1. A method (100) for adjusting an air supply system (300, 400), wherein the method (100) comprises the steps of:

calibrating (101) the gas sensor (303, 401) with a defined concentration of a test gas at a first calibration time point (t1), wherein a first calibration result (S1) is determined during calibration,

and wherein at least one air supply measurement (M1) is determined at a point in time (t2) before the first calibration point in time (t 1);

determining (103) a gas supply reference value (G1) by substituting at least one gas supply measurement value (M1) with the first calibration result (S1) and a calibration result (S0) of the gas sensor (303, 401) determined at a time point (t0) preceding the first calibration time point (t 1);

-adjusting (105) the air supply system according to the air supply reference value (G1).

2. The method (100) according to claim 1, wherein the calibration of the gas sensor (303, 401) and the determination of the gas supply reference value are repeated at a later point in time compared to the first calibration point in time (t1), wherein the first calibration result (S1) is subsequently used as a further calibration result, the calibration result determined at the later point in time is used as a first calibration result, and at least one gas supply measurement value determined at a point in time preceding the later point in time is used as at least one gas supply measurement value (M1).

3. The method (100) according to claim 1 or 2, wherein the gas supply reference value (G1) is determined by multiplying the ratio of a further calibration result (S0) and the first calibration result (S1) with at least one of the gas supply measurement values (M1).

4. The method (100) according to any one of the preceding claims, wherein at least one of the supply air measurements (M1) is determined by one of the following determination steps:

determining an integral of a sensor response of the gas sensor (303, 401),

determining a slope of a sensor response of the gas sensor (303, 401),

determining a response time of a sensor response of the gas sensor (303, 401),

determining a profile change in a sensor response of the gas sensor (303, 401).

5. The method (100) according to any one of the preceding claims, wherein an alarm is output as a function of a comparison of the air supply reference value (G1) with a preset criterion.

6. The method (1) according to claim 5, characterized in that an alarm for replacing the gas supply device (305) of the gas supply system (300, 400) is output if the difference between the gas supply measurement value (M1) and the gas supply reference value (G1) is different from a preset threshold value.

7. The method (100) according to any one of the preceding claims, wherein a value of the concentration of the test gas provided by means of the gas supply device (305) is corrected to the gas supply reference value or the gas supply device (305) is controlled using the gas supply reference value such that the concentration of the test gas provided by means of the gas supply device (305) corresponds to a preset nominal value.

8. An air supply system (300, 400) with a regulating function, wherein the air supply system (300, 400) comprises:

an interface (301) for a gas sensor (303),

an air supply device (305),

a calculation unit (307),

wherein the calculation unit (307) is configured to determine a first calibration result (S1) at a first calibration time point (t1) with a defined concentration of a test gas for calibrating the gas sensor (303) connected to the interface,

at least one air supply measurement value (M1) is determined at a time point (t2) before the first calibration time point (t1), and

determining (103) a gas supply reference value (G1) by substituting at least one gas supply measurement value (M1) with the first calibration result (S1) and a further calibration result (S0) of the gas sensor (303) which has been determined at a time point (t0) preceding the first calibration time point (t1), and

-adjusting the air supply system (300, 400) according to the air supply reference value (G1).

9. The gas supply system (300, 400) according to claim 8, wherein the computing unit (307) is configured for performing the method (100) according to any one of claims 2 to 7.

10. Gas supply system (300, 400) according to any of the preceding claims, characterized in that the gas supply device (305) has a gas generator or a gas bottle.

Background

Electrochemical and catalytic sensors are often used to monitor toxic or explosive gases and vapors. It is known that sensors, in particular electrochemical sensors, change over their service life and therefore their measurement properties, in particular their sensitivity, i.e. their sensitivity and/or their response time, must be checked, in particular calibrated, frequently until the measured values reach 90% of the actual applied gas concentration.

Calibration or correction is usually done in a two-step process, wherein in the first step the zero point is determined by applying a so-called "zero gas", i.e. a gas without a mixture. In a second step, the sensitivity of the respective sensor is determined by applying a test gas, i.e. a gas having a defined concentration of the mixture.

The test gas may be generated using a gas generator that produces the test gas at a conventional distance, for example, for automated inspection or calibration of the respective sensor. Alternatively, a gas bottle may be used to provide the test gas.

In a calibration without a gas generator, the operator or user must manually carry out the calibration on site of the respective sensor by means of a gas bottle, which is cumbersome on the one hand and may be dangerous for the operator under the respective atmosphere on the other hand.

In order to avoid misinterpretation of the measured values determined by the sensors, the respective measuring system can be adjusted by adapting or correcting the zero point and the sensitivity of the sensor as a function of deviations between the current state of the sensor and a reference state, which are identified during the examination or calibration.

If the gas generator is used for calibration or adjustment, the gas generator undergoes an aging process and produces less and less gas under the same excitation over the service life, the automated system interprets the less and less gas used for calibrating or adjusting the sensor as a decrease in the response behavior of the sensor, so that situations can arise in which the sensor is unnecessarily replaced or reported as faulty. The sensitivity of the sensor is underestimated accordingly.

Disclosure of Invention

Against the background of the foregoing, it is an object of the invention to propose an air supply system which is at least partly free from the above-mentioned disadvantages. The aim of the invention is, in particular, to maximize the time span between two calibration processes for the calibration of a sensor of a gas measuring device.

The above object is solved by a method and a gas supply system having the features of the respective independent claims. Further features and details of the invention emerge from the dependent claims, the description and the drawings. The features and details described in connection with the method according to the invention are of course suitable here in connection with the gas supply system according to the invention and vice versa, respectively, so that in the various aspects of the disclosure of the invention reference is made or can be made to each other.

A method for adjusting an air supply system is therefore proposed. The method comprises the following steps: a calibration step of calibrating the gas sensor with a defined concentration of a test gas at a first calibration time point, wherein a first calibration result is determined during the calibration, and wherein at least one gas supply measurement value is determined at a time point before the first calibration time point; a determination step of determining a gas supply reference value by substituting the at least one gas supply measurement value with the first calibration result and a calibration result of the gas sensor determined at a time point before the first calibration time point into the mathematical relationship; and an adjusting step, namely adjusting the air supply system according to the air supply reference value.

Calibration or alignment or correction can be understood within the scope of the present invention as a process in which the current state of the gas sensor and/or the gas supply of the gas measuring device set is determined relative to a reference state.

Adjusting or regulating can be understood within the scope of the present invention as a process in which the gas sensor and/or the gas supply of the gas supply system of the arrangement is adapted or controlled, i.e. controlled or regulated, depending on the currently determined state of the gas sensor and/or the gas supply. The adjustment can be understood in particular as a process in which the calibration result is used to correct the air supply system with regard to deviations between the current state and the reference state. For example, the respective measured values or response behavior of the respective gas sensor can be adapted or corrected during the adjustment.

Within the scope of the present invention, a computing unit can be understood as a programmable processing unit or a sub-processing unit. The computing unit may be implemented as a computer, in particular as a distributed computing system, and is communicatively connected to a memory, for example a network memory or a solid material memory. The computing unit may be, in particular, a control device, for example a microprocessor.

In the context of the present invention, a test gas of a defined concentration can be understood as a test gas of a predetermined or known concentration, which is supplied manually, for example, by a test gas bottle or by means of a gas generator during a calibration process. In this case, the defined concentration of the test gas can float by a certain amount of error.

The proposed method is used in particular for adjusting a gas supply device, in particular for calibrating or adjusting a gas generator of a sensor. For this purpose, it is proposed that the gas supply device is also adjusted during the calibration or adjustment of the respective sensor.

By using the adjusted supply air, false detections of the sensor, for example caused by a false actuation of the supply air, can be avoided. The time range between the two calibration processes of the sensor can be selected and maximized independently of the aging state of the gas supply device.

The proposed method is based on a current or first calibration procedure using the sensor in order to deduce the state of ageing of the gas supply device applying the test gas to the sensor. For this purpose, a first calibration result of the sensor is determined during a first calibration process, i.e. at a first calibration time point, i.e. the sensitivity of the sensor is determined by applying a test gas.

In addition to determining the first calibration result, at least one measured value of the supply air is also determined at a point in time, which measured value is detected by the sensor, in particular directly in time before the first calibration point in time. In combination with a further calibration result, which is determined, for example, before the first calibration time point, a supply air reference value can be determined from the supply air measurement value and the first calibration result. This means that the change in sensor sensitivity between the two calibration processes is assigned to the mathematical relationship with the measured value of the gas supply determined before the first calibration process, in particular the last measured value of the gas supply before the first calibration process, in order to determine the gas supply reference value.

As long as the gas supply reference value is known, it can be used to adjust the respective gas supply device, i.e. to set the amount of test gas to be generated by the gas supply device, or to determine the activation time of the gas supply device using the gas supply reference value.

In order to determine the supply gas measurement values, it can be provided that the test gas is usually applied to the respective sensor, in particular between the respective calibration processes.

By substituting the change in the sensitivity of the sensor or the aging of the sensor into the mathematical relationship with the measured value of the supplied air, the magnitude of the deviation of the measured value of the supplied air from the nominal value, which is determined by the aging of the supplied air device, can be determined. Once the quantity part of the deviation of the measured value of the air supply from the nominal value, which can be determined by the aging of the air supply, is known, this part can be used to adjust the air supply such that this part is compensated or taken into account in other calibration processes.

Furthermore, the criterion for when the gas supply device has to be replaced can be determined in part from the number of deviations of the measured gas supply values from the nominal values, i.e. the aging of the gas supply device, since the amount of gas generated and the corresponding signal-to-noise ratio are too small.

In particular, the aging of the gas sensor can be determined by the proposed method as a function of the adjustment of the gas sensor, i.e. the degradation of the measured values as a function of the physical properties of the gas sensor since a calibration or adjustment prior to the gas sensor is determined. This aging of the gas sensor can be compared with the sensitivity reduction result of the gas supply device. The relative aging of the gas generator corresponds to the ratio of the currently determined reference value and the old or valid reference value prior to the currently determined reference value. If the reference values determined at different points in time are constant or unchanged, the gas generator is accordingly not aged.

The substitution of the mathematical relationship proposed according to the invention may comprise determining a droop characteristic, for example the slope of a plurality of supply air measurements. Accordingly, the determined droop characteristic can be corrected in the course of the adjustment according to the invention by configuring the air supply system for compensating for the droop characteristic. For this purpose, for example, the gas supply reference value of the gas supply system can be adjusted and/or the response behavior of the respective gas sensor can be adapted or corrected.

It may be provided that the calibration of the gas sensor and the determination of the gas supply reference value are repeated at a later time point relative to the first calibration time point, wherein the first calibration result is used as a further calibration result, the calibration result determined at the later time point is used as the first calibration result, and at least one gas supply measurement value determined at a time point before the later time point is used as at least one gas supply measurement value.

By repeatedly carrying out the respective steps of the proposed method, the respective aging process of the gas supply device can be continuously monitored and correspondingly corrected. The influence of the aging process of the gas supply device on the calibration process can thus be minimized and the corresponding sensor can be adjusted independently of the aging state of the gas supply device.

It may furthermore be provided that the air supply reference value is determined by multiplying the ratio of the further calibration result and the first calibration result by the at least one air supply measured value.

The calculation criterion (1) for determining the gas supply reference value has proven to be particularly advantageous, wherein the following is specified: s1 corresponds to a first calibration result, S0 corresponds to another calibration result, M1 corresponds to the air supply measurement value, and G1 corresponds to the air supply reference value. Here, M1 may be, for example, the median or median of the last N air supply measurements used to determine the first calibration result S1 prior to the first calibration procedure.

G1＝M1·(S0/S1)

It can also be provided that at least one supply air measurement value (M1) is determined using one of the following determination steps:

a) determining an integral of a sensor response of the gas sensor (303, 401),

b) determining a slope of a sensor response of the gas sensor (303, 401),

c) determining a response time of a sensor response of the gas sensor (303, 401),

d) a profile change in a sensor response of a gas sensor (303, 401) is determined.

It can also be provided that the gas supply reference value is compared with a preset criterion to determine whether the gas supply device has to be replaced.

In particular, it can be provided that an alarm for replacing the air supply device is output if the difference between the measured air supply value and the reference air supply value differs from a predetermined threshold value.

Since the difference between the supplied air measurement value and the supplied air reference value reflects the state of aging of the supplied air device, the difference can be used as a criterion for replacing the supplied air device. Thus, if, for example, the difference is greater than a preset threshold value, it can be concluded that the gas supply is too old or has been switched off and is no longer suitable for calibration of the sensor.

It can also be provided that the concentration value of the test gas provided by means of the gas supply device is corrected to a gas supply reference value, i.e. for example the concentration is added to the gas supply reference value, or the gas supply device is controlled using the gas supply reference value such that the concentration of the test gas provided by means of the gas supply device corresponds to a preset setpoint value.

The gas supply device can be controlled, i.e., controlled or regulated, by means of the gas supply reference value calculated according to the invention, in order to compensate for aging-related changes of the gas supply device.

The desired shape of the check gas curve of the gas supply system can be calibrated and adjusted to adjust the gas supply system proposed according to the invention. In this case, for example, for the case in which the state of a blockage of the sensor input is determined by checking the gas curve shape and the gas curve shape changes over time is checked, the shape of the reference curve can also be adjusted when calibrating the sensor.

Furthermore, the supply gas signal, for example the so-called "time to peak test gas pulse" for determining the response time, for example the so-called "T90 time" of the respective sensor, can be calibrated and/or adjusted by means of the proposed method.

In a second aspect, the invention relates to an air supply system with an adjustment function. The gas supply system comprises an interface for a gas sensor, a gas supply device and a calculation unit. The calculation unit is configured to determine a first calibration result at a first calibration time point with a defined concentration of the test gas, and to determine at least one gas supply measurement value at a time point preceding the first calibration time point. The calculation unit is furthermore configured to determine a gas supply reference value by substituting the at least one gas supply measured value into the mathematical relationship with the first calibration result and a further calibration result of the gas sensor which has been determined at a time point before the first calibration time point, and to adjust the gas supply system according to the gas supply reference value.

The proposed method is particularly useful for operating the proposed air supply system.

The proposed gas supply system comprises an interface for the gas sensor, so that a computing unit of the gas supply system is in communicative connection with the gas sensor and can receive, for example, measurement values determined by the gas sensor. The interface can be designed here as a wired connection or as a wireless connection. The gas sensor can accordingly be designed as an integrated component of the gas supply system or as an external module which is connected to the gas supply system only via an interface. This means that the gas supply system can be configured to adjust itself or to adjust an external gas sensor.

The gas supply system may comprise a gas bottle with a controllable or adjustable valve for releasing the test gas or a gas generator for generating the test gas.

Drawings

The measures which improve the invention, which are shown in the drawing, result from the following description of several embodiments of the invention. All features and/or advantages which are derived from the claims, the description or the figures, together with structural details and spatial arrangements, can represent a basic idea of the invention both individually and in various combinations. The figures each schematically show:

fig. 1 shows a schematic flow of a possible design of the proposed method;

fig. 2 shows a diagram with measured values for performing the proposed method;

fig. 3 shows a possible design of the proposed gas supply system with integrated gas sensor;

fig. 4 shows a possible design of the proposed gas supply system with an external gas sensor.

Fig. 1 to 3 each denote elements with the same function and mode of action with the same reference numerals.

Detailed Description

Fig. 1 illustrates a method 100. The method 100 comprises: a calibration step 101 of calibrating the gas sensor with a defined concentration of a test gas at a first calibration time point, wherein a first calibration result is determined during the calibration, and wherein at least one gas supply measurement value is determined at a time point before the first calibration time point; a determination step 103 of determining a gas supply reference value by substituting the at least one gas supply measurement value with the first calibration result and a further calibration result of the gas sensor which has been determined at a time point before the first calibration time point into a mathematical relation; and an adjustment step 105 of adjusting the gas supply system according to the gas supply reference value.

Fig. 2 shows a graph 200. The diagram 200 extends on its abscissa 201 with respect to time and on its ordinate 203 with respect to sensor sensitivity in μ a/ppm.

At a first calibration time t1, the gas sensor of the gas supply system is calibrated, for example, by the user with a test gas bottle containing a defined concentration of the target gas or test gas.

The test particles emerging from the test gas bottle are transferred to the gas sensor, so that the gas sensor measures a gas supply measurement with a sensor sensitivity of, for example, 1.5 μ a/ppm, which corresponds to the first calibration result S1.

At a first calibration time t1, the air supply reference value G0 is set on the air supply system, for example, to 2000ppm · s, which is determined or preset at a time t0 before the first calibration time t 1. During the service time of the gas sensor and the gas generator, a reduced gas generator signal 205 is generated, so that the measured gas supply value (M1) determined at a time (t2) before the first calibration time corresponds to, for example, 1000ppm · s.

Starting from the supply measurement (M1), the supply system assigns a sensitivity of M1/G0 of 1 μ a/ppm to the gas sensor, since the drop in the gas generator signal 205 is completely assigned to the gas sensor.

However, the gas generator has actually aged, so that the user, with calibration at the first calibration time t1, finds a "true" sensor sensitivity of 1.5 μ a/ppm at S1.

This means that the gas sensor and the gas generator age at the same rate. From this knowledge, a new air supply reference value G1 can be determined by means of the calculation criterion (1), wherein S1 corresponds to a first calibration result, S0 corresponds to another calibration result, M1 corresponds to an air supply measurement value, and G1 corresponds to an air supply reference value. Here, M1 may be the median or median of the last N gas generator signals used to determine the first calibration result S1 prior to the first calibration process.

G1＝M1·(S0/S1) (1)

The method 100 can be applied, for example, as a sensor raw value of the electrochemical sensor current or as an already calculated concentration value of the sensor.

To determine the sensitivity of the gas sensor during calibration, a "permanent application" may be performed using the gas. Next, stable measurements are expected and sensitivity is determined. For this purpose, for example, an integral of the sensor response of the gas sensor to the applied test gas, the slope of the sensor response of the gas sensor to the applied test gas, or the time until an inflection point of the sensor response of the gas sensor to the applied test gas can be used.

Fig. 3 shows an air supply system 300. The gas supply system 300 includes an interface 301 to which a gas sensor is connected, a gas sensor 303, a gas supply device 305, and a calculation unit 307. The calculation unit is configured to determine a first calibration result at a first calibration time point for calibrating the gas sensor with a defined concentration of the test gas.

Furthermore, the calculation unit 307 is configured to determine at least one air supply measurement value at a point in time before the first calibration point in time.

Furthermore, the calculation unit 307 is configured to determine the gas supply reference value by substituting the at least one gas supply measurement value into the mathematical relation with a first calibration result of the gas sensor and a further calibration result determined at a time point before the first calibration time point.

Further, the calculation unit 307 is configured to adjust the air supply system 300 according to the air supply reference value.

In the example shown in fig. 3, the gas sensor 303 is communicatively connected to the interface 301 via an electrical connection, such as a cable or soldered connection. The gas sensor 303 transmits the measured values accordingly via the interface 301 and the calculation unit 307.

Fig. 4 shows an air supply system 400. The gas supply system 400 is identical to the gas supply system 300 according to fig. 3, with the exception that the interface 301 is connected via a wireless interface to an external gas sensor 401, for example in a gas measuring device 407. Accordingly, the gas supply system 400 forms a portable module for testing different gas sensors.

Here, the interface 301 may include a first communication module 403 for wireless communication via, for example, WLAN (wireless local area network), bluetooth, near field communication, Zigbee (Zigbee) or mobile radio signals like 5G, a second communication module 405 for connecting a cable, for example, a COM port or a USB port.

Optionally, the gas supply system 400 may comprise an output unit 409, such as an LED, a microphone and/or a display, for outputting an alarm, such as a prompt to replace the gas sensor 401.

List of reference numerals

100 method

101 calibration step

103 determining step

105 adjustment step

200 diagram

201 abscissa

203 ordinate of the product

205 gas generator signal

t1 first calibration time Point

S1 first calibration result

M1 measured value of air supply

Point in time before t2

G0 reference value for air supply

Reference value for G1 new air supply

300 gas supply system

301 interface

303 gas sensor

305 gas supply device

307 calculation unit

400 air supply system

401 external gas sensor

403 first communication module

405 second communication module

407 gas measuring device

409 output unit.