Systems and methods for sensing component conditions

Abstract

A system for sensing a condition of a component including a structure covered by a coating. The first electrical signal and the second electrical signal are communicated to a computer system via a single communication channel, and in the computer system, the signals are separated and subsequently used in combination to provide an indication of the condition or humidity of the component.

Description

Technical Field

[0001] The present invention relates to a system and method for sensing the condition of a coated structure. Background Art

[0002] Various structures, such as those made of steel or concrete, are covered with coatings. Typically, the coating comprises one or more layers of cured coating. The cured coating can be used for different purposes, in particular protection against atmospheric degradation (including corrosion, fading, and UV degradation, etc.), reduction of dirt, wear resistance, chemical resistance, anti-reflection, or simply to provide an aesthetically pleasing appearance.

[0003] In this document, reference is made to an assembly comprising a structure having a coating covering a surface of the structure, ie the assembly comprises both the structure and the coating.

[0004] Under ideal conditions, the coating system exhibits predefined desired properties, e.g., a specific level of protection against intrusion of air, water, or corrosive materials, thereby maintaining the intended condition of the structure. Over time, cracks or coating degradation (i.e., defects or changes in one or more layers of the cured coating) reduce the desired effect, and scheduled maintenance or repair may be required.

[0005] Embedding conductive electrodes between layers of a coating is a known principle for monitoring barrier properties of a coating and / or surface corrosion of an underlying structure. See, for example, Kittel et al., Progress in Organic Coatings (2001), 41:93-98; Su et al., Corrosion Science (2008), 50:2381-2389.

[0006] It is known from the literature to use electrical resistance (ER) or electrical impedance spectroscopy (EIS) to detect the condition of coatings and corrosion and cracks in the underlying structure.

[0007] Known environmental sensors can determine the environment and parameters, including pollutant levels, rainfall, relative humidity, acidity (pH) and temperature. Such parameters often characterize corrosive or destructive conditions and can predict remaining life or the need for preventive measures (such as re-coating, etc.).

[0008] When predicting the condition of a coating or structure, environmental sensors can improve the prediction based on the signal from the ER or EIS sensor. In addition, the signal used by the EIS sensor is sometimes adjusted based on temperature and humidity.

[0009] Thus, configuring many sensors for different parameters (eg, EIS, humidity, temperature, etc.) can improve the predictability of conditions - especially when the signals from the different sensors are considered in combination.

[0010] The sensor may comprise electrodes applied directly on the surface of the (coated) structure, electrodes applied to the structure under the coating, or electrodes embedded between layers of the coating. For sensors where the electrodes are applied under the coating or embedded between layers of the coating, the sensor is usually wired through the outer surface of the coating, thereby compromising the quality of the coating to prevent the ingress of air and water.

[0011] Some computer systems combine different physical properties and provide an indication of the condition of a component based on these properties. For example, there are computer systems in which temperature and humidity can be combined to predict the condition of a coating. In order to make such an assessment, the computer system communicates with multiple sensors and combines the signals transmitted by these sensors. When reading signals from multiple sensor signals, specific challenges arise. The accuracy of the assessment depends on the reproducible conversion from the physical properties to the electrical signals representing the physical properties. If the signals from each sensor do not always consistently represent the same physical condition, for example, the same voltage represents the same temperature, then the assessment may be wrong.

[0012] Signal communications present special challenges in this regard. When different signals are transmitted over different communication channels, different characteristics of the channels and different conditions (e.g., temperature, cable length, cable condition (such as humidity or physical shape of the cable, etc.)) may affect the channels differently. Thus, an indication of a condition may be based on a combination of signals with incompatible signals. If a signal is transmitted over a communication channel whose characteristics have changed relative to the characteristics of the communication channel used to transmit another signal, then the signal combination may not represent the physical condition in a predictable manner.

[0013] Furthermore, the transmission of the signal consumes energy. With regard to sensing the condition of the coated structure, a large number of sensors distributed over the area of ​​the coated structure are typically used. The sensors are often distributed over a large area, and the signal distribution uses long cables extending between the multiple sensors. Since the sensors are far from the power grid, the signals are often generated by battery power. Thus, energy efficient handling of the signals is important.

[0014] Furthermore, while sensors configured to determine different parameters can improve the predictability of conditions, the increased number of wires penetrating the coating can reduce lifetime. Furthermore, multiple signals and wires between different types of sensors are difficult to manage in practice and the risk of incorrect connections can lead to erroneous results.

[0015] Published applications related to monitoring of coated structures include WO2021 / 028480 and WO2022 / 043569, both of which are incorporated herein by reference. Summary of the invention

[0016] In this context, an object of the embodiments disclosed herein is to facilitate more correct distribution of multiple signals, which are combined by the recipient to provide an indication of the condition of the component. Another object is to provide simpler, smarter and / or faster signal communication without reducing the protective quality of the coating. Another object is to reduce the risk of incorrect connections and make system assembly and data acquisition easier and more efficient. Another object is to enable multiple sensor readings to be obtained substantially simultaneously using a single channel of an I / O device that is part of a computer system. Another object is to facilitate energy-efficient signal communication and allow extensive use of battery power in sensing systems.

[0017] To these and other objects, the present disclosure provides, in a first aspect, a system and method for providing an indication of a condition of a component according to the independent claims, with optional features specified in the dependent claims.

[0018] The system is configured to sense the condition of a component, such as a ship or similar structure of steel or fiberglass, etc., a bridge or a building, etc. Such a component may include a structure covered by the coating.

[0019] The system includes: at least one first sensor configured to convert a first physical property into a first electrical signal; at least one second sensor configured to convert a second physical property into a second electrical signal; at least one additional sensor including at least one electrode embedded in the coating and configured to provide at least one additional signal; and a computer system.

[0020] The computer system includes an I / O device having a plurality of separate channels and a computer unit communicating with the I / O device.

[0021] The first sensor and the second sensor are connected to one of the separate channels via the first communication channel, and the additional sensor is connected to the other of the separate channels via the second communication channel. Thus, the I / O device is capable of transmitting AC signals with the first sensor and the second sensor via the first communication channel, and transmitting AC signals with the additional sensor via the second communication channel.

[0022] The first electrical signal is transmitted in a first frequency domain of a first communication channel, and the second electrical signal is transmitted in a second frequency domain of the first communication channel.

[0023] The additional sensor having at least one electrode embedded in the coating can be used, among other purposes, for ER or EIS evaluation of the coating condition, while the first and second signals can be used for other purposes, for example, for detecting temperature and humidity. Since the signal from the additional sensor is transmitted in a separate channel, it can utilize the entire spectrum of the frequency sweep without interference from other signals. At the same time, the first and second sensors are combined into a single communication channel to reduce the number of communication channels, thereby reducing energy consumption, especially the complexity related to wiring, and reducing the number of channels and size of I / O devices without reducing the ability to analyze the signals from the additional sensor. Thus, optimal sensing conditions can be maintained with reduced power consumption and complexity.

[0024] Furthermore, when a single communication channel transmits both the first and second electrical signals from the two sensors to the computer system, it ensures that the two signals are transmitted under the same communication conditions. External conditions such as temperature, air pressure, humidity, etc. affect the single channel and therefore affect the two signals in a more consistent manner. Thus, if the communication of the signal affects the signal itself, then the two signals combined by the computer system will be affected. This can potentially increase accuracy when the signals are subsequently combined by the computer system to provide an indication of the condition of the component.

[0025] In this context, physical properties refer to properties that characterize the environment, such as degradation characteristics of components and / or external environmental conditions. One of the first and second signals may represent temperature, while the other may represent humidity, or pollutant levels, rainfall, or corrosive parameters (such as pH or sulfur levels), air pressure, or other physical properties.

[0026] The coating may consist of any kind of paint system or the like, preferably a one or two component paint system for steel or concrete, such as coating systems for reducing water diffusion. The latter are well known, for example, for protection of pipelines or in ballast tanks of ships.

[0027] The coating may include a resin matrix material that forms a binder, such as an acrylic polymer, an alkyd polymer, or an epoxy polymer. For example, the coating may include the following binders: acrylic, epoxy, polyaspartic, polyurethane, polysiloxane, alkyd, zinc silicate, silicone, polyurea Hybrid technologies: epoxy / acrylic, epoxy / silicone, epoxy / zinc silicate.

[0028] The coating may include pigments, for example, to provide color or to constitute a filler material. Any color pigments are contemplated, for example yellow, orange, red, violet, brown, blue, green or black, which are part of an official pigment numbering system, for example described as pigment white xxx (x=1 to 999), pigment yellow xxx (x=1 to 999), pigment orange (x=1 to 999), pigment red xxx (x=1 to 999), pigment brown (x=1 to 999), pigment violet (x=1 to 999), pigment green (x=1 to 999), pigment blue PB (x=1 to 999), pigment black (x=1 to 999), etc.

[0029] Examples of such pigments are: zinc oxide, zinc-containing phosphates and polyphosphates, iron oxide, aluminum-containing phosphates, zinc borates, graphite, oxidized carbon black, coated mica, fluorescent pigments, cuprous oxide, aluminum paste pigments (leafing and non-leafing), metallic pigments, zinc powder, organic pearlescent pigments, ammonium polyphosphate, colored silica sand, polyacrylic acid / calcium carbonate, azo, phthalocyanine and anthraquinone derivatives (organic pigments), titanium dioxide (titanium (IV) oxide), etc.

[0030] The coating may, for example, include the following fillers: carbonates, such as: calcium carbonate, calcite, dolomite (=calcium / magnesium carbonate), magnesium silicate / carbonate, polycarbonate. Also included are mixtures, calcined grades and surface treated grades. Silicates, such as: aluminum silicate (kaolin, china clay), magnesium silicate (talc, talc / chlorite), potassium aluminum silicate (feldspar (plastorite), glimmer (glimmer)), potassium sodium aluminum silicate (nepheline syenite), calcium silicate (wollastonite), aluminum silicate (bentonite), layered silicates (mica). Oxides: silicon dioxide (such as quartz, diatomaceous earth), metal oxides (such as calcium oxide, aluminum oxide, iron oxide and micaceous iron oxide). Hydroxides / hydrates, such as: aluminum hydroxide, aluminum trihydrate, sulfates: barium sulfate. Other fillers: barium metaborate, silicon carbide, perlite (volcanic glass), glass spheres (solid and hollow), glass flakes, glass and silicate fibers, organic fibers, polyvinylidene chloride acrylonitrile, polystyrene acrylate.

[0031] Also included are mixtures of the above fillers as well as natural, synthetic, calcined or surface treated grades.

[0032] The coating system may include several layers of paint, for example, including a primer, such as an anti-corrosion primer applied to the substrate surface. For example, the substrate surface may be initially treated by sandblasting. Over one or more layers of primer, the coating may include one or more intermediate coatings, such as a coating that promotes adhesion, and / or one or more top coatings. For example, the top coating may include one or more fouling control surface coating systems, which are particularly useful for marine structures. Electrodes may be arranged between such different layers of paint.

[0033] The anticorrosion primer may for example be an epoxy type anticorrosion primer and it may be a zinc containing or zinc free primer.An example of an anticorrosion primer with an epoxy based binder system may be found in WO 2014 / 032844.

[0034] The different paint layers may be based on epoxy, silicone or polyurethane, and it may comprise, for example, a fouling control top coating system comprising one or more antifouling coatings, or a silicone system, wherein the silicone system may comprise similar layers or different layers of silicone coatings. Examples of suitable top coatings for fouling control may be found in particular in patent publication WO 2011 / 076856.

[0035] The I / O device communicates input and output signals with a sensor having embedded electrodes based on known principles, for example based on electrochemical impedance spectroscopy (EIS) and using, for example, AC signals. For more information about EIS, see A. Amirudin, D. Thieny, "Application of electrochemical impedance spectroscopy to study the degradation of polymer-coated metals", Progress in Organic Coating, Vol. 26(1): 1-28; "Determination of Coating Deterioration with EIS", F. Mansfeld, CH Tsai, Corrosion, 1991, Vol. 47(12): 958-963; "Re-evaluating Electrochemical Impedance Spectroscopy (EIS) for the Field Inspector's Toolbox: A First Approach"; B. J. Merten, A. Skaja, D. Tordonato, D. Little, U.S. Bureau of Reclamation, Office of Research and Development, Science and Technology Program, Materials Engineering and Research Laboratory (USA), 2014; "Use of Embedded Corrosion Sensors and Sensor Blankets to Detect Paint Deterioration", Journal of the American Society of Corrosion and Molecular Biology, ... "Degradation"; G.D. Davis and C.M. Degraders, Corrosion 2003, Paper 3441; "Continuous Monitoring of Atmospheric Corrosion and Coating Degradation" D. Ellicks, F. Friedersdorf, M. Merrill, P. Kramer NACE-2017-8834 March 2017. These and other publications explain the principles of determining degradation, for example, by using EIS.

[0036] The coated structure may be a CUI structure (Coating Under Insulation), wherein the coating is in the invisible region and the sensor is used to detect degradation of the coating or under-film corrosion. The I / O device may be specifically configured for AC signals or pulsed DC signals. In such an embodiment, the index may, for example, relate to a combination between two of "water detection", "coating degradation", "corrosion" and / or "cracking".

[0037] The computer system can be configured to extract the first and second electrical signals as separate signals and use them in combination to provide an indication of the condition of the component. Furthermore, the computer system can be configured to use the first and second signals in combination with at least one additional signal to provide an indication of the condition of the component.

[0038] The I / O device may be configured to communicate a data string with the computer unit, wherein the data string comprises a data record for each individual channel. The data record may be, for example, a frequency spectrum from a single frequency sweep. The first and second electrical signals from the first and second sensors may be communicated in a single data record, i.e., for example, by communicating the response from a single frequency sweep in the form of a single frequency spectrum.

[0039] The spectrum is transmitted from the I / O device to the computer unit. When the computer unit receives this spectrum, the first and second signals can be derived from the spectrum and used to provide an indication of the component.

[0040] Integrating both signals into a single data record (eg represented by a single swept frequency spectrum) simplifies communication and reduces the amount of data exchanged between the I / O device and the computer unit.

[0041] The computer unit may be configured to receive a single data record and to perform extraction of the first and second electrical signals as separate signals and use them in combination to provide an indication of the condition of the component. Thus, the two signals are not extracted as separate signals until the data string containing the data record is transmitted to the computer unit. This allows simple data transfer between the I / O device and the computer unit.

[0042] The interface computer unit may be arranged to receive data strings from the I / O devices and distribute the data strings to the computer unit. The interface computer unit may, for example, bundle data from a plurality of I / O devices together before transmitting the data to the computer unit. In particular, the communication between the I / O devices and the interface computer unit may use a single data record containing both the first and second signals in a single data record.

[0043] At least one of the I / O devices and the interface computer unit may be battery operated to allow remote operation away from the power grid and to allow easy and quick installation without extensive power line wiring. The computer unit may be remotely located, for example, at a facility with easy access to power so it can be operated by power from the power grid rather than by batteries.

[0044] In particular, the first signal may represent temperature and the second signal may represent humidity, and the computer system (in particular, the computer unit) may be configured to provide a humidity identifier, which is an indication of humidity based on both the second signal and the first signal - that is, the second signal representing humidity can be corrected or adjusted based on the measured temperature indicated by the first signal.

[0045] This is particularly relevant, for example, when the humidity sensor is a capacitive sensor, where the conversion from capacitance to temperature is temperature dependent.

[0046] The computer system can be configured to use signals from at least one additional sensor to provide an indication of the condition of the coating, for example, via ER or EIS. To this end, the computer system can use a moisture identifier and temperature in combination with the ER or EIS signal to improve the indication of the condition.

[0047] At least one of the first and second sensors may include at least one electrode embedded in the coating. This may be used, for example, for temperature measurement, and embedding the electrode in the coating may improve the reading of the true temperature of the structure or coating. This may also be used for humidity measurement, thereby enabling measurement of humidity within the coating.

[0048] At least one of the first and second sensors may comprise at least one electrode located outside the coating. This may be particularly relevant if the first and second sensors are configured for determining external, environmental, physical properties such as temperature and / or relative humidity or air pressure, etc.

[0049] Both the first and second sensors can be integrated in a single component such as an integrated circuit (IC). For example, they can be connected in series or in parallel in the IC, and the IC can be embedded in the coating, or can be located outside the coating, for example, on the surface of the coating.

[0050] If the first and second sensors are implemented in an IC, this IC can additionally be configured to process the data. For example, the IC can perform pre-processing, such as filtering, on the signals before they enter the I / O device and the computer unit.

[0051] A part of the first communication channel, in particular the part connecting the first and second sensors, may be implemented in the IC. Furthermore, the IC may be directly attached to the I / O device, for example, plugged into a motherboard of the I / O device.

[0052] The system includes at least one additional sensor. The additional sensor may refer to another type of sensor that communicates with each channel of the I / O device through each communication channel.

[0053] In one example, the at least one additional sensor may include several sensors, such as a third, fourth, fifth, and sixth sensor, or even more sensors.

[0054] The third sensor is connected to the computer system via the second communication channel, and a fourth, fifth, sixth or more sensors may also be connected via the second communication channel, or they may be connected via separate third, fourth, fifth or sixth communication channels.

[0055] These sensors may be used to characterize corrosion for structural monitoring and / or characterize coating condition. At least one of the at least one additional sensor may be configured and used by ER to detect corrosion. At least one of the at least one additional sensor may be configured and used by EIS.

[0056] In one example, the at least one additional sensor may include a third sensor including at least one electrode embedded in the coating, and wherein the computer system is configured to use the signal from the third sensor in combination with the signals from the first and second sensors to provide an indication of the condition. In this case, the indication is provided at least in part by ER or EIS and at least in part by the physical properties determined by the first and second sensors.

[0057] The signal from the third sensor may in particular represent an EIS signal indicative of coating degradation.

[0058] ER or EIS sensors can be used to indicate corrosion, degradation or damage of the structure or coating, while physical properties can be used for verification purposes. In one example, poor coating condition can be caused by high temperature and humidity that shorten the useful life of the coating.

[0059] The output from the electrodes is usually temperature dependent. In particular, the measurement of impedance is temperature dependent and may also depend on humidity, etc. In addition, several environmental parameters indicate degradation. Incident sunlight, corrosive gases, rainfall, humidity and temperature all affect the rate of degradation or corrosion of a structure or coating.

[0060] Thus, the computer system may be configured to use the signal from the sensor in combination with the signals from the first and second sensors to provide an indication of the condition of the component through ER or EIS combined with environmental parameters such as temperature and humidity.

[0061] The third sensor may be connected to the computer system via the first communication channel or via a separate second communication channel.

[0062] The computer system can be configured to apply an AC signal and a first electrical signal within a certain frequency range (frequency sweep), and the second electrical signal can be a response signal caused by the applied AC signal. The first electrical signal and the second electrical signal are frequency-dependent, and therefore should be read in separate frequency domains accordingly. For example, the first and second signals can constitute part of the same sweep, whereby the two signals are transmitted substantially simultaneously, with at least a time delay equivalent to the duration of a single frequency sweep, and the typical range of frequencies is between 0.1 Hz and 100 kHz. In the example of 0.1-100 kHz, a total of 6 decades of frequency sweeps (3-5 points per decade) produce 18-30 specific frequencies of interest in each sweep, which can be used to identify signals from specific sensors in the two sensors.

[0063] The above mentioned data record transferred from the I / O device to the computer unit may in particular be a response from a sweep, referred to herein as a spectrum.

[0064] The computer system, in particular the computer unit, may be configured to distinguish signals propagated through the first communication channel by distinguishing at least one of a resistive, capacitive or inductive component having a frequency dependency, for example, the distinction being performed during or subsequently to application of an AC signal within a certain frequency range (e.g., when the computer unit receives the signal). The AC signal may be defined by a current or a voltage, and the distinction of the at least one resistive, capacitive or inductive component may be performed in a single frequency sweep out of a plurality of frequency sweeps.

[0065] An AC signal can be defined in the form of a sine wave.

[0066] In addition to the first and second signals, the first communication channel may also transmit other signals to the computer system, for example for determining further environmental parameters, such as air pressure or tension in the structure.

[0067] The first electrical signal may have a first impedance characteristic that is the same as the impedance characteristic of a resistor, and the second electrical signal may have a second impedance characteristic that is the same as the impedance characteristic of a capacitor. In one embodiment, the temperature measurement is represented by an ohmic resistance, and the humidity measurement is represented by a capacitance. Both are derived from the measured impedance modulus and phase, or real and imaginary parts of the impedance.

[0068] As mentioned previously, while the first sensor may include at least one electrode embedded in the coating, the second sensor may not necessarily include any electrodes embedded in the coating. In one embodiment, the second sensor is applied to environmental characteristics that are not directly related to the condition of the coating, for example, parameters that may have an impact on degradation but do not describe the actual condition. Examples of such parameters include rainfall measurement and incident light measurement. In some embodiments, both the first and second sensors include electrodes located outside the coating, and as mentioned previously, they can be integrated into a single IC.

[0069] The first communication channel may be formed by an electric line and a plurality of sensors, wherein at least one combination of a first sensor and at least one second sensor is arranged at different positions on the same electric line.

[0070] The computer system can be configured to distinguish the impedance of each sensor of the multiple sensors at different locations from the impedance of other sensors at other locations by determining a fit of the impedance spectrum according to the equivalent circuit of the multiple sensors during a single frequency sweep in the multiple frequency sweeps and detecting the value of the impedance for each sensor and associating the impedance with the physical property.

[0071] Thus, the computer system may be configured to identify the signals from each sensor located at different lengths of the wire remote from the computer system so that the signals can be utilized individually. This will enable the computer system to determine not only the condition or failure or degradation of the structure or coating, but also indicate the location of the failure or degradation along the wire.

[0072] In a second aspect, the present disclosure provides a method of providing an indication of a status of a component, the method comprising:

[0073] - providing a first sensor configured to provide a first signal representative of a first physical characteristic;

[0074] - providing a second sensor configured to provide a second signal representative of a second physical characteristic;

[0075] - providing at least one additional sensor comprising at least one electrode embedded in the coating;

[0076] - providing a computer system comprising an I / O device having a plurality of separate channels and a computer unit communicating with the I / O device;

[0077] - transmitting a first electrical signal from a first sensor and a second electrical signal from a second sensor to one of a plurality of separate channels of an I / O device via a first communication channel, wherein the first electrical signal is transmitted in a first frequency domain of the first communication channel and the second electrical signal is transmitted in a second frequency domain of the first communication channel;

[0078] - transmitting an AC signal between the at least one additional sensor and another individual channel of the plurality of individual channels via the second communication channel, and

[0079] - Using the computer system and the first and second electrical signals in combination with a signal from at least one additional sensor to provide an indication of a condition of the component.

[0080] The computer system may be used to extract the first electrical signal and the second electrical signal into separate signals for use in combination to provide an indication of the condition of the component.

[0081] The functions of the system can be implemented using standard hardware circuits, using software programs and data in conjunction with appropriately programmed digital microprocessors or general purpose computers or cloud computers, and / or using application specific integrated circuit systems and / or using one or more digital signal processors. The software program instructions and data can be stored on a non-transitory computer readable storage medium or in the cloud, and when the instructions are executed by a computer or other suitable processor control, the computer or processor performs the functions associated with those instructions. Thus, the present disclosure includes software readable by a computer component for performing the method and thereby providing a system for sensing the condition of a component.

[0082] In a third aspect, the present disclosure provides a system for determining humidity, the system comprising at least one first sensor (5) configured to convert temperature into resistance, and at least one second sensor (6) configured to convert humidity into capacitance, the system further comprising a computer unit configured to receive signals from the first and second sensors, wherein the computer unit is configured to determine impedance, and determine a resistance corresponding to a real part of the impedance and a reactance corresponding to an imaginary part of the impedance based on the impedance, and wherein the computer unit is configured to derive temperature based on the resistance and derive humidity based on the reactance.

[0083] The computer unit may be configured to correct the humidity based on the temperature.

[0084] The system may be particularly useful in combination with EIS or ER sensing, where humidity and / or temperature may affect the EIS or ER results and the system may be used to correct the results. BRIEF DESCRIPTION OF THE DRAWINGS

[0085] The embodiments will be described in further detail below with reference to the accompanying drawings:

[0086] Figure 1 -3 illustrates a structure having a coating and an electrode embedded in and applied to the coating;

[0087] Figure 4 -9 shows the results of the experiment;

[0088] Fig.10 illustrates an example of electrodes constituting a sensor; and

[0089] Fig.11 A system including an interface computer is illustrated. DETAILED DESCRIPTION

[0090] The detailed description and specific examples, while indicating embodiments, are given by way of illustration only, since various changes and modifications within the scope of the claims will become apparent to those skilled in the art from this detailed description.

[0091] Figure 1 A system 1 for sensing a condition of a component is illustrated. The component comprises a structure 2 having a surface 3 covered by a coating 4.

[0092] The system comprises at least one first sensor 5 consisting of an electrode embedded in a coating. The first sensor 5 is configured to convert a first physical property into a first electrical signal.

[0093] The system further comprises at least one second sensor 6 constituted by an electrode embedded in the coating. The second sensor is configured to convert the second physical property into a second electrical signal.

[0094] The system comprises a computer system comprising a computer unit 7 and an I / O device 8. The computer system communicates with the sensors via a first communication channel constituted by wires 9 connecting the first and second sensors to the computer system. The I / O device handles inputs and outputs and is implemented by a combined multiplexer and potentiostat inserted between the computer unit 7 and the sensors 5, 6.

[0095] The multiplexer and potentiostat communicate AC signals with the sensor by inducing the signal into the sensor and reading the output signal from the sensor. The I / O energizes the wire 9 and transmits the response signal received from the wire 9 to the computer unit 7 as a data record in a data string.

[0096] For example, the I / O device may be configured for an AC output signal with a frequency of 10 μHz to 1 MHz, such as between 0.1 Hz and 200 kHz. The I / O device may be configured for a current range of 100 pA to 100 mA and a potential range of ±2 V, such as a typical range of 10 mV to 1 V, with a default value of 50 mV.

[0097] To enable communication between two or more sensors using only a single communication channel, the communication is based on a first frequency domain of a first communication channel and a second frequency domain of the first communication channel, each frequency domain being used for transmitting signals with a specific sensor.

[0098] As shown, it can be wired to the electrodes of the sensor - alternatively, it can communicate with the electrodes wirelessly. Wireless communication enables the sensor to be fully embedded in the coating, providing a more robust system while still taking advantage of using only a single communication channel, thus simplifying communications.

[0099] The I / O device 8 communicates electrical signals with the computer unit 7, and the computer unit is configured to derive the condition of the coating, the condition of the structure or the condition of the interface between the structure and the coating, ie the condition of the component, from the electrical signals from the sensors.

[0100] The I / O device 8 may transmit the response signal or a signal derivable from the response signal to the computer unit 7, and it may include internal storage to allow intermittent communication with the computer unit 7. By including internal storage, the local CPU unit further defines a data logger that can log data from the sensor. Data logging may also be performed in a separate computer unit between the I / O device and the computer unit 7. As an alternative to or in combination with the local computer unit 7 shown, cloud computing and / or cloud data storage may be used for processing and data storage.

[0101] The I / O device may include, for example, PalmSens 4 TM Or a potentiostat / galvanostat CS350 from Corrtest Instruments or similar commercially available potentiostats, galvanostats or similar impedance analysis equipment. In addition, it may include a multiplexer to share signals between multiple groups of electrodes. Another available potentiostat may be the Ivium PocketSTAT2 from Ivium Technologies. Alternatively, a proprietary custom potentiostat and multiplexer unit may be implemented, for example, including an integrated communication module (LoRa) and powered by a battery, for example.

[0102] The I / O device has a plurality of individual I / O channels 12, and the first communication channel 9 is attached to one of these individual channels.

[0103] The system comprises an additional sensor 10 comprising electrodes embedded in the coating and connected to a separate one of the I / O channels 12 via a separate communication channel 13 .

[0104] The computer unit 7, for example in the form of a local computer unit and / or a cloud computer, is configured to further process the response signals, to present results based on the response signals, or to collect and optionally compare and / or present response signals from a plurality of I / O devices, each of which is connected to two or more modes via bus-wiring. The computer system also includes a data logger for collecting the collected data.

[0105] Based on the response signal, two different output signals are determined at different positions of the frequency sweep.

[0106] During the frequency sweep, a set of response signals is obtained for multiple frequencies, the set of response signals including impedance modulus and phase angle. The impedance modulus including real and imaginary parts can also be defined as:

[0107]

[0108] Where R is the resistance and corresponds to the real part of the impedance, and X is the reactance and corresponds to the imaginary part of the impedance. The relationship between resistance and reactance can be expressed through the phase angle The expression is as follows:

[0109]

[0110] Resistance and reactance can be described accordingly:

[0111]

[0112] For a resistor-based sensor, the impedance will be purely resistive, exhibit no phase shift (0°), and the impedance will be independent of frequency.

[0113] For a capacitance based sensor, the impedance will be purely reactive, exhibiting a 90° phase shift, and the impedance is inversely proportional to the applied signal frequency.

[0114] For a combination of resistor and capacitor based sensors connected in series or parallel, a frequency sweep will provide a set of impedance and phase values ​​that are frequency dependent. In this case, a phase angle versus frequency plot can be used as an indication of the frequency domain where the capacitive and resistive impedances dominate. Analyzing the resistance (real part of the impedance) and reactance (imaginary part of the impedance) in the corresponding frequency domain where the impedance of a particular sensor in the circuit dominates will allow differentiation of the resistance and capacitance corresponding to a particular environmental sensor in a single frequency sweep using a single communication channel.

[0115] Alternatively, the resistance and reactance of the circuit can be determined using conventional equivalent circuit analysis and fitting. More information on equivalent circuit fitting can be found elsewhere, see Kittel et al., Progress in Organic Coatings (2001), 41: 93-98; Su et al., Corrosion Science (2008), 50: 2381-2389.

[0116] Figure 2 An embodiment is illustrated that also includes a fourth sensor 14, which includes at least one electrode embedded in the coating. The computer system is configured to use the signal from the third sensor in combination with the signal from the first and second sensors to provide an indication of the condition. In this case, the indication is provided at least in part by EIS or ER and at least in part by physical parameters. One of the electrodes 5 is directly attached to the surface of the structure under the coating. The other sensors 6, 10 and 14 each include an electrode embedded in the coating, that is, in contact with the coating on all surfaces.

[0117] Figure 3a An embodiment is illustrated in which one of the sensors 5 comprises an electrode located outside the coating, in this example attached to the surface of the coating, while the other sensors 6 and 10 each comprise an electrode embedded in the coating. The two sensors 5 and 6 communicate on a common communication channel 9.

[0118] Figure 3b An embodiment is illustrated in which a first communication channel is connected to a first sensor 5 and a second sensor 11 located outside the coating, while a second communication channel is connected to other sensors 6 and 10 consisting of electrodes embedded in the coating. The sensors consisting of non-embedded electrodes can, for example, determine humidity and temperature outside the coating, while the sensors consisting of embedded electrodes can be EIS or ER sensors and determine the condition of the coating and / or the underlying structure.

[0119] If the first signal represents temperature and the second signal represents humidity, the computer system may be configured to provide a humidity identifier based on both the second signal and the first signal.

[0120] Table 1 below provides an example of a specific capacitive humidity sensor with a nominal capacitance of 300pF ± 40pF (at 30% RH and 23°C). The capacitance of the sensor depends on RH and its sensitivity is 0.45pF / %RH. The sensor capacitance also depends on temperature and must be corrected for to have an accurate RH reading. The temperature dependency is further described as:

[0121] Δ%RH=(B1x%RH+B2)xT[℃]+(B3x%RH+B4), (5)

[0122] in

[0123] B1=0.0011[1 / ℃];

[0124] B2 = 0.0892 [% RH / °C];

[0125] B3=-0.0268;

[0126] B4 = -2.079 [%RH].

[0127] If no correction is performed, the Δ%RH described by equation (5) can be considered as an RH error.

[0128] Table 1 shows an example of RH error calculated using equation (5) as a function of T and for three RH levels, 20%, 40% and 60%.

[0129]

[0130]

[0131] Table 1: Example of T correction for RH readings. Both sensors can be read using a single channel.

[0132] Figure 4 Example showing impedance vs. frequency response

[0133] a. For a single resistor, and

[0134] b. For a single capacitor

[0135] These components may represent physical sensors used, for example, for temperature and humidity sensing.Area 40 in the graph indicates an exemplary range in which impedance may vary with changes in the sensed parameter.

[0136] The frequency dependence of the impedance of resistors and capacitors is described as follows:

[0137] Z(f)=R1 (1)

[0138]

[0139] As from Figure 4 As can be seen from equations (6) and (7), the impedance of a resistor is independent of frequency, while the impedance of a capacitor decreases with frequency. Assuming that two components are connected in series or in parallel in a circuit, the corresponding impedance can be determined in different frequency domains. Figure 5 and Figure 6 Visualization.

[0140] Figure 5is the Bode plot of a 1nF capacitor connected in series with a 50kOhm resistor, and Figure 6 Here is the Bode plot of a 1nF capacitor connected in parallel with a 50kOhm resistor.

[0141] exist Figure 5 , an upward arrow 50 indicates a decrease in capacitance and a downward arrow 51 indicates an increase in capacitance. An upward arrow 52 indicates an increase in resistance and a downward arrow 53 indicates a decrease in resistance. A leftward arrow 54 indicates an increase in capacitance and / or resistance, and a rightward arrow 55 indicates a decrease in capacitance and / or resistance.

[0142] exist Figure 6 , an upward arrow 60 indicates a decrease in capacitance and a downward arrow 61 indicates an increase in capacitance. An upward arrow 62 indicates an increase in resistance and a downward arrow 63 indicates a decrease in resistance. A leftward arrow 64 indicates an increase in capacitance and / or resistance, and a rightward arrow 65 indicates a decrease in capacitance and / or resistance.

[0143] exist Figure 5 and Figure 6 middle:

[0144] a. Impedance modulus vs. frequency

[0145] b. Phase and frequency

[0146] The following equations 8 and 9 describe the frequency dependence of the impedance of a capacitor connected in series and in parallel with a resistor, respectively:

[0147]

[0148] According to Figure 3 and Figure 4 In the visualization, by changing the values ​​of resistors and capacitors connected in series or parallel in a circuit, a corresponding change in the frequency domain occurs in which the impedance of each component dominates.

[0149] This is Figure 5 and Figure 6 A change in the resistance or capacitance of a sensor shifts both the impedance and the frequency range in which the corresponding value can be read.

[0150] Based on this concept, the value of each resistor and capacitor connected either in series or in parallel to a single channel can be customized so that the two parameters can be distinguished in a single frequency sweep when the corresponding resistance and capacitance values ​​are read over different frequency domains.

[0151] For example, for a series connection of R and C, with Figure 5As shown in the graph in Figure 1, increasing the resistor value shifts the frequency domain where the resistive impedance dominates towards lower frequencies, while reducing the resistance to 100Ohm shifts the frequency domain towards higher frequencies, making it almost undetectable within a given frequency range of the spectrum. A similar effect can be achieved by changing the capacitor value.

[0152] Customization of the resistance or capacitance values ​​(each value may correspond to a physical sensor) may enable measurement of a combination of sensors within a single impedance sweep. Based on this concept, a multi-parameter sensing system may be used using only a single measurement channel (referred to herein as the first communication channel).

[0153] Examples of such systems with sensors including embedded electrodes are:

[0154] · Series connection of coating degradation sensor (parallel RC) + temperature sensor (R)

[0155] Series connection of coating degradation sensor (parallel RC) + crack / mechanical damage sensor (R)

[0156] Series connection of coating degradation sensor (parallel RC) + corrosion sensor (R) An example of such a system with external sensors (i.e. electrodes not embedded in the coating) is:

[0157] · Humidity sensor (C) + temperature sensor (R) connected in parallel and in series

[0158] · Parallel connection of pressure sensor (C) + temperature sensor (R)

[0159] · Humidity / gas sensor (C) + corrosion sensor (R) connected in parallel or in series

[0160] This approach is not limited to the examples provided above, and can also be used with various conventional sensor types that have R, C, or L dependencies on the sensed parameter.

[0161] experiment

[0162] The concept was demonstrated on an in-house fabricated temperature and relative humidity probe (T / RH dual sensor), where a commercial T sensor with a positive temperature coefficient and a nominal resistance of 10 kOhm was connected in series with a commercial capacitive humidity sensor with a nominal resistance of 300 pF.

[0163] The RH sensor is the MK33-W from Innovative Sensor Technology IST AG with a nominal capacitance of 300pF±40pF.

[0164] The temperature sensor is a Texas Instruments TMP61-Q1 thermistor with a nominal resistance of 10kOhm and packaged in a TO-92S. As an alternative to the thermistor used in this example, a resistance temperature detector (RTD) with a nominal resistance of 10kOhm could be used. This would further improve the accuracy and extend the service temperature range of the sensor.

[0165] Both sensors are used at temperatures up to 200 degrees Celsius, making them suitable for monitoring T and RH conditions in different applications, especially coating under insulation, or CUI for short (for detecting corrosion under insulation).

[0166] Figure 7 is a diagram illustrating the actual sensor and housing being tested, and FIG. 8 illustrates temperature and relative humidity measurements obtained with a single channel dual sensor consisting of a 10 kOhm positive temperature coefficient thermistor and a 300 pF capacitive humidity sensor.

[0167] To verify the dual sensor concept, the assembled T / RH sensor was exposed to varying T and RH profiles and the impedance was continuously measured over a range of frequencies. The measurements consisting of multiple frequency sweeps (spectra) performed throughout the test are shown in Figure 9.

[0168] Figure 9a and Figure 9b 8 is the Bode plot of the dual T / RH sensor obtained throughout the test. The "RH readings" indicated by arrow 90 and the "T readings" indicated by arrow 91 in the graph indicate the corresponding frequency domains where the T and RH readings were taken to construct the graph shown in FIG8 .

[0169] exist Figure 8a and Figure 8b , temperature and relative humidity are shown on the ordinate Y axis, respectively. The direct relationship between the impedance in different frequency domains and the temperature and relative humidity as measured by two different sensors connected in series indicates the practical use of a single communication channel for communication.

[0170] Fig.10 The diagram illustrates electrode layouts considered for the first and second sensors. The depicted layout may represent: i) an EIS sensor for coating degradation + a resistance-based crack sensor or ER electrode connected in series, and ii) an electrode for the EIS sensor for coating degradation + a temperature sensor, both electrodes being embedded within the coating. The latter configuration may improve the accuracy of the embedded electrodes for estimating the coating condition, since the impedance has a strong dependence on temperature. Such a layout would also eliminate the need for a separate and externally mounted temperature sensor. Further layouts of electrodes for the sensors may be found in particular in WO2021 / 028480, for example, at Figure 10-1 4 in.

[0171] Fig.11 A setup is illustrated in which a battery powered I / O device 8 communicates electrical signals with a gateway 110. The gateway may be a LoRaWAN gateway that communicates with the battery powered I / O device and with a database, for example, a cloud based database 111. The computer unit 7 communicates with the database 111 and may read and visualize the electrical signals and may extract the first and second electrical signals as separate signals and use them in combination to provide an indication of the condition of the component.

[0172] The illustrated I / O device may, for example, have 8 input / output channels and may be configured to measure impedance over a certain frequency range. The I / O device may be ATEX certified and may be powered by non-rechargeable batteries. The charge consumption of the device determines the operating time of the device before the batteries must be replaced. The device consumes the charge stored in the battery during the following periods:

[0173] i) during measurements of sensors connected via a wired connection, and

[0174] ii) During data transmission via LoRaWAN gateway.

[0175] The charge consumed during the measurement depends on the frequency and the total number of frequencies per impedance spectrum. Lower frequencies require longer measurement times and therefore consume more charge (mAh) over time, see Table 3:

[0176] The charge consumption during data transmission depends on the propagation factor, which is associated with the transmission power and transmission speed determined by the network conditions between the I / O device and the LoRaWAN gateway.

[0177] Tables 1 and 2 below illustrate the measurement costs for different frequency ranges in the spectrum, and the transmission costs for different spreading factors SF, respectively.

[0178] Range [Hz] Time[s] Current [mA] Charge [mAh] 0.3125-0.6249 66 15 0,275 0.625-1.249 33 15 0,1375 1.25-2.49 22,3 15 0,09292 2.5-4.99 11,3 15 0,04708 5-1023 3,5 15 0,01458 1024-250000 0,45 15 0,00188

[0179] Table 2: Measurement costs shown for different frequencies of impedance spectroscopy.

[0180]

[0181]

[0182] Table 3: Transmission costs shown for various spreading factors.

[0183] Example of charge consumption

[0184] The following example illustrates the charge consumption and savings gained by using the first communication channel to communicate with both the first and second sensors. The example is based on an 8-channel I / O device and Fig.11 The settings shown in .

[0185] The total charge consumption (current times time) of an I / O device is the sum of the charge used for measurement and the charge used for data transfer plus a small consumption when the device is inactive (approximately 0.006 mA times the total time).

[0186] For example, when all 8 channels of the I / O device are configured to acquire an impedance spectrum consisting of 16 frequencies, i.e., 100 kHz, 25 kHz, 12.5 kHz, 6.25 kHz, 3.125 kHz, 1.562 kHz, 780 Hz, 390 Hz, 190 Hz, 90 Hz, 40 Hz, 20 Hz, 10 Hz, 5 Hz, 1 Hz, the time required to complete the measurement of all frequencies once will take 575.6 seconds (calculated using the data shown in Table 1).

[0187] Assuming that the data is transmitted using a spreading factor of SF6, it will take 24.32 seconds to transmit the data (calculated using the data shown in Table 3).

[0188] The total charge required to measure all 8 channels of the I / O device and transfer data will be:

[0189]

[0190] This gives a charge consumption of 0.347mAh per channel. This is the battery saving that can be achieved when measuring several sensors in the case of a single channel of an I / O device.

[0191] For a total charge of 5200 mAh supplied by the battery, 1873 measurements and data transfers of all channels can be performed. If the same amount of information can be obtained using 7 channels instead of 8, 2140 measurements can be completed. Or alternatively, all 8 channels can be used, thus measuring more sensors with the same charge consumption. Since the device consumes a small amount of charge when inactive, the actual number of measurements will be slightly less, and for simplicity, it is not included in this example.

[0192] The above examples are for indicative purposes only. Regardless of the frequency of each spectrum measurement or the spreading factor used to transmit the data, reducing the number of channels required to measure the same number of sensors will result in savings in charge consumption, thereby extending the operating time of the I / O device.

[0193] An additional advantage of using a single channel for measurements of several sensors is the reduction of the data set in the database, which also reduces data processing time.

[0194] List of numbered embodiments

[0195] In another aspect, the present disclosure provides a system and method according to the following list of numbered embodiments.

[0196] 1. A system for sensing a condition of a component including a structure covered by a coating, the system comprising: at least one first sensor, the at least one first sensor being configured to convert a first physical characteristic into a first electrical signal; at least one second sensor, the at least one second sensor being configured to convert a second physical characteristic into a second electrical signal; a computer system; and a first communication channel, the first communication channel connecting the first sensor and the second sensor to the computer system, wherein the first electrical signal is transmitted in a first frequency domain of the first communication channel and the second electrical signal is transmitted in a second frequency domain of the first communication channel, and wherein the computer system is configured to extract the first electrical signal and the second electrical signal as separate signals and use the first electrical signal and the second electrical signal in combination to provide an indication of the condition of the component.

[0197] 2. The system of embodiment 1, wherein at least one of the first sensor and the second sensor comprises at least one electrode embedded in the coating.

[0198] 3. The system of embodiment 1, wherein at least one of the first sensor and the second sensor comprises at least one electrode located outside the coating.

[0199] 4. The system of embodiment 3, wherein the first sensor and the second sensor are integrated into a single component.

[0200] 5. The system of embodiment 4, wherein the single component is an integrated circuit (IC).

[0201] 6. The system of embodiment 5, wherein the first sensor and the second sensor are connected in series or in parallel in the IC.

[0202] 7. The system of any of embodiments 4-6, wherein the individual components are located outside of the coating.

[0203] 8. The system of embodiments 5-7, wherein the computer system is at least partially implemented in an integrated circuit.

[0204] 9. The system of embodiment 8, wherein the single communication channel is implemented entirely in an integrated circuit.

[0205] 10. The system of embodiments 5-9, wherein the first electrical signal is transmitted in a first frequency domain and the second electrical signal is transmitted in a second frequency domain over a single communication channel internal to the integrated circuit.

[0206] 11. A system according to any of the preceding embodiments, further comprising a third sensor comprising at least one electrode embedded in the coating, and wherein the computer system is configured to use a signal from the third sensor in combination with signals from the first sensor and the second sensor to provide an indication of a condition, the indication being provided at least in part by the EIS.

[0207] 12. The system of embodiment 11, wherein the third sensor is connected to the computer system via a second communication channel.

[0208] 13. The system of any of the preceding embodiments, wherein the computer system is configured to apply an AC signal within a frequency range in a plurality of frequency sweeps, and wherein the first electrical signal and the second electrical signal are comprised of a portion of the AC signal.

[0209] 14. A system according to embodiment 13, wherein the computer system is configured to distinguish signals propagating through the first communication channel by distinguishing at least one of resistive, capacitive, or inductive components having frequency dependence, the distinction being performed during application of an AC signal within a frequency range.

[0210] 15. The system of embodiment 14, wherein the AC signal is defined by current or voltage.

[0211] 16. The system of embodiment 14 or 15, wherein the differentiation of the at least one resistive, capacitive or inductive component is performed in a single frequency sweep.

[0212] 17. The system of any one of the preceding embodiments, comprising a fourth sensor connected to the computer system via the first communication channel or the further communication channel.

[0213] 18. The system of any one of the preceding embodiments, wherein the first electrical signal has a first impedance characteristic that is the same as an impedance characteristic of a resistor, and the second electrical signal has a second impedance characteristic that is the same as an impedance characteristic of a capacitor.

[0214] 19. A system according to any of the preceding embodiments, wherein at least one of the first sensor and the second sensor includes at least one electrode located outside the coating, and the second signal from the electrode represents a physical property not directly related to the condition of the coating, such as an environmental condition, such as temperature.

[0215] 20. A system according to any of embodiments 18-19, wherein a single communication channel is formed by a wire, and wherein the multiple sensors have at least one combination of a first sensor and at least one second sensor arranged at different locations on the same wire, and wherein the computer system is configured to distinguish the impedance of each of the multiple sensors at different locations from the impedance of other sensors at other locations by determining an impedance spectrum fit according to an equivalent circuit of the multiple sensors during a single frequency sweep in the multiple frequency sweeps and detecting an impedance value for each sensor and associating the impedance with a physical property.

[0216] 21. The system of any one of the preceding embodiments, wherein at least one of the first sensor and the second sensor comprises at least one electrode attached to the structure.

[0217] 22. The system of claim 21, wherein the at least one electrode attached to the structure is attached beneath a coating.

[0218] 23. A method of transmitting at least a first electrical signal from a first sensor and a second electrical signal from a second sensor to a computer system of a system for sensing a condition of a component of a structure covered by a coating, the method comprising transmitting the first electrical signal in a first frequency domain of a first communication channel and transmitting the second electrical signal in a second frequency domain of the first communication channel, and using the computer system to extract the first electrical signal and the second electrical signal as separate signals for combined use to provide an indication of the condition of the component.

[0219] 24. The method of embodiment 23, wherein the first sensor consists of a coating degradation sensor providing a signal that is considered a parallel resistor / capacitor coupling, and the second sensor consists of a temperature sensor providing a signal that is considered a resistor.

[0220] 25. The method of embodiment 23, wherein the first sensor consists of a coating degradation sensor providing a signal that is viewed as a parallel resistor / capacitor coupling, and the second sensor consists of a crack / mechanical damage or ER sensor providing a signal that is viewed as a resistor.

[0221] 26. The method of embodiment 23, wherein the first sensor is comprised of a coating degradation sensor that provides a signal that is viewed as a parallel resistor / capacitor coupling, and the second sensor is comprised of a corrosion sensor that provides a signal that is viewed as a resistor.

[0222] 27. The method according to embodiment 23, wherein the first sensor is constituted by a humidity sensor providing a signal interpreted as a capacitance, and the second sensor is constituted by a temperature sensor providing a signal interpreted as a resistance.

[0223] 28. The method according to embodiment 23, wherein the first sensor is constituted by a pressure sensor providing a signal regarded as a capacitance, and the second sensor is constituted by a temperature sensor providing a signal regarded as a resistance.

[0224] 29. The method of embodiment 23, wherein the first sensor is constituted by a pressure / gas sensor providing a signal interpreted as a capacitance, and the second sensor is constituted by a corrosion sensor providing a signal interpreted as a resistance.

Claims

1. A system (1) for sensing a condition of a component, the component comprising a structure (2) covered by a coating (4), the system comprising: at least one first sensor (5), the at least one first sensor (5) being configured to convert a first physical characteristic into a first electrical signal; at least one second sensor (6), the at least one second sensor (6) being configured to convert a second physical property into a second electrical signal; at least one additional sensor (10), the at least one additional sensor (10) comprising at least one electrode embedded in the coating and configured to provide at least one additional signal; and a computer system comprising an I / O device (8) having a plurality of separate channels and a computer unit (7) communicating with the I / O device, wherein: - the first sensor and the second sensor are connected to one of the individual channels via the first communication channel (9), and the additional sensor is connected to the other of the individual channels via the second communication channel (13), so that the I / O device can communicate AC signals with the first sensor and the second sensor via the first communication channel and with the additional sensor via the second communication channel, and - The first electrical signal is transmitted in a first frequency domain of a first communication channel and the second electrical signal is transmitted in a second frequency domain of the first communication channel.

2. The system of claim 1, wherein the computer system is configured to extract the first electrical signal and the second electrical signal as separate signals and use them in combination to provide an indication of the condition of the component. 3 . The system of claim 2 , wherein the computer system is configured to use the first signal and the second signal in combination with the at least one additional signal to provide an indication of a condition of the component.

4. A system according to any of the preceding claims, wherein the I / O device is configured to transmit a data string with the computer unit (7), wherein the data string comprises a data record for each individual channel and wherein the first electrical signal and the second electrical signal are transmitted in a single data record.

5. A system according to claim 4, wherein the data record is a frequency swept spectrum.

6. A system according to claim 4 or 5, wherein the computer unit (7) is configured to receive the single data string and perform extraction of the first electrical signal and the second electrical signal as separate signals and use the first electrical signal and the second electrical signal in combination to provide an indication of the condition of the component.

7. System according to any of the preceding claims, wherein the I / O devices are battery operated and the computer unit (7) is operated by electricity from the grid.

8. A system according to any preceding claim, wherein the first signal represents temperature and the second signal represents humidity, and the computer system is configured to provide a humidity identifier based on both the second signal and the first signal.

9. A system according to any preceding claim, wherein the computer system is configured to use the signal from the at least one additional sensor to provide an indication of the condition of the coating by EIS.

10. The system according to claims 8 and 9, wherein the indication is based on a humidity identifier and a temperature.

11. The system of any of the preceding claims, wherein at least one of the first sensor and the second sensor comprises at least one electrode embedded in the coating.

12. The system of any of the preceding claims, wherein at least one of the first sensor and the second sensor comprises at least one electrode located external to the coating.

13. The system of any of the preceding claims, wherein the first sensor and the second sensor are integrated into a single component.

14. The system of claim 13, wherein the single component is an integrated circuit (IC).

15. The system of claim 14, wherein the first sensor and the second sensor are connected in series or in parallel in the IC.

16. The system of any of claims 13-15, wherein the individual components are located external to the coating.

17. The system of any of the preceding embodiments, wherein the computer system is configured to apply an AC signal within a frequency range applied in a plurality of frequency sweeps, and wherein the first electrical signal and the second electrical signal are included in a response from the AC signal.

18. The system of claim 17, wherein the computer system is configured to distinguish signals propagating through the first communication channel by distinguishing at least one of resistive components, capacitive components, or inductive components having a frequency dependency.

19. A system according to claim 17 or 18, wherein differentiation of at least one resistive component, capacitive component or inductive component is performed on a signal representing a single frequency sweep.

20. The system of any of the preceding claims, wherein the first electrical signal has a first impedance characteristic that is the same as an impedance characteristic of a resistor, and the second electrical signal has a second impedance characteristic that is the same as an impedance characteristic of a capacitor.

21. The system according to any of the preceding claims, comprising a plurality of sensors including several combinations of first sensors and second sensors arranged at different locations along the first communication channel.

22. The system of claims 17 and 21, wherein the computer system is configured to differentiate the impedance of each of the plurality of sensors at different locations from the impedance of other sensors at other locations by determining an impedance spectrum fit according to an equivalent circuit of the plurality of sensors during a single frequency sweep in the plurality of frequency sweeps and detecting a value of impedance for each sensor and associating the impedance with a physical property.

23. A method of providing an indication of a condition of a component, the component comprising a structure covered by a coating, the method comprising: - providing a first sensor, the first sensor being configured to provide a first signal representative of a first physical characteristic; - providing a second sensor, the second sensor being configured to provide a second signal representative of a second physical characteristic; - providing at least one additional sensor comprising at least one electrode embedded in the coating; - providing a computer system comprising an I / O device having a plurality of separate channels and a computer unit (7) communicating with the I / O device; - transmitting a first electrical signal from a first sensor and a second electrical signal from a second sensor to one of the plurality of separate channels of the I / O device via a first communication channel, wherein the first electrical signal is transmitted in a first frequency domain of the first communication channel and the second electrical signal is transmitted in a second frequency domain of the first communication channel; - transmitting an AC signal between the at least one additional sensor and another individual channel of the plurality of individual channels via a second communication channel, and - using the computer system and the first and second electrical signals combined with the signal from the at least one additional sensor to provide an indication of a condition of the component.

24. A method according to claim 23, comprising using a computer unit (7) to extract the first and second electrical signals as separate signals for use in combination with signals from additional sensors to provide an indication of the condition of the component.

25. A method according to claim 23 or 24, wherein the first electrical signal is taken as a signal from a parallel resistor / capacitor coupling and this signal is used to determine coating degradation, humidity, pressure or gas content.

26. The method according to any of claims 23-25, wherein the second signal is regarded as a signal from a resistor and applied to determine temperature, cracks / mechanical damage or corrosion.

27. A system for determining humidity, the system comprising at least one first sensor (5) configured to convert temperature into resistance and at least one second sensor (6) configured to convert humidity into capacitance, the system further comprising a computer unit (7) configured to receive signals from the first sensor and the second sensor, wherein the computer unit is configured to determine impedance from the signals and to determine from the impedance a resistance corresponding to the real part of the impedance and a reactance corresponding to the imaginary part of the impedance, and wherein the computer unit is configured to derive temperature from the resistance and humidity from the reactance.

28. The system of claim 27, wherein the computer unit is configured to correct humidity based on temperature.

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