Method and Device for Determining an Ambient Pressure

Abstract

The disclosure relates to a method and a device for determining an ambient pressure that prevails around a control unit. The control unit includes a housing, which has an opening, and a membrane having a particular permeability, which covers the opening. A pressure sensor is arranged inside the housing. The method includes: recording a pressure measurement value with the pressure sensor, the pressure measurement value being characteristic of an internal pressure inside the housing; determining a correction value, which includes a constant and a variable; and determining the ambient pressure by way of the pressure measurement value that has been determined and the correction value that has been determined.

Claims

1. A method for determining an ambient pressure that prevails around a control unit, the control unit includes a housing having an opening, and a membrane having a particular permeability and covering the opening, a pressure sensor is arranged inside the housing, the method comprises: recording a pressure measurement value with the pressure sensor, the pressure measurement value being characteristic of an internal pressure inside the housing; determining a correction value comprising a constant and a variable; and determining the ambient pressure by the pressure measurement value that has been determined and the correction value that has been determined.

2. The method of claim 1, wherein the variable of the correction value comprises a pressure variation over a time inside the housing, the pressure variation being determined by a profile of the recorded pressure measurement value of the pressure sensor.

3. The method of claim 1, wherein the constant of the correction value comprises a first constant, which involves specific properties of the membrane.

4. The method of claim 2, further comprising: recording, at a temperature sensor arranged inside the housing, a temperature measurement value that is characteristic of an internal temperature inside the housing, wherein the variable of the correction value comprising a temperature variation over a time inside the housing, the temperature variation being determined by a profile of the recorded temperature measurement value of the temperature sensor.

5. The method of claim 4, wherein the constant of the correction value comprises a second constant, which involves specific properties of the membrane.

6. The method of claim 5, wherein the second constant is determined during a time span within which the control instrument is not moved or is moved only slightly relative to its environment, so that the ambient pressure is constant, and wherein the internal temperature initially lies above an ambient temperature and subsequently approaches the ambient temperature.

7. The method of claim 5, wherein the first constant is based on the second constant that has been determined.

8. The method of claim 5, wherein the constant of the correction value is a combination of the first constant and the second constant.

9. A control unit comprises: a housing having an opening; a membrane having a particular permeability, which covers the opening, a pressure sensor arranged inside the housing; a microcontroller arranged inside the housing, the microcontroller configured to carry out a method, the method comprising: recording a pressure measurement value with the pressure sensor, the pressure measurement value being characteristic of an internal pressure inside the housing; determining a correction value comprising a constant and a variable; and determining an ambient pressure by the pressure measurement value that has been determined and the correction value that has been determined.

10. The control unit of claim 9, wherein the variable of the correction value comprises a pressure variation over a time inside the housing, the pressure variation being determined by a profile of the recorded pressure measurement value of the pressure sensor.

11. The control unit of claim 9, wherein the constant of the correction value comprises a first constant, which involves specific properties of the membrane.

12. The control unit of claim 11, further comprising: a temperature sensor arranged inside the housing, the temperature sensor recording a temperature measurement value that is characteristic of an internal temperature inside the housing, wherein the variable of the correction value comprises a temperature variation over a time inside the housing, the temperature variation being determined by a profile of the recorded temperature measurement value of the temperature sensor.

13. The control unit of claim 12, wherein the constant of the correction value comprises a second constant, which involves specific properties of the membrane.

14. The control unit of claim 13, wherein the second constant is determined during a time span within which the control instrument is not moved or is moved only slightly relative to its environment, so that the ambient pressure is constant, and wherein the internal temperature initially lies above an ambient temperature and subsequently approaches the ambient temperature.

15. The method of claim 13, wherein the first constant is based on the second constant that has been determined.

16. The method of claim 14, wherein the constant of the correction value is a combination of the first constant and the second constant.

17. A vehicle having a control unit as claimed in claim 8.

Description

DESCRIPTION OF DRAWINGS

[0029] FIG. 1 shows a first schematic representation of a control unit according to a first example.

[0030] FIG. 2 shows a second schematic representation of a control unit according to a second example.

[0031] Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

[0032] FIG. 1 shows a control unit 100. The control unit 100 includes a housing 110. The housing 110 has an opening 112. The opening 112 is intended for a fluid exchange to be possible between surroundings 200 of the control unit 100 and the interior of the housing 110 of the control unit 100. The control unit 100 furthermore includes a membrane 120. The membrane 120 fully covers the opening 112, so that fluid exchange between the surroundings 200 and the internal volume 220 of the housing 110 of the control unit 100 is possible only through the membrane 120 itself. The membrane 120 has a particular permeability, that is to say a particular perviousness for fluid (for example air). The control unit 100 additionally includes a pressure sensor 130, which is arranged inside the housing 110. The pressure sensor 130 is adapted to record a pressure measurement value that is characteristic of an internal pressure 210 prevailing inside the housing 110. According to the present disclosure, the ambient temperature 200 prevailing around the control unit 100 is determined by way of the recorded pressure measurement value and a correction value that has been determined, which includes a constant and a variable. The constant of the correction value may, for example, be a first constant C. The first constant C may, for example, record parameters of the membrane 120 and be saved inside the control unit 100, and be used to determine the ambient pressure 200. The control unit 100 in this regard includes for example a microcontroller, which performs the calculation for determining the ambient pressure 200. The microcontroller may accordingly receive the pressure measurement value that has been determined by way of the pressure sensor 130. In addition, an internal volume 220 of the housing 110, which remains constant, may be provided to the microcontroller or saved on the microcontroller. By way of the data that are provided and the pressure measurement value that is recorded by way of the pressure sensor 130, the ambient pressure 200 may accordingly be determined.

[0033] FIG. 2 differs from FIG. 1 in that a temperature sensor 140, which records a temperature prevailing inside the control unit 100, is additionally arranged inside the control unit 100. In this regard, a temperature measurement value is recorded by way of the temperature sensor 140 and, for example, made available to the microcontroller of the control unit 100. In addition, the control unit 100 includes a heat source 150. The heat source 150 may, for example, be a microcontroller that emits a certain amount of heat during operation of the control unit 100. This heat given off by the microcontroller or the heat source 150 may be calculated and taken into account when determining the temperature measurement value of the temperature sensor 140. In order to determine the ambient pressure 200, the constant of the correction value may additionally or alternatively include a second constant D. By way of the pressure measurement value recorded by the sensor 130 and the correction value, which in some examples is defined by the second constant D and a pressure change as a function of a temperature change, the ambient pressure 200 may accordingly be deduced. The internal pressure 210 inside the housing 110, recorded by way of the pressure sensor 130, may accordingly be provided to the microcontroller. In addition, the internal temperature 230 inside the housing 110, recorded by way of the temperature sensor 140, may be provided to the microcontroller. The internal temperature 230 that has been determined and the internal pressure 210 that has been determined may in this case be recorded as a function of time, so that profiles of the internal pressure 210 and of the internal temperature 230 are recorded. Accordingly, a pressure variation of the internal pressure 210 and a temperature variation of the internal temperature 230 may be deduced, or they may be determined. The variation of the internal pressure 210 and the variation of the internal temperature are in this case proportional to a pressure difference between the ambient pressure and the internal pressure. Because the profile of the internal pressure 210 and the profile of the internal temperature 230 can be determined, or are known, the ambient pressure 200 may accordingly be determined or calculated. The first constant C required for this and the second constant D, for example additionally required for this, may for example be determined during the development of the control unit 100 in the laboratory, or on a test rig, and stored on or inside the control unit 100, for example in a memory, and provided to the microcontroller. The first constant C and the second constant D may, for example, take ageing effects of the membrane 120 into account. This may, for example, also be envisioned if the first constant C or the second constant D, or both constants C, D, are continuously redetermined and resaved during operation of the control unit 100, so that ageing effects of the membrane 120 may advantageously be represented.

[0034] A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the disclosure. Accordingly, other implementations are within the scope of the following claims.