Classifications

• • 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
  • G01N21/55—Specular reflectivity
  • G01N21/552—Attenuated total reflection
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01V—GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS
  • G01V8/00—Prospecting or detecting by optical means
  • G01V8/10—Detecting, e.g. by using light barriers
  • G01V8/12—Detecting, e.g. by using light barriers using one transmitter and one receiver
  • G01V8/14—Detecting, e.g. by using light barriers using one transmitter and one receiver using reflectors

Definitions

• the present invention relates to the measurement and control of the level of condensation inside a chamber that is being sterilised using a gaseous delivery method of the sterilant.
• condensation is the single most important factor in achieving surface sterilisation when using gases, such as hydrogen peroxide, it is important that the amount of the condensation is measured and controlled. It would be a simple matter to 'inject' sufficient gas to cause gross condensation and hence achieve the required level of biological kill.
• gases such as hydrogen peroxide
• Patent W098/12546 describes a technique for measuring the proportion of the surface area that is obscured by the formation of droplets.
• the technique taught in this patent is to shine a light onto a specially prepared surface and measure the change in the reflected light as the droplets are deposited on the surface. Whilst the technique gives excellent results it has the disadvantage that the instrument needs to be placed inside the chamber to be sterilised, and it must be in intimate thermal contact with the chamber surface.
• the present invention overcomes this problem by placing the instrument on the outside of a window fitted to the wall of the isolator, and measuring the droplet formation on the inside of the window.
• This invention provides a condensation monitor for measuring condensation on one side of a window from the other side thereof, the window being located in an enclosure mounted on a chamber wall with a part opening with the interior of the chamber, the monitor comprising a pair of optical devices positioned on the other side of the window at spaced apart locations to provide transmission of an obliquely angled beam of light into the window and transmission of an obliquely angled beam of light out of the window, a light source adjacent one of the devices to provide a parallel beam of light to be transmitted by said device into the window to travel along the window by reflection from side to side to the other device from where the light beam emerges and a light sensor to measure the amount of light emerging from the window, the amount of light transmitted along the portion between the optical devices being dependent on the amount of condensation on said one side of the window, condensation facilitating transmission of the light beam through said one side by refraction to reduce the amount of light transmitted along the window to the light sensor.
• a light beam directed from the outside of the chamber into a glass window at an oblique angle may be trapped by total internal reflection between the two surfaces of the glass, in the same way that light is trapped in an optical fibre.
• the enclosure may project into the chamber, the monitor is mounted on a side of the window on the inside of the chamber and the other side of the window is exposed to the interior of the chamber.
• a fan means may be provided for causing an air flow over the condensation monitor within the enclosure.
• the enclosure maybe located on the outside of the chamber, the monitor is mounted on the outside of the window externally of the chamber and the fan means are provided for drawing an air flow from the chamber into the enclosure over the window to monitor the condensation in the air flow.
• the optical devices may comprise prisms mounted on said one side of the window to transmit light into and receive light from the window respectively.
• the prisms may be adhered by light transmitting contact pads to said one side of the window.
• the light source may have a lens for producing a parallel beam of light from the source.
• the light sensor may have a lens for focussing the parallel beam of light from the window to a point on the light sensor.
• the window is formed in a wall of a chamber within which a condensation dependent process is performed to measure the level of condensation in the chamber.
• Figure 1 is a detailed view of a condensation measure monitor
• Figures 2 and 3 illustrate different applications of the monitor
• Figure 4 illustrates to an enlarged scale, the build up of moisture in the droplets on a surface.
• FIG. 1 The basic instrument is best understood by reference to Figure 1, in which 10 is a glass window in the wall of the chamber indicated at 11 to be sterilised.
• a light source 12 passes light through a lens 13, which is selected and positioned so that it produces a parallel beam of light, which is projected into a right angled prism 14 mounted on the window with the hypotenuse 14a of the prism extending obliquely to the window a second side 14b lying parallel to the window and the strict side 14c extending at right angles to the window.
• the contact pad is positioned between face 14b of the prism and the glass window to ensure that substantially all the light passes into the interior of the glass window.
• the contact pad is constructed from an optically clear gel type material that has a refractive index sufficiently high as to avoid any reflection at the surface. A suitable material would be an optically clear pad of soft silicon.
• the light Once the light has entered the interior of the glass window it is reflected internally several times between the parallel faces 16, 17 of the window as indicated at 18 until it reaches a second contact pad 19, which is similar to the contact pad 15, where because of the refractive index of the pad, the light escapes from the glass window into a further prism 20 through face 20b of the prism.
• the light is reflected inside the prism by face 20c which lies at right angles to the window before escaping through the hypotenuse face 20a.
• the light is directed how the prism into a lens 21 which concentrates the beam onto light sensors 22.
• the wavelength of the light emitted by the source 12 is matched to the sensitivity of the sensors 22 to minimise the effects of stray light.
• the inside surface of the glass window is clean and all of the light is reflected inside the glass window and is directed onto the light sensors.
• the refractive index At the point of formation of dew on the surface there will be a change in the refractive index and light will escape through the droplet thus reducing the amount of light energy arriving at the light sensor.
• the process of formation or evaporation of droplets occurs there will be a change in the amount of light energy that escapes and hence the amount of light energy arriving at the light sensor.
• the amplifier may either have a voltage or current output depending on the requirements of the monitoring or control systems.
• the sensors may be calibrated by first setting the zero point, i.e. with no droplets and a clean glass window, and then setting the full scale by placing a large contact pad on the interior surface which allows all of the light to escape from the window. Intermediate calibration points can be achieved by attaching the sensor to various glass windows, which have different areas that have been etched. The etching disrupts the internal reflections and hence changes the amount of light arriving at the light sensor. This method has been tried with various areas of etching and calibration points at 25%, 50% and 75% of full scale have been achieved.
• One of the most critical parameters in measuring the condensation is the temperature of the glass window. If the glass window is part of the wall of the chamber this condition will be satisfied providing no local heating or cooling is applied to the area of the glass.
• Fig 2 the condensation monitor as shown in Figure 1 is mounted inside a box 23 on the glass window 10.
• the box 23 is then mounted on a chamber wall 24 on the inside the chamber 11 to be sterilised and is connected to atmospheres by a suitable short pipe or conduit 25.
• the whole of the box 23 and short pipe 25 are constructed to be airtight and free from leaks.
• a small axial fan 26 is placed in a tube inside the short pipe to draw air out of the box. The act of drawing air out of the box causes airflow of room air at room temperature into the box, thus keeping the inside surface of the box and glass window at a temperature similar to that of the rest of the enclosure.

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• General Physics & Mathematics (AREA)
• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Immunology (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Pathology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Geophysics (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Apparatus For Disinfection Or Sterilisation (AREA)
• Measurement Of Levels Of Liquids Or Fluent Solid Materials (AREA)
• Apparatus Associated With Microorganisms And Enzymes (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9888106

Family Applications (1)

Country Status (6)

Families Citing this family (6)

Citations (1)

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• 2000
  • 2000-03-21 GB GB0006822A patent/GB2360583A/en not_active Withdrawn
• 2001
  • 2001-03-20 AU AU2001239403A patent/AU2001239403A1/en not_active Abandoned
  • 2001-03-20 JP JP2001569257A patent/JP2003528310A/ja active Pending
  • 2001-03-20 CA CA002403745A patent/CA2403745A1/en not_active Abandoned
  • 2001-03-20 WO PCT/GB2001/001224 patent/WO2001071321A1/en not_active Application Discontinuation
  • 2001-03-20 EP EP01914014A patent/EP1266205A1/de not_active Withdrawn

Patent Citations (1)

Non-Patent Citations (1)

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