for storing the point of incidence of a reflected beam on the optical sensor array during a calibration procedure.
A fluid sampling device as claimed in claim 1 or claim 2, in which the predetermined point is a point disposed at or adjacent the centre of the array.
A fluid sampling device as claimed in any preceding claim, in which the processor is arranged to continuously adjust the distance between the surface of the culture media and the inlet.
A fluid sampling device as claimed in any of claims 1 to 3, in which the processor is arranged adjust the distance between the surface of the culture media and the inlet at a set number of rotational positions of the turntable.
A fluid sampling device as claimed in claim 5, in which the turntable is advanced in a plurality of rotational steps, the processor being arranged adjust the distance between the surface of the culture media and the inlet at each or a set number of said rotational steps.
7. A fluid sampling device as claimed in any preceding claim, in which the optical sensor array is a unitary device.
8. A fluid sampling device as claimed in any of claims 1 to 6, in which optical sensor array is a plurality of discrete devices.
9. A fluid sampling device as claimed in any preceding claim, in which the array is elongate and is arranged such that the longitudinal axis thereof extends in the direction in which the distance between the surface of the culture media and the inlet is adjusted.
10. A fluid sampling device as claimed in any preceding claim, in which the array is 1 pixel wide and over 3 pixels long.
1 1. A fluid sampling device as claimed in any preceding claim, in which the point on the surface of the culture media at which the laser is directed is at or adjacent a region on the surface of the culture media at which the fluid flow is directed through the inlet.
12. A fluid sampling device as claimed in any preceding claim, in which the laser is directed onto the surface of the culture media at an angle of incidence which less than 45%.
13. A fluid sampling device as claimed in any preceding claim, comprising an input for setting the desired impact efficiency of the device, the processor being arranged to determine the predetermined point of incidence of the beam and to adjust the distance between the surface of the culture media and the inlet according to the set desired impact efficiency.
14. A method of sampling a fluid, the method comprising:
placing a container containing a culture media onto a major surface of a turntable;
rotating the turntable about an axis of rotation extending normal to said major surface;
directing a laser beam onto a point on the surface of the culture media which is radially offset from the axis of rotation; receiving, in an optical sensor, a portion of the beam reflected from said point; determining in a processor the position of the reflected beam on the sensor; and
outputting a control signal from the processor to an actuator to adjust the distance between the surface of the culture media and a fluid inlet to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point.
15. A method as claimed in claim 14, in which the predetermined point on the optical sensor is determined during a calibration procedure.
16. A method as claimed in claim 15, in which the calibration procedure comprises placing a reflective surface at the desired separation distance and storing the resultant point of incidence of the reflected beam on the optical sensor to provide a point of reference for the control signal.
17. A method as claimed in any of claims 15 to 16, comprising continuously adjusting the distance between the surface of the culture media and the inlet during rotation of the turntable.
18. A method as claimed in any of claims 14 to 16, comprising adjusting the distance between the surface of the culture media and the inlet at a set number of rotational positions of the turntable.
19. A method as claimed in any of claims 14 to 18, comprising directing the laser a point on the surface of the culture media which is at or adjacent a region on the surface of the culture media at which the fluid flow is directed through the inlet.
20. A fluid sampling device comprising fluid inlet, a turntable having a major surface for supporting a container containing culture media onto which a fluid flow through the inlet is directed, means for rotating the turntable about an axis of rotation extending normal to said major surface, an input for setting the desired impact efficiency of the device, a detector for detecting the distance between the surface of the culture media and the inlet, a processor connected to the detector and arranged to output a control signal to an actuator to adjust the distance between the surface of the culture media and the inlet according to the set desired impact efficiency.
21. A fluid sampling device as claimed in claim 20, in which the detector comprises a laser arranged to direct a light beam onto a point on the surface of the culture media which is radially offset from the axis of rotation and an optical sensor array arranged to receive a portion of the beam reflected from said point.
22. A fluid sampling device as claimed in claim 21 , in which the processor may output a control signal to the actuator to adjust the distance between the surface of the culture media and the inlet to maintain the point of incidence of the reflected beam on the optical sensor array substantially at a predetermined point according to the desired impact efficiency.
23. A fluid sampling device as claimed in any of claims 20 to 22, in which the processor is arranged to output a further control signal to control the flow rate of the fluid entering the device.
24. A fluid sampling device as claimed in any of claims 20 to 23, in which the input may comprise means for entering or selecting the percentage impact efficiency and/or particle size related to the efficiency.
25. A method of sampling a fluid, the method comprising:
placing a container containing a culture media onto a major surface of a turntable;
setting the desired impact efficiency of the device;
detecting the distance between the surface of the culture media and a fluid inlet of the device and adjusting the distance according to the set desired impact efficiency; and
rotating the turntable about an axis of rotation extending normal to said major surface.
26. A method as claimed in claim 25, in which the distance is adjusted by a control signal output by a processor to an actuator which varies the distance between the surface of the culture media and the fluid inlet.
27. A method as claimed in claim 26, in which the processor determines the distance required for the set impact efficiency using an algorithm or a memory of stored values.
28. A method as claimed in any of claims 25 to 27, in which the processor outputs a further control signal to control the flow rate of the fluid entering the device.
EP17702155.7A 2015-11-24 2017-01-24 Fluid sampling device Withdrawn EP3574300A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB1520758.2A GB2549445A (en) 2015-11-24 2015-11-24 Fluid sampling device
PCT/GB2017/050174 WO2017089841A1 (en) 2015-11-24 2017-01-24 Fluid sampling device

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EP3574300A1 true EP3574300A1 (en) 2019-12-04

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EP (1) EP3574300A1 (en)
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WO (1) WO2017089841A1 (en)

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GB201905931D0 (en) * 2019-04-29 2019-06-12 Pinpoint Scient Limited Improvements in air sampling devices

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3799844A (en) * 1971-06-02 1974-03-26 Us Health Instrumental method for plating and counting aerobic bacteria
US3972226A (en) * 1975-08-12 1976-08-03 Calvin Briggs Rountree Slit impact air sampler
JPH09215491A (en) * 1996-02-09 1997-08-19 Nippon Keieishiya Kyokai Keiei Kenkyu Shidou Center:Kk Distributer for microorganism
JP3607060B2 (en) * 1997-09-09 2005-01-05 アマノ株式会社 Airborne bacteria collector and nozzle windshield
US5831182A (en) * 1997-10-31 1998-11-03 Swenson; Erik A. Remote sampling device for determining air borne bacteria contamination levels in controlled environments

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GB201520758D0 (en) 2016-01-06
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