Analysis device and analysis method with self-test for leaks

Abstract

The invention relates to an analysis device (100). In a released end position, a valve (2, 13) releases a fluid guide unit between a measuring chamber (3) and the environment. In a closed end position, the valve (2, 13) closes this fluid guide unit. A gas sensor (50) measures the concentration of a target gas in a gas sample in the measuring chamber. A decision is automatically made as to whether the valve in the closed end position actually seals the fluid guide unit fluid-tight or not. For this decision, the valve (2, 13) remains in the closed end position throughout a test period. During this test period, a pressure sensor (12.1, 12.2) repeatedly measures the difference between the pressure in the measuring chamber and the pressure in the environment. If the pressure in the measuring chamber deviates sufficiently from the ambient pressure throughout the test period, the valve actually seals fluid-tight.If at the end of the test period the pressure in the measuring chamber deviates significantly less from the ambient pressure, the valve is leaking.

Description

The invention relates to an analytical device which is capable of measuring the concentration or amount of a target gas in a gas sample and is capable of automatically checking itself for tightness. The invention further relates to a method for automatically checking such an analytical device and to an analytical method using such an analytical device.Analytical instruments with electrochemical sensors have become known. An analytical device according to the invention can also have such an electrochemical sensor. The reliability of such an analytical device critically depends on the current state of the electrochemical sensor.An analytical device according to the invention can also comprise at least one different type of gas sensor, for example a photo-optical or photo-acoustic or oxidizing (catalytic) sensor, also called a heat tone sensor.One possible application of the analytical device according to the invention is the following: A subject is to be examined for a substance which can be located in the body of the test subject and which can be detected in a breath sample of the test subject, wherein the substance is in particular alcohol.It is an object of the present invention to provide an analyzer, a checking method and an analyzing method which are capable of measuring the concentration or amount of a target gas in a gas sample and have higher reliability than known analyzers, checking apparatuses, checking methods and analyzing methods.The object is achieved by an analysis device having the features of claim 1, by a checking method having the features of claim 7, by a checking method having the features of claim 8 and by an analysis method having the features of claim 9. Advantageous embodiments of the analytical device according to the invention are, insofar as appropriate, also advantageous embodiments of the checking device according to the invention, of the checking method according to the invention and of the analytical method according to the invention and vice versa.The analytical device according to the invention comprises a measuring chamber and a gas sensor. The measuring chamber is capable of receiving a gas sample to be examined, for example a part of a breathing sample of a test subject. The gas sensor is capable of measuring the concentration and / or the amount of a predetermined target gas in the gas sample while the gas sample is in the measurement chamber. The same component may comprise the gas sensor and provide the measurement chamber. It is possible that the gas sensor is able to measure the respective concentration or quantity of a plurality of predetermined target gases in the same gas sample in the measuring chamber or also the sum of the target gas concentrations or target gas quantities. It is of course also possible that the target gas is not contained in the gas sample at a concentration above a detection limit.Note: The formulation that a sensor is capable of measuring a physical quantity means the following: The sensor is capable of directly measuring the physical quantity or a detection quantity which correlates with the quantity to be measured, that is to say is a measure of the quantity to be measured. If the physical variable is the concentration or quantity of a target gas, the correlating variable is, for example, the electrical voltage which is present at an electrically conductive component, or the electrical current intensity or electrical power of the current which flows through the component, or the electrical charge or also the electrical resistance or the temperature of the component through which current flows. The measurement provides a value of the physical quantity to be measured.In one application of the invention, the gas sample is from a breath sample that has delivered a subject, and the target gas is breath alcohol or other constituent that is or may be included in a breath sample. The subject is to be examined whether or not alcohol is present in his blood circulation. When alcohol is present in the blood circulation of the subject, a breath sample generally contains breath alcohol, as is known. The gas sample can also originate from an area to be monitored. The target gas can also be, for example, a combustible or toxic target gas or target gas that is otherwise harmful to humans, or also oxygen or an anesthetic or carbon dioxide.A fluid guidance unit of the analysis device is capable of establishing a fluid connection between the measurement chamber and an environment of the analysis device. A "fluid guidance unit" is understood to mean a component which is capable of guiding a fluid along a trajectory predetermined by the construction and arrangement of the component and ideally prevents the fluid from leaving this trajectory. The term "fluid guidance unit" comprises in particular a tube, a smooth tube and a pleated tube.A valve of the analysis device can be transferred into a releasing end position, into an intermediate closing position and into a closing end position. The intermediate sealing position differs from the final sealing position. During a transfer (movement) from the one end position into the other end position, the valve reaches the intermediate closing position. When the valve is in the releasing end position or in a position between the releasing end position and the intermediate closing position, a gas sample is allowed to flow from the environment through the fluid guiding unit into the measuring chamber. This can be done in particular by the gas sample being sucked through the fluid guidance unit into the measuring chamber and / or diffusing into the measuring chamber.When the valve is in a closing position, the fluid guidance unit is closed, so that ideally no fluid connection is established between the measuring chamber and the environment, but rather the measuring chamber is completely separated from the environment in a fluid-tight manner. A "closing position" is understood to mean the intermediate closing position, the end closing position or a position between the intermediate closing position and the end closing position. In other words: The valve closes the fluid guidance unit when the valve is in a position belonging to a closing position range, wherein this closing position range is the range between the intermediate closing position and the end closing position, inclusive. "Ideally" means: when the valve closes ideally free of faults and thus in a fluid-tight manner. The feature that the intermediate closing position differs from the end closing position results in particular from the fact that at least one component of the valve is normally elastically deformable.As a rule, the valve also allows the gas sample to flow through the fluid guiding unit when the valve is in a position which is neither the releasing end position nor a closing position, but a position between the intermediate closing positions under the releasing end position. Often, however, the volume flow is then lower than in the end position released with the valve.As long as the fluid connection is released, the pressure in the measuring chamber is generally equal to the ambient pressure. On the other hand, as long as the measuring chamber is completely fluid-tightly separated from the environment, a difference may occur permanently between the pressure in the measuring chamber and the ambient pressure, provided that the valve actually closes the fluid connection in a fluid-tight manner.A pressure sensor arrangement of the analysis device comprises at least one pressure sensor and is capable of measuring a pressure difference. This pressure difference is the difference between the pressure in the measuring chamber and the pressure in the environment of the analytical device. Of course, it is possible for the pressure sensor arrangement to measure a pressure difference of zero at least temporarily. The or each pressure sensor measures the pressure at a measurement position in each case. The or a measurement position of this pressure sensor arrangement is located, for example, on or in the measurement chamber or on or in the fluid guidance unit and there between the valve and the measurement chamber or also on or in an optional further fluid guidance unit, which connects the measurement chamber to an optional suction unit.A signal processing control unit (control unit) of the analysis device is able to automatically decide whether or not the valve actually closes the fluid guide unit in a fluid-tight manner when the valve is in the closing end position. The control device is part of the checking device according to the invention. For this decision, the control device causes the valve to be continuously in the closing end position in a test time period, wherein the test time period has at least a predefined minimum time period. The test time period can last longer than the minimum time duration. The control device has caused the valve to be transferred from the intermediate closing position or another position into the end closing position before the test period. Naturally, no gas sample or any other fluid or particle from the environment can enter the measuring chamber during this test period, provided that the valve actually closes the fluid guidance unit in a fluid-tight manner. Furthermore, the control device has the effect that the pressure sensor arrangement measures the differential pressure several times, namely at least twice, in the test period, for example with a fixed sampling rate. The following configuration is possible: In the test period in which the valve is continuously in the closing end position, or in a measurement period overlapping the test period or including the test period, the gas sensor measures the concentration or quantity of the target gas in the measurement chamber.The control device decides at least that the valve actually closes the fluid-conducting unit in a fluid-tight manner if it has detected the following situation: In the entire test time period, i.e. at each sampling time in the test time period, the measured pressure in the measuring chamber deviates from the ambient pressure by at least a predefined minimum deviation, namely upwards or downwards depending on the design of the analytical device. The pressure in the measuring chamber can thus be greater than the ambient pressure over the entire test period or can also be less than the ambient pressure over the entire test period if the valve closes the fluid guide unit in a fluid-tight manner.The control device decides at least in the event that the valve does not close the fluid-conducting unit in a sufficiently fluid-tight manner if it has detected the following situation: at least at the end of the test period, the pressure in the measuring chamber deviates from the ambient pressure by at most a predefined fraction of the minimum deviation. The fraction is defined by a number greater than or equal to 0 and less than 1. The fraction is preferably less than or equal to 0.5, particularly preferably less than or equal to 0.25, i.e. is, for example, half or a quarter.If the control device has not detected either result or the other, a state of the valve cannot be detected with certainty. In one embodiment, the control device then automatically causes the check just described to be carried out again, for example with a longer check period. In another embodiment, the control device causes a corresponding message to be output in this situation. This message can be used by a user to check the analytical instrument.A preferred method for automatically checking an analytical device having a measuring chamber, a fluid guidance unit between the measuring chamber and the environment, a valve for the fluid guidance unit and a gas sensor comprises the following steps, which are carried out automatically:causing the valve to be continuously in the closing end position during the test period.In the test period, the difference between the pressure in the measuring chamber and the pressure in the environment is repeatedly measured.Automatically, it is decided whether or not the valve in the closing end position actually closes the fluid guide unit in a fluid-tight manner.At least then, it is decided that the valve actually closes in a fluid-tight manner if the measured pressure in the measuring chamber deviates from the ambient pressure by at least the predefined minimum deviation during the entire test period.At least then, it is decided that the valve does not close in a fluid-tight manner if, at the end of the test period, the pressure in the measuring chamber deviates from the ambient pressure by at most the predefined fraction of the minimum deviation.A checking device according to the invention has the effect that the steps just described are carried out.As already stated, the operation causes the valve to be moved away from the releasing end position: the valve first reaches the intermediate closing position and then the final closing position. In the case of a valve operating without faults, the fluid guide unit is closed in a fluid-tight manner in each closing position of the valve. Because the intermediate sealing position differs from the final sealing position, the volume of a space inside the analytical instrument also changes, this space being available for a gas sample. This space comprises the measuring chamber and that segment of the fluid guidance unit which is located between the valve and the measuring chamber. If the valve in each closing position actually closes the fluid guiding unit in a fluid-tight manner, the quantity of the gas sample in this space does not change. Therefore, the movement of the valve results in a difference between the pressure in this space and the ambient pressure. This pressure difference is determined and evaluated.If the valve does not close the fluid-conducting unit in a fluid-tight manner, the following undesirable situations can occur: chemical substances of the gas sensor designed as an electrochemical sensor can evaporate. Harmful substances from the environment can reach the measuring chamber through the fluid guidance unit and damage the gas sensor there. Water vapor may enter the measurement chamber, and water may condense on a wall of the measurement chamber. This is undesirable in particular when the sensor comprises a radiation source and a detector and when at least one wall of the measuring chamber reflects the radiation in order to lengthen the optical path. Water can also condense on a window of the measuring chamber, electromagnetic radiation passing through this window.In order for a gas sample to be able to flow from the environment through the fluid guidance unit into the measuring chamber, the valve must necessarily be moved out of a closing position. In order that the aforementioned undesired situations occur as rarely as possible, the valve should actually close the fluid guide unit in a fluid-tight manner, unless a gas sample flows through the fluid guide unit into the measuring chamber, or the measuring chamber is flushed out through the fluid guide unit in order subsequently to be able to take up a new gas sample.The situation may arise in which the valve does not completely close the fluid guide unit in a fluid-tight manner even in the closing end position. This can be caused, for example, by material fatigue or by a defect of an actuating drive which moves a component of the valve. Or at least one particle is fixed between a movable and a fixed part of the valve. It was explained above why this situation is undesirable.As already explained, the gas sensor may be damaged over time if the valve does not completely close the fluid guide unit in a fluid-tight manner even in the closing end position. Therefore, it is necessary to detect this undesirable event. The invention provides a way to automatically check (test) whether the valve in the closing end position actually completely seals the fluid guide unit in a fluid-tight manner. This check does not require a user's action. Rather, the control device is able to automatically trigger the steps required for checking and to automatically carry out the required evaluation. The analytical instrument is thus capable of automatically checking itself. This check can be carried out repeatedly, for example each time the analytical device is switched on or when a predetermined time period has elapsed since the last check or after N gas samples have flowed into the measuring chamber, wherein N>=1 is a predetermined number, or when the gas sensor has detected a predetermined amount of the target gas overall since the last check.It is possible that a user can additionally trigger the steps required for checking manually. For example, the user actuates a corresponding actuating element of the analysis device.The control device, which belongs to the checking device and initiates the steps for checking the analysis device, receives and processes a signal of the pressure sensor arrangement. The control device can be a component of the analysis device. It is also possible for the control device to be arranged spatially remote from a housing of the analysis device and for the measurement chamber, the gas sensor, the fluid guidance unit and the pressure sensor arrangement and optionally a drive to be arranged in the housing. In this embodiment, a data connection, preferably a wireless data connection, is established at least temporarily between the pressure sensor arrangement and the spatially remote control device.If the control device has detected that the valve does not close the fluid guidance unit in a fluid-tight manner, the control device preferably causes at least one output unit to output a corresponding message in at least one form perceptible to a human. The or an output unit can be a component of the analytical device. It is also possible for the or an output unit to be spatially remote from the analytical device.As a rule, the valve comprises a part which is movable relative to the fluid guide unit and a part which is fixed relative to the fluid guide unit, namely a movable valve body (closing part) and a fixed valve body seat. In each closing position of the valve, the valve body contacts the valve body seat. During the process of transferring the valve from a releasing position into the closing end position, the following effect typically occurs: First, the valve body reaches the valve body seat. The intermediate closing position is then reached. Because the valve body seat is usually elastic and the valve body and / or further components of the analysis device can also be elastic, the valve body moves even further after it has already reached the valve body seat. This changes the volume of a space comprising the measuring chamber and that segment of the fluid guiding unit which is located between the measuring chamber and the valve body seat. In the case of a valve closing without defects, i.e. in a fluid-tight manner, this space is no longer in fluid communication with the environment as soon as the valve body has reached the valve body seat, i.e. after reaching the intermediate closing position and before reaching the end closing position. Therefore, the pressure in the space just mentioned changes after the valve body reaches the valve body seat, while the ambient pressure does not practically change in the test period. The effect just described thus has the effect that the pressure difference between the pressure in the space and the pressure in the environment changes.According to the invention, the control device causes, during a check, that the valve remains in the closing end position with the predetermined minimum time duration in the check time period. If the valve then actually closes the fluid-conducting unit in a fluid-tight manner, this pressure difference remains in the entire test period. More specifically, the amount of the pressure difference is greater than or equal to the minimum deviation over the entire test time period and thus at each sampling time in the test time period. If, on the other hand, during the test period, the pressure in this space approaches the ambient pressure from above or from below, even though the valve is in the closing end position, the valve does not close the fluid guide unit in a sufficiently fluid-tight manner.In many cases, the invention does not require that an existing analysis device be supplemented by a sensor or by another part. This is because a pressure sensor is often already present, which measures the pressure in the measuring chamber. A signal of this pressure sensor is used, for example, to measure the volume flow into and / or out of the measuring chamber. This already present pressure sensor measures the pressure difference to the ambient pressure in many cases.If the analysis device is used to record a breath sample of a test subject, the signal of the pressure sensor arrangement is also used, for example, to measure the volume flow during the delivery of the breath sample and to derive from this the volume of the breath sample delivered up to now and / or to detect the event that the subject has finished delivering the breath sample. This makes it possible to determine whether or not a subject has actually entered a sufficiently large breath sample.This already present pressure sensor can be additionally used for the invention in many cases. In many cases, the invention can be implemented on an existing analysis device by loading appropriate software onto the control device without a further change being required. In particular, often no sensor needs to be supplemented.Preferably, the control device causes an alarm to be issued in a form perceptible by a human if the undesired event is detected that the valve does not close the fluid guide unit in a fluid-tight manner in the closing end position. This alarm is preferably output on an output unit of the analysis device.In the test period in which the valve is caused to be in the closing end position, the analysis device cannot be used for the analysis of a gas sample. Preferably, the control device causes a corresponding message to be output in this test period, i.e. a message that the analytical device cannot currently take a gas sample. This reduces the risk that a user will wish to use the analysis device in the test period and / or erroneously keep the analysis device defective.According to the invention, the control device has the effect that a sequence of steps is carried out at least once, wherein this sequence automatically checks whether or not the valve actually seals the fluid guide unit in a fluid-tight manner in the closing end position. This sequence is preferably carried out repeatedly, for example regularly with a predetermined sampling frequency or if a predetermined time period has elapsed since the last check. In one embodiment, the sequence is always carried out when the analytical instrument is switched on and, after switching on, first carries out a self-test, or it is carried out after the analytical instrument has investigated N gas samples, wherein N>=1 is a predefined number, preferably N>=10.Preferably, the valve comprises a valve body and a valve body seat. The valve body is movable relative to the valve body seat. When the valve body contacts the valve body seat, the valve is in a closing position. At least when the valve body is at the greatest possible distance from the valve body seat, the valve is in the releasing end position. When the valve body is at the greatest possible distance from the position in the releasing end position, the valve is in the closing end position.In a first embodiment, the valve body seat is located between the valve body and the measuring chamber. In the first embodiment, a movement of the valve body relative to the valve body seat towards the measuring chamber causes the valve to be transferred (moved) into the closing end position. In a second embodiment, conversely, the valve body is located between the valve body seat and the measuring chamber. In the second embodiment, a movement of the valve body relative to the valve body seat away from the measuring chamber causes the valve to be transferred into the closing end position. A movement of the valve body in the respective opposite direction has the effect in both forms of realization that the valve is transferred into the releasing end position.It is possible for the gas sample to diffuse into the measuring chamber. If the gas sample originates from a breathing sample that has delivered a subject, the kinetic energy that the subject applies in delivering the breathing sample may be sufficient to deliver (promote) the gas sample into the measurement chamber. In a preferred embodiment, on the other hand, the analysis device comprises a fluid conveying unit. The fluid delivery unit comprises, for example, a piston-cylinder unit or a pump or a blower or a chamber with variable volume, in particular a bellows, as well as an actuating drive or a motor or another drive. The fluid conveying unit is capable of aspirating a gas sample through the fluid guiding unit into the measuring chamber. Conversely, the fluid conveying unit is capable of flushing out the measuring chamber, preferably with ambient air. For example, the fluid conveying unit causes the gas in the measuring chamber to be replaced by ambient air.In one possible embodiment, the analysis device comprises an actuating drive in addition to the fluid conveying unit. This actuator is mechanically connected to the fluid delivery unit and to a movable part of the valve. The actuating drive is able to transfer the valve selectively into the releasing or into the closing end position, in particular in that the actuating drive moves the valve body relative to the valve body seat. Unlike a motor, an actuator is capable of moving only along a limited range and oscillating within that range.In one embodiment, an actuating drive of the fluid conveyor unit is connected to a movable part of the valve. It is also possible for an actuating drive for the valve to be present, but not a fluid conveying unit. In this embodiment, too, the actuating drive transfers the valve from one position to the other position.In one embodiment, the fluid delivery unit is mechanically coupled to the valve. During the aspiration of a gas sample, the fluid conveying unit transfers the valve into the releasing end position. Conversely, the fluid conveying unit transfers the valve into the closing end position during flushing out. This embodiment saves a separate actuator for the valve. It is also possible for the fluid conveying unit to transfer the valve into the closing end position during the suction and to return to the releasing end position during the flushing out.A preferred embodiment has been described above, in which a fluid conveying unit is able to suck a gas sample through the fluid guiding unit into the measuring chamber and at the same time is able to transfer the valve from the one end position into the other end position. In one embodiment, the fluid conveying unit causes the valve to be transferred into the releasing end position while the gas sample is being sucked in. In an alternative embodiment, the fluid conveying unit, conversely, causes the valve to be transferred into the closing end position while the gas sample is being sucked in.In one embodiment, the fluid conveying unit comprises a suction chamber unit and an actuating drive. The suction chamber unit provides a variable volume chamber. For example, the suction chamber unit includes a piston capable of oscillating in a cylinder or a bellows. The chamber provided is in fluid communication with the measurement chamber. The actuating drive is mechanically connected to the intake chamber unit and is capable of both increasing and decreasing the volume of the chamber provided. An enlargement of the chamber provided causes a gas sample to be sucked into the measuring chamber. A reduction in the volume causes the measuring chamber to be flushed out.This configuration in many cases leads to a relatively compact analysis device. It is sufficient that the actuator can perform a linear movement in two mutually opposite directions over a relatively short distance. As a rule, the volume of the chamber still changes after the valve has reached the intermediate closing position. In many cases, when the valve is moved from the intermediate sealing position to the final sealing position, the effect that the change in chamber volume causes overlaps the effect that movement of the valve causes. As a rule, the change in volume has a greater effect than the movement of the valve. In this case, too, the pressure difference is an indication as to whether or not the valve closes the fluid guidance unit in a fluid-tight manner in the closing end position.The configuration with the suction chamber unit can be combined with the configuration in which the valve comprises a valve body seat and a valve body movable relative to the valve body seat.In one embodiment, the actuator comprises two components:a restoring element, which preferably comprises at least one mechanical or pneumatic spring, andan electric drive, for example a lifting magnet.The electric drive strives to change the volume of the chamber provided and to move the valve body, namely counter to the restoring force of the restoring element. When the electric drive is deactivated, the restoring element changes the volume of the chamber and moves the valve body. Preferably, the restoring torque tends to transfer the valve into the closing end position and to hold it in the latter.After the gas sensor has analyzed the gas sample, it is generally necessary to flush out the measuring chamber in order subsequently to examine a further gas sample. Flushing reduces the risk that the old gas sample would falsify a measurement result for the new gas sample. In a preferred embodiment, the measuring chamber is flushed out through the fluid guidance unit. This embodiment obviates the need to provide an additional fluid guidance unit separately for flushing out the measuring chamber. During the step of flushing out the measuring chamber, the fluid conveying unit preferably transfers the valve into the closing end position, alternatively into the releasing end position. This embodiment also obviates the need to provide an additional actuator for the valve.According to the invention, the gas sensor of the analysis device is capable of measuring the target gas concentration in a gas sample while the gas sample is in the measurement chamber. Different configurations of this gas sensor are possible.In one configuration, the gas sensor is an electrochemical sensor. An electrochemical sensor comprises a measuring electrode and a counter electrode and an ionically conductive electrolyte between these two electrodes, optionally additionally a reference electrode. The target gas causes an electrochemical reaction that causes current to flow from one electrode to the other electrode. The electrochemical reaction depends on the target gas concentration and influences a detection variable of the gas sensor, preferably an electrical detection variable, in particular the electrical charge. A detection quantity sensor is capable of measuring the detection quantity. This detection variable correlates with the sought target gas concentration. In many cases, an analyzer with an electrochemical sensor consumes less electrical energy than an analyzer with a different sensor.In another embodiment, the gas sensor is an opto-electric (photoelectric) sensor. A radiation source emits electromagnetic radiation into the measuring chamber. The electromagnetic radiation penetrates the measuring chamber and impinges on a photodetector. The photodetector generates an electrical signal that depends on the intensity of incident electromagnetic radiation. As a rule, target gas to be detected absorbs a part of the electromagnetic radiation in a wavelength range depending on the target gas, so that the electrical signal of the photodetector correlates with the target gas concentration. Instead of electromagnetic radiation, the radiation source can also emit sound.The gas sensor can also be designed as a photo-acoustic sensor. Modulated electromagnetic radiation is emitted. The emitted radiation penetrates the measurement chamber, where the target gas absorbs a part of the radiation. The absorption causes a local temperature change which modulates depending on the emitted radiation. The temperature change caused causes an acoustic effect in a reference chamber. An acoustic sensor measures the acoustic effect brought about. This acoustic effect correlates with the sought-after target gas concentration.In one configuration, the gas measuring device comprises two gas sensors, preferably two different type gas sensors, in particular an electrochemical sensor and an opto-electrical sensor. In one embodiment, the two gas sensors are arranged in parallel, and a gas sample reaches the two parallel gas sensors. The two gas samples originate, for example, from the same breath sample of a test subject. In another embodiment, the two gas sensors are connected in series, and the same gas sample reaches both gas sensors one after the other. The embodiment with two gas sensors increases the reliability and enables a plausibility check in which the two signals of the two gas sensors are compared with one another. In many cases, two gas sensors having different sampling frequencies can also be used. Moreover, the analytical device can in many cases still be used even if one of the two gas sensors has failed.In one embodiment, the analysis device comprises an input unit, in particular a mouthpiece. The input unit can preferably be detachably connected to a base body of the analysis device. The input unit is capable of receiving a breath sample from a test subject. The subject enters this breath sample into the input unit. The input unit is in fluid communication with the fluid guide unit. The analyzer uses, as the gas sample flowing into the measurement chamber, a part of a breath sample that has input a subject to the input unit and that is received by the input unit, or the entire breath sample. This part of the breath sample flows through the input unit and through the fluid guidance unit into the measuring chamber. As a rule, the remainder of the breath sample flows past the measuring chamber back into the environment. In this embodiment, the or a target gas is preferably breath alcohol.According to the invention, the pressure sensor arrangement is designed to measure the difference between the pressure in the measuring chamber and the ambient pressure repeatedly during the test period. In the embodiment described below, it is sufficient that the pressure sensor arrangement comprises a pressure sensor. This pressure sensor is capable of measuring the pressure at a measurement position, this measurement position being located at one of the following positions:in or on the fluid guiding unit between the measuring chamber and the environment of the analytical device and there at a position between the valve and the measuring chamber, i.e. downstream of the valve,in or on the measuring chamber,in or on an optional further fluid guide unit, wherein this further fluid guide unit connects the measuring chamber to an optional suction unit.The control device causes the pressure sensor to measure the pressure at the measurement position as follows:On the one hand, the pressure sensor repeatedly measures the pressure in the test time period. In this test period, the valve is in the closing end position.On the other hand, the pressure sensor measures the pressure at least once, preferably several times, when the valve is in a releasing position, in particular in the releasing end position.A releasing position is understood to mean the releasing end position or a position between the releasing end position and the closing intermediate position. In a releasing position, the valve is fully or at least partially opened and the fluid guiding unit is at least partially released.When the valve is in a releasing position, fluid communication is established between the environment and the measurement chamber, and therefore the pressure at the measurement position approximately matches the pressure in the environment. As a rule, the assumption is justified that the pressure in the environment does not change appreciably, while the valve is transferred from the one end position into the other end position.The control unit determines the ambient pressure as a function of at least one pressure which was measured at the measurement position when the valve was in an enabling position. In one embodiment, the control device uses the pressure at the measurement position as the ambient pressure, wherein the pressure sensor has measured this pressure when the valve was in an enabling position. In another embodiment, the control device averages over a plurality of pressures, which were measured at the measurement position with the valve in different releasing positions.This embodiment requires only a single pressure sensor. Such a pressure sensor is often already present.In one embodiment, the analysis device comprises its own voltage supply unit and can therefore be used as a mobile device. It is also possible for the analysis device to be connectable to a stationary voltage supply network. These two forms of realization can be combined with one another.In one embodiment, the analytical device comprises its own output unit. The analytical device is able to output information on this output unit. In particular, the analytical device is capable of outputting at least one of the following information items, preferably all of the following information items:the measured concentration or amount of the or at least one, preferably each, target gas in the gas sample,whether the measured concentration or quantity is within or outside a predefined value range,whether or not the analytical device is carrying out the self-test according to the invention and is therefore not currently capable of receiving a new gas sample,whether a separate voltage supply unit of the analysis device is still capable of supplying sufficient electrical energy, andwhether or not the valve in the closing end position actually closes the fluid guide unit in a fluid-tight manner.In one embodiment, the analysis device comprises a communication unit. With the aid of this communication unit, a data connection can be established at least temporarily between the analysis device and a spatially remote receiver. The analysis device is able to transmit a measurement result to the receiver via this data connection. In one embodiment, the analysis device is also capable of transmitting to the receiver the result that the valve no longer closes in a fluid-tight manner in the closing end position.The invention is described below with reference to an exemplary embodiment. This shows FIG. 1 is a perspective view from the side of the analyzer of the embodiment, with the housing and the actuator omitted; FIG. 2 is a cross-sectional view from the side of the analytical device of FIG. 1 ; FIG. 3 shows a detailed view of the representation of FIG. 2 ; FIG. 4 is a plan view of the analytical instrument of the exemplary embodiment, with a cover of the housing being omitted; FIG. 5 shows an exemplary time profile of the pressure difference with the valve intact; FIG. 6 schematically shows the respective time profile of the pressure difference in the case of an intact and in the case of a defective (leaky) valve.FIG. 1 shows a schematic illustration of an analysis device 100 according to the exemplary embodiment. The analyzer 100 is capable of measuring the content of breath alcohol in a breath sample. As is known, the content of breath alcohol in a breath sample that has delivered a subject correlates with the content of alcohol in the subject's blood.The subject enters a breath sample A into a schematically shown funnel-shaped mouthpiece 30. A part of the breath sample A functions as a gas sample Gp. The gas sample Gp flows through an inlet piece 1 and through a fluid guide unit described in more detail below into a measuring chamber. In the exemplary embodiment, the measuring chamber is rotationally symmetrical with respect to a central axis MA. The remainder of the breathing sample A preferably flows back into the environment without reaching the measuring chamber.The housing of the analyzer 100 is omitted from FIG. 1. The analytical device 100 comprises a measuring chamber, of which only a cover plate 17 and the central axis MA are shown in FIG. 1, as well as an electrochemical sensor 50, which is known from the prior art. The electrochemical sensor 50 is capable of analyzing the gas sample Gp in the measuring chamber for breath alcohol and operates according to the principle of a fuel cell with alcohol as the fuel.The sensor 50 is constructed as follows: A measuring electrode 21 is electrically contacted by a contact wire 34. A counter electrode 20 is electrically contacted by a contact wire 33. Between the two electrodes 20 and 21 there is an electrolyte with an ionically conductive medium. The medium is, for example, sulfuric acid or phosphoric acid or perchloric acid diluted with water. Ions can move in the electrolyte. The electrolyte establishes an ionically conductive connection between the measuring electrode 21 and the counter electrode 20, but electrically isolates the two electrodes 20 and 21 from one another. Both the electrodes 20 and 21 and the two contact wires 33 and 34 are made of a material which is not chemically attacked by the electrolyte, for example platinum or gold.As already explained, the electrochemical sensor 50 operates according to the principle of a fuel cell. A gas sample Gp reaches the measuring chamber with the cover plate 17. the electrochemical sensor 50 oxidizes the breathing alcohol in the gas sample Gp, ideally the entire breathing alcohol in the gas sample Gp. As a result of the chemical reaction during oxidation, an electric current flows between the measuring electrode 21 and the counter electrode 20, and a detection quantity sensor, not shown, measures the electric charge, i.e., the total quantity of the electric current flowing through a connecting wire between the two electrodes 20 and 21 (principle of coulometry). For a given volume of gas sample Gp in the measurement chamber, the more breath alcohol contained gas sample Gp prior to oxidation, the higher the electrical charge measured. Therefore, the measured electric charge is a measure for the content of respiratory alcohol in the gas sample Gp and thus for the content of alcohol in the blood of the test subject.FIG. 2 shows a cross-sectional representation of the analytical device 100 from FIG. 1, and in FIG. 2 the electrochemical sensor 50 is omitted. The cylindrical measuring chamber 3 is located below the measuring electrode 21 and is indicated in FIG. 2 by a dashed rectangle. In one configuration, the measuring electrode 21 forms a wall of the measuring chamber 3.The gas sample Gp flows through a tube 31 and through a subsequent cavity 15 into the measuring chamber 3. A sealing ring 14 is inserted into a circumferential groove of the larger part 16.2. On the surface of the connecting piece 16 facing the measuring chamber 3 is applied a further sealing ring 13 which is elastic and functions as a valve body seat. In cooperation with the valve body seat 13, a movable valve body 2 is able to selectively close or release a fluid connection between the cavity 15 and the measuring chamber 3. The fluid communication is established by a fluid guiding unit comprising the tube 31 and the cavity 15. In FIGS. 2 and 3, the valve 2, 13 is shown in the closing end position.A rod 4 mechanically connects the valve body 2 to a lifting magnet 7 and is passed through the measuring chamber 3. The activated lifting magnet 7 displaces the rod 4 and thus the valve body 2 to the left, namely in the example of FIGS. 1 to 3, and thereby opens the valve 2, 13. When the lifting magnet 7 is deactivated, a restoring element, not shown, strives to hold the valve 2, 13 in the closing end position. The activated lifting magnet 7 thus overcomes the force of the restoring element.The rod 4 is mechanically secured to a plate 6. The plate 6 is connected to one end of a bellows 5. The opposite end of the bellows 5 is connected to a connector 10. This connecting piece 10 is firmly connected to a wall of the measuring chamber 3. A movement of the plate 6 relative to the connecting piece 10 changes the volume of the bellows 5. in the example of FIGS. 1 and 2, the volume of the bellows 5 is increased when the plate 6 is moved away from the inlet piece 1 and from the valve body seat 13 relative to the connecting piece 10, i.e. to the right in the example of FIGS. 1 and 2. The volume of the bellows 5 is reduced when the plate 6 is moved toward the inlet piece 1 and the valve body seat 13, that is, toward the left. In the example of FIGS. 1 and 2, the bellows 5 is shown with a maximum volume. If the volume of the bellows 5 is increased, a gas sample Gp is sucked into the measuring chamber 3 through the inlet piece 1 and the cavity 15.If the volume of the bellows 5 is reduced again, this gas sample Gp is ejected from the measuring chamber 3 through the cavity 15 and the inlet piece 1.FIG. 3 shows, in an enlarged detail of FIG. 2, the inlet piece 1, the connection piece 16, the sealing ring 14, the valve body 2, the valve body seat 13, the rod 4 and a part of the measuring chamber 3. The cavity 15 is connected to a tube 18 via a gap Sp. The tube 18 surrounds the rod 4. Several inlets 22.1, 22.2 connect the tube 18 to the measuring chamber 3. A guide 19 guides the rod 4 in the tube 18. Also shown is a part of the housing 9.The valve body 2 can move linearly back and forth in the cavity 15. In the example of FIGS. 2 and 3, the valve 2, 13 is shown in the closing end position. The valve body 2 is located between the valve body seat 13 and the inlet piece 1. the valve 2, 13 is opened in this embodiment, and the gap Sp is released by the rod 4 displacing the valve body 2 away from the valve body seat 13 and from the gap Sp and towards the inlet piece 1. The reverse implementation form is also possible, in which the valve body seat 13 is located between the valve body 2 and the inlet piece 1. In this reverse embodiment (not shown), the gap Sp is released by moving the valve body 2 away from the inlet piece 1 and towards the measuring chamber 3.FIG. 4 shows the analytical device 100 in a plan view. The same reference numerals have the same meanings as in FIGS. 1 to 3. Of the housing 9, only one base plate is shown. The rod 4 is guided through a sleeve 11. Preferably, the sleeve 11 is rigidly connected to the rod 4 and to the plate 6. A mouthpiece 30 is placed on the inlet piece 1. Also shown schematically is a signal processing control unit (control unit) 60.An optional pressure sensor 12.1, shown schematically, measures the pressure at a measurement position MP.1. The measurement position MP.1 is in fluid communication with the cavity 15 and therefore in fluid communication with the environment. The same or another pressure sensor 12.2, also shown only schematically, measures the pressure at a measurement position MP.2. The measurement position MP.2 is in fluid communication with the measurement chamber 3 and is separated from the environment and therefore also from the measurement position MP.1 in a fluid-tight manner when the valve 2, 13 is closed. In one embodiment, the two pressure sensors 12.1 and 12.2 belong to the pressure sensor arrangement of the exemplary embodiment.The control device 60 receives a signal from the two pressure sensors 12.1 and 12.2 and is able to derive the following information from this:Depending on the pressure at the measuring position MP.1, the control device 60 derives the information as to whether the subject is inputting a breathing sample A into the mouthpiece 30, and if so, the beginning and the end of the input.Depending on the difference between the time-varying pressures at the measurement positions MP.1 and MP.2, the control device 60 approximately derives the volume flow into the measurement chamber 3. From this, the control device 60 approximately derives the volume of the gas sample Gp in the measuring chamber 3. If a subject enters a breath sample A, the pressure at the measurement position MP.1 is generally higher than the ambient pressure because the subject generates an overpressure. If no breathing sample A is input, then in the exemplary embodiment the pressure at the measurement position MP.1 is equal to the ambient pressure.Depending on the pressure at the measuring position MP.2 or on the difference between the time-varying pressures at the measuring positions MP.1 and MP.2, the control device 60 automatically checks whether or not the valve 2, 13 is actually capable of closing the gap Sp in a fluid-tight manner in the closing end position. This is explained in more detail below.FIG. 5 shows an exemplary profile of the pressure at the measurement position MP.2. The time curve shown is obtained in a situation in which no breath sample is input. The time is plotted on the x-axis, and the pressure difference ΔP in [mbar] is plotted on the y-axisthe pressure at the measurement position MP.2 and thus in the measurement chamber 3, on the one hand, andthe ambient pressure, on the other hand, wherein the ambient pressure is usually approximately equal to the pressure at the measurement position MP.1.In the embodiment just described, a pressure sensor 12.1 measures the pressure at the measurement position MP.1, and a pressure sensor 12.2 measures the pressure at the measurement position MP.2. In an alternative embodiment, only the pressure sensor 12.2 is used for the pressure at the measurement position MP.2, while no pressure sensor is required for the pressure at the measurement position MP.1. It is therefore sufficient that the pressure sensor arrangement comprises only one pressure sensor.According to the alternative embodiment, the pressure sensor 12.2 measures the pressure at the measurement position MP.2 at least once in a situation in which the valve 2, 13 is in the releasing end position or in a releasing intermediate position. In this situation, the pressure at the measurement position MP.2 approximately corresponds exactly to the ambient pressure. As a rule, it is justified to assume that the ambient pressure does not substantially change while the valve 2, 13 is closed or opened.In this example, the valve 2, 13 is realized in such a way that a movement of the valve body 2 away from the inlet piece 1 and towards the measuring chamber 3 transfers the valve 2, 13 into the closing end position. This embodiment is shown in Figs. 2 and 3, wherein the valve 2, 13 is shown in the closing end position.The following description refers to FIG. 5 Initially, the same pressure prevails in the measuring chamber 3 as in the environment, so that ΔP=0 applies. The valve 2, 13 is in the releasing end position. At time t stroke the actuating drive, for example the lifting magnet 7, causes an intake stroke to be carried out. The volume of the bellows 5 is increased by an intake stroke, and a negative pressure ΔP relative to the environment of up to 150 mbar occurs in the measuring chamber 3, i.e. 0>ΔP>=-150 mbar. A gas sample Gp is sucked into the measurement chamber 3 by the negative pressure ΔP. Between the times t stroke and t close the valve 2, 13 is still fully or at least partially open and the pressure in the measuring chamber 3 balances itself with the ambient pressure through the open gap Sp. Until time t close the volume of the bellows 5 remains unchanged and the valve body 2 remains in the same position relative to the valve body seat 13.Immediately before time t close the valve body 2 is moved relative to the valve body seat 13. The valve 2, 13 is in the intermediate closing position at the time t close. Because the valve body seat 13 and other components are elastic, in particular the bellows 5, the valve body 2 moves even slightly further after it has reached the valve body seat 13. In particular, the bellows 5 still moves after the valve body 2 has reached the valve body seat 13. After completion of this movement, namely at the time t final, the valve 2, 13 is in the closing end position. The valve 2, 13 reaches the closing end position at the time t final. Between the two times t close and t final the volume of the space defined by the bellows 5 changes. In the embodiment shown, this effect results in the volume of the space comprising the measuring chamber 3 and the tube 18 increasing still somewhat. Because the valve 2, 13 separates this space from the environment in a fluid-tight manner, the pressure at the measurement position MP.2, in the example shown, decreases by ΔP limit= 5 mbar due to this increase in volume. The ambient pressure and thus the pressure at the measurement position MP.1, however, remain the same. In the reverse embodiment, the pressure would increase accordingly, for example by 5 mbar. If the valve 2, 13 actually permanently seals the gap Sp in a fluid-tight manner, this pressure difference ΔP is maintained. This is indicated in FIG. 5.The control unit 60 evaluates the signal of the pressure sensor 12.2 and detects the time t final. The control unit 60 ensures that the valve 2, 13 remains in the closing end position in a test time period with a predetermined minimum time period, i.e. no new intake stroke is carried out in this test time period. This test time period is denoted by T min and begins at the time t final. It is possible for the test time period T min to overlap with a time period at which the sensor 50 analyzes a gas sample Gp in the measuring chamber 3.The control device 60 checks whether the following conditions are cumulatively fulfilled:The pressure in the space formed by the measuring chamber 3 and the tube 18 deviates by at least ΔP limit from the ambient pressure.This applies to the entire test time period T min, which begins at the time t final and has at least the minimum time duration.The pressure difference ΔP remains almost constant. More specifically, the time variation of the pressure difference ΔP is within a predetermined variation tolerance band.These conditions apply both to the embodiment according to FIGS. 2 and 3, in which the valve 2, 13 is closed when the volume of the bellows 5 is increased, and to the reverse embodiment.Preferably, the control device 60 causes the analysis device 100 to output a message in the test time period T min. This informs a user that the analytical device 100 cannot record any further breath sample in this test period T min.If at least one of the conditions just mentioned is not fulfilled, the control device 60 causes the analysis device 100 to output an alarm in at least one form perceptible to a human.FIG. 6 schematically illustrates the difference between a valve 2, 13 closing in a fluid-tight manner and a leaking valve. The pressure profile ΔP dense occurs in the case of a valve 2, 13 closing in a fluid-tight manner, the pressure profile ΔP leaky occurs in the case of a leaking valve 2, 13.List of reference characters1 Inlet piece, surrounds the tube 31 2 valve body, 3 cylindrical measuring chamber firmly connected to the rod 4, accommodates the electrochemical sensor 50, is bounded by the side wall 40 and the cover plate 17, is in fluid communication with the measuring position MP.2 4 rod, transmits a movement of the lifting magnet 7 to the plate 6 and the valve body 2 5 bellows, on the one hand connected to the connecting piece 10, on the other hand accommodates the plate 6, has a variable volume 6 plate firmly connected to the rod 4, changes the volume of the bellows 5 7 lifting magnet, moves the rod 4 against the force of a restoring element on the inlet piece 1 to 9 housings of the analytical device 100 10 connecting piece on the side wall 40, holds the bellows 5 11 sleeve, If the rod 4 12.1 pressure sensor surrounds, measures the pressure at the measurement position MP.1 12.2 pressure sensor, measures the pressure at the measurement position MP.2 13 valve body seat in the form of a sealing ring on the connecting piece 16 14 sealing ring, 15 cavity in the connecting piece 16 inserted into a groove of the connecting piece 16 15 cavity in the connecting piece 16, is in fluid communication with the measurement position MP.1 16 connecting piece, comprises a smaller part 16.1 and a larger part 16.2, the tube 15 16.1 surrounds the smaller part of the connecting piece 16, connects the inlet piece 1 to the tube 18 16.2 surrounds the larger part of the connecting piece 16, takes the sealing ring 14 onto 17 cover plate of the measuring chamber 3 18 tube which surrounds the tube when the valve 2 is open, 13 connects the measuring chamber 3 to the cavity 15 and thus to the environment 19 connects guide unit in the tube 18, the rod 4 connects 20 counterelectrode, the measuring electrode electrically contacted by the contacting wire 33 connects 21 the measuring electrode, the contacting wire 34 connects 22.1 inlets into the measuring chamber 3 connects 22.2 connects 30 the funnel-shaped mouthpiece, can be placed detachably on the inlet piece 1, takes a breath sample A onto 33 contacting wire for the counterelectrode 20 connects 34 contacting wire for the measuring electrode 21 connects 40 the side wall of the measuring chamber 3 50 the electrochemical sensor, comprises the electrodes 20 and 21, comprises a control device that processes electrolyte between the electrodes 20 and 21 and the contacting wires 33 and 34 60, controls the lifting magnet 7 and receives and processes signals from the pressure sensors 12.1, 12.2 100 the analytical device, comprises the measuring chamber 3, the sensor 50, the lifting magnet 7, the bellows 5, the plate 6, the inlet piece 1, the connecting piece 6, the housing 9 and, in one embodiment, the control device 60A breath sample which has introduced a test band into the mouthpiece 30 Gpgas sample, consists of a part of the breath sample A, reaches the measuring chamber 3 MP.1 measuring position of the pressure sensor 12.1, is in fluid communication with the cavity 15 and therefore in fluid communication with the environment MP.2 measuring position of the pressure sensor 12.2, is in fluid communication with the measuring chamber 2Spgloc connecting the cavity 15 to the tube 18, it is possible to close ΔP dense temporal profile of the pressure difference ΔP in the case of a valve 2 closing in a fluid-tight manner, 13 ΔP leaky temporal profile of the pressure difference ΔP in the case of a leak, by the valve 2, 13, Thus, the valve 2, 13 closing in a fluid-tight manner is not as great as the minimum deviation ΔP limit ΔP limit the minimum deviation between the pressure in the measuring chamber 3 and the ambient pressure when the valve 2, 13 closes in a fluid-tight manner, and therefore at the measuring position MP.2, on the one hand, and the ambient pressure, on the other hand, is at least as great as the minimum deviation ΔP ΔP the minimum deviation between the pressure in the measuring chamber 3 and the ambient pressure when the valve 2, 13 closes in a fluid-tight manner in the closing end position t close the time at which the valve body 2 reaches the valve body seat 13 and the valve 2, 13 in the closing intermediate position t final the time at which the valve 2, 3, 10 is in the closing end position, at the same time the beginning of the test time t stroke the time, At which an intake stroke begins T min test time period, during which the valve 2, 13 remains in the closing end position and is checked for tightness, begins at time t final

Claims

Analysis device (100) comprising - a measuring chamber (3), - a gas sensor (50), - a fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) which is capable of establishing a fluid connection between the measuring chamber (3) and an environment of the analysis device (100), - a valve (2, 13), - a pressure sensor arrangement with at least one pressure sensor (12.1, 12.2) and - a signal processing control device (60), wherein the valve (2, 13) can be transferred into a releasing end position, into a closing intermediate position and into a closing end position, wherein the closing intermediate position is located between the two end positions, wherein the analysis device (100) is configured such that - when the valve (2, 13) is in the releasing end position, a gas sample (Gp) from the environment can be transferred through the fluid guidance unit (31, 15, Sp, 18, 18, 22.1, 22.2) flows or at least can flow through into the measuring chamber (3), and - when the valve (2, 13) is in a closing position, the fluid guide unit (31, 15, Sp, 18, 22.1, 22.2) is closed, wherein a closing position is the intermediate closing position, the end closing position or a position between the intermediate closing position and the end closing position, wherein the gas sensor (50) is configured to measure the concentration and / or amount of a predetermined target gas in a gas sample (Gp) in the measuring chamber (3), wherein the pressure sensor arrangement (12.1, 12.2) is configured to repeatedly measure the difference (ΔP) between the pressure in the measuring chamber (3) and the pressure in the environment, wherein the control device (60) is configured to automatically decide to, whether or not the valve (2, 13) actually seals the fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) in a fluid-tight manner in the closing end position, wherein the control device (60) is configured to, for the decision - to cause the valve (2, 13) to be continuously in the closing end position in a test period (T min) of a predetermined minimum period of time, - to cause the pressure sensor arrangement (12.1, 12.2) to repeatedly measure the pressure difference (ΔP) in the test period (T min) - to decide at least then that the valve (2, 13) actually seals in a fluid-tight manner, if, during the entire test period (T min) the pressure in the measuring chamber (3) deviates from the ambient pressure by at least a predetermined minimum deviation (ΔP limit) and - at least then it is decided that the valve (2, 13) does not close in a fluid-tight manner if, at the end of the test period (T min) the pressure in the measuring chamber (3) deviates from the ambient pressure by at most a predetermined fraction of the minimum deviation (ΔP limit).The analytical device (100) according to claim 1, characterized in that the valve (2, 13) comprises a valve body seat (13) and a valve body (2) movable relative to the valve body seat (13), wherein in each closing position the valve body (2) contacts the valve body seat (13) and wherein the analytical device (100) - in a first alternative is configured such that a movement of the valve body (2) relative to the valve body seat (13) towards the measuring chamber (3) causes the valve (2, 13) to be transferred into the closing end position, and - in a second alternative is configured such that a movement of the valve body (2) relative to the valve body seat (13) away from the measuring chamber (3) causes the valve (2, 13) to be transferred into the closing end position.The analytical device (100) according to any one of the preceding claims, characterized in that the analytical device (100) comprises a fluid conveying unit (4, 5, 6, 7), wherein the fluid conveying unit (4, 5, 6, 7) is configured to - suck a gas sample (Gp) through the fluid guiding unit (31, 15, Sp, 18, 22.1, 22.2) into the measuring chamber (3) and - flush out the measuring chamber (3) through the fluid guiding unit (31, 15, Sp, 18, 22.1, 22.2), wherein the fluid conveying unit (4, 5, 6, 7) in a first alternative is further configured to - during the suction transfer the valve (2, 13) into the releasing end position and - during the flushing out transfer the valve (2, 13) into the closing end position, and wherein the fluid conveying unit (4, 5, 6, 7) is further configured in a first alternative to - transfer the valve (2, 13) into the releasing end position, In a second alternative, the valve ( 2, 13) is further configured to transfer into the closing end position during the intake and to transfer the valve ( 2, 13) into the releasing end position during the flushing out.The analytical device (100) according to claim 3, characterized in that the fluid conveying unit (4, 5, 6, 7) comprises an intake chamber unit (5, 6) and an actuator (7), wherein the intake chamber unit (5, 6) provides a chamber (5) with a variable volume, wherein the provided chamber (6) is in fluid communication with the measuring chamber (3), wherein the actuator (7) is configured to change the volume of the provided chamber (6), and wherein the analytical device (100) is configured such that an enlargement of the provided chamber (6) causes a gas sample (Gp) to be sucked into the measuring chamber (3).The analytical device (100) according to any one of the preceding claims, characterized in that the analytical device (100) comprises an input unit (30), wherein the input unit (30) is configured to receive a breath sample (A) from a test subject, wherein the fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) is in fluid communication with the input unit (30), and wherein the analytical device (100) is configured to use an entire breath sample (A) or at least a part of the breath sample (A) as the gas sample (Gp), wherein the breath sample (A) has been received by the input unit (30).Analysis device (100) according to one of the preceding claims, characterized in that the or a pressure sensor (12.2) is configured to measure the pressure at a measurement position (MP.2), wherein the measurement position (MP.2) is located at the fluid guiding unit (31, 15, Sp, 18, 22.1, 22.2) and there between the valve (2, 13) and the measurement chamber (3) or in or on the measurement chamber (3), wherein the control device (60) is configured to cause the pressure sensor (12.2) to measure the pressure at the measurement position (MP.2) - on the one hand repeatedly in the test period (T min) and - on the other hand at least once when the valve (2, 13) is in a releasing position, wherein a releasing position is the releasing end position or a position between the releasing end position and the closing intermediate position, and wherein the control device (60) is further configured to determine the ambient pressure depending on at least one pressure which the pressure sensor (12.2) measured when the valve (2, 13) was in the releasing position, and preferably to use this pressure as the ambient pressure.Checking device for checking an analysis device (100), wherein the analysis device (100) to be checked comprises - a measuring chamber (3), - a gas sensor (50), - a fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) which is capable of establishing a fluid connection between the measuring chamber (3) and an environment of the analysis device (100), and - a valve (2, 13), wherein the valve (2, 13) can be transferred into a releasing end position, into a closing intermediate position and into a closing end position, wherein the closing intermediate position is located between the two end positions, wherein the analysis device (100) is configured such that - when the valve (2, 13) is in the releasing end position, a gas sample (Gp) from the environment can be transferred through the fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) flows or can flow through into the measuring chamber (3), and - when the valve (2, 13) is in a closing position, the fluid guide unit (31, 15, Sp, 18, 22.1, 22.2) is closed, wherein a closing position is the intermediate closing position, the end closing position or a position between the intermediate closing position and the end closing position, wherein the gas sensor (50) is configured to measure the concentration or amount of a predetermined target gas in a gas sample (Gp) in the measuring chamber (3), and wherein the checking device is configured to automatically - cause the valve (2, 13) to be continuously in the end closing position in a checking period (T min) of a predetermined minimum duration, -, that in the test time period (T min) the difference (ΔP) between the pressure in the measuring chamber (3) and the pressure in the environment is repeatedly measured and - to decide whether or not the valve (2, 13) actually seals the fluid guide unit (31, 15, Sp, 18, 22.1, 22.2) in a fluid-tight manner in the closing end position, wherein the checking device is configured to automatically decide that the valve (2, 13) actually seals in a fluid-tight manner at least when the measured pressure in the measuring chamber (3) deviates from the ambient pressure by at least a predetermined minimum deviation (ΔP limit) in the entire test time period (T min) and wherein the checking device is configured to decide at least that the valve (2, 13) does not seal in a fluid-tight manner, if, at least at the end of the test period (T min) the pressure in the measuring chamber (3) deviates from the ambient pressure by at most a predefined fraction of the minimum deviation (ΔP limit).Checking method for checking an analysis device (100), wherein the analysis device (100) to be checked comprises - a measuring chamber (3), - a gas sensor (50), - a fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) which is capable of establishing a fluid connection between the measuring chamber (3) and an environment of the analysis device (100), and - a valve (2, 13), wherein the valve (2, 13) can be transferred into a releasing end position, into a closing intermediate position and into a closing end position, wherein the closing intermediate position is located between the two end positions, wherein the analysis device (100) is configured such that - when the valve (2, 13) is in the releasing end position, a gas sample (Gp) from the environment can be transferred through the fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) flowing or able to flow through into the measuring chamber (3), and - when the valve (2, 13) is in a closing position, the fluid guiding unit (31, 15, Sp, 18, 22.1, 22.2) is closed, wherein a closing position is the intermediate closing position, the end closing position or a position between the intermediate closing position and the end closing position, wherein the gas sensor (50) is configured to measure the concentration or amount of a predetermined target gas in a gas sample (Gp) in the measuring chamber (3), and wherein the checking method comprises the automatically performed steps of - causing the valve (2, 13) to be continuously in the end closing position in a checking period (T min) of a predetermined minimum duration, in the test time period (T min) the difference (ΔP) between the pressure in the measuring chamber (3) and the pressure in the environment is repeatedly measured, and it is decided whether or not the valve (2, 13) actually seals the fluid guide unit (31, 15, Sp, 18, 22.1, 22.2) in a fluid-tight manner in the closing end position, wherein it is decided at least that the valve (2, 13) actually seals in a fluid-tight manner if the measured pressure in the measuring chamber (3) deviates from the ambient pressure by at least a predefined minimum deviation (ΔP limit) in the entire test time period (T min) and wherein it is decided at least that the valve (2, 13) does not seal in a fluid-tight manner, if, at least at the end of the test period (T min) the pressure in the measuring chamber (3) deviates from the ambient pressure by at most a predefined fraction of the minimum deviation (ΔP limit).Analysis method which is carried out using an analysis device (100), wherein the analysis device (100) comprises - a measurement chamber (3), - a gas sensor (50), - a fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) which is capable of establishing a fluid connection between the measurement chamber (3) and an environment of the analysis device (100), and - a valve (2, 13), wherein the analysis method comprises a measurement method and a checking method, wherein the measurement method comprises the steps of - the valve (2, 13) is transferred into a released end position and releases the fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2), - a gas sample (Gp) flows from the environment through the fluid guidance unit (31, 15, Sp, 18, 22.1, 22.2) into the measurement chamber (3), - the valve (2, 13) is transferred into an intermediate closing position and subsequently from the intermediate closing position into an end closing position, - the valve (2, 13) closes the fluid guiding unit (31, 15, Sp, 18, 22.1, 22.2) from the time at which it reaches the intermediate closing position, and - the gas sensor (50) measures the concentration or quantity of a predetermined target gas in a gas sample (Gp) in the measuring chamber (3), and wherein the checking method comprises the automatically carried out steps of - causing the valve (2, 13) to be continuously in the end closing position in a checking period (T min) of a predetermined minimum duration, in the test time period (T min) the difference (ΔP) between the pressure in the measuring chamber (3) and the pressure in the environment is repeatedly measured, and it is decided whether or not the valve (2, 13) actually seals the fluid guide unit (31, 15, Sp, 18, 22.1, 22.2) in a fluid-tight manner in the closing end position, wherein it is decided at least that the valve (2, 13) actually seals in a fluid-tight manner if the measured pressure in the measuring chamber (3) deviates from the ambient pressure by at least a predefined minimum deviation (ΔP limit) in the entire test time period (T min) and wherein it is decided at least that the valve (2, 13) does not seal in a fluid-tight manner, if, at least at the end of the test period (T min) the pressure in the measuring chamber (3) deviates from the ambient pressure by at most a predetermined fraction of the minimum deviation (ΔP limit).

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