ANALYSIS APPARATUS FOR ANALYZING A GAS SAMPLE

Abstract

The present invention relates to an analysis apparatus for analyzing a gas sample comprising a concentration measurement path receiving the gas sample; a light transmitter for transmitting light signals into the concentration measurement path; a detector for detecting light signals exiting the concentration measurement path; an evaluation unit which is adapted to determine the concentration of at least one substance present in the gas sample on the basis of the intensity of the detected light signals and on the basis of the length of the concentration measurement path; and a measurement device which is configured to determine the length of the time of flight path of the transmitted light signals optically using the light transmitter, with the evaluation unit being adapted to determine the length of the concentration measurement path on the basis of the determined length of the time of flight path.

Claims

1. An analysis apparatus for analyzing a gas sample, comprising a concentration measurement path having a length and receiving the gas sample; a light transmitter for transmitting light signals into the concentration measurement path; a detector for detecting light signals exiting the concentration measurement path; an evaluation unit adapted to determine a concentration of at least one substance present in the gas sample on the basis of an intensity of the detected light signals and on the basis of the length of the concentration measurement path; and a measurement device adapted to determine a length of a time of flight path of the transmitted and detected light signals optically using the same light transmitter, with the evaluation unit further being adapted to determine the length of the concentration measurement path on the basis of the determined length of the time of flight path.

2. The analysis apparatus in accordance with claim 1, wherein an algorithm for calculating the concentration of the at least one substance on the basis of the intensity of the detected light signals is stored in the evaluation unit and the algorithm uses the length of the concentration measurement path determined on the basis of the time of flight path as a parameter.

3. The analysis apparatus in accordance with claim 1, wherein the measurement device is adapted to determine the length of the time of flight path using the detector.

4. The analysis apparatus in accordance with claim 1, wherein the measurement device is adapted to determine the length of the time of flight path on the basis of the time of flight of the transmitted light signals.

5. The analysis apparatus in accordance with claim 1, wherein the measurement device is adapted to determine the length of the time of flight path on the basis of a phase shift between the transmitted light signals and the detected light signals.

6. The analysis apparatus in accordance with claim 5, wherein the measurement device is adapted to modulate the light transmitter with a measurement frequency.

7. The analysis apparatus in accordance with claim 1, wherein the evaluation unit is adapted to determine both the concentration of the at least one substance and the length of the concentration measurement path on the basis of the same light signal transmitted by the light transmitter.

8. The analysis apparatus in accordance with claim 1, wherein the measurement device is adapted to determine the length of the time of flight path after the occurrence of a request event, with the request event comprising at least one of an elapse of a predefined time period, a temperature change and a user request influencing the length of the concentration measurement path.

9. A method of analyzing a gas sample which is located within a concentration measurement path having a length, comprising the steps: transmitting light signals into the concentration measurement path by means of a light transmitter; detecting light signals exiting the concentration measurement path; and determining a concentration of at least one substance present in the gas sample on the basis of an intensity of the detected light signals and on the basis of the length of the concentration measurement path; with the length of the concentration measurement path being determined optically using the light transmitter.

10. The method in accordance with claim 9, further comprising the step of: determining the concentration of the at least one substance on the basis of the determined length of the concentration measurement path.

11. The method in accordance with claim 10, wherein the step of determining the concentration of the at least one substance on the basis of the determined length of the concentration measurement path is carried out using an algorithm for calculating the substance concentration on the basis of the intensity of the detected light signals which uses the determined length of the concentration measurement path as a parameter.

12. The method in accordance with claim 9, wherein both the concentration of the at least one substance and the length of the concentration measurement path are determined on the basis of the same light signal transmitted by the light transmitter.

Description

[0024] The invention will be described in the following with reference to an embodiment and to the drawing. There is shown:

[0025] FIG. 1 a schematic representation of a sample space at which an analysis apparatus in accordance with the invention is arranged.

[0026] FIG. 1 shows in a simplified form an analysis apparatus 10 in accordance with the invention which is arranged at a sample space configured as a flow passage 12.

[0027] The analysis apparatus 10 comprises a measurement probe 14 arranged at the flow passage 12. The measurement probe 14 has a perforated measurement tube 16 which projects through an opening 30 provided in a wall of the flow passage 12 into the interior of the flow passage 12.

[0028] The measurement probe 14 comprises a light transmitter 18, for example a laser or a laser diode, which transmits light signals into the measurement tube 16. The light signals are reflected by a mirror 20 arranged at the end of the measurement tube 16 in the direction of a detector 22 arranged adjacent to the light transmitter 18.

[0029] The part of the time of flight path of the transmitted light signals which extends between the light transmitter 18, the mirror 20 and the detector 22 and which extends within the gas sample to be analyzed is called a concentration measurement path 32. The gas sample to be analyzed moves as a part of a gas flow flowing through the flow passage 12 through the apertures of the measurement tube 16 into the region of the concentration measurement path 32. Any part sections of the time of flight path extending outside the gas sample are not shown separately for reasons of clarity in FIG. 1.

[0030] In accordance with a modification, the measurement tube 16 and the mirror 20 can be dispensed with, with the light signals being reflected by a mirror 20 (shown dashed) which is arranged at a wall of the flow passage 12 disposed opposite the opening 30.

[0031] In accordance with a further modification (not shown), the light transmitter and the detector can be arranged at oppositely disposed sides of the flow passage 12, with the mirror 20 or 20 being able to be dispensed with and, optionally, also the measurement tube 16.

[0032] The measurement probe 14 is connected to a control unit 24 which comprises an evaluation unit 26 which is adapted to determine the concentration of at least one substance present in the gas sample on the basis of the intensity of the light signals detected by the detector 22 and on the basis of the length of the concentration measurement path 32.

[0033] The control unit 24 is adapted to determine the length of the concentration measurement path 32 on the basis of the time of flight path of the transmitted light signals, with the time of flight path being determined optically with the aid of a measurement device 28 provided in the control unit 24 while using the light transmitter 18 and the detector 22. In an embodiment which is not shown, the evaluation unit takes over the function of the measurement device so that the separate measurement device is dispensed with.

[0034] The length determination can take place in accordance with the time of flight method or on the basis of a phase shift between the transmitted light signals and the detected light signals. The length of the time of flight path hereby determined can optionally be reduced by the length of one or more part sections extending outside the gas sample to obtain the length of the concentration measurement path 32. These part sections are known from the geometry of the structure.

[0035] In the embodiment shown here, the detector 22 is used both for the measurement of the substance concentration and for the length measurement of the time of flight path or of the concentration measurement path 32. In accordance with a further modification, not shown, separate detectors can be provided for both measurements. It is thus possible, for example, to use a detector for the measurement of the substance concentration which is optimized with respect to the light sensitivity, whereas a detector is used for the length measurement of the time of flight path or of the concentration measurement path 32 which is optimized with respect to its response time.

[0036] The calculation of the substance concentration on the basis of the intensity of the detected light signals can take place in the evaluation unit 26 such that an algorithm is used for this purpose which uses the determined length of the concentration measurement path 22 as the parameter. For example, the evaluation unit 26 can evaluate the quotient form the absorbed energy and the length of the concentration measurement path 32, for this purpose.

[0037] The analysis apparatus 10 can determine both the substance concentration and the length of the concentration measurement path 32 on the basis of the same light signal transmitted by the light transmitter 18 by determining the time of flight or phase shift of this light signal while considering the described, optionally required corrections (in particular with respect to the optionally present difference between the time of flight path and the concentration measurement path). In this manner, the substance concentration and the length of the time of flight path or of the concentration measurement path are determined simultaneously such that no time delay occurs on the consideration of length changes. The method steps of determining the concentration of at least one substance present in the gas sample and the method step of determining the length of the time of flight path or of the concentration measurement path thus take place simultaneously or synchronously.

[0038] Alternatively, the analysis apparatus 10 can be provided such that it can be operated in two different modes of operation, with the measurement of the substance concentration taking place in the one mode of operation and the length measurement taking place in the other mode of operation. The two above-named method steps are carried out after one another in time in this respect.

REFERENCE NUMERAL LIST

[0039] 10 analysis apparatus [0040] 12 flow passage [0041] 14 measurement probe [0042] 16 measurement tube [0043] 18 light transmitter [0044] 20, 20 mirror [0045] 22 detector [0046] 24 control unit [0047] 26 evaluation unit [0048] 28 measurement device [0049] 30 opening [0050] 32 concentration measurement path