JP6177334B2 - Method for operating an air mass flow meter - Google Patents

Description

  The present invention relates to a method for operating an air mass flow meter.

  An air mass flow meter or an air flow meter is used, for example, in an automobile to measure the mass of air taken in by an internal combustion engine. Based on as reliable information as possible about the intake air mass, the electronic control unit of the internal combustion engine ensures that the quantity of fuel closely matched to that air mass is supplied to the individual combustion chambers and combustion is performed. Can be optimized. As a result of such optimization, energy use efficiency can be increased while reducing the discharge of harmful substances.

  According to DE 44 07 209 A1, an air mass flow meter is known which is inserted into an intake pipe for measuring air mass, in which case a defined proportion of the total flow flows through the air flow sensor. For this purpose, the air mass flow meter described above is configured as a plug-in duct type air mass flow meter. The air mass flow meter includes a sensor element disposed in a measurement duct, an electronic device disposed in a casing for evaluating and / or detecting a measured value of the sensor element, and an exhaust disposed on the other side of the sensor element. It has a duct. In order to save space, the duct or air guide path described above is formed in a U-shape, S-shape or C-shape, thus providing an overall compact device configured as a plug-in member. It is formed.

  An air mass flow meter constructed in accordance with the disclosure of WO 03/089884 A1 is formed as a hot film anemometer, and basically the effectiveness of this air mass flow meter has been demonstrated.

  The recent development of air mass flowmeters that operate on the basis of multiple sensor elements configured as microelectromechanical systems (MEMS) has revealed that the measurement results of these sensor elements are particularly adversely affected by contamination. Is to be exerted. For example, contamination that can be caused by oil droplets in the air mass flow can cause signal drift in the sensor element over time, which can cause errors in the measured air mass flow.

  However, sensor elements configured as microelectromechanical systems have a number of advantages, and these advantages should not be let go. Accordingly, an object of the present invention is to eliminate errors in measurement results due to contamination of sensor elements, or to suppress such errors to at least a narrow range.

  This problem is solved by the features described in the independent claims. Advantageous embodiments are described in the dependent claims.

According to the present invention, the following steps are implemented to solve the above problems:
A: obtaining a first measurement value relating to the absolute temperature of the second thermoelectric element of the air mass flow meter.
B: storing a first measurement value relating to the absolute temperature of the second thermoelectric element of the air mass flow meter in an electronic storage device.
C: A step of operating an internal combustion engine and measuring an air mass flow supplied to the internal combustion engine with an air mass flow meter.
D: A step of obtaining a second measured value related to the absolute temperature of the second thermoelectric element of the air mass flow meter after the operation of the internal combustion engine.
E: comparing the first measured value for the absolute temperature of the second thermoelectric element with the second measured value for the absolute temperature of the second thermoelectric element.
F: A step of correcting the offset of the characteristic curve of the sensor element if a deviation is detected between the first measurement value and the second measurement value.

  After the operation of the internal combustion engine, a second measured value related to the absolute temperature of the second thermoelectric element in the air mass flow meter is obtained, and the first measured value related to the absolute temperature of the second thermoelectric element is calculated as the absolute value of the second thermoelectric element. By comparing with the second measured value for temperature, signal drift occurring during operation of the internal combustion engine can be detected and corrected. In this way, a sensor element that operates with high accuracy over a long period of time is realized, and as a result, a reliable measurement result can be obtained with respect to the air mass flow.

  According to one embodiment of the method according to the invention, in step A, a first measured value for the absolute temperature of the first thermoelectric element is additionally determined. This provides a base for identifying signal drift caused by contamination of the first sensor element.

  According to one embodiment of the present invention, after step A, before step B, as step A1, the first measured value of the absolute temperature of the second thermoelectric element and the absolute temperature of the first thermoelectric element A difference from the first measured value is formed. Information regarding signal drift can also be obtained from the difference between these absolute temperatures.

  In step B, additionally, the first measured value relating to the absolute temperature of the first thermoelectric element and / or the first measured value of the absolute temperature of the second thermoelectric element and the absolute temperature of the first thermoelectric element If the difference from the first measured value is stored in an electronic storage device, after the operation of the internal combustion engine, to detect the signal drift, and also the location that caused the signal drift caused by dirt All possible comparison values can be used to find out.

  It is advantageous for this purpose to additionally obtain a second measured value for the absolute temperature of the first thermoelectric element in step D. The second measured value related to the absolute temperature is obtained after the internal combustion engine has been operating for a predetermined time, and at that time, the sensor element is in a state where dirt is occasionally accumulated.

  More advantageously, after step D and before step E, as step D1, a second measured value of the absolute temperature of the second thermoelectric element and a second value of the absolute temperature of the first thermoelectric element. Forming a difference with the measured value. These measurements can identify signal drift and can additionally provide information about the location that caused the signal drift. For example, if the second measured value related to the absolute temperature of the first thermoelectric element has changed greatly, but the measured value of the second thermoelectric element remains substantially the same, the first thermoelectric element is contaminated with high probability. It is in the state.

  This is identified in step E by making an additional comparison as follows: That is, the first value related to the absolute temperature of the first thermoelectric element and / or the first measured value of the absolute temperature of the second thermoelectric element and the first measured value of the absolute temperature of the first thermoelectric element. And / or the second measurement of the absolute temperature of the first thermoelectric element and / or the second measurement of the absolute temperature of the second thermoelectric element and the first Identification is made by additionally comparing the difference between the thermoelectric element's absolute temperature and the second measured value.

  In this case, as an advantageous technique, in step F, the first measured value relating to the absolute temperature of the first thermoelectric element and / or the first measured value of the absolute temperature of the second thermoelectric element and the first The difference from the first measured value of the absolute temperature of the first thermoelectric element is from the second measured value related to the absolute temperature of the first thermoelectric element and / or the second measured absolute temperature of the second thermoelectric element. If a separation is detected from the difference between the value and the second measured value of the absolute temperature of the first thermoelectric element, the offset of the characteristic curve of the sensor element is corrected.

  Other features and advantages of the present invention will be illustrated by the following description of embodiments with reference to the drawings. In the following, although the drawings will be different, the same terms and the same reference numerals will be used for the same components.

Diagram showing air mass flow meter The figure which shows the sensor element formed as a micro electro mechanical system (MEMS) The figure which shows the sensor element formed as a micro electro mechanical system (MEMS) and arrange | positioned in the auxiliary pipe | tube of an air mass flowmeter The figure which shows the situation where the air mass flow is flowing into the auxiliary pipe of the air mass flow meter through the intake opening The figure which shows the sensor element formed in the air mass flowmeter as a micro electro mechanical system (MEMS), and was integrated in the intake pipe as a plug-in finger. The figure which shows the sensor element provided with the 1st temperature sensor element and the 2nd temperature sensor element The figure which shows the sensor element of the air mass flow meter Flowchart detailing the method according to the invention for operating an air mass flow meter FIG. 8 illustrates one embodiment of the method disclosed in FIG.

  FIG. 1 shows a mass flow sensor, which here is configured as an air mass flow meter 2. The air mass flow meter 2 is shown as a plug-in finger in this embodiment, which is inserted into the intake pipe 1 and fixedly connected to the intake pipe. The intake pipe 1 guides the mass flow, here the air mass flow 10, towards the cylinders of the internal combustion engine. What is needed to efficiently burn power fuel in a cylinder of an internal combustion engine is to obtain accurate information about the mass of air supplied. Based on the supplied air mass, it is possible to estimate the available amount of oxygen that is essential for the combustion of the fuel injected into the cylinder. Further, the air mass flow meter 2 shown in FIG. 1 has a first temperature sensor element 7 and a second temperature sensor element 8. The first temperature sensor element 7 and the second temperature sensor element 8 are arranged at different locations. These temperature sensor elements 7 and 8 are formed by a thermopile generally called a resistance or a thermoelectric element, and have different resistance values depending on the temperature generated at these temperature sensor elements. A heating element 12 is formed between the first temperature sensor element 7 and the second temperature sensor element 8. The air mass flow 10 flowing into the casing 3 of the air mass flow meter 2 through the intake opening 4 first passes over the first temperature sensor element 7 and then over the heating element 12 and then The air mass flow 10 reaches the second temperature sensor element 8 and is guided along the auxiliary pipe 5 toward the exhaust opening 6 of the air mass flow meter 2. The air mass flow 10 reaches the first temperature sensor element 7 at a predetermined temperature. This temperature is measured as an absolute temperature by the first temperature sensor element 7. Thereafter, the air mass flow 10 passes over the heating element 12 and the air mass flow 10 is heated to some extent depending on the mass flowing through the heating element 12. When the heated air mass flow 10 reaches the second temperature sensor element 8, the current temperature of the air mass flow 10 is determined as an absolute temperature by the second temperature sensor element 8. From the difference between the absolute temperature measured by the first temperature sensor element 7 and the absolute temperature measured by the second temperature sensor element 8, the mass of air that has passed through can be obtained. For this purpose, the air mass flow meter 2 itself can be provided with an evaluation electronic device 13 for evaluating the measurement signals of the first temperature sensor element 7 and the second temperature sensor element 8. The information relating to the air mass flow 10 obtained in this way is transferred to an engine control device not shown here.

  Although the present invention will be described here based on an air mass flow meter, it does not mean that the method according to the present invention for operating the air mass flow meter is limited to the measurement of air mass flow. Please note that. Using the method according to the invention, other mass flows can also be advantageously captured and measured.

  FIG. 2 shows a sensor element 15 for the air mass flow meter 2. The sensor element 15 is formed on a single silicon chip as a micro electro mechanical system (MEMS). The sensor element 15 operates according to the differential temperature method, whereby the mass of the air stream 10 flowing through it is determined. For this purpose, the first temperature sensor element 7 and the second temperature sensor element 8 are formed on the thin diaphragm 17. The first temperature sensor element 7 and the second temperature sensor element 8 are provided at different locations on the surface 16 of the diaphragm 17. A heating element 12 is disposed between the first temperature sensor element 7 and the second temperature sensor element 8. An evaluation electronic device 13 is also incorporated in the sensor element 15 formed as a microelectromechanical system. The evaluation electronic device 13 immediately evaluates the measurement signals of the temperature sensor elements 7, 8 to obtain an air mass flow 10. Can be converted to a signal proportional to. However, the evaluation electronic device 13 may be integrated into a subsequent electronic device. Information about the air mass flow 10 can be transferred via a connection pad 19 and a connection wire 18 to a subsequent engine electronic control unit not shown here.

  FIG. 3 shows a sensor element 15 for the air mass flow meter 2 formed as a microelectromechanical system (MEMS), which sensor element 5 is located in the auxiliary pipe 5 of the air mass flow meter 2. Formed on a single substrate. In the case of FIG. 3, the air mass flow 10 does not flow through the intake opening 4, which corresponds to a case where the internal combustion engine is stopped, for example. This state is also called zero mass flow. When electric energy is supplied to the heating element 12 provided in the sensor element 15, a symmetrical temperature distribution 20 as shown in the figure is generated with the heating element 12 as the center. Therefore, in this case, the first temperature sensor element 7 and the second temperature sensor element 8 measure the same absolute temperature, and after forming the difference between the temperature measurement signals of these temperature sensor elements 7 and 8, the evaluation electronic device 13 It is identified that there is no air mass flow 10 in the auxiliary pipe 5 of the air mass flow meter 2. However, such an ideal equilibrium state of the temperature signal when the mass flow is zero may be disturbed by, for example, dirt on the sensor element 15.

  FIG. 4 shows a situation in which the air mass flow 10 flows into the auxiliary pipe 5 of the air mass flow meter 2 through the intake opening 4. In such a situation, it can be seen that the temperature distribution 20 around the heating element 12 is shifted in the direction of the second temperature sensor element 8. Therefore, in this case, the second temperature sensor element 8 measures a temperature significantly higher than that of the first temperature sensor element 7. The air mass flow 10 can then be determined by determining the differential temperature of both these temperature sensor elements 7, 8 in the evaluation electronics 13. However, the influence of dirt on the sensor element may still have an effect, and if so, such an effect will be superimposed on the measurement result. Depending on the air mass flow 10, the sum of the temperatures also reacts. However, the sum of the temperatures also reacts with the thermal properties of the air mass, for example with the heat capacity and / or thermal conductivity of the air mass flow 10 flowing through. For example, if the air mass flow 10 remains the same and the thermal conductivity of the air mass increases, the system cools and the temperature sum is significantly reduced. However, the differential temperature between the first temperature sensor element 7 and the second temperature sensor element 8 is maintained unchanged in the first order approximation. For this reason, a change in the thermal characteristics of the air mass, such as a change in heat capacity or thermal conductivity, can be measured by the sum signal of the first temperature sensor element 7 and the second temperature sensor element 8. If the sum temperature signal is supplemented with the difference temperature, the change in the thermal conductivity and / or the change in the heat capacity of the air mass flowing through it can be estimated.

  FIG. 5 shows a state in which an air mass flow meter sensor element 15 formed as a micro electromechanical system (MEMS) is provided in an air mass flow meter 2 incorporated in the intake pipe 1 as a plug-in finger. It is shown. In this case as well, the air mass flow 10 reaches the intake opening 4 and flows into the auxiliary pipe 5. It can be seen that the first temperature sensor element 7 and the second temperature sensor element 8 are provided on the surface 16 of the diaphragm 17. A heating element 12 is disposed between the first temperature sensor element 7 and the second temperature sensor element 8. The air mass flow 10 first reaches the first temperature sensor element 7, then passes over the heating element 12 and then reaches the second temperature sensor element 8.

  FIG. 5 shows that the air mass flow 10 also contains contaminants 9. By means of the air mass flow 10, for example, water droplets 6, oil droplets 11 and / or dust particles 14 are conveyed towards the air mass flow meter 2. These contaminants 9 reach the sensor element 15 through the intake opening 4 of the air mass flow meter 2. If the contaminant 9 accumulates in the region of the first temperature sensor element 7 and the second temperature sensor element 8, the measured value of the air mass flow 10 may become significantly incorrect over time. Since such errors are further increased by the accumulation of contaminants on the sensor element 15 over time, the term air mass flow meter 2 signal drift is also used in this context. Such signal drift is undesirable and must be suppressed and / or compensated.

  FIG. 6 shows a sensor element 15 including a first temperature sensor element 7 and a second temperature sensor element 8, and a heating element 12 arranged between these temperature sensor elements 7 and 8. . The direction of the air mass flow 10 is represented by arrows. Accordingly, when viewed in the flow direction of the air mass flow 10, the first temperature sensor element 7 is disposed in front of the heating element 12, and the second temperature sensor element 8 is disposed behind the heating element 12. According to this embodiment, both the first temperature sensor element 7 and the second temperature sensor element 8 are configured as an electrical series circuit including one measuring resistor 22 and at least two comparison resistors 21. . As can be seen from this figure, the measurement resistor 22 is disposed in the inner region of the thin diaphragm, and the comparison resistor 21 is disposed in the peripheral region of the diaphragm 17.

  Furthermore, FIG. 6 shows that contaminants 9, in particular oil droplets 11, are transported to the sensor element 15 together with the air mass flow 10. In particular, oil droplets 11 are deposited on the sensor element 15. As can be clearly seen from this figure, the oil droplets 11 are particularly marked on the sensor element 15 in the region of the second sensor element located behind the heating element 12 when viewed in the flow direction of the air mass flow 10. It is accumulating. This asymmetric deposition of the oil droplets 11 on the sensor element 15 causes a signal drift, which ultimately causes an error in the absolute temperature measured by the sensor element 15 and thus An error is caused in the measured value of the air mass flow 10. Moreover, most of the contaminants are deposited in the peripheral region of the diaphragm 17. There is a physical reason for the oil droplets 11 to be deposited asymmetrically, particularly because the temperature of the region of the second sensor element 8 is higher and due to the temperature gradient of the peripheral region of the film 17. doing.

  FIG. 7 shows the sensor element 15 of the air mass flow meter 2. The first temperature sensor element 7 and the second temperature sensor element 8 of the sensor element 15 are formed as a thermopile 23. Thermopile 23, also referred to as thermoelectric element 23, converts heat into electrical energy. The thermoelectric element 23 is made of two different metals joined together at one end. Due to the heat flow in the metal, a voltage is generated due to the temperature difference.

  The occurrence of a potential difference between two locations at different temperatures in one conductor is called the Seebeck effect. This potential difference is substantially proportional to the temperature difference and depends on the conductor material. When both ends of a single measuring conductor are at the same temperature, the potential difference is always canceled out. However, when two different conductor materials are connected together, a thermoelectric element 23 is formed. In the case of a measurement system based on the Seebeck effect, a significant number of individual thermoelectric elements 23 are usually connected in series.

  When selecting a material pair for measurement, we want to generate the highest possible thermal voltage with a high degree of linearity between temperature and voltage changes. The thermopile 23 shown in FIG. 7 is constituted by one row in which the first metal 24 is connected to the second metal 25 at the connection point 26. As clearly shown in FIG. 7, dirt 9 mainly present as oil droplets 11 is deposited in the region of the second temperature sensor element 8 constructed by the plurality of thermoelectric elements 23. These stains 9 cause errors in the absolute temperature measured by the temperature sensor elements 7 and 8. The resulting signal drift has already been mentioned in the description of the drawings given so far. According to the method of the present invention, this signal drift can be compensated, and the measurement result of the air mass flow meter 2 can be used in a very stable state over a long period of time.

  FIG. 8 depicts a flow chart detailing the method according to the invention for operating an air mass flow meter. This method according to the invention can be used very effectively in an air mass flow meter with sensor elements manufactured as a microelectromechanical system. The fact that microelectromechanical systems are susceptible to contamination and the resulting signal drift in their sensor elements has been described above.

  In order to avoid signal drift or to compensate for such signal drift, a first measurement is determined in step A regarding the absolute temperature of the second thermoelectric element of the air mass flow meter. The second thermoelectric element is disposed behind the heating element when viewed in the flow direction of the air mass flow, and is particularly affected by dirt due to oil droplets contained in the air mass flow. The first measured value for the absolute temperature of the second thermoelectric element of the air mass flow meter is stored in an electronic storage device in step B. Next, in step C, the internal combustion engine is operated, and the air mass flow supplied to the internal combustion engine is measured by an air mass flow meter. By operating the internal combustion engine, the dirt is carried along with the air mass flow toward the sensor element, and oil droplets accumulate particularly in the peripheral region of the second thermoelectric element. Such contamination of the thermoelectric element can cause undesirable signal drift, which can lead to errors in the measurement results of the air mass flow meter. At this time, the internal combustion engine may stop. In order to compensate for errors occurring in the air mass flow meter reading due to contamination, in step D, the second thermoelectric element absolute temperature of the air mass flow meter after operation of the internal combustion engine is Two measurements are obtained. Next, in step E, a comparison is made between the first measurement value relating to the absolute temperature of the second thermoelectric element and the second measurement value relating to the absolute temperature of the second thermoelectric element. In step F, it is determined whether or not there is a deviation between the first measurement value and the second measurement value. If there is a deviation between these measured values, the offset of the sensor element characteristic curve is corrected in step F1. If no deviation has occurred, the method starts anew from step A. Even if a deviation is detected, the method is started anew from step A after the offset of the characteristic curve is corrected. In this way, the offset correction of the sensor element characteristic curve is continuously performed, and thereby, a highly accurate measurement result of the air mass flowmeter is maintained for a long period of time.

  FIG. 9 illustrates one embodiment of the method disclosed in FIG. In step A, in addition to determining a first measurement value for the absolute temperature of the second thermoelectric element of the air mass flow meter, a first measurement value for the absolute temperature of the first thermoelectric element is also determined. Next, in step A1, a difference is formed between the first measurement value relating to the absolute temperature of the second thermoelectric element and the first measurement value relating to the absolute temperature of the first thermoelectric element. Thereafter, in step B, in addition to the first measurement value relating to the absolute temperature of the second thermoelectric element, the first measurement value relating to the absolute temperature of the first thermoelectric element and / or the second measurement value in the air mass flowmeter The difference between the first measured value of the absolute temperature of the first thermoelectric element and the first measured value of the absolute temperature of the first thermoelectric element is stored in an electronic storage device.

  In subsequent step C, the internal combustion engine is operated and the air mass flow supplied to the internal combustion engine is measured by an air mass flow meter. When the internal combustion engine is operated, the sensor element can become dirty, particularly in the peripheral region of the second thermoelectric element. Such contamination, usually caused by oil droplets, causes errors in the measurement signal of the thermoelectric element, resulting in so-called signal drift. In that case, the internal combustion engine may stop.

  Then, in step D, the air mass flow meter after the operation of the internal combustion engine is additionally provided with the second measurement value relating to the absolute temperature of the second thermoelectric element and the second measurement value relating to the absolute temperature of the first thermoelectric element. Detection is performed. Thereafter, in step D1, a difference between the second measured value of the absolute temperature of the second thermoelectric element and the second measured value of the absolute temperature of the first thermoelectric element is formed.

  In step E, the first measured value for the absolute temperature of the second thermoelectric element is compared with the second measured value for the absolute temperature of the second thermoelectric element. In addition to this, the first measured value relating to the absolute temperature of the first thermoelectric element and / or the first measured value of the absolute temperature of the second thermoelectric element and the absolute temperature of the first thermoelectric element. The difference from the first measured value is compared with a second measured value relating to the absolute temperature of the first thermoelectric element and / or the second measured value of the absolute temperature of the second thermoelectric element and the first measured value. The absolute temperature of the thermoelectric device is compared with the difference from the second measured value.

  If a deviation is detected between the first measurement value and the second measurement value in step F, the offset of the sensor element characteristic curve is corrected in step F1. The method can then be executed anew starting from step A. If no deviation is detected between the first measurement value and the second measurement value, the method can be started immediately from step A and executed anew.

Claims (8)

A method for operating an air mass flow meter for measuring an air mass flow (10) supplied to an internal combustion engine comprising:
The air mass flow meter (2) includes a sensor element (15) formed of a microelectromechanical structure, and the sensor element (15) includes a heating element (12),
The sensor element (15) has a first thermoelectric element (7) arranged upstream from the heating element (12), and a second thermoelectric element (7) downstream from the heating element (12). A thermoelectric element (8) is arranged,
In a method for operating an air mass flow meter,
A: obtaining a first measurement value relating to the absolute temperature of the second thermoelectric element (8) of the air mass flow meter (2);
B: storing the first measurement value relating to the absolute temperature of the second thermoelectric element (8) of the air mass flow meter (2) in an electronic storage device;
C: operating the internal combustion engine to measure the air mass flow (10) supplied to the internal combustion engine with the air mass flow meter (2);
D: after the operation of the internal combustion engine, after the internal combustion engine is stopped again , obtaining a second measurement value relating to the absolute temperature of the second thermoelectric element (8) of the air mass flow meter (2);
E: comparing the first measured value for the absolute temperature of the second thermoelectric element (8) with the second measured value for the absolute temperature of the second thermoelectric element (8);
F: Correcting an offset of a characteristic curve of the sensor element (15) if a deviation is detected between the first measurement value and the second measurement value. ,
A method for operating an air mass flow meter for measuring an air mass flow (10) supplied to an internal combustion engine. In step A, a first measurement value relating to the absolute temperature of the first thermoelectric element (7) is additionally obtained.
A method for operating an air mass flow meter (2) according to claim 1. After Step A, before Step B, as Step A1, the first measured value of the absolute temperature of the second thermoelectric element (8) and the absolute temperature of the first thermoelectric element (7) Forming a difference from the first measurement value of
A method for operating an air mass flow meter (2) according to claim 2. In the step B, in addition, a first measured value relating to the absolute temperature of the first thermoelectric element (7) and / or the first measurement of the absolute temperature of the second thermoelectric element (8). Storing the difference between the value and the first measured value of the absolute temperature of the first thermoelectric element (7) in the electronic storage device;
A method for operating an air mass flow meter (2) according to claim 2 or 3. In step D, a second measurement value relating to the absolute temperature of the first thermoelectric element (7) is additionally obtained.
Method for operating an air mass flow meter (2) according to claim 3 or 4. After Step D and before Step E, as Step D1, the second measured value of the absolute temperature of the second thermoelectric element (8) and the absolute temperature of the first thermoelectric element (7) Forming a difference from the second measured value of
Method for operating an air mass flow meter (2) according to claim 4. In the step E, additionally, the first measured value relating to the absolute temperature of the first thermoelectric element (7) is compared with the second measured value relating to the absolute temperature of the first thermoelectric element (7). To
And / or
The difference between the first measured value of the absolute temperature of the second thermoelectric element (8) and the first measured value of the absolute temperature of the first thermoelectric element (7) is expressed as the second thermoelectric element. Comparing the difference between the second measured value of the absolute temperature of (8) and the second measured value of the absolute temperature of the first thermoelectric element (7);
A method for operating an air mass flow meter (2) according to claim 5 or 6. In step F, the first measurement value relating to the absolute temperature of the first thermoelectric element (7) is separated from the second measurement value relating to the absolute temperature of the first thermoelectric element (7). If detected, the offset of the characteristic curve of the sensor element (15) is corrected.
And / or
The difference between the first measured value of the absolute temperature of the second thermoelectric element (8) and the first measured value of the absolute temperature of the first thermoelectric element (7) is the second thermoelectric element. If it is detected from the difference between the second measured value of the absolute temperature of (8) and the second measured value of the absolute temperature of the first thermoelectric element (7), A method for operating an air mass flow meter (2) according to claim 7, wherein the offset of the characteristic curve of the sensor element (15) is corrected.

Images