Method for comprehensive diagnostics of sorption-capacitive humidity sensor based on electrical capacitance, impedance, dielectric loss tangent, and hysteresis

Abstract

FIELD: diagnostics.SUBSTANCE: invention relates to comprehensive diagnostics of the sorption-capacitive humidity sensor. The electrical parameters of a finished sensor are measured, wherein the electrical capacitance, impedance and dielectric loss tangent are measured for a sorption-capacitive humidity sensor, hysteresis is additionally determined based on the results of measuring the electrical capacitance of the sensor on the forward and reverse course of changing the moisture state of the gas medium, the values of the electrical capacitance, impedance, dielectric loss tangent and hysteresis are compared with the permissible ranges established based on the results of preliminary calibration and / or testing, and based on the results of said comparison, the sensor is assigned to a diagnostic category characterizing its technical condition, metrological stability and suitability for operation.EFFECT: increasing the reliability of diagnostics of the condition of a sorption-capacitive humidity sensor, as well as providing the ability to identify sensors with increased hysteresis and unstable electrical characteristics.10 cl, 5 dwg

Description

[0001] The invention relates to measurement and control equipment, specifically to methods for monitoring and diagnosing sorption-capacitive humidity sensors used to measure the condition of gaseous media, including determining the water dew point temperature in natural gas and aggressive gaseous media. The invention can be used in the manufacture, testing, diagnostics, screening, and operation of sorption-capacitive humidity sensors used in humidity analyzers, hygrometers, and water dew point temperature converters.

[0002] In this description, impedance is understood to mean the complex electrical resistance of a sorption-capacitive humidity sensor, measured at a given frequency of the test signal and characterizing the combined influence of the active and reactive components of the electrical response of the sensor.

[0003] The dielectric loss tangent is a parameter that characterizes the dielectric losses in the oxide moisture-sensitive layer of a sorption-capacitive humidity sensor.

[0004] Hysteresis is understood as the difference in the values ​​of the electrical capacitance of a sorption-capacitive humidity sensor, measured in the forward and reverse course of the change in the condition of the gas environment at the same value of the dew point temperature for water and / or relative humidity.

[0005] The following notations are used in this description:

[0006] C - electric capacitance of the sorption-capacitive humidity sensor;

[0007] Z - impedance of the sorption-capacitive humidity sensor;

[0008] D - tangent of the dielectric loss angle of the sorption-capacitive humidity sensor;

[0009] H - hysteresis of the sorption-capacitive humidity sensor.

[0010] Thin-film sorption-capacitive gas humidity sensors are known from the prior art, comprising an aluminum substrate, an oxide moisture-sensitive layer, and a moisture-permeable electrode [patent RU222946U1, published 01 / 24 / 2024]. A method for manufacturing a thin-film humidity sensor is known, including preparing an aluminum substrate, forming an oxide moisture-sensitive layer, and applying a moisture-permeable electrode [patent RU2820096C1, published 05 / 29 / 2024].

[0011] There are known studies on the technology of manufacturing a sorption-capacitive humidity sensor based on thin films obtained by microarc oxidation and magnetron sputtering, in which the structure of the oxide moisture-sensitive layer, its electrical resistance, thickness and porosity, as well as the parameters of the moisture-permeable electrode are investigated [Mikhin S. O., Egorov D. K., Koshkur O. N., Romanov A. E. Topology of manufacturing a sorption-capacitive humidity sensor based on thin films obtained by microarc oxidation and magnetron sputtering / / Control. Diagnostics. 2023. Vol. 26, No. 10. Pp. 38-48].

[0012] There are known studies of a thin-film sorption-capacitive sensor for monitoring the well-being of gas environments, in which, after the formation of an oxide moisture-sensitive layer by electrochemical anodizing and the application of a moisture-permeable electrode, the electrical capacitance, electrical resistance, dielectric loss tangent and hysteresis in the range of the water dew point temperature are studied [Mikhin S. O., Ganzha V. A., Koshkur O. N., Romanov A. E. Thin-film sorption-capacitive sensor for monitoring the well-being of gas environments / / Control. Diagnostics. 2025. Vol. 28, No. 9. Pp. 56-62].

[0013] A prior art technology discloses a natural gas water dew point temperature transmitter [Patent RU191918U1, published August 28, 2019], comprising humidity and temperature sensors connected via a sealed electrical input to an electronic board housed in a housing. In this technical solution, the humidity sensor and temperature sensor are located in a controlled gas environment, and the gas dew point temperature is calculated by the device's electronic board based on readings from the humidity and temperature sensors.

[0014] The disadvantage of this solution, as applied to the claimed invention, is the lack of a comprehensive diagnostic of the technical condition of the sorption-capacitive humidity sensor based on the combination of electrical capacitance, impedance, dielectric loss tangent, and hysteresis, which does not allow for a reliable assessment of metrological stability, identification of signs of degradation, and making a diagnostic decision on the suitability of the sensor for operation.

[0015] Technical problem

[0016] The technical problem that the claimed invention is aimed at solving is the insufficient completeness and reliability of diagnostics of the technical condition of a sorption-capacitive humidity sensor, as a result of which sensors with unsatisfactory metrological stability, increased hysteresis, degradation of electrical characteristics and reduced reliability may be allowed for operation or further testing.

[0017] Technical result

[0018] The technical result consists in increasing the reliability of diagnostics of the technical condition of a sorption-capacitive humidity sensor, ensuring the identification of sensors with increased hysteresis and unstable electrical characteristics, as well as increasing the reliability of the selection of sensors suitable for operation and metrological testing.

[0019] Achieving a technical result

[0020] The technical result is achieved in that in the method for comprehensive diagnostics of a sorption-capacitive humidity sensor, including measuring the electrical parameters of a finished sensor, according to the invention, the electrical capacitance, impedance and dielectric loss tangent are measured for the sorption-capacitive humidity sensor, hysteresis is additionally determined based on the results of measuring the electrical capacitance of the sensor on the forward and reverse course of changing the welfare of the gas environment, the values ​​​​of the electrical capacitance, impedance, dielectric loss tangent and hysteresis are compared with the permissible ranges established based on the results of preliminary calibration and / or testing, and based on the results of the said comparison, the sensor is assigned to a diagnostic category that characterizes its technical condition, metrological stability and suitability for operation.

[0021] In a preferred embodiment, hysteresis is defined as the difference in the values ​​of the electrical capacitance of the sensor measured on the forward and reverse strokes at the same value of the water dew point temperature and / or relative humidity.

[0022] In one embodiment, the hysteresis is determined in absolute and / or relative units.

[0023] In one embodiment, the measurement of the electrical capacitance, impedance and dielectric loss tangent is carried out at a given frequency of the test signal, preferably in the frequency range from 0.1 to 2.0 MHz, for example at a frequency of 1 MHz.

[0024] In one embodiment, the change in the welfare of the gas environment when determining the hysteresis is carried out in the range of water dew point temperature from +20 to -100°C.

[0025] In one embodiment, based on the results of the comprehensive diagnostics, the sensor is assigned to at least one of the following diagnostic categories: operational, metrologically stable, unstable, degrading, or unsuitable for operation.

[0026] In one embodiment, during the forward and reverse course of the change in the Welfare of the gas environment, the impedance and / or the tangent of the dielectric loss angle of the sorption-capacitive humidity sensor are additionally measured, and the change in the said parameters is taken into account when classifying the sensor into a diagnostic category.

[0027] It is permissible to carry out measurements on the forward and reverse strokes with a time delay at each control point until the electrical parameters of the humidity sensor stabilize.

[0028] It is allowed to use a precision capacitance and immittance meter of an electric circuit to measure the capacitance, impedance and dielectric loss tangent.

[0029] The invention is based on the fact that capacitance, impedance, and dielectric loss tangent characterize the electrical properties of the oxide moisture-sensitive layer and the sensor as a whole, while hysteresis additionally characterizes the difference in sensor response during the forward and reverse phases of changes in the gas environment's condition. Changes in the gas environment's condition alter not only the electrical capacitance of the sorption-capacitive humidity sensor but also its impedance and dielectric loss tangent. Combined use of these parameters allows for a more comprehensive diagnosis of the sensor's technical condition, identifying signs of instability and degradation, and improving the reliability of decisions regarding its suitability for use.

[0030] Implementation of the claimed method

[0031] The invention explains:

[0032] - diagram of a sorption-capacitive humidity sensor connected to a means for measuring electrical parameters, shown in Fig. 1;

[0033] - a structural diagram of the implementation of the method for complex diagnostics of a sorption-capacitive humidity sensor, shown in Fig. 2;

[0034] - a block diagram of the sequence of operations of the claimed method, shown in Fig. 3;

[0035] - a diagram for determining hysteresis based on the values ​​of electrical capacitance in the forward and reverse course of changing the state of the gas environment, shown in Fig. 4;

[0036] - diagram of sensor assignment to diagnostic categories based on the results of complex diagnostics, presented in Fig. 5.

[0037] List of designations:

[0038] 1 - aluminum substrate;

[0039] 2 - moisture-sensitive oxide layer;

[0040] 3 - moisture-permeable electrode;

[0041] 4 - measuring contacts;

[0042] 5 - electrical parameter measuring instrument;

[0043] 6 - means for setting and / or controlling the welfare of the gas environment;

[0044] 7 - computing unit;

[0045] 8 - diagnostic decision making block;

[0046] 9 - forward capacitance curve;

[0047] 10 - reverse capacitance curve;

[0048] 11 - hysteresis;

[0049] 12 - working sensor;

[0050] 13 - metrologically stable sensor;

[0051] 14 - unstable sensor;

[0052] 15 - degrading sensor;

[0053] 16 - sensor unsuitable for use.

[0054] The sorption-capacitive humidity sensor, in relation to which the claimed method is carried out, contains an aluminum substrate 1, an oxide moisture-sensitive layer 2 and a moisture-permeable electrode 3.

[0055] As shown in Fig. 1, the sorption-capacitive humidity sensor is connected via measuring contacts 4 to the means for measuring electrical parameters 5. In this case, the means for measuring electrical parameters 5 is intended for measuring the electrical capacitance C, impedance Z and the dielectric loss tangent D of the sensor.

[0056] As shown in Fig. 2, to implement the method, a sorption-capacitive humidity sensor is placed in the zone exposed to a gaseous environment, the state of which is set and / or controlled by means 6. The sensor, connected to the electrical parameter measuring means 5, is linked to the computing unit 7, in which the hysteresis H is determined based on the measurement results and the values ​​of C, Z, D, and H are compared with the permissible ranges. The comparison result is sent to the diagnostic decision-making unit 8.

[0057] As shown in Fig. 3, the method includes the following successive steps:

[0058] S1 - connection of the sorption-capacitive humidity sensor to the instrument measuring electrical parameters;

[0059] S2 - measurement of electrical capacitance C;

[0060] S3 - impedance measurement Z;

[0061] S4 - measurement of the dielectric loss tangent D;

[0062] S5 - measurement of electrical capacitance C in the forward course of change of the gas environment condition;

[0063] S6 - measurement of electrical capacitance C on the reverse course of change of the gas environment condition;

[0064] S7 - determination of hysteresis H;

[0065] S8 - comparison of C, Z, D and H values ​​with acceptable ranges;

[0066] S9 - assignment of the sensor to the diagnostic category.

[0067] In one embodiment, the measurement of the electrical capacitance C, impedance Z, and dielectric loss tangent D is performed at a given test signal frequency. Preferably, these measurements are performed in the frequency range from 0.1 to 2.0 MHz, for example, at a frequency of 1 MHz.

[0068] When determining hysteresis H, the state of the gas environment affecting the sensor is varied. In one embodiment, the water dew point temperature is used as the state parameter. The water dew point temperature is varied, for example, in the range from +20 to -100°C. At each control point on the forward and reverse strokes, a time sufficient for the sensor's electrical parameters to stabilize is maintained. During this process, the electrical capacitance C is determined on the forward and reverse strokes, and in one embodiment, the impedance Z and dielectric loss tangent D are additionally monitored, changes in which are taken into account when forming the diagnostic conclusion.

[0069] As shown in Fig. 4, when the gas environment condition changes, the electrical capacitance of the sensor on the forward stroke 9 and on the return stroke 10 takes on different values. Hysteresis 11 is defined as the difference between the electrical capacitance values ​​measured on the forward and return strokes at the same value of the water dew point temperature and / or relative humidity. Fig. 4 shows, as an example, a circuit for determining the hysteresis based on the electrical capacitance values ​​on the forward and return strokes of a change in the water dew point temperature in the range from 0°C to minus 100°C. Depending on the diagnostic task, the hysteresis can be determined in absolute and / or relative units. Simultaneously, in one embodiment, the impedance Z and the dielectric loss tangent D are additionally determined on the forward and return strokes, the change of which is also taken into account in the comprehensive diagnostics of the technical condition of the sensor.

[0070] Based on the results of measuring parameters C, Z, D, and H, a diagnostic conclusion is generated in computing unit 7. The values ​​of electrical capacitance, impedance, dielectric loss tangent, and hysteresis, as well as, in one embodiment, the nature of the change in impedance and dielectric loss tangent during the forward and reverse motions, are compared with the permissible ranges established based on the results of preliminary calibration and / or testing.

[0071] As shown in Fig. 5, based on the results of the comprehensive diagnostics, the sensor can be assigned to at least one of the following diagnostic categories: a working sensor 12, a metrologically stable sensor 13, an unstable sensor 14, a degrading sensor 15, or a sensor 16 unsuitable for operation.

[0072] In one embodiment, a sensor is considered operational and metrologically stable if its C, Z, D, and H values ​​are within the permissible limits established by preliminary calibration and / or testing. If the permissible hysteresis value H is exceeded, the D values ​​deviate upward, the C and / or Z values ​​deviate from the permissible ranges, or if any of these symptoms occur simultaneously, the sensor is classified as unstable, degrading, or unfit for use.

[0073] The proposed method provides a more comprehensive diagnosis of the sensor's technical condition compared to solutions that evaluate only a single electrical parameter or determine only the water dew point temperature. By combining capacitance, impedance, dielectric loss tangent, and hysteresis, as well as, in one embodiment, changes in impedance and dielectric loss tangent during the forward and reverse motions, the reliability of the assessment of the sensor's metrological stability and suitability for use is increased.

[0074] Example of the method implementation

[0075] To implement the method, thin-film sorption-capacitive humidity sensors were used. These sensors contained an aluminum substrate, a moisture-sensitive oxide layer, and a moisture-permeable electrode. The sensors were connected to a precision capacitance and immittance meter via measuring contacts and placed in a zone exposed to a gaseous environment with an adjustable ambient temperature.

[0076] Measurements of the electrical capacitance C, impedance Z, and dielectric loss tangent D were performed at a frequency of 1 MHz. The dew point temperature of the water was varied in the range of +20 to -100°C, with the electrical capacitance values ​​sequentially recorded on the forward and reverse strokes. At each control point, a time was maintained until the sensor's electrical parameters stabilized.

[0077] After this, for each control point, the hysteresis I was determined as the difference in the capacitance values ​​obtained during the forward and reverse runs at the same water dew point temperature. The impedance Z and dielectric loss tangent D values ​​were also analyzed, including their changes during the forward and reverse runs.

[0078] Based on the combination of parameters C, Z, D, and H, a diagnostic conclusion was formed about the sensor's technical condition. Sensors characterized by acceptable D values, stable Z values, acceptable electrical capacitance C values, and low hysteresis H were classified as operational and metrologically stable. Sensors with increased losses, increased hysteresis, and electrical parameter deviations from established ranges were classified as unstable, degrading, or unsuitable for use.

[0079] The use of the claimed method has made it possible to increase the reliability of the assessment of the technical condition of sensors and ensure a more reliable selection of samples suitable for operation and further metrological testing.

Claims

1. A method for the comprehensive diagnostics of a sorption-capacitive humidity sensor, including the measurement of the electrical parameters of a finished sensor, characterized in that the electrical capacitance, impedance, and dielectric loss tangent of the sorption-capacitive humidity sensor are measured, hysteresis is additionally determined based on the results of measuring the electrical capacitance of the sensor on the forward and reverse course of changing the moisture state of the gas medium, the values ​​of the electrical capacitance, impedance, dielectric loss tangent, and hysteresis are compared with the permissible ranges established based on the results of preliminary calibration and / or testing, and based on the results of the said comparison, the sensor is assigned to a diagnostic category characterizing its technical condition, metrological stability, and suitability for operation.

2. The method according to paragraph 1, characterized in that the hysteresis is determined as the difference in the values ​​of the electrical capacitance of the sensor, measured on the forward and reverse strokes at the same value of the dew point temperature for water and / or relative humidity.

3. The method according to paragraph 1 or 2, characterized in that the hysteresis is determined in absolute and / or relative units.

4. The method according to any of paragraphs 1-3, characterized in that the measurement of electrical capacitance, impedance and dielectric loss tangent is carried out at a given frequency of the test signal.

5. The method according to paragraph 4, characterized in that the measurement of electrical capacitance, impedance and dielectric loss tangent is carried out in the frequency range from 0.1 to 2.0 MHz, namely at a frequency of 1 MHz.

6. The method according to any of paragraphs 1-5, characterized in that the change in the moisture state of the gaseous medium when determining the hysteresis is carried out in the range of the water dew point temperature from +20 to -100 °C.

7. The method according to any of paragraphs 1-6, characterized in that the measurements on the forward and reverse strokes are carried out with a time delay at each control point until the electrical parameters of the sensor are stabilized.

8. The method according to any one of paragraphs 1-7, characterized in that, based on the results of the comprehensive diagnostics, the sensor is assigned to at least one of the following diagnostic categories: operational, metrologically stable, unstable, degrading, or unsuitable for operation.

9. The method according to any of paragraphs 1-8, characterized in that a precision meter of electrical capacitance and immittance of an electrical circuit is used to measure the electrical capacitance, impedance and dielectric loss tangent.

10. The method according to any of paragraphs 1-9, characterized in that during the forward and reverse course of the change in the moisture state of the gas medium, the impedance and / or the tangent of the dielectric loss angle are additionally measured and their change is taken into account when classifying the sensor into a diagnostic category.

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