Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N25/00—Investigating or analyzing materials by the use of thermal means
  • G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
  • G01N25/66—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point
  • G01N25/68—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point by varying the temperature of a condensing surface
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B60—VEHICLES IN GENERAL
  • B60S—SERVICING, CLEANING, REPAIRING, SUPPORTING, LIFTING, OR MANOEUVRING OF VEHICLES, NOT OTHERWISE PROVIDED FOR
  • B60S1/00—Cleaning of vehicles
  • B60S1/02—Cleaning windscreens, windows or optical devices
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
  • G01K11/00—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00
  • G01K11/12—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in colour, translucency or reflectance
  • G01K11/14—Measuring temperature based upon physical or chemical changes not covered by groups G01K3/00, G01K5/00, G01K7/00 or G01K9/00 using changes in colour, translucency or reflectance of inorganic materials
• • 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
  • G01N21/59—Transmissivity
  • G01N21/5907—Densitometers
  • G01N21/5911—Densitometers of the scanning type
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N25/00—Investigating or analyzing materials by the use of thermal means
  • G01N25/18—Investigating or analyzing materials by the use of thermal means by investigating thermal conductivity
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N25/00—Investigating or analyzing materials by the use of thermal means
  • G01N25/56—Investigating or analyzing materials by the use of thermal means by investigating moisture content
  • G01N25/66—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point
  • G01N25/70—Investigating or analyzing materials by the use of thermal means by investigating moisture content by investigating dew-point by varying the temperature of the material, e.g. by compression, by expansion

Definitions

• the present invention relates to a sensor unit according to the preamble of claim 1 and a method for avoiding condensation of a gas, in particular water vapor, on a surface of an object according to the preamble of claim 12. Furthermore, the invention relates to a device for avoiding condensation of a gas. especially water vapor, on a surface of an object.
• a generic sensor unit for a device for avoiding condensation of a gas, in particular water vapor, on a surface of an object has the following components: a temperature measuring device for measuring an object temperature, a dew point determination device for determining a dew point temperature of the gas in an atmosphere surrounding the object, and a Regulation and control device that is in active connection with the temperature measuring device and with the dew point determination device and with which an adjusting device for increasing a temperature distance between the object temperature and the dew point temperature depending on the data obtained from the temperature measuring device and the dew point determination device can be controlled in such a way that a decrease in the Object temperature at or below the dew point temperature is avoided-
• the following method steps are carried out: (a) measuring an object temperature, (b).
• Determining a dew point temperature of the gas in an atmosphere surrounding the object and (c) increasing the object temperature and / or reducing the dew point temperature as a function of the object temperature measured in step (a) and / or the dew point temperature determined in step (b) to avoid a decrease in the Object temperature at or below the dew point temperature.
• Capacitive moisture sensors determine the "relative humidity" as the actual measurement variable, ie a measurement variable with which the water vapor partial pressure and thus the dew point temperature of the gas can be determined when the temperature is known.
• the basis for this determination is the relationship between vapor pressure p and drying temperature at a certain relative humidity.
• the entirety of these curves is usually plotted in an "hx" diagram.
• the sample gas has different "relative humidities" at different drying temperatures.
• Decisive for "fogging" or condensing on a surface is the dew point temperature, which can be determined from the curve for 100% relative humidity.
• Capacitive moisture sensors also have the disadvantage of drifting, i.e. that they are not long-term stable. These drifts occur particularly at high and very low humidity levels, which can be attributed to saturation and drying effects.
• capacitive humidity sensors are susceptible to contamination, which is noticeable, for example, when smoking in a passenger compartment of a car.
• the object of the invention is to provide a sensor unit and a method of the type specified above. create which can be used variably and in which condensation can be reliably avoided. Furthermore, the sensor unit should be able to be manufactured particularly inexpensively.
• a sensor unit of the type specified above is further developed according to the invention in that the dew point determination device is designed as a dew point sensor for direct measurement of the dew point and in that the temperature measuring device is designed as a contactlessly operating temperature sensor.
• a method of the type mentioned above is further developed according to the invention in that the dew point temperature of the gas is measured directly with a dew point sensor and in that the object
• a first core idea of the present invention can be seen in the fact that the dew point temperature is no longer determined indirectly by measuring the relative humidity as before, but rather that a direct measurement of the dew point temperature is carried out with the aid of a dew point sensor. Since the uncertainties no longer play a role in determining the relative humidity for the dew point temperature, condensation on the object surface can be prevented much more reliably.
• a second key concept of the invention relates to the measurement of the object temperature, which is carried out without contact.
• the sensor unit according to the invention and the experience according to the invention can thus be used in a particularly variable manner. For example, a moving object can also be monitored and condensation on its surface can be avoided.
• the contactless temperature has the advantage that no energy is extracted from the measurement object. This is particularly advantageous when the temperature of a surface is to be determined, since it is often the case with surface temperature measurements the problem arises that the sensor element used withdraws energy from the surface, which leads to incorrect measurements. Furthermore, the non-contact temperature measurement allows a measuring field to be selected by suitably selecting a distance and an opening angle, which also makes it possible, for example, to measure the surface integrally. Monitoring moving objects can be particularly important for industrial manufacturing processes.
• the sensor unit according to the invention is inexpensive to manufacture and can be mass-produced in large numbers at a low price.
• a wetting sensor is preferably used as the dew point sensor.
• This is a measuring component in which the wetting of a measuring surface with the gas in question, i.e. the condensation of this gas is measured.
• This has the advantage that the state on the object surface on which condensation is to be prevented is simulated in the dew point sensor itself. In this way, condensation on the object surface can be prevented particularly reliably.
• a sensor is particularly preferably used as the dew point sensor in which the change in light reflection and / or light scattering, in particular internal reflection, is used as the measuring principle when the gas condenses on a measuring surface.
• Such sensors are known, for example, from DE 199 32 438 and, in a compact and inexpensive construction, have a very low sensitivity to contamination and, at the same time, are easy to clean.
• a sensor in which the change in an internal reflection due to condensation of the measurement gas on the measurement surface is measured is particularly preferred, since this change in reflection is largely independent of any contamination, such as dust, on the measurement surface.
• An infrared sensor can be used as the temperature sensor, in principle any detector suitable for the infrared spectral range can be used, for example a photoresist cell, a thermocouple, a bolometer or a semiconductor detector, such as e.g. a photodiode. However, a thermopile detector is preferably used as the detector. Such detectors are available inexpensively and enable precise temperature measurements.
• the accuracy of the temperature measurement can be further increased if the temperature sensor is provided with a spectral filter.
• this can be an 8 - 14 ⁇ m window, i.e. an atmospheric window, act.
• a further temperature measuring device can also be provided for determining an atmospheric temperature of the atmosphere surrounding the object.
• a determination of an interior temperature in a passenger compartment of a motor vehicle comes into consideration here.
• a Corresponding control device can use the measured interior temperature, provided a corresponding dew point distance, the climate in the passenger compartment can be controlled in the comfort zone. This has considerable advantages for the occupants.
• the sensor unit according to the invention is accommodated in a common housing.
• a compact structure enables the sensor unit to be used in a variety of ways and easily exchangeable.
• the invention also relates to a device for avoiding condensation of a gas, in particular water vapor, on a surface of an object, which has a sensor unit according to the invention, as well as an actuating device for increasing a temperature difference between the object temperature and the dew point temperature.
• the actuating device can be designed as a heating device. This can be a device for direct heating of the object, such as a rear window heater, and / or a device for indirect heating of the object, such as a heating fan.
• the actuating device is preferably designed as a drying device for reducing a gas portion, in particular a water vapor content, in the atmosphere surrounding the object.
• the device according to the invention has a main area of use as a device for preventing fogging of the window panes of a motor vehicle. Because of the above-described differences in principle of the sensor unit according to the invention compared to the prior art and the advantages achieved thereby, condensation of water vapor on the window panes, i.e. a "fogging", prevented particularly reliably and thus the safety for the passengers are significantly increased.
• control device is preferably controlled by the regulating and control device in such a way that the temperature distance between the object temperature and the dew point temperature is kept above a predetermined minimum temperature distance.
• Fig. 1 is a schematic view of a device according to the invention with a sensor unit according to the invention and
• Fig. 2 is a schematic view of a dew point sensor of the type that can be used in the sensor unit according to the invention.
• the device shown in FIG. 1 has a sensor unit 10 according to the invention and an actuating device 18, which can be, for example, a heating fan or a rear window heater.
• a temperature sensor 40 as a temperature measuring device 12, which is a thermopile sensor, the surface temperature of an object 20 is determined.
• the temperature sensor 40 detects the infrared radiation of a measurement spot 22 on the surface 21 of the object 20 without contact, an acceptance area of the temperature sensor 40 being schematically represented by an opening cone 13.
• the temperature sensor 40 is connected to a regulating and control device 16.
• the sensor device 10 also has a dew point sensor 50 as a dew point determination device 14, which is also connected to the regulating and control device 16. With the help of the dew point sensor 50, a dew point temperature of a schematically represented gas 28 is determined, which can in particular be water vapor and which surrounds the object.
• the dew point sensor 50 is preferably designed as a wetting sensor and in particular as a sensor of the type described in DE 199 32 438.
• Temperature sensor 40, dew point sensor 50 and regulating and control device 16 are accommodated in a common housing 26, so that a very compact construction is ensured.
• the measured surface temperature serves as a reference variable. If there is a critical temperature difference between the object temperature and the dew point temperature that entails the risk of condensation, appropriate remedial measures must be taken.
• the climate By determining the actual (real) dew point temperature, it is possible to carry out several actions in a targeted manner.
• the climate assuming a corresponding temperature distance from the dew point, can be regulated in the comfort zone. This has considerable advantages for the occupants.
• the object temperature is used as a reference variable for this.
• the dew point sensor 50 is regulated to a temperature which is below the object temperature by the ⁇ DT value (for example 5 C). As soon as. Condensation occurs at the dew point sensor 50, the actions a) to d) executed.
• the actions can be designed differently depending on the object temperature.
• FIG. 2 shows a dew point sensor of the type which is preferably used in the sensor unit according to the invention.
• the core component of this sensor is an arrangement of a light guide 52, into which light 56 from a transmitter or a source 54, which can be, for example, a light emitting diode, is coupled. After a plurality of internal reflections on the outer surfaces of the light guide 52, outcoupled light 66 reaches a receiver 68, which can be a photodiode.
• a Peltier element 74 with which the light guide 52 can be cooled in a defined manner, is attached to a rear side of the light guide 52.
• the Peltier element 74 cools the light guide 52 until a gas 28 to be examined, which can in particular be water vapor, condenses on an outer surface 60 of the light guide 52.
• a gas 28 to be examined which can in particular be water vapor
• Such a condensation layer 58 is shown schematically in the left region of the surface 60 of the light guide 52.
• the sensor 50 shown in FIG. 2 has the particular advantage that dirt particles 64 cause almost no deterioration in the measurement accuracy, since these dirt particles, as long as they are dry, only in one because of their negligible contact area with the surface 60 of the light guide 62 compared to the total area negligible area share cause a change in the critical angle for total reflection.
• the entire dew point sensor 50 is compactly arranged in a transistor housing 70, on the underside of which connections 72 are provided for actuating the transmitter 54, the Peltier element 74 and for reading out a signal from the receiver 68.
• the dew point sensor 50 shown is characterized by a very small, compact design, which is designed for mass production, and by its traceability. Because of the measurement principle used, a change in reflection in the case of condensation on a measurement surface, it is a primary method in which a back calculation to the actual size to be determined, here: the dew point temperature, is not necessary, so that high accuracy can be achieved.
• the signs of aging in such a sensor are compared, e.g. with capacitive sensors, minimal.
• the sensor actively simulates what would take place on the pane at the appropriate temperature, i.e. if necessary, condensation.
• the dew point sensor 50 Due to the measuring principle used, the dew point sensor 50 already has a high long-term stability, so that recalibrations are not necessary. A low maintenance and. maintenance-friendly operation is also thanks to the Extensive insensitivity to soiling explained above and also achieved by the easy cleanability of the sensor. These advantageous properties of the dew point sensor 50 thus permit measurements, in particular also in-situ measurements in dusts, granules, such as, for example, grain, etc. o
• the sensor can be used from -40 to +100 C.
• the temperature range can be expanded, in which case the Peltier element used is limiting.

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• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Immunology (AREA)
• Analytical Chemistry (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Pathology (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Inorganic Chemistry (AREA)
• Investigating Or Analyzing Materials Using Thermal Means (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)

Priority Applications (4)

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Cited By (4)

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Citations (4)

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• 2002
  • 2002-07-02 DE DE10229628A patent/DE10229628B4/de not_active Expired - Fee Related
• 2003
  • 2003-06-10 US US10/520,019 patent/US20060063120A1/en not_active Abandoned
  • 2003-06-10 AU AU2003242660A patent/AU2003242660A1/en not_active Abandoned
  • 2003-06-10 JP JP2004518519A patent/JP2005531776A/ja active Pending
  • 2003-06-10 CN CN03820821.0A patent/CN1678482A/zh active Pending
  • 2003-06-10 WO PCT/EP2003/006073 patent/WO2004005089A1/de not_active Ceased
  • 2003-06-10 KR KR1020047021711A patent/KR20050042267A/ko not_active Ceased
  • 2003-06-10 EP EP03762484A patent/EP1521693A1/de not_active Withdrawn
  • 2003-06-10 KR KR1020077025999A patent/KR20070121045A/ko not_active Ceased

Patent Citations (5)

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