SENSOR ARRANGEMENT WITH AN ELECTROCHEMICAL SENSOR AND A TEMPERATURE SENSOR AND METHOD USING SUCH A SENSOR ARRANGEMENT

Description

[0001] The invention relates to a sensor arrangement and a method for analyzing a gas for at least one predetermined gas component, wherein the sensor arrangement comprises an electrochemical sensor with a measuring electrode and a counter electrode, wherein an electrolyte is arranged between these two electrodes and wherein the method is carried out using such a sensor arrangement.

[0002] Such electrochemical sensors are used, for example, in alcohol analysis devices. Such an analyzer examines the breath alcohol content, particularly ethanol, in a breath sample exhaled by a test subject. The percentage of breath alcohol in the breath sample is a measure of the alcohol content in the test subject's blood.

[0003] US 2015 / 0 076 007 A1 describes an electrochemical sensor with a measuring electrode (working electrode, sensing electrode), a counter electrode, and an electrolyte between the two electrodes. Different electrical voltages can be applied to the measuring electrode, resulting in different positive potentials of the measuring electrode relative to a reference electrode. Two different electrochemical reactions are induced: oxidation or reduction of a first chemical substance, and oxidation or reduction of a second chemical substance. A temperature sensor measures a first electrical potential, at which the first electrochemical reaction takes place, and a second electrical potential, at which the second electrochemical reaction takes place, both at the same temperature.The temperature of the measuring electrode is approximately derived from the difference between the two measured electrical potentials.

[0004] US 3,518,179 A discloses an electrochemical sensor cell with a thermistor attached to the back of one of the electrodes for temperature control.

[0005] The invention is based on the object of providing a sensor arrangement for analyzing a gas, wherein the sensor arrangement comprises a measuring electrode, a counter electrode, and an electrolyte, and is intended to have greater reliability than known sensor arrangements of this type. Furthermore, the invention is based on the object of providing a method for analyzing a gas, wherein the method is carried out using such a sensor arrangement and is intended to have greater reliability than known methods.

[0006] The object is achieved by a sensor arrangement having the features of claim 1 and by a method having the features of claim 9. Advantageous embodiments of the sensor arrangement according to the invention are, where appropriate, also advantageous embodiments of the method according to the invention and vice versa.

[0007] The sensor arrangement and method according to the invention are capable of analyzing a gas for at least one predetermined gas component. The gas is, for example, air, in particular exhaled air from a test subject, or ambient air. The predetermined gas component is preferably oxidizable and can be, for example, ethanol, carbon monoxide, or methanol.

[0008] In one application, the sensor arrangement and method automatically decide whether the quantity and / or concentration (content) of the gas component or at least one gas component in the gas is below or above a predetermined threshold. In another application, the sensor arrangement and method at least approximately measure the quantity and / or concentration of the gas component or at least one gas component in the gas, optionally measuring the summed concentrations of all gas components.

[0009] It is also possible for the sensor arrangement and the method to measure a quantity of the gas component in a quantity of a sample of the gas, wherein the quantity or volume of the gas sample is known, wherein the desired concentration of the gas component is derived from the measured quantity of the component and the known quantity of the gas sample.

[0010] The sensor arrangement according to the invention comprises an electrochemical sensor. This electrochemical sensor comprises a measuring electrode, a counter electrode, an electrical contact for the measuring electrode, an electrical contact for the counter electrode and an electrolyte between the measuring electrode and the counter electrode.

[0011] The sensor arrangement is capable of measuring a detection variable of the electrochemical sensor. The measured detection variable is preferably an electrical variable, for example, an electrical voltage between the two electrical contacts or the strength of an electrical current flowing through a connection between the two electrical contacts, an electrical charge (amount of flowing current), or an electrical resistance.

[0012] The detection quantity correlates with the presence and / or quantity and / or concentration of the gas component or at least one gas component in the gas. For example, the gas component causes a chemical reaction in or on the electrochemical sensor, and the chemical reaction influences the detection quantity, in particular the electrical voltage or the strength of an electrical current. The measured detection quantity is therefore a measure of the quantity of the gas component in a specific amount of gas and / or of the concentration of the gas component in the gas. The detection quantity is generally larger or smaller, the larger the desired quantity or concentration of the gas component in the gas.

[0013] The sensor assembly further comprises a temperature sensor unit capable of at least approximately determining the current temperature of the measuring electrode and / or the current temperature of the counter electrode. The temperature sensor unit comprises an electrically conductive measuring element and a temperature sensor. The measuring element comprises a contact segment and a connecting segment. These two segments are electrically and / or thermally conductively connected to each other.

[0014] The contact segment is in surface contact with a measuring object of the electrochemical sensor. Thanks to this surface contact, thermal contact is established between the contact segment and the measuring object. Ideally, the contact segment and the measuring object have the same temperature thanks to the thermal contact. The term "measurement object" in the sensor arrangement refers to the measuring electrode, the counter electrode, the electrical contact for the measuring electrode, or the electrical contact for the counter electrode. The contact segment is therefore in surface contact with the measuring electrode, the counter electrode, the electrical contact for the measuring electrode, or the electrical contact for the counter electrode.It is also possible that the same contact segment is in surface contact with two different measuring objects or that two different contact segments are in surface contact with one measuring object each, whereby the same connecting segment or two different connecting segments is / are connected to the two contact segments.

[0015] The connecting segment electrically and / or thermally connects the contact segment(s) to the temperature sensor. Preferably, both the connecting segment and the temperature sensor are spatially spaced from both the two electrodes and the two electrical contacts for these electrodes.

[0016] The temperature sensor is capable of measuring a value at a measuring position that correlates with the temperature of the contact segment. This measured value is, in particular, a value that correlates with the temperature of the connecting segment at the measuring position. The measured value can also be the temperature of the connecting segment directly at the measuring position. The measuring position can comprise a single measuring point or two individual measuring points, for example, two measuring points between which an electrical voltage is measured.

[0017] The term "measured size of a segment" refers to the correlating size of this segment at the measurement position. The measurement position is spatially spaced from both electrodes and both electrical contacts, preferably also spatially spaced from the contact segment.

[0018] The temperature sensor unit is capable of determining the current temperature of the measuring electrode and / or the current temperature of the counter electrode depending on the quantity that correlates with the temperature of the contact segment and that was measured at the measuring position.

[0019] The method according to the invention is carried out using such a sensor arrangement and comprises the following steps: The detection variable of the electrochemical sensor is measured. This detection variable correlates with the desired presence and / or concentration of the gas component or at least one gas component in the gas. The temperature sensor measures the variable at the measuring position that correlates with the temperature of the contact segment. Depending on the variable that correlates with the temperature of the contact segment, the temperature of the measuring electrode and / or the temperature of the counter electrode is determined, at least approximately.

[0020] According to the invention, a detection variable is measured, whereby this detection variable depends on the quantity and / or concentration of the component in the gas. However, the detection variable often depends not only on the quantity and / or concentration of the component, but also on the temperature of the measuring electrode and / or the temperature of the counter electrode. This electrode temperature is generally influenced by ambient conditions, in particular by the ambient temperature and / or the temperature in a measuring chamber of the sensor arrangement, and to a lesser extent also by the humidity and temperature of the gas to be analyzed.

[0021] In many cases, the lower the temperature of the measuring electrode, the longer the gas analysis takes. In some cases, a long analysis time leads to relatively high measurement noise. Particularly at a relatively low ambient temperature, moisture can condense in a fluid guide unit, for example in a hose, where this fluid guide unit leads to the electrochemical sensor. The condensed moisture can change the chemical composition of the gas and therefore falsify the measurement result of the electrochemical sensor. With a measuring electrode at a low temperature, moisture can also condense on the measuring electrode in some cases, which can also falsify the measurement result. Furthermore, different temperatures can occur at different points in the electrochemical sensor at the same time.In particular, in order to capture the dynamic effects just described and ideally compensate them computationally, it is desirable to know the current temperature of at least one electrode of the electrochemical sensor with sufficient accuracy.

[0022] The temperature sensor unit is capable of at least approximately determining the current temperature of the measuring electrode and / or the temperature of the counter electrode. Knowing the electrode temperature often makes it possible to automatically compensate for the influence of the electrode temperature on the measurement result to a certain extent and / or to regulate the electrode temperature.

[0023] According to the invention, the temperature sensor is capable of measuring a value at a measuring position that correlates with the temperature of the contact segment. Thanks to the surface contact and the resulting thermal contact, the contact segment has approximately the same temperature as the measured object. "Approximately the same temperature" means that possible temperature differences are so small that they can be neglected for applications of the invention and / or are smaller than a specified tolerance.

[0024] The measurement object can be the electrode or an electrode whose temperature is to be measured. The measurement object can also be the electrical contact for this electrode. Typically, the electrical contact for an electrode has approximately the same temperature as the contacted electrode itself. Therefore, in many cases, the temperature of the electrode can be measured with sufficient accuracy even if the contact segment contacts the electrical contact for the electrode but is spatially separated from the electrode itself. In some applications, it is easier to bring the contact segment into surface contact with the electrical contact than with the electrode itself.

[0025] In some other cases, a given calculation rule can be applied to the measured quantity to derive the temperature of the electrode, whereby this calculation rule is determined by the design of the sensor arrangement, which is why the application of the calculation rule does not require an additional sensor.

[0026] According to the invention, the temperature sensor is capable of measuring a value at the measuring position that correlates with the temperature of the contact segment. The correlating value is, for example, the electrical resistance or a measurable value that correlates with the electrical resistance. The measuring position can be in or on the connecting segment. The temperature sensor is then capable of measuring a value that correlates with the temperature of the connecting segment.

[0027] According to the invention, the quantity that correlates with the temperature of the contact segment is measured at the spatially remote measurement position. This eliminates the need to measure the temperature at a measurement position located at, on, or within the measurement object or the contact segment. Rather, the connecting segment helps bridge the distance between the measurement object and the contact segment on the one hand, and the measurement position on the other.

[0028] Thanks to the invention, the temperature of at least one electrode can be measured while the sensor arrangement and thus an analysis device comprising the sensor arrangement according to the invention are in use. Thanks to the invention, it is no longer necessary to put the sensor arrangement into a special mode to measure the electrode temperature. Furthermore, thanks to the invention, it is no longer necessary to supply the sensor arrangement with a chemical substance specifically for the purpose of measuring the electrode temperature. In many cases, measuring the electrode temperature requires only a relatively short time, which often makes it possible to quickly regulate the electrode temperature to a predetermined value.

[0029] According to the invention, the temperature sensor is capable of measuring the quantity that correlates with the contact segment temperature at the measuring position. This measuring position is spatially spaced from both electrodes and both electrical contacts. Preferably, the entire sensor arrangement, or at least the electrochemical sensor, is arranged inside a housing. The measuring position is preferably located inside this housing. This reduces the risk of the housing distorting a measurement. Furthermore, the risk of a significant time delay occurring between a temperature change and the detection of this temperature change is reduced.

[0030] According to the invention, the temperature sensor unit is capable of measuring the temperature of the measuring electrode and / or the temperature of the counter electrode, optionally the respective temperature of both electrodes. The electrochemical sensor often also includes a reference electrode and an electrical contact for the reference electrode. The electrical potential of the reference electrode is generally kept constant. Ideally, a gas sample under investigation often does not reach the reference electrode. The detection parameter also generally depends on the temperature of the reference electrode.

[0031] In one embodiment, the temperature sensor unit is additionally capable of measuring the temperature of the reference electrode. The contact segment of the measuring element or a contact segment of another measuring element is in planar contact with the reference electrode or the electrical contact for the reference electrode in such a way that thermal contact is established. The temperature sensor according to the invention or another temperature sensor is capable of measuring a value at a spatially spaced measuring position that correlates with the temperature of the contact segment that contacts the reference electrode or the electrical contact for the reference electrode. In many cases, this embodiment also makes it possible to regulate the temperature of the reference electrode and, in particular, to keep it constant.

[0032] According to the invention, the so-called Seebeck effect (thermoelectric effect) is used to measure the temperature of the electrode. This Seebeck effect is initially described generally with reference to Figure 1 explained.

[0033] The temperature of an object at a point P1 is to be measured. An electrical conductor A is electrically connected to an electrical conductor B at point P1. The temperatures of the two conductors A and B at P1 and the desired object temperature at P1 match sufficiently closely. The two conductors A and B have two different Seebeck coefficients, k(A) and k(B). The property "Seebeck coefficient" is also referred to as "thermal performance" or "thermoelectric sensitivity" and is a material-specific constant. The unit is preferably microvolts per kelvin.

[0034] According to the Seebeck effect, a so-called thermoelectric voltage U(Th) occurs. This thermoelectric voltage U(Th) occurs between a point P3 on conductor A and a point P2 on conductor B, with a distance between P1 and P2, between P1 and P3, and between P2 and P3. For example, conductor A extends from P1 to P3 and conductor B from P1 to P2. The temperature of conductor A in P3 and the temperature of conductor B in P2 are assumed to be sufficiently similar. The thermoelectric voltage U(Th) depends on the two Seebeck coefficients k(A) and k(B), usually the difference k(A) - k(B), and also on the temperature Temp(P1) in P1 and the temperature Temp(P3) of conductor A in P3, which corresponds to the temperature Temp(P2) of conductor B in P2.The two Seebeck coefficients k(A) and k(B) are known by design, and the thermoelectric voltage U(Th) as well as the temperature Temp (P3) of conductor A in P3 and / or the temperature Temp(P2) of conductor B in P2 are measured. The desired Temp(P1) can then be derived. In many cases, the following applies with sufficient accuracy: U Th = k A − k B * Temp P 1 − Temp P 2 = k A − k B * Temp P 1 − Temp P 3 .

[0035] In this calculation, Temp(P1) is the only unknown.

[0036] According to the invention, the Seebeck effect is utilized as follows: The area in which the contact segment is in surface contact with the measurement object acts as or encompasses point P1. At least at point P1, the contact segment is additionally electrically connected to the measurement object. Electrical conductor A includes a segment of electrical contact for an electrode. The electrically conductive connecting segment acts as the electrical conductor B. The two points P2 and P3 are each located at a spatially distant reference measuring position, for example, on a circuit board to which the two conductors A and B are connected. Preferably, the two points P2 and P3 together function as the spatially distant measuring position. The electrically conductive measuring element, or at least the connecting segment, has a different Seebeck coefficient than electrical conductor A.As a rule, it is reasonable to assume that the connecting segment, optionally even the entire measuring element, has the same Seebeck coefficient throughout, and that the electrical conductor A also has the same Seebeck coefficient throughout. The two Seebeck coefficients are known from the design of the sensor array or can be determined empirically in advance.

[0037] In addition to the temperature sensor, the temperature sensor unit also includes a voltage sensor. The voltage sensor is spatially spaced from both electrodes and is capable of measuring the thermal voltage U(Th) between points P2 and P3. The measured thermal voltage U(Th) thus occurs between the connecting segment, on the one hand, and the measurement object or the electrical contact for the measurement object, on the other. According to the invention, the temperature sensor is capable of measuring a quantity that correlates with the temperature of the connecting segment. The temperature sensor unit uses the temperature of the connecting segment as the temperature at point P2 and / or at point P3, or derives the temperature at point P2 or at point P3 from the temperature of the connecting segment. In many cases, the temperatures at points P2 and P3 do not differ significantly from one another. The temperature sensor unit derives the temperature at point P1. the measured thermo-voltage, the measured temperature at point P2 and / or P3 and the two Seebeck coefficients, preferably the difference between the two Seebeck coefficients.

[0038] This eliminates the need to directly measure the temperature of the contact segment or a value correlated with the temperature of the contact segment. Furthermore, it is possible, but not required, for the contact segment to be in good thermal contact with the connecting segment. Rather, according to the invention, a temperature is measured at a spatially distant measuring position, namely at point P2 or P3. In many cases, considerably more space is available for a temperature sensor at point P2 or P3 than at point P1. Furthermore, the temperature or a value correlated with the temperature can be measured more reliably and / or more quickly at point P2 or P3 than at point P1. In many cases, this also eliminates the need to electrically isolate the electrically conductive measuring element or at least the contact segment from the measuring object.Such electrical insulation requires space and can leak, thus allowing unwanted electrical contact. An unwanted electrical contact can distort the measurement results of the sensor array.

[0039] A further embodiment of the invention is described below. According to this embodiment, the measurement object is the measuring electrode or the counter electrode. The contact segment thus contacts an electrode. The connecting segment has a different Seebeck coefficient than the electrical contact of the electrode that acts as the measurement object. The voltage sensor is capable of measuring the thermal voltage that occurs between the connecting segment and the electrical contact of the measurement object.

[0040] According to this design, the contact segment of the measuring element makes thermal and electrical contact with the electrode at point P1. In many cases, the desired temperature of this electrode can be more accurately determined than if the contact segment were to make contact with the electrical contact of the electrode rather than the electrode itself. The existing electrical contact of the electrode is also used to measure the thermoelectric voltage.

[0041] According to the invention, the temperature sensor is capable of measuring a quantity that correlates with the temperature of the connecting segment. In one embodiment, the measuring electrode or the counter electrode is used as the measurement object. According to the invention, the temperature of the electrical contact of the electrode acting as the measurement object is measured as the quantity that correlates with the temperature of the connecting segment. In turn, the thermoelectric voltage between the measuring element and the electrical contact is measured. In some cases, this refinement increases the reliability with which the desired electrode temperature is determined using the Seebeck effect.

[0042] According to the invention, the contact segment is in thermal contact with the measurement object. The temperature sensor is preferably capable of measuring a value that correlates with the temperature of the contact segment. In one embodiment, this value is a value that correlates with the temperature of the connecting segment. In some cases, the temperature of the connecting segment does not deviate significantly from the temperature of the measurement object. In other cases, the temperature of the contact segment and thus the temperature of the electrode can be derived from the temperature of the connecting segment, for example, as just described by utilizing the Seebeck effect.

[0043] In order to prevent the contact segment from distorting a measurement result of the electrochemical sensor, according to a non-inventive

[0044] According to a preferred embodiment of the invention, the contact segment is electrically insulated from the measurement object, for example, by an insulating sheath around the contact segment. The connecting segment is spatially spaced from both electrodes and from both electrical contacts and therefore does not necessarily need to be electrically insulated. Thanks to the thermal contact between the measurement object and the contact segment, the contact segment has the same temperature as the measurement object with sufficient accuracy, despite the electrical insulation. The measurement object is particularly preferably the measuring electrode or the counter electrode. The temperature sensor is capable of measuring the quantity that correlates with the temperature of the contact segment at the spatially spaced measurement position. The measurement position is located, for example, at the connecting segment.

[0045] The alternative embodiment just described, not according to the invention, eliminates the need for two electrically conductive components with different Seebeck coefficients. Furthermore, a voltage sensor is not necessarily required. The temperature sensor is spatially spaced from the measurement object and the contact segment.

[0046] In one embodiment, a measure of the electrical resistance of the contact segment is measured as the quantity that correlates with the temperature of the contact segment. For example, an electrical circuit is created, at least temporarily, that encompasses the contact segment. The electrical voltage applied to the contact segment and the strength of the current flowing through the contact segment are measured. It is known that the electrical resistance of an electrically conductive element correlates with its temperature. Because the electrical resistance of the contact segment is measured, in many cases it is not necessary to electrically contact the measurement object in order to measure the electrical resistance. This reduces the risk that the measurement of the electrical resistance will falsify a measurement result of the electrochemical sensor.

[0047] In a preferred embodiment, the sensor arrangement according to the invention additionally comprises a controllable heater. The controlled and thereby activated heater is capable of heating the measuring electrode and / or the counter electrode.

[0048] Depending on the configuration with the heater, a signal-processing control unit of the sensor array can regulate the actual temperature of the measuring electrode and / or the actual temperature of the counter electrode. The control objective of this control is to ensure that the actual electrode temperature remains within a specified temperature range. To increase the actual electrode temperature and thereby reduce the control deviation, the control unit can control and activate the heater. To achieve the control objective and thus control the heater, the control unit uses a signal from the temperature sensor unit. The control unit can also deactivate the heater.

[0049] An advantageous embodiment of the method according to the invention is carried out using a controllable heater and a signal-processing control unit and includes the additional step of automatically controlling the actual temperature of the measuring electrode and / or the counter electrode. The goal of this closed-loop control is to ensure that the actual temperature of the electrode remains within a predetermined temperature range. The control unit uses a signal from the temperature sensor unit for control.

[0050] Then, when the measured actual temperature is below the temperature range, the control unit activates the heater. The activated heater heats the electrode. Later, when the actual temperature is back within the temperature range, the control unit deactivates the heater again.

[0051] The preferred embodiment in which the electrode temperature is automatically controlled has the particular advantages described below.

[0052] At a very high temperature of the measuring electrode, there is a greater risk of thermal damage to the measuring electrode or another component of the sensor assembly, of part of the electrolyte evaporating, and / or of deposits forming on the measuring electrode. Furthermore, in some cases, a high level of electrical energy is consumed, which is particularly disadvantageous when the sensor assembly cannot be permanently connected to a stationary power supply network, but an analyzer with the sensor assembly according to the invention includes its own power supply unit. The analyzer can be a portable device.

[0053] Thanks to the control system according to the invention, the temperature of the measuring electrode is maintained within the specified temperature range. Both the disadvantages of very low and very high temperatures are avoided. Compared to a design without temperature control, this reduces the time required to analyze the gas. Furthermore, the influence of ambient conditions on the analysis result is computationally compensated to a certain extent. It is not necessary to measure an environmental condition, for example, the ambient temperature.

[0054] In one embodiment, the temperature of the measuring electrode is directly controlled; in another embodiment, the temperature of the counter electrode is controlled, which influences the temperature of the measuring electrode. This prevents both excessively low and excessively high temperatures of the measuring electrode. It is also possible to control both the temperature of the measuring electrode and the temperature of the counter electrode. Therefore, the heater is preferably switched on only as long as necessary. It is also possible to additionally control the temperature of the optional reference electrode.

[0055] According to the invention, the contact segment is in thermal contact with the measurement object. In one embodiment, the measurement object is the measuring electrode or the counter electrode. Even if the measurement object is an electrical contact, the measurement object generally has approximately the same temperature as the measuring electrode and the counter electrode. On the one hand, the measurement position is spatially spaced from both electrodes and both electrical contacts. On the other hand, the measurement position is sufficiently close to at least one electrode and, in particular, within a housing. At a measurement position further away from the electrode, however, there could be a longer time delay between a temperature change and a corresponding response from the control unit.This risk is particularly present when the sensor assembly is located inside a housing and the measuring position is located outside the housing or even at a distance from the housing. Furthermore, with a large distance between the measuring position and the electrode, there is a greater risk that a disturbance in the form of another heat or cold source will distort the temperature measurement.

[0056] The temperature sensor unit, particularly thanks to the contact segment feature, delivers a signal for the current temperature of the measuring object. This signal quickly follows temperature changes in the measuring object. The control unit is therefore able to react quickly to a temperature change in the measuring object and thus in an electrode. Thanks to this rapid response, in many cases the actual electrode temperature remains outside the specified temperature range only for very short periods of time.

[0057] In one embodiment, the temperature sensor is capable of measuring both the actual temperature of the measuring electrode and the actual temperature of the counter electrode. In a further development of the embodiment with the heater, one component of the heater is capable of heating the measuring electrode, while another component is capable of heating the counter electrode. These two components can preferably be controlled independently of one another. Depending on the measured actual temperature of the measuring electrode, the control unit controls the component for heating the measuring electrode, and depending on the actual temperature of the counter electrode, the component for heating the counter electrode. It is possible for the same desired temperature range to be specified for the measuring electrode and for the counter electrode. It is also possible for different temperature ranges to be specified.

[0058] In one embodiment of the heater configuration, the heater comprises a controllable radiation source. The radiation source is capable of emitting electromagnetic radiation, in particular infrared radiation, toward the measuring electrode and / or the counter electrode. The control unit is capable of adjusting the intensity and / or energy of the radiation emitted by the radiation source to a value calculated by the control unit. To calculate this value, the control unit uses a signal from the temperature sensor unit.

[0059] According to the invention, the contact segment of the measuring unit is in thermal contact with the measurement object. According to the embodiment just described, a heater can heat the measuring electrode and / or the counter electrode. In one embodiment, the measurement object is simultaneously the heated electrode. The heater comprises an electrically conductive heating element. This electrical heating element comprises the contact segment and / or provides the contact segment. This contact segment is in thermal contact with the measurement object, in this case, with the heated electrode. The contact segment is preferably electrically insulated from the heated electrode to reduce the risk of electrical contact distorting a measurement result of the electrochemical sensor.

[0060] According to this design, the electrically conductive heating element has two functions: First, the temperature sensor measures a value that correlates with the current temperature of the heating element, and the temperature sensor unit derives the temperature of the contacted electrode from the measured value. Knowledge of the heating element temperature is preferably used to control or regulate the heating. Second, the same heating element heats the electrode. This design thus eliminates the need to provide a contact segment and an additional, spatially spaced heating element.

[0061] According to this embodiment, a value is measured that correlates with the temperature of the contact segment. In one implementation, the sensor unit measures a measure of the electrical resistance of the electrically conductive heating element. As is well known, the electrical resistance of an electrically conductive element correlates with the element's temperature.

[0062] According to a preferred embodiment of the heater configuration, the control unit calculates a setpoint for the electrical voltage to be applied to the heater. This value for the applied electrical voltage determines the temperature that the heater delivers to the electrode. To calculate the setpoint for the electrical voltage, the control unit uses a signal from the temperature sensor unit. The control unit controls the heater with the goal of ensuring that the electrical voltage actually applied to the heater equals the setpoint.

[0063] Preferably, the control unit controls the heater and then activates the heater when the measured actual temperature of the measuring electrode and / or the counter electrode is below the lower limit of the specified temperature range. In one embodiment, one-sided control of the actual electrode temperature is sufficient because the actual electrode temperature is not, or not significantly, greater than the upper limit of the temperature range. This is particularly the case when the temperature of the electrode is lower or not significantly greater than the ambient temperature. Furthermore, in many cases the goal of avoiding an excessively low temperature is more important than the goal of avoiding an excessively high temperature, because an excessively low temperature often impairs the sensitivity and reliability of the sensor arrangement more than an excessively high temperature.

[0064] In a further development of this embodiment, one-sided control is implemented, i.e., only heating or not heating. In another development of this embodiment, the control unit can also control a cooling system, i.e., a cooling element, of the sensor array. If the measured actual temperature is above the specified temperature range, the control unit activates the cooling system. Later, namely, when the actual temperature is back within the temperature range, the control unit deactivates the cooling system.

[0065] In one embodiment, the sensor arrangement also includes a controllable cooling system. This cooling system can cool the measuring electrode and / or the counter electrode. The control unit controls the cooling system and thus activates it when the actual temperature is above the specified temperature range. The control unit can also deactivate the cooling system again.

[0066] In one embodiment, the sensor arrangement according to the invention belongs to an analysis device, preferably a portable analysis device. In one application of the invention, the gas that the sensor arrangement is capable of analyzing is a portion of a breath sample that a test subject inputs into a mouthpiece or other input unit of the analysis device. The gas component for which the gas is to be analyzed is breath alcohol, in particular ethanol, or another substance that can be present in the exhaled breath of a test subject and that can be detected. In a further development of this embodiment, the sensor arrangement measures the concentration of breath alcohol in the breath sample and derives the alcohol content in the test subject's blood from this breath alcohol concentration. The analysis device preferably outputs the alcohol content in a form that is perceptible to a human.

[0067] The invention is described below using an exemplary embodiment. Figure 1 schematically shows the Seebeck effect; Figure 2 schematically shows the operation of an electrochemical sensor; Figure 3 a control circuit according to the invention; Figure 4 how the temperature of the measuring electrode is measured using a thermocouple with a contact segment on the measuring electrode; Figure 5 a modification of the design of Figure 4 , wherein the contact segment is arranged at the electrical contact of the measuring electrode; Figure 6 shows how the temperature of the measuring electrode is measured using a straight measuring wire on an end face (non-inventive example); Figure 7 shows how the temperature of the measuring electrode is measured using a wound measuring wire on the end face (non-inventive example); Figure 8 shows how the measuring electrode is heated using an array of LEDs.

[0068] In the exemplary embodiment, the sensor arrangement according to the invention is a component of an analysis device, the rest of the analysis device not being shown in the figures. The analysis device with the sensor arrangement is used to analyze a test subject's breath sample for a predetermined substance, in particular for breath alcohol. If breath alcohol is the substance, in one application the test subject is to be examined to determine whether or not there is alcohol in their blood above a predetermined detection limit. In another application the alcohol content in their blood is to be measured. In one embodiment the test subject can hold the analysis device in one hand. The analysis device preferably comprises its own power supply unit.

[0069] The test subject places a breath sample into a mouthpiece of the analyzer. If the test subject has consumed a beverage or food containing a significant amount of alcohol, the breath sample will contain breath alcohol, particularly gaseous ethanol. In the following, the term "breath alcohol" is used to refer to a possible gaseous substance for which the analyzer, using the sensor arrangement according to the invention, is to test a breath sample—i.e., the specified gas component.

[0070] A portion of the breath sample flows into a measuring chamber of the analyzer. This portion is referred to below as the "measuring chamber sample." An electrochemical sensor in or on the measuring chamber measures the content or quantity of breath alcohol or another specified substance in this measuring chamber sample. The following description refers to breath alcohol as the substance. The invention can also be used, in particular, for another substance that may be present in the exhaled breath of a test subject or in the ambient air.

[0071] The electrochemical sensor is capable of generating a signal that correlates with the concentration of breath alcohol in the sample contained in the measuring chamber.

[0072] Various suitable electrochemical sensors are known from the state of the art.

[0073] The analyzer derives the breath alcohol concentration in the input breath sample from the amount or concentration of breath alcohol in the measuring chamber sample and the volume of the measuring chamber sample. The volume of the measuring chamber sample is derived, for example, from the volume of the measuring chamber, which is known from the design of the analyzer, and / or a measured and integrated volume flow into the measuring chamber. The analyzer or a remote evaluation unit derives the alcohol content in the subject's blood from the breath alcohol concentration or amount of breath alcohol in the breath sample. Of course, the analysis can lead to the conclusion that there is no alcohol in the subject's blood above a detection limit.

[0074] As the breath sample flows through the mouthpiece, first air from the subject's mouth, then air from the upper respiratory tract, and finally air from the subject's lungs flows through the mouthpiece. To determine whether the subject's blood contains alcohol, a gas from the portion of the breath sample that comes from the lungs must be analyzed. Ideally, only gas from the subject's lungs flows into the measuring chamber, and the measuring chamber sample contains only air from the lungs. The remaining portion of the breath sample flows out of openings in the mouthpiece without reaching the measuring chamber. A mouthpiece with such openings is described, for example, in DE 10 2017 008 008 A1.

[0075] In one embodiment, the analyzer comprises a pump or other fluid delivery unit. This fluid delivery unit is switched on after the test subject has begun to introduce the breath sample into the mouthpiece. Ideally, the pump draws in the portion of the breath sample that originates from the test subject's lungs. Preferably, the fluid delivery unit flushes the measuring chamber after the electrochemical sensor has analyzed the sample from the measuring chamber. This allows the same analyzer to be used for multiple breath samples in rapid succession. It is also possible for the sample from the measuring chamber to flow into the measuring chamber by diffusion without the use of a fluid delivery unit.

[0076] The analysis device of the embodiment comprises a sensor arrangement 100 with an electrochemical sensor 10. Figure 2shows schematically the operation of an electrochemical sensor 10 as is known from the prior art. The representation of Figure 2 is not necessarily to scale. In one embodiment, the analysis device according to the invention comprises such a sensor arrangement 100 and takes a breath sample Ap.

[0077] The electrochemical sensor 10 comprises a housing 11 enclosing a measuring chamber 1. A measuring chamber sample Pr to be analyzed flows through an inlet opening Ö.e into the interior of the housing 11 and from there to the measuring chamber 1, for example by diffusion or by actively sucking the measuring chamber sample Pr through the opening Ö.e into the interior of the housing 11. The measuring chamber sample Pr flows out of the measuring chamber 1 through an outlet opening Ö.a and then out of the housing 11. Therefore, the same sensor 10 can analyze several measuring chamber samples Pr in succession.

[0078] The electrochemical sensor 10 comprises a measuring electrode 20 which is electrically contacted by a contacting wire 2, a counter electrode 21 which is electrically contacted by a contacting wire 3, an electrolyte 28 between the two electrodes 20 and 21, a connecting wire 12 which electrically connects the two contacting wires 2 and 3 and comprises an electrical measuring resistor 29, and a current sensor 13 which measures the strength of the current flowing through the connecting wire 12.

[0079] Such an electrochemical sensor 10 is also referred to below as a membrane electrode electrolyte assembly (MEEE).

[0080] The electrolyte 28 is an electrically conductive medium, for example, sulfuric acid, phosphoric acid, or perchloric acid diluted with water. Ions can move within the electrolyte 28. A membrane preferably provides the electrolyte 28. The electrolyte 28 establishes an ionically conductive connection between the measuring electrode 20 and the counter electrode 21, but prevents a short circuit between the two electrodes 20 and 21.

[0081] The sensor 10 is designed such that the measuring chamber sample Pr only reaches the measuring electrode 20, but not the counter electrode 21. In the example shown, the measuring electrode 20 is located on a wall of the measuring chamber 1, and the housing 11 and the electrolyte 28 prevent a relevant amount of the measuring chamber sample Pr from reaching the counter electrode 21.

[0082] The two contact wires 2 and 3 are electrically conductive and made of a material that is not chemically attacked by the electrolyte 28, for example, platinum or gold. The electrodes 20 and 21 are also made of a chemically resistant material, for example, platinum or gold. In many cases, the chemically resistant material also acts as a catalyst for a chemical reaction that is induced and used for the measurement.

[0083] In one implementation, the electrochemical sensor 10 operates according to the principle of a fuel cell. The chemical reaction used for the measurement involves the step of oxidizing the breath alcohol in the measuring chamber sample Pr in the measuring chamber 1. Ideally, the entire amount of breath alcohol in the measuring chamber sample Pr is oxidized. As a result of the chemical reaction, an electrical voltage arises between the measuring electrode 20 and the counter electrode 21, and therefore an electrical current flows through the connecting wire 12. The current sensor 13 measures the current I and thus a measure of the electrical charge, i.e., the total amount of electrical current flowing through the connecting wire 12 (principle of coulometry). As is well known, the electrical charge is the integral of the current over time.For a given volume of the measuring chamber sample Pr in the measuring chamber 1, the measured electrical charge is higher the more breath alcohol the measuring chamber sample Pr contains before oxidation. The measured electrical charge is therefore a measure of the amount of breath alcohol in the measuring chamber sample Pr and thus of the breath alcohol content in breath sample A and the alcohol content in the subject's blood. The electrical charge is therefore the detection parameter of the exemplary embodiment.

[0084] The electrochemical sensor 10 delivers an electrical signal that is a measure of the breath alcohol content in the measuring chamber sample Pr. However, this signal depends not only on the amount or concentration of breath alcohol in the measuring chamber sample Pr, but is also influenced by the temperature of the two electrodes 20 and 21. To ensure that the sensor 10 can deliver a reliable measurement result, in the exemplary embodiment the temperature of the electrodes 20, 21 is controlled with the control objective that the temperature should remain within a predetermined temperature range. A special case is where a constant target temperature is specified and the temperature of the electrodes 20, 21 is controlled with the control objective that the temperature should remain constant at this target temperature.Closed-loop control rather than open-loop control of the electrode temperature is used because the temperature of electrodes 20 and 21 is particularly influenced by the ambient temperature. Direct measurement of the ambient temperature is possible, but not necessary, thanks to the control system.

[0085] Preferably, the specified temperature range covers the typical temperature of a human breath sample. This average temperature is between 32°C and 38°C, particularly preferably 35°C. The temperature range should not be too low for the following reasons: The higher the temperature of the electrodes 20, 21, the faster the sensor 10 delivers a result. The higher the temperature, the faster the electrochemical reaction occurs. A short time requirement to deliver the result is particularly important if the same analyzer is to be used consecutively to test several breath samples for breath alcohol. The longer the analysis of the measuring chamber sample Pr requires, the greater the measurement noise in many cases. One possible cause of the measurement noise is that the electrical charge is determined numerically by an inevitably only approximate integration over several measured current values. The measurement noise is generally greater the longer the period over which the numerical integration is carried out. One reason for this is that a calculated zero point is used for the analysis, and the calculation of the zero point is inevitably subject to errors.These errors often become more pronounced the longer the time period. If the temperature of the electrodes 20, 21 is too low, there is a risk that moisture will condense in the measuring chamber 1 or on a fluid guide unit leading to the measuring chamber 1. Breath alcohol can condense and / or dissolve in the condensed moisture. The electrochemical sensor 10 may then measure an alcohol content that is too low. In addition, condensed moisture could enter the measuring chamber 1 as part of the measuring chamber sample Pr. This can also lead to an incorrect measurement result.

[0086] However, a very high temperature of the electrodes 20, 21 can damage the sensor 10. In particular, a plastic housing 11 can be damaged, or part of the electrolyte 28 can evaporate, or harmful substances can settle on an electrode 20, 21. Furthermore, a high temperature requires more electrical energy than necessary. Therefore, the electrode temperature should not be higher than necessary, especially if the analyzer is not connected to a stationary power supply network but has its own power supply unit.

[0087] For the following additional reasons, the temperature of the electrodes 20, 21 should not differ too much from measurement to measurement: For a given amount of breath alcohol in the measuring chamber sample Pr, the measured value, in particular the measure of the electrical charge, is lower the lower the temperature in measuring chamber 1. The lower the temperature in measuring chamber 1, the less sensitive the sensor 10 is. This temperature dependence makes adjustment and calibration of sensor 10 more difficult. The measure of the electrical charge is generally measured by measuring a measure of the current strength at several sampling points in time and then integrating the measured current values. This procedure inevitably results in measurement noise. The influence of this measurement noise is greater the longer the measurement lasts, i.e. the more time elapses for the breath alcohol to oxidise in measuring chamber 1. Therefore, the influence of the measurement noise is greater the lower the temperature in measuring chamber 1.

[0088] In one embodiment, the temperature of the measuring electrode 20 is controlled, and any possible temperature difference between the temperatures of the two electrodes 20, 21 is neglected. An alternative embodiment is described below.

[0089] In the figures described below, the entire sensor arrangement is designated by the reference numeral 100. The sensor arrangement 100 comprises an electrochemical sensor 10, which is as described with reference to Figure 2 described can be constructed.

[0090] Figure 3 shows a schematic of a control loop for regulating the temperature of the measuring electrode 20 of the sensor 10. In the example shown, the reference variable is a predetermined target temperature Temp Soll, whereby the measuring electrode 20 should constantly have this target temperature Temp Soll. The controlled variable is the measured actual temperature Temp Ist of the measuring electrode 20. The control deviation Temp Soll - Temp Ist is denoted by ΔTemp.

[0091] This control loop includes the following components: a control system 50, which in this case comprises the two electrodes 20 and 21 and the electrolyte 28, wherein the temperature of the measuring electrode 20 is to be controlled (kept at a constant value Temp Soll), a sensor 51, which measures the controlled variable Temp Ist and is described below, an actuator 52, which influences the controlled variable Temp Ist, in this case a heater, which is able to increase the temperature of the electrode 20, and a controller (signal processing control unit) 53, which controls the actuator 52 depending on the determined control deviation ΔTemp.

[0092] Disturbances are in particular the ambient temperature and the temperature of the breath sample A and thus of the measuring chamber sample Pr. Chemical reactions in the sensor 10 can also influence the temperature of the measuring electrode 20 and are a possible further disturbance.

[0093] The control objective of this control is to reduce the control deviation ΔTemp to zero. Because the ambient temperature is usually lower or only negligibly higher than the setpoint temperature Temp setpoint, a one-way control is often sufficient, in which the actuator 52 can increase but not decrease the value of the controlled variable. If the sensor arrangement 100 is to be used at a high ambient temperature, it is also possible for the sensor arrangement 100 to additionally have a controllable cooling system.

[0094] Several embodiments for the sensor 51 and for the actuator 52 are described below. The sensor 51 measures the controlled variable at a measuring position on or in a measurement object. In the exemplary embodiment, the measurement object is the measuring electrode 20 or the electrical contact 2 of the measuring electrode 20. The counter electrode 21 or the electrical contact 3 of the counter electrode 21 can also function as the measurement object. Because the measuring position is in or on the measurement object 20, 2, the controlled variable (the actual temperature Temp Ist ) is measured with only a small error and a very short delay (latency). If the temperature Temp of the measuring electrode 20 were measured at a measuring position outside the electrochemical sensor 10, the measured temperature at this spatially distant measuring position can deviate significantly from the actual temperature Temp Ist of the measuring electrode 20 at the time of measurement.

[0095] Figure 4and Figure 5 schematically show a configuration of the temperature sensor 51 for regulating the electrode temperature. Furthermore, an exemplary configuration of a region of the sensor arrangement 100 is shown. Between an end face of the measuring electrode 20 and an end face of the counter electrode 21 is a membrane impregnated with the electrolyte 28. Thanks to the membrane 28, good thermal contact is established between the two electrodes 20 and 21. Therefore, the two electrodes 20 and 21 as well as the two electrical contacts 2 and 3 often have approximately the same temperature. A circuit board 4, shown schematically, is adjacent to the cylindrical measuring chamber 1.

[0096] Between the two wires 2 and 3, which contact the measuring electrode 20 and the counter electrode 21, respectively, a connecting wire 12 with a measuring resistor 29 is arranged. As already explained, oxidation of breath alcohol causes an electric current to flow through the connecting wire 12. This current causes a voltage drop U(29) across the measuring resistor 29. A voltage sensor 5 on the circuit board 4 measures the voltage drop U(29) across the measuring resistor 29. This voltage drop U(29) is a measure of the breath alcohol content in the measuring chamber sample Pr and thus in the breath sample A. In this embodiment, the voltage drop U(29) is an additional detection variable.

[0097] In the design according to Figure 4 and Figure 5A thermocouple described below indirectly measures the matching temperature of the two electrodes 20 and 21 and the two electrical contacts (platinum wires) 2 and 3. In many cases, these temperatures differ from each other only by a negligible amount. This thermocouple utilizes the Seebeck effect, which was already described above. Embodiments of the thermocouple according to the invention are described below.

[0098] In the embodiments according to Figure 4 and Figure 5The electrical contact 2 for the measuring electrode 20 comprises a platinum wire. The measuring electrode 20 and the electrical contact 2 belong to conductor A. Conductor B has a measuring element with a different Seebeck coefficient. This measuring element comprises a contact segment 7 and a connecting segment 6. The contact segment 7 is made of gold, platinum, or iridium, for example, and is in thermal and electrical contact with the measuring electrode 20. This contact between the contact segment 7 of the measuring electrode 20 is established, for example, in the form of a winding around the measuring electrode 20 or by spot welding. Thanks to the thermal contact, the contact segment 7 has approximately the same temperature as the measuring electrode 20. The connecting segment 6 functions as a measuring wire that electrically and thermally connects the contact segment 7 to the circuit board 4.

[0099] What is needed is the temperature Temp(P1) at a point P1. This temperature Temp(P1) at point P1 corresponds sufficiently accurately to the desired temperature of the measuring electrode 20. The point P1 belongs in the embodiment according to Figure 4 to the area in which the contact segment 7 contacts the measuring electrode 20. In the example shown, the contact segment 7 is connected to the connecting segment 6 at point P1. Preferably, a distance occurs between point P1 and the area in which the electrical contact 2 touches the measuring electrode 20.

[0100] The above-mentioned conductor A (measuring electrode 20 and electrical contact 2) connects point P1 on the measuring electrode 20 with point P3 on the circuit board 4. The conductor B (connecting segment 6) connects point P1 with point P2 on the circuit board 4, cf. Figure 4 and Figure 5Preferably, the connecting segment 6 has the same Seebeck coefficient k(B) throughout. In one embodiment, even the entire measuring element 6, 7 has the same Seebeck coefficient k(B) throughout. The latter is preferably achieved by making the two segments 6 and 7 from the same electrically conductive material. It is also possible to use a Seebeck coefficient k(B) averaged over the length of the connecting segment 6 or the measuring element 6, 7 for the temperature measurement.

[0101] The Seebeck coefficient k(B) of the connecting segment 6 differs from the Seebeck coefficient k(A) of conductor A. The Seebeck coefficient k(A) depends on the Seebeck coefficient of the electrical contact 2 and optionally on that of the measuring electrode 20. Both Seebeck coefficients k(A) and k(B) are known from the design of the sensor arrangement 100. Furthermore, the assumption is used that the Seebeck coefficients k(A) and k(B)—or at least the difference k(A) - k(B) between them—remain constant throughout the temperature range in which the sensor arrangement 100 is used.

[0102] It is also possible that the contact segment 7 does not contact the measuring electrode 20, but is spaced apart from the measuring electrode 20 and contacts the electrical contact 2. For example, the contact segment 7 is wound or twisted around the electrical contact 2. This different design is described in Figure 5The same reference symbols have the same meaning as in Figure 4 . The point P1 is located in the area where the contact segment 7 contacts the electrical contact 2, and preferably at the connection between the contact segment 7 and the connection segment 6.

[0103] It is also possible for the connecting segment 6 to contact the measuring electrode 20 or the electrical contact 2 at only one point P1. In this case, this idealized point-like contact area functions as the contact segment. The Seebeck coefficient k(A) is then preferably equal to the Seebeck coefficient of the measuring electrode 20 or the electrical contact 2.

[0104] The connecting segment (the measuring wire 6) and the electrical contact 2 are connected to the circuit board 4. The connection point between the electrical contact 2 and the circuit board 4 functions as point P2, and the connection point between the connecting segment 6 and the circuit board 4 functions as point P3. A reference temperature sensor 9 on the circuit board 4 measures the temperature Temp(P2), i.e., the temperature of the electrical contact 2 at point P2, which corresponds sufficiently accurately to the temperature of the connecting segment 6 at point P3. It is also possible for the reference temperature sensor 9 to measure the temperature of the connecting segment 6 at point P3. The reference temperature sensor 9 is designed, for example, as an NTC thermistor (NTC = Negative Temperature Coefficient).

[0105] A voltage sensor 8 measures the electrical voltage between points P2 and P3 on circuit board 4. This measured voltage serves as the thermoelectric voltage U(Th). The only unknown is the temperature Temp(P1) at the measurement position P1 near the electrode.

[0106] To the thermocouple of the design according to Figure 4 and Figure 5 include the connection segment 6, the contact segment 7 and the sensors 8 and 9. The electrical contact 2 also performs a function in the thermocouple.

[0107] In the embodiment shown in Figure 4 and Figure 5As shown, a thermocouple is used which measures the temperature Temp(P1) of the measuring electrode 20. In many cases, it can be assumed with sufficient accuracy that the counter electrode 21 always has the same temperature as the measuring electrode 20. It is also possible to provide another thermocouple which measures the temperature of the counter electrode 21 and is preferably constructed in the same way as the thermocouple in Figure 4 .

[0108] An advantage of the designs according to Figure 4 and Figure 5 is that neither the contact segment 7 nor the connecting segment 6 necessarily need to be electrically insulated from the measuring electrode 20. Generally, no significant current flows through the connecting segment 6. The measuring element 6, 7 is preferably made of a metal that is chemically resistant to the electrolyte 28.

[0109] Figure 6shows an alternative non-inventive embodiment of the sensor 51 for the controlled variable, wherein in the example shown the temperature of the measuring electrode 20 is the controlled variable. The same reference numerals denote the same components as in Figure 4 and Figure 5 .

[0110] A contact segment 40 in the form of a wire is in thermal contact with an end face of the measuring electrode 20. In the implementation shown, this is the end face facing the measuring chamber 1. It is also possible for the other end face to be in thermal contact with the contact segment 40. An electrical insulation 37 electrically insulates the contact segment 40 from the measuring electrode 20. It is possible, but thanks to the electrical insulation 37, in many cases not necessary, for the material of the contact segment 40 to be chemically resistant to the electrolyte 28. However, a chemically resistant contact segment 40 will not be attacked by the electrolyte 28 even if the electrical insulation 37 has a defect (leak).The electrical insulation 37 has a sufficiently high thermal conductivity and preferably comprises an insulating sheath around the contact segment 40, for example, made of thin-walled polytetrafluoroethylene (PTFE). The electrical insulation 37 is also chemically resistant to the electrolyte 28 and does not alter the electrolyte 28.

[0111] The contact segment 40 is in the form of a wire that passes through the electrical insulation 37. This contact segment 40 is contacted at both ends by a connecting segment 36. The connecting segments 36 connect the two ends of the contact segment 40 to a voltage sensor 38. The two segments 40, 36 are components of an electrical circuit through which a current flows. This electrical circuit is preferably electrically connected to a power supply unit of the analyzer. This power supply unit is not shown in the figures.

[0112] Thanks to the thermal contact, the temperature of the contact segment 40 matches the temperature of the measuring electrode 20 with sufficient accuracy. As is well known, the electrical resistance of an electrically conductive material depends on the material's temperature, generally such that the higher the temperature, the greater the electrical resistance (positive temperature coefficient). The connecting segments 36 exhibit a lower electrical resistance than the contact segment 40 at any temperature encountered during use. For the two reasons just mentioned, the electrical resistance of the contact segment 40 or even of the entire measuring element 40, 36 is a measure of the temperature of the measuring electrode 20.

[0113] The voltage sensor 38 measures the voltage drop U(40) between the two ends of the contact segment 40. Because the contact segment 40 is electrically conductive, this voltage drop U(40) correlates with the temperature Temp(P1) of the contact segment 40. A current sensor 39 measures the strength I of the current flowing through the circuit with the contact segment 40 and the connecting segments 36. It is possible that the strength I of the current flowing through this circuit is controlled with the control objective of keeping the current constant. In many cases, the desired temperature of the measuring electrode 20 is then proportional to the voltage drop U(40) with sufficient accuracy. It is also possible to keep the voltage drop U(40) constant through control. The current strength I is then proportional to the desired temperature Temp(P1) with sufficient accuracy.

[0114] Figure 7(non-inventive example) shows a preferred embodiment of the measuring element 40, 36. The central axis of the cylindrical, in particular disc-shaped, measuring electrode 20 is perpendicular to the plane of the drawing of Figure 7. Figure 7 shows how the contact segment 40 is in thermal contact with an end face of the measuring electrode 20. To extend the length of the section of the contact segment 40 that is in thermal contact with the measuring electrode 20, the contact segment 40 preferably has several turns. Figure 7 the electrical insulation 37 is not shown.

[0115] Figure 4 to Figure 7 show various configurations for measuring the current temperature of an electrode 20, 21. It is possible to combine two configurations. In particular, it is possible for the contact segment 40 to be in thermal contact with both an end face and the outer surface of the electrode 20, 21.

[0116] The following description refers to the measuring electrode 20 as the electrode whose temperature is measured. In an alternative embodiment, the current temperature of the counter electrode 21 is measured instead or additionally, for example, also by one of the embodiments according to Figure 4 to Figure 7 .

[0117] Ideally, the measuring electrode 20 and the counter electrode 21 always have the same temperature; in practice, they usually differ from each other. If the temperature of the measuring electrode 20 differs from the temperature of the counter electrode 21 by more than a predetermined threshold, a signal-processing evaluation unit (not shown) of the sensor arrangement 100 preferentially detects this event and particularly preferably generates a message. This message is output in a form perceivable by a human.

[0118] If the temperature difference exceeds the threshold, it is often impossible for sensor 10 to reliably measure the breath alcohol content in a breath sample A. It is possible to use sensor arrangement 100 for a measurement again only when the difference between the two electrode temperatures has decreased and is below the threshold. In another embodiment, the measured temperature of counter electrode 21 is used to computationally correct a measurement result of measuring electrode 20.

[0119] The Figure 3 The control circuit shown comprises an actuator 52 in the form of a heater capable of heating at least the measuring electrode 20. Because the counter electrode 21 is in good thermal contact with the measuring electrode 20, the heater 52 generally also heats the counter electrode 21. Two preferred embodiments of this heater 52 are described below.

[0120] In the design according to Figure 8 The heater 52 comprises a radiation source in the form of an LED arrangement 30 with at least one LED, preferably a plurality of LEDs. Three LEDs 31.1 to 31.3 are shown as an example. A different number is also possible. Each LED 31.1 to 31.3 emits electromagnetic radiation. The measuring electrode 20 and the counter electrode 21 are preferably made of a dark material and therefore absorb a significant portion of the incident electromagnetic radiation. This heats up the measuring electrode 20 and the counter electrode 21. This configuration makes it possible to heat the measuring electrode 20 and the counter electrode 21 without contact. The LEDs 31.1 to 31.3 can be switched on and off again virtually without delay, and when the LEDs 31.1 to 31.3 are switched on, the measuring electrode 20 and the counter electrode 21 heat up rapidly.

[0121] In one embodiment, either all LEDs 31.1 to 31.3 or only at least a subset of the LEDs can be switched on. This makes it possible to emit at least two different amounts of thermal energy and thereby heat the measuring electrode 20 optionally by a greater or smaller amount, or faster or slower. With a large control deviation ΔTemp, all LEDs 31.1 to 31.3 are preferably switched on; with a small control deviation ΔTemp, only a subset of the LEDs are switched on. It is also possible to vary the electrical voltage applied to the LEDs or the strength of the electrical current flowing through the LEDs. This changes the electrical power consumed and thus also the emitted radiation power.

[0122] In a further embodiment, the LEDs 31.1 to 31.3 are operated in a pulsed manner. Pulse width modulation adjusts the actual amount of heat emitted to the desired amount of heat to be emitted. The higher the pulse frequency for a constant pulse duration, or the higher the pulse duration for a constant pulse frequency, the higher the amount of heat emitted. It is also possible to increase the duration of a pulse in order to increase the amount of heat emitted. The pulse frequency is set such that the thermal time constants of the electrodes 20, 21 are longer than the pulse frequency. This is possible because the LEDs 31.1 to 31.3 have a low thermal mass and can also be switched on and off quickly. The embodiment with pulse width modulation can be combined with the embodiment in which all or only some of the LEDs 31.1 to 31.3 can be switched on and off as required.The design with pulse width modulation also makes it possible to adjust the amount of heat energy emitted and to constantly switch all LEDs 31.1 to 31.3 on and off.

[0123] In a preferred embodiment, the LED array 30 is mounted outside the housing 11, for example, on the outside of a housing of the analyzer. This embodiment makes it easier to replace a defective LED 31.1 to 31.3 or even the entire LED array 30. The LED array 30 can be configured as described in DE 10 2019 003 021 A1.

[0124] Preferably, each LED 31.1 to 31.3 emits radiation in a wavelength range between 400 and 500 nm. Wavelengths in this range penetrate many types of plastic without the plastic absorbing a significant portion of the transmitted radiation, particularly if the plastic is light in color or nearly transparent, so that electromagnetic radiation transmits through the plastic without significant absorption. Preferably, the housing of the analysis device with the sensor arrangement 100 is made of such a plastic that is transparent to electromagnetic radiation. Preferably, the maximum rated power of the LED arrangement 30 is between 5W and 7W. This configuration is sufficient to heat the measuring electrode 20 and the counter electrode 21 sufficiently quickly and intensely, while still consuming relatively little electrical energy.

[0125] In an alternative embodiment, the measuring electrode 20, optionally also the counter electrode 21, is heated by a heating wire. This heating wire is in thermal contact with the electrode 20, 21 to be heated and is electrically insulated from this electrode 20, 21. Particularly preferably, the measuring element 40, 36 is connected to the contact segment 40 by Figure 6 and / or Figure 7 additionally used as a heating wire. This design saves an additional heating wire. The heating wire / measuring element 40, 36 is heated to heat the measuring electrode 20, and also as described above with reference to Figure 6As described, the electrical resistance of the heating wire / contact segment 40 is measured and acts as a measure of the temperature of the measuring electrode 20. Because the voltage U(40) applied to the contact segment 40 and / or the strength I of the current flowing through the circuit with the contact segment 40 is measured, it is possible to regulate the temperature Temp Ist of the measuring electrode 20 using the contact segment 40.

[0126] In one embodiment, the heating wire / contact segment 40 is printed on a plastic film. This design allows for rapid and automated production of the heating wire / contact segment 40 in many cases. List of reference symbols

[0127] 1 Measuring chamber, holds the measuring chamber sample Pr, surrounds the electrochemical sensor 10 2 Contact wire made of platinum or gold, electrically contacts the measuring electrode 20 3 Contact wire made of platinum or gold, electrically contacts the counter electrode 21 4 Circuit board on which voltage sensors 5 and 6 are mounted 5 Voltage sensor, measures the voltage drop U(29) at the measuring resistor 29 6 Connecting segment made of gold or platinum, connects the contact segment 7 with the point P2 on the circuit board 4 7 Contact segment made of gold or platinum, is in thermal and optionally additional electrical contact with the measuring electrode 20 or the electrical contact 2 8 Voltage sensor, measures the voltage that occurs between the two wires 2 and 6 due to the Seebeck effect 9 Reference temperature sensor, measures a measure of the temperature of the wire 6 at a reference position on the board 4 10 electrochemical sensor in the measuring chamber 1, comprises the electrodes 20, 21, the electrical contacts 2 and 3 and the electrolyte 28 11 Sensor housing 10 12 Connecting wire between contact wires 2 and 3 13 Current sensor, measures the strength of the current flowing through the connecting wire 12 20 Measuring electrode of the sensor 10, preferably made of platinum or gold 21 Counter electrode of the sensor 10, preferably made of platinum or gold 28 Electrolyte (sulfuric acid) inside the measuring chamber 1, arranged between the electrodes 20 and 21 29 electrical measuring resistance between the two electrodes 20, 21 30 LED arrangement with LEDs 31.1, ..., acts as a radiation source and thus as a heater 31.1, ... LEDs of the LED array 30 emit electromagnetic radiation onto the electrodes 20, 21 to 36 Connecting segments, connect the two ends of the contact segment 40 with the voltage sensor 38 37 electrical insulation around the contact segment 40 38 Voltage sensor, measures the voltage drop U(40) between the two ends of the contact segment 40 39 Current sensor, measures the strength I of the current flowing through the measuring element 40, 36 40 Contact segment, is in thermal contact with an end face of the measuring electrode 20, electrically insulated from the measuring electrode 20 by the insulation 37, connected at its two ends to the two connecting segments 36, in one embodiment also functions as a heating element 50 Control system for controlling the electrode temperature, includes the electrodes 20, 21 and the sensor 51 51 Temperature sensor that measures the controlled variable (actual temperature of the electrodes 20, 21) 52 Actuator (electrode heater) that changes the controlled variable 53 Controller (signal processing control unit) which controls the actuator 52 100 The sensor arrangement according to the invention comprises the electrochemical sensor 10, the temperature sensor, the heating, the optional cooling and the control unit 53, and belongs to an analysis device A electrical conductor from point P1 to point P3 Ap breath sample provided by the subject, the measuring chamber sample Pr B electrical conductor from point P1 to point P2 Ö.a outlet-side opening in the housing 11 through which the measuring chamber sample Pr flows out of the measuring chamber 1 Ö.e inlet-side opening in the housing 11 through which the measuring chamber sample Pr flows into the measuring chamber 1 P1 Point of the contact segment 7, 40, in which the two conductors A and B begin P2, P3 Points on the board 4, between which the thermoelectric voltage U(Th) occurs Pr Measuring chamber sample, that is the part of the breath sample A given by the test person that enters the measuring chamber 1, ideally comes from the test person's lungs, is tested for breath alcohol ΔTemp Control deviation of the controlled system 50, equal to Temp Target - Temp Actual Temp Target specified target temperature of the control system 50 Temp Actual measured actual temperature of the controlled system 50 U(29) Voltage drop across measuring resistor 29, measured by voltage sensor 5 U(40) Voltage drop between the two ends of the contact segment 40, measured by the voltage sensor 38 U(Th) Thermoelectric voltage between wires 2 and 6 on board 4 and thus between points P2 and P3, measured by voltage sensor 8

Claims

1. Sensor arrangement (100) for analyzing a gas (Pr) for at least one predetermined gas component, the sensor arrangement (100) comprising - an electrochemical sensor (10) and - a temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51), the electrochemical sensor (10) comprising - a measurement electrode (20), - a counter electrode (21), - an electrical contact (2) for the measurement electrode (20), - an electrical contact (3) for the counter electrode (21), and - an electrolyte (28) between the measurement electrode (20) and the counter electrode (21), the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) comprising an electrically conductive measurement element (6, 7, 36, 37, 40), the sensor arrangement (100) being configured to measure a detection variable of the electrochemical sensor (10), the measurable detection variable correlating with the presence and / or concentration of the or at least one gas component, the measurement element (6, 7, 36, 37, 40) comprising a contact segment (7, 40) and a connecting segment (6, 36), the contact segment (7, 40) being in planar contact with a measurement object (20, 21, 2, 3) of the electrochemical sensor (10) in such a way that thermal contact is established between the contact segment (7, 40) and the measurement object (20, 21, 2, 3), the measurement object (20, 21, 2, 3) being the measurement electrode (20), the counter electrode (21), the electrical contact (2) for the measurement electrode (20), or the electrical contact (3) for the counter electrode (21), and the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) being configured to determine, at least approximately, the temperature of the measurement electrode (20) and / or the temperature of the counter electrode (21) depending on a measured variable correlating with the contact segment temperature, characterized in that the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) additionally comprises a temperature sensor (9, 38, 39) and a voltage sensor (8), the contact segment (7, 40) additionally being electrically conductively connected to the measurement object (20, 21, 2, 3), the connecting segment (6, 36) electrically and / or thermally connecting the contact segment (7, 40) to the temperature sensor (9, 38, 39), the connecting segment (6, 36) having a different Seebeck coefficient to the measurement object (20, 21, 2, 3), the voltage sensor (8) being configured to measure an amount of a thermovoltage [U(Th)] which occurs between - the connecting segment (6, 36) and - the measurement object (20, 21) or the electrical contact (2, 3) for the measurement object (20, 21), the temperature sensor (9, 38, 39) being configured to measure, at a measuring position (P2, P3), a variable that correlates with the temperature of the connecting segment (6, 36) as the variable that correlates with the temperature of the contact segment (7, 40), the measuring position (P2, P3) being spatially at a distance from the two electrodes (20, 21) and from the two electrical contacts (2, 3), and the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40) being configured, depending on - the measured thermovoltage [U(Th)] and - the measured variable that correlates with the temperature of the connecting segment (6, 36), to determine the temperature (TempIst) of the measurement object (20, 21).

2. Sensor arrangement (100) according to claim 1, characterized in that the measurement object is the measurement electrode (20) or the counter electrode (21), the connecting segment (6, 36) has a different Seebeck coefficient to the electrical contact (2, 3) of the measurement object (20, 21), and the voltage sensor (8) is configured to measure an amount of a thermovoltage [U(Th)] which occurs between - the connecting segment (6, 36) and - the electrical contact (2, 3) of the measurement object (20, 21).

3. Sensor arrangement (100) according to claim 2, characterized in that the temperature sensor (9, 38, 39) is configured to measure - the temperature of the electrical contact (2, 3) of the measurement object (20, 21) or - a variable that correlates with the temperature of the electrical contact (2, 3) of the measurement object (20, 21).

4. Sensor arrangement (100) according to any of the preceding claims, characterized in that the sensor arrangement (100) additionally comprises - a controllable heating system (30, 36, 37, 38, 39, 52) and - a signal-processing control unit (53), the heating system (30, 36, 37, 38, 39, 52) being configured to heat the measurement electrode (20) and / or the counter electrode (21), and the control unit (53) being configured - to control the actual temperature (TempIst) of the measurement electrode (20) and / or the counter electrode (21) with the control objective that the controlled temperature (TempIst) remains in a predetermined temperature range (TempSoll), and - to control the heating system (30, 36, 37, 38, 39, 52) depending on a signal from the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) in order to control the actual temperature (TempIst).

5. Sensor arrangement (100) according to claim 4, characterized in that the heating system (30, 36, 37, 38, 39, 52) comprises a controllable radiation source (30), the radiation source (30) being configured to emit electromagnetic radiation in the direction of the measurement electrode (20) and / or the counter electrode (21), and the control unit (53) being configured, depending on a signal from the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51), to cause the intensity and / or the energy of the radiation emitted by the radiation source (30) to be adjusted to a value.

6. Sensor arrangement (100) according to either claim 4 or claim 5, characterized in that the control unit is configured to calculate a target value for the electrical voltage to be applied to the heating system (30, 36, 37, 38, 39, 52) depending on a signal from the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51), and the sensor arrangement (100) (100) is configured to adjust the electrical voltage actually applied to the heating system (30, 36, 37, 38, 39, 52) to the target value.

7. Sensor arrangement (100) according to any of claims 4 to 6, characterized in that the sensor arrangement (100) additionally comprises a controllable cooling system, the cooling system being configured to cool the measurement electrode (20) and / or the counter electrode (21), and the control unit (53) being configured to additionally control the cooling system depending on a signal from the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) in order to control the temperature (TempIst).

8. Analysis device comprising - a sensor arrangement (100) according to any of the preceding claims, and - an input unit, wherein the input unit is configured to receive a breath sample (Ap) from a test subject, and wherein the analysis device is configured to direct at least a portion of the breath sample (Ap) received by the input unit to the electrochemical sensor (10).

9. Method for analyzing a gas (Pr) for at least one predetermined gas component using a sensor arrangement (100) which comprises - an electrochemical sensor (10) and - a temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51), the electrochemical sensor (10) comprising - a measurement electrode (20), - a counter electrode (21), - an electrical contact (2) for the measurement electrode (20), - an electrical contact (3) for the counter electrode (21), and - an electrolyte (28) between the measurement electrode (20) and the counter electrode (21), the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) comprising an electrically conductive measurement element (6, 7, 36, 37, 40), the measurement element (6, 7, 36, 37, 40) comprising a contact segment (7, 40) and a connecting segment (6, 36), the contact segment (7, 40) being in planar contact with a measurement object (20, 21, 2, 3) of the electrochemical sensor (10) in such a way that thermal contact is established between the contact segment (7, 40) and the measurement object (20, 21, 2, 3), the measurement object (20, 21, 2, 3) being the measurement electrode (20), the counter electrode (21), the electrical contact (2) for the measurement electrode (20) or the electrical contact (3) for the counter electrode (21), the connecting segment (6, 36) electrically and / or thermally connecting the contact segment (7, 40) to the temperature sensor (9, 38, 39), the method comprising the following automatically performed steps: - a detection variable is measured, the measured detection variable correlating with the presence and / or concentration of the or at least one gas component, - a variable that correlates with the temperature of the contact segment (7, 40) is measured, and - the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) determines, at least approximately, the temperature of the measurement electrode (20) and / or the temperature of the counter electrode (21) depending on the measured variable correlating with the contact segment temperature, characterized in that the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) additionally comprises a temperature sensor (9, 38, 39) and a voltage sensor (8), the contact segment (7, 40) additionally being electrically conductively connected to the measurement object (20, 21, 2, 3), the connecting segment (6, 36) electrically and / or thermally connecting the contact segment (7, 40) to the temperature sensor (9, 38, 39), the connecting segment (6, 36) having a different Seebeck coefficient to the measurement object (20, 21, 2, 3), the method additionally comprising the following automatically performed steps: the temperature sensor (9, 38, 39) measures, at a measuring position (P2, P3), a variable that correlates with the temperature of the connecting segment (6, 36) as the variable that correlates with the temperature of the contact segment (7, 40), the measuring position (P2, P3) being spatially at a distance from the two electrodes (20, 21) and from the two electrical contacts (2, 3), the voltage sensor (8) measures an amount of a thermovoltage [U(Th)] which occurs between - the connecting segment (6, 36) and - the measurement object (20, 21) or the electrical contact (2, 3) for the measurement object (20, 21), and the temperature sensor unit (6, 7, 8, 9, 36, 37, 38, 39, 40, 51) determines the temperature (TempIst) of the measurement object (20, 21) depending on - the measured thermovoltage [U(Th)] and - the measured variable that correlates with the temperature of the connecting segment (6, 36).

10. Method according to claim 9, characterized in that the sensor arrangement (100) additionally comprises - a controllable heating system (30, 36, 37, 38, 39, 52) and - a signal-processing control unit (53), and the method additionally comprises the following automatically performed step: the control unit (53) controls the actual temperature (TempIst) of the measurement electrode (20) and / or the counter electrode (21) with the control objective that this actual temperature (TempIst) remains in a predetermined temperature range (TempSoll), if the determined actual temperature (TempIst) is below the temperature range (TempSoll), - the control unit (53) activating the heating system (30, 36, 37, 38, 39, 52), - the activated heating system (30, 36, 37, 38, 39, 52) heating the measurement electrode (20) and / or the counter electrode (21), and - the control unit (53) later deactivating the heating system (30, 36, 37, 38, 39, 52) again.