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
  • G01N21/47—Scattering, i.e. diffuse reflection
  • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
  • G01N21/53—Scattering, i.e. diffuse reflection within a body or fluid within a flowing fluid, e.g. smoke
• • 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
  • G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
  • G01N21/27—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands using photo-electric detection ; circuits for computing concentration
  • G01N21/274—Calibration, base line adjustment, drift correction
• • 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
• • 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
  • G01N1/2247—Sampling from a flowing stream of gas
  • G01N1/2252—Sampling from a flowing stream of gas in a vehicle exhaust
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
  • G01N15/00—Investigating characteristics of particles; Investigating permeability, pore-volume or surface-area of porous materials
  • G01N15/06—Investigating concentration of particle suspensions
  • G01N15/075—Investigating concentration of particle suspensions by optical means
• • 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
  • G01N21/49—Scattering, i.e. diffuse reflection within a body or fluid
  • G01N21/51—Scattering, i.e. diffuse reflection within a body or fluid inside a container, e.g. in an ampoule

Definitions

• the invention relates to a device for measuring a particle concentration in automotive exhaust gases.
• a scattered light method is often used, in which the colloid to be measured is passed through a measuring chamber.
• a laser is used as the light source in such a way that the light emitted by the light source is scattered by particles present in the colloid.
• at least one, but more preferably a plurality of light sensors are present, which detect the light scattered by the particles (scattered light).
• the light sensors may be arranged at different angles with respect to the irradiation direction of the light.
• the components involved such as the light source, light sensors and the electronic evaluation circuit of the sensor signals, have various offset and drift mechanisms, which are time-invariant but as a rule very slow. These mechanisms include, for example, a temperature drift of the light power emitted by the light source, a drift of the sensors, a drift of the evaluation circuit, offset quantities of these components and aging effects.
• these measurement errors caused by the electronic components further possible sources of error also occur in scattered-light methods. Examples of this are reflections on the measuring chamber geometry when the light source is switched on, even when there are no particles in the measuring chamber, and other signal components due to particles, because the measuring chamber is filled with a medium, e.g. a gas or ambient air which contains a certain amount of particulate matter, albeit smaller than that of the exhaust gases.
• An inventive device for measuring a particle concentration in automotive exhaust gases has a measuring chamber which can be filled with a gas-particle mixture (colloid) to be measured and has at least one light source and at least one light sensor, wherein the light sensor is designed to radiate from the light source and to detect scattered light from the particles present in the gas-particle mixture (scattered light).
• the device according to the invention also has an exhaust gas feed device and a zero gas source.
• the exhaust gas supply device is designed to direct exhaust gas to be measured into the measuring chamber.
• the zero gas source is designed to supply a low-particle zero gas to the measuring chamber.
• a switching element which is arranged between the exhaust gas supply device and the measuring chamber, is suitable for selectively permitting or suppressing the supply of exhaust gas into the measuring chamber.
• a zero balance can be easily performed, without, for example Hoses must be removed and / or repositioned. Regularly performing a zero adjustment improves the accuracy of the measurement results determined by the measuring device.
• Such a device also makes it possible to automatically carry out a zero adjustment of the measuring system and thus automatically ensure a sufficient accuracy of the measurement results.
• a switching element is provided, which is arranged between the zero gas source and the measuring chamber and is suitable for selectively permitting or suppressing the supply of zero gas into the measuring chamber.
• the switching element is a switching element configured to inhibit the supply of exhaust gas to the measuring chamber when it permits the supply of zero gas and to allow the supply of zero gas when it inhibits the supply of exhaust gas. Because either exclusively zero gas or exclusively exhaust gas can be introduced into the measuring chamber, both the zero balance (only zero gas in the measuring chamber) and the actual measurement (only exhaust gas in the measuring chamber) can be carried out particularly effectively and with high accuracy.
• the zero gas source has at least one filter. By filtered with a filter ambient air suitable zero gas can be provided particularly cost.
• the zero gas source comprises a two-part filter.
• a two-part filter which in particular has a coarse filter and a fine filter arranged behind the coarse filter in the flow direction, can filter sucked in ambient air in a particularly effective manner. Also, the maintenance costs are reduced because the coarse and fine filters can be cleaned or replaced independently if necessary.
• the zero gas source has at least one pressure sensor. By a pressure sensor, the pressure of the supplied zero gas can be monitored and adjusted appropriately via a suitable control device. In addition, by determining the pressure drop of the zero gas occurring at the filter, the degree of contamination of the filter can be determined.
• the zero gas source has at least one pump. With the help of a pump, the zero gas can be conveyed into the measuring chamber particularly effectively.
• the pump is arranged in the flow direction behind the measuring chamber. If the pump is located downstream of the measuring chamber, a negative pressure can be generated in the measuring chamber after filling the measuring chamber with zero gas by shutting off the zero gas supply and continuing the pump. Since the concentration of particles in a gas is proportional to its pressure, by lowering the pressure, the particle concentration in the measuring chamber can be lowered below the particle concentration in the zero gas. This lowers the zero level and improves the sensitivity of the measuring device.
• the zero gas source is connected to the measuring chamber in such a way that zero gas flowing from the measuring chamber is fed to the air supply to the zero gas source. This creates a closed circuit for the zero gas and the zero gas is used particularly effectively. The fact that the zero gas in the circuit is repeatedly passed through the or the filter, the
• Particle concentration in zero gas can be further lowered.
• the emission measuring device is set up so that the zero balance is carried out automatically.
• An automatic zero calibration ensures that the instrument is independent of the instrument
• An automatic zero balance can be triggered in each case after a predetermined number of measurements and / or at predetermined time intervals.
• the method can also be set up so that a zero adjustment is automatically carried out if either a predetermined number of measurements are obtained. has been reached or if the time interval between two successive measurements exceeds a predetermined time interval, depending on which criterion is met first.
• the accuracy of the zero point adjustment needs to be ensured only over the period between two consecutive zero adjustments. Measuring errors due to drift phenomena can be reliably prevented or minimized.
• a zero calibration can be performed compulsorily and automatically before each individual measurement in order to obtain measurement results with particularly high accuracy.
• FIG. 1 shows schematically a first exemplary embodiment of a measuring device according to the invention.
• Figure 2 shows schematically an alternative embodiment of a measuring device according to the invention.
• Figure 3 shows schematically a third embodiment of a measuring device according to the invention.
• the measuring device 1 shown in FIG. 1 has a measuring chamber 26 with a light source 4 which, for B. is designed as a laser and emits light into the measuring chamber 26 during operation.
• the measuring chamber 26 is equipped with two light sensors 6a, 6b.
• the light sensors 6a, 6b are shown outside the measuring chamber 26 for reasons of clarity, although in reality they are at least partially inside or at the measuring chamber
• the light sensors 6a, 6b detect light emitted from the light source 4 which has been scattered by particles present in the measuring chamber 26 (stray light).
• the light sensors 6a and 6b are preferably arranged such that they respectively detect light which has been scattered in various directions.
• the two light sensors 6a, 6b are connected to an evaluation unit 8, which evaluates the signals output by the light sensors 6a, 6b and in particular determines the particle concentration in the measuring chamber 26.
• the results of the evaluation are output via an output device 10.
• the output device 10 may be a display device (display), a
• the exhaust gases to be measured of a motor vehicle 24 shown schematically are received by an exhaust gas probe 22, which is mounted in or on the exhaust of the motor vehicle 24, and fed through an exhaust hose and a switching element 30 of the measuring chamber 26 (exhaust stream B).
• a pump not shown in the figure 1 may be provided to assist the exhaust gas flow in addition to the exhaust pressure generated by the engine of the motor vehicle 24.
• the switching element 30 is connected to a control unit 28 and between an open state in which it allows an influx of exhaust gases from the motor vehicle 24 in the measuring chamber 26, and a closed state in which the influx of exhaust gases from the motor vehicle 24 in the measuring chamber 26 is switched off, switchable.
• the control unit 28 is, for example, electrically, mechanically or hydraulically connected to the switching element 30, the z. B. is designed as a switching valve.
• a measuring device 1 additionally has a zero gas source 12, which provides so-called zero gas, ie gas with a particularly low particle concentration.
• the zero gas source 12 has an air supply 14, which receives air from the environment. If the measuring device 1 is operated in a particularly polluted and / or dusty environment, such as a workshop, then the air supply 14 may be formed with a pipe or chimney to allow the ambient air from a greater distance, z. B. from outside the building introduce. Alternatively, very clean air can also be taken from supplied gas cylinders.
• the air supply 14 supplies the received ambient air to a filter unit 16, which is designed to reduce the particle concentration in the intake air.
• the filter unit 16 has at least one fine filter 16b (eg a so-called HEPA filter), which is able to filter the supplied air so cleanly that the concentration of the particles which after filtering still contain zero gas lower than the particulate concentration in exhaust gases emitted by vehicles with a well-functioning exhaust gas
• Particle filter are delivered.
• the fine filter 16b is preceded by a coarse filter 16a, which filters out particularly coarse particles from the supplied air before they pass into the fine filter 16b, thus preventing rapid fouling and / or clogging of the fine filter 16b. Thereby, the maintenance intervals for changing or cleaning the filters 16a and 16b can be extended.
• the coarse filter 16a and the fine filter 16b can also be exchanged or cleaned separately according to the respective degree of contamination. These measures can reduce the maintenance costs.
• a pump 18 Downstream of the filter unit 16, a pump 18 is provided, which sucks in ambient air through the air supply 14 and the filter unit 16 and outputs to the measuring chamber 26 (zero gas flow A).
• a pressure sensor 20 is provided which measures the pressure of the supplied air in the zero gas source 12 and passes the result to a control unit not shown in FIG. The pressure measured in this way can be used to control the pump 18 in order to ensure a sufficient zero gas flow A from the zero gas source 12 into the measuring chamber 26.
• the power of the pump 18 is known, it is possible to deduce the degree of contamination of the filter unit 16 from the pressure of the supplied air or from the pressure drop occurring at the filter unit 16, since a large pressure drop occurs via a dirty filter unit 16 than via a clean filter unit 16 If the pressure drop across the filter unit 16 exceeds a predetermined limit value, then a warning signal is output which indicates the user indicates that at least one filter of the filter unit 16 is to be replaced. Also, the pump 18 can be turned off when a predetermined limit value is exceeded, which is equal to or higher than the limit at which a warning is issued, when the contamination of the filter unit 16 is so strong that a reliable function of the zero gas source 12 is no longer guaranteed is.
• a second pressure sensor 20 may be disposed upstream between the air supply 14 and the filter unit 16.
• the zero gas flowing out of the measuring chamber 26 is supplied again to the air feed 14 (zero gas return flow C).
• the particle concentration in the zero gas can be further reduced.
• the need for externally supplied gas is reduced, which is particularly advantageous when used as a zero gas particularly clean but also expensive gas from gas cylinders.
• control unit 28 controls the switching element 30 so that no exhaust gases flow from the motor vehicle 24 into the measuring chamber 26.
• the pump 18 is turned on, so that filtered by the filter unit 16 filtered zero gas from the zero gas source 12 into the measuring chamber 26.
• the control unit 28 controls the switching element 30 so that the supply of exhaust gases from the motor vehicle 24 is opened in the measuring chamber 26 and exhaust gases from the motor vehicle 24 through the measuring chamber flow (exhaust gas flow B, C), so that the particle concentration in the exhaust gases can be measured.
• the switching of the switching element 30 can be done mechanically by the operator. In this case, can on a motor o.ä. to dispense with switching the switching element 30.
• the zero gas flow A is not switched off during the measurement of the particle concentration in the exhaust gases.
• the zero gas from the zero gas source 12 flows simultaneously through the measuring chamber 26 with the exhaust gases to be measured.
• FIG. 2 schematically shows an alternative embodiment of a measuring device 2 according to the invention.
• this measuring device 2 substantially corresponds to the embodiment shown in Figure 1.
• the same elements are provided with the same reference numerals and, as far as they match in structure and function with the first embodiment, not described again.
• the measuring device 2 differs from the measuring device 1 of the first embodiment in that the switching element 32 is designed as a switching element, so that the gas supply in the measuring chamber 26 is selectively switchable between exhaust gases from the motor vehicle 24 and zero gas from the zero gas source 12 , That is, during the measuring operation, when exhaust gases from the motor vehicle 24 are guided into the measuring chamber 26 to determine the particulate concentration in the exhaust gases, no zero gas flows from the zero gas source 12 into the measuring chamber 26. Likewise, during zero balancing, when the zero gas from the zero gas source 12 is passed through the metering chamber 26, no exhaust gas flows through the metering chamber 26.
• FIG. 3 shows a third exemplary embodiment of a measuring device 3 according to the invention. Again, the elements having the same structure and function as in the previously shown embodiments will not be described again.
• a measuring device 3 according to the third embodiment differs from the previously shown measuring devices 1, 2 in that the pump 18, which is provided for conveying the zero gas, not within the zero gas source 12 upstream of the measuring chamber 26, but downstream of the measuring chamber 26 in an exhaust pipe 40 is arranged, which is provided to remove the exhaust gases from the measuring chamber 26.
• the pump 18 promotes the zero gas from the zero gas source 12 by sucking the zero gas through the measuring chamber 26. At the same time supports the pump 18, although it is operated during the measurement process, the exhaust gas flow B from the motor vehicle 24 through the measuring chamber 26th ,
• the switching element 34 is configured such that it can not only switch between the zero gas flow A and the exhaust flow B, unlike the second embodiment shown previously, but also has a setting in which both the supply of the exhaust stream B and the supply of the zero gas stream A are shut off.
• a negative pressure in the measuring chamber 26 can be generated. Since the particle concentration in a gas volume is proportional to its pressure, by lowering the pressure or generating a negative pressure in the measuring chamber 26, the particle concentration in the measuring chamber 26 can be lowered even further. Thus, a lower zero level of the measuring device 3 is achieved and the detection threshold for particles in the exhaust gas flow B can be lowered even further. As a result, the accuracy achievable with the measuring device 3 can be further increased.
• Each of the measuring devices 1, 2, 3 shown in the three embodiments according to the invention can advantageously be designed such that a
• Measurement can only be performed if a zero calibration has been performed previously.
• the measuring devices 1, 2, 3 can be designed such that a zero balance is automatically provided before each measurement. is taken. This prevents a necessary null balance from being omitted for forgetfulness or convenience of the operator, and a measurement is made that provides incorrect readings due to the lack of nullification.
• a measuring device which carries out the zero adjustment automatically, provides particularly reliable measurement results with the best possible accuracy.

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• Chemical & Material Sciences (AREA)
• Physics & Mathematics (AREA)
• Life Sciences & Earth Sciences (AREA)
• Health & Medical Sciences (AREA)
• Analytical Chemistry (AREA)
• General Physics & Mathematics (AREA)
• Pathology (AREA)
• Immunology (AREA)
• Engineering & Computer Science (AREA)
• Biochemistry (AREA)
• General Health & Medical Sciences (AREA)
• Food Science & Technology (AREA)
• Combustion & Propulsion (AREA)
• Medicinal Chemistry (AREA)
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• Theoretical Computer Science (AREA)
• Spectroscopy & Molecular Physics (AREA)
• Investigating Or Analysing Materials By Optical Means (AREA)
• Sampling And Sample Adjustment (AREA)

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• 2010
  • 2010-02-26 DE DE102010002424A patent/DE102010002424A1/de not_active Withdrawn
• 2011
  • 2011-01-04 IN IN4975DEN2012 patent/IN2012DN04975A/en unknown
  • 2011-01-04 WO PCT/EP2011/050048 patent/WO2011104043A1/de not_active Ceased
  • 2011-01-04 US US13/581,284 patent/US20130047703A1/en not_active Abandoned
  • 2011-01-04 CN CN201180011159.8A patent/CN102770745B/zh not_active Expired - Fee Related
  • 2011-01-04 EP EP11700518.1A patent/EP2539681B1/de active Active

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