Sensors and Systems

Abstract

To provide a thermocouple sensor which requires a smaller number of connecting wires.SOLUTION: Provided is a sensor 100 comprising: a metal body 101: a thin film laminate 102, which is formed on at least a part of a surface of a metal body, and comprises: an electric insulation film 103; a metal film on the electric insulation film, where a first electric conductor 104 is defined on the metal film, the metal film is formed of a metal alloy different from the metal body, the first electric conductor is electrically insulated from the metal body using the electric insulation film, and the first electric conductor comprises: a connection point 108 connected to a first terminal W0 via a conductor wire at a first end part 106; and a sensor structure 110 defined in the metal film at a second end part 107, which is a sensor structure comprising a contact point 105 of the metal film, which penetrates the electric insulation film up to the metal body, and whereby, a thermocouple is formed.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to the field of sensors, and more particularly to the field of thin film sensors on metal substrates. [Background technology]

[0002] Within the art of temperature measurement, there are two main types of temperature sensors. The first type of temperature sensor is a resistive type where the change in resistance of a material is related to temperature using tabulated data or a mathematical model. The second type of temperature sensor is a thermocouple, which involves sensing a small voltage generated at the junction between two dissimilar metals by the Seebeck effect. This small voltage is then used with tabulated data or a mathematical formula to derive the measured temperature. A typical sensor of the first type is the PT-100 sensor, which is a platinum wire placed on a ceramic substrate. An example of the second type is the K-type thermocouple, which uses a welded junction between a chromel wire and an alumel wire as the temperature sensor, to which a very precise voltmeter is connected, and the measured voltage is then used to determine the sensed temperature using either tabulated data or a mathematical model.

[0003] Both types of sensors use at least two conductors for connection to the signal conditioning electronics, which can result in multiple conductors to be routed and connected, especially if several sensors are used.

[0004] In strain gauge measurements, a bridge configuration is often used to mitigate the temperature effects on the strain gauge. In practice, this solution uses a first strain gauge that is configured to sense the strain on the specimen, and a second strain gauge is placed so that it experiences the same temperature as the first strain gauge, but without strain. In this way, if the first and second strain gauges are placed in a first branch of a bridge, the bridge becomes temperature compensated. If it is not possible to place the second strain gauge on the specimen so that it is strain-free, the strain measured by the first strain gauge must be compensated by subtracting the strain caused by the thermal expansion of the sensor and the strain caused by the resistance change due to temperature change. By knowing the temperature of the strain gauge precisely, the contributions of these strains can be calculated and subtracted. Thus, it is very important to be able to measure the temperature of the strain gauge precisely, but in practice this can be very difficult, because the strain gauges are often very small and it is very difficult to place a temperature sensor close to the sensing wire of the strain gauge. There is therefore a great interest in temperature sensors that can be incorporated into the strain sensors.

[0005] Therefore, there is great interest in reducing the number of conductors used to connect sensors.

[0006] There is also great interest in a temperature sensor that can be integrated into the strain sensor with a small number of connecting wires.It is an aspect of the present disclosure to provide a solution that eliminates or mitigates at least the problems disclosed above.

[0007] It is a further aspect of the present disclosure to provide an improved sensor. Summary of the Invention

[0008] The present disclosure therefore provides sensors that require fewer connecting wires. Additionally, the present disclosure also provides sensors with fewer connecting wires that can be incorporated into strain sensors.

[0009] The present disclosure thus relates to a sensor comprising a metal object; a thin film stack formed on at least a portion of a surface of the metal object, the thin film stack comprising an electrically insulating film; a metal film on the electrically insulating film, a first electrical conductor defined in the metal film, the metal film being composed of a metal alloy different from the metal object, the first electrical conductor being electrically insulated from the metal object using the electrically insulating film, the first electrical conductor comprising a connection point at a first end connected to a first terminal via a conductive wire; and a sensor structure defined in the metal film at a second end, the sensor structure comprising a junction of the metal film that penetrates the electrically insulating film to the metal object, such that a thermocouple is formed; and a metal object terminal connected to the connection point of the metal object via a conductive wire, the metal object terminal being configured such that the connection point of the first electrical conductor and the connection point of the metal object are adjacent to each other and are in an isothermal relationship with each other.

[0010] The sensor defined above or below may further comprise a second electrical conductor defined in the metal film, the second electrical conductor having a connection point at a first end, the sensor region further comprising a strain sensitive portion between the first end and the second end, the sensor region configured to change resistance in response to an applied mechanical strain of the metal object, the first end of the strain sensitive portion connected to the first electrical conductor, the second end of the strain sensitive portion connected to the second electrical conductor, and the contact configured to sense a temperature of the strain sensitive portion.

[0011] The contacts of the sensors defined above or below may be formed in the strain sensitive portion.

[0012] The metal objects referred to herein may be metal tubes or metal strips.

[0013] The metal films described herein may be selected from metals or metal alloys, for example, but not limited to nickel-chromium alloys.

[0014] By the phrase "the metal film is composed of a different metal alloy than the metal body," it is meant that the metal or metal alloy from which the metal body or metal film is composed must not have the same range of all alloying elements contained therein, since the composition of the alloy must be different in order to integrate a working thermocouple sensor.

[0015] According to the present invention, only one metal material is required to form the thermocouple sensor because the object itself is metallic and therefore only one additional metal material is required to form the thermocouple.

[0016] The electrical insulating film described herein may be selected from metal oxides or metal nitrides, which allows for the selection of an electrical insulating film with a similar heat capacity as the metal object, thereby allowing for a minimum temperature difference between the surface of the metal object and the electrical insulating film.

[0017] The present disclosure also relates to a sensor system for sensing strain and temperature of a metal object, comprising: a sensor according to embodiments disclosed herein; a cold junction temperature detector configured to detect an isothermal temperature of a junction of a first electrical conductor and the metal object; a temperature circuit connected to the first terminal and to the metal object terminal and configured to measure a temperature of the junction, the temperature circuit further connected to the cold junction temperature detector to compensate for the cold junction temperature of the junction; a strain circuit connected to the first terminal and to the second terminal to determine a strain based on a change in resistance of the strain sensitive portion; and a calculation circuit connected to the temperature circuit and to the strain circuit, the calculation circuit configured to determine a strain caused by mechanical strain on the metal object and a temperature induced strain of the metal object.

[0018] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. [Brief description of the drawings]

[0019] [Figure 1] FIG. 2 is a three-dimensional view of a sensor according to one embodiment of the present disclosure. [Diagram 2] 2 is a cross-sectional view taken along line AA' of FIG. 1, disclosing a cross-section of a sensor according to the embodiment disclosed in FIG. 1. [Diagram 3] FIG. 2 is a three-dimensional view of a sensor according to one embodiment of the present disclosure. [Figure 4] 4 is a cross-sectional view taken along line AA' of FIG. 3, disclosing a cross-section of a sensor according to the embodiment disclosed in FIG. 3. [Diagram 5] FIG. 1 is a schematic block diagram of a system according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] FIG. 1 illustrates a metal object 101, a thin film stack 102 formed on at least a portion of a surface of the metal object, an electrically insulating film 103, and a metal film on the electrically insulating film, the metal film defining a first electrical conductor 104, the metal film being composed of a metal alloy different from that of the metal object, the first electrical conductor 104 being electrically insulated from the metal object 101 using the electrically insulating film 103, the first electrical conductor 104 having a connection point 108 at a first end 106 connected to a first terminal W0 via a wire, and a connection point 108 at a second end 107 connected to a gold alloy terminal W0. 1 illustrates a sensor, generally designated 100, comprising a thin film stack comprising a metal film, a sensor structure 110 defined in the metal film, the sensor structure comprising a junction 105 of the metal film penetrating the electrically insulating film to the metal object so that a thermocouple is formed, and a metal object terminal W1 connected to a connection point 109 of the metal object via a conductor, the connection point 108 of the first electrical conductor and the connection point 109 of the metal object being configured to be adjacent to each other and in an isothermal relationship with each other. Because the junction is close to the interior of the tube, the junction 105 will be able to measure the process temperature inside the tube in a very accurate manner, and thus the junction will be affected only by the thermal gradient governed by the thickness of the tube wall and not by the thermal conductivity of the electrically insulating layer.

[0021] The connection point 108 of the first electrical conductor and the connection point 109 of the metal object have the same temperature due to their isothermal relationship. This means that if the temperature of the connection point is measured, cold junction compensation can be performed by subtracting the temperature of the connection point from the measured temperature to calculate the temperature of the junction 105. In addition to placing the connection points as close to each other as possible to achieve an isothermal relationship, some insulation may be required.

[0022] FIG. 2 discloses a cross-sectional view of the sensor structure 110 along line A-A' in FIG. 1. FIG. 2 illustrates a metal object 101 on which a thin film stack 102 is formed. The thin film stack comprises an electrically insulating film 103, preferably a metal oxide or metal nitride. A metal film 104 is formed on the electrically insulating film 103 and at a junction 105 the metal film penetrates the electrically insulating film and contacts the metal object. The metal film may be a nickel-chromium alloy. A thermocouple is thus formed between the metal object and the metal film. A connector for the thermocouple is formed by the first electrical conductor and the metal object.

[0023] In Fig. 1, the metal object is a metal tube onto which the thin film stack 102 is directly formed, for example using thermal spraying, evaporation or sputtering. This means that the thin film stack will adhere to the metal object without the use of adhesives. To facilitate adhesion of the thin film stack, the surface of the metal object may have to be roughened. This roughening may be done, for example, using a sandblaster or grinding.

[0024] FIG. 3 discloses an embodiment of a sensor 300 . The sensor comprises a metal object 301, a thin film stack 302 formed on at least a portion of a surface of the metal object, the thin film stack comprising: an electrically insulating film 303; a metal film on the electrically insulating film, a first electrical conductor 304 defined in the metal film, the metal film being composed of a metal alloy different from the metal object, the first electrical conductor being electrically insulated from the metal object using the electrically insulating film, the first electrical conductor comprising a connection point 308 connected at a first end 306 to a first terminal W0 via a conductor; and a sensor structure 310 defined in the metal film at a second end 307, the sensor structure comprising a junction 305 of the metal film that penetrates the electrically insulating film to the metal object such that a thermocouple is formed; and a metal object terminal W1 connected to the connection point 309 of the metal object via a conductor, the metal object terminal being configured such that the connection point 308 of the first electrical conductor and the connection point 309 of the metal object are adjacent to each other and are in an isothermal relationship with each other.

[0025] The sensor 300 disclosed in FIG. 3 differs from the embodiment disclosed with reference to FIG. 1 in that the sensor also comprises a second electrical conductor 311 defined in the metal film and having a connection point 312 at the first end 306, and in that the sensor area 310 further comprises a strain sensitive portion between the first end 314 and the second end 313, the sensor area 310 being configured to change resistance in response to an applied mechanical strain of the metal object 301, the first end 314 of the strain sensitive portion being connected to the first electrical conductor 304, the second end 313 of the strain sensitive portion being connected to the second electrical conductor 311, and the contact 305 being configured to sense the temperature of the strain sensitive portion.

[0026] FIG. 4 discloses a cross-sectional view of the sensor structure 310 along the line A-A' in FIG. 3. The cross-sectional view in FIG. 4 illustrates the sensor structure 310, which comprises a first strain-sensitive conductor 401 defined in the metal film. The first strain-sensitive conductor 401 is connected to a first end 314. The sensor structure 310 further comprises a second strain-sensitive conductor 402 connected to a second end 313. The sensor structure further comprises a third strain-sensitive conductor 403 connected to the first and second strain-sensitive conductors 401, 402. The third strain-sensitive conductor 403 is also defined by the metal film and penetrates the electrically insulating film at a contact 305 between the metal film and the metal object. This contact 305 may be formed by laser etching. The contact 305 is thus formed in the strain-sensitive portion.

[0027] The metal object is a metal tube or a metal strip.

[0028] The metal film may be selected from a nickel-chromium alloy.

[0029] The electrically insulating film may be selected from a metal oxide or a metal nitride.

[0030] FIG. 5 discloses a sensor system, generally designated 500, for sensing strain and temperature of a metal object. The sensor system comprises a sensor 300 according to the embodiment disclosed herein above, and a cold junction temperature detector 501 configured to detect the isothermal temperature of the junctions 308, 309 of the first electrical conductor and the metal object. The sensor system further comprises a temperature circuit 502 connected to the first terminal W0 and to the metal object terminal W1 and configured to measure the temperature of the junction. The temperature circuit is further connected to the cold junction temperature detector to compensate for the cold junction temperature of the junctions 308, 309. The sensor system further comprises a strain circuit 503 connected to the first terminal W0 and to the second terminal W2 to determine the strain based on the change in resistance of the strain sensitive portion, and a calculation circuit 504 connected to the temperature circuit 502 and to the strain circuit 503. The calculation circuit is configured to determine the strain caused by the mechanical strain on the metal object and the temperature induced strain of the metal object.

Claims

1. A sensor (100, 300), A metal object (101, 301); a thin film stack (102, 302) formed on at least a portion of a surface of the metal object; An electrical insulating film (103, 303); a metal film on the electrically insulating film, a first electrical conductor (104, 304) defined in the metal film, the metal film being composed of a metal alloy different from the metal object, the first electrical conductor being electrically insulated from the metal object using the electrically insulating film, the first electrical conductor being: a connection point (108, 308) connected to a first terminal (W0) via a conductor at a first end (106, 306); a sensor structure (110, 310) defined in the metal film at a second end (107, 307), the sensor structure comprising a junction (105, 305) of the metal film that penetrates the electrically insulating film to the metal object, thereby forming a thermocouple; and a metal object terminal (W1) connected to the connection point (109, 309) of the metal object via a conductor, the connection point (108, 308) of the first electrical conductor and the connection point (109, 309) of the metal object being configured to be adjacent to each other and in an isothermal relationship with each other; a second electrical conductor (311) defined in the metal film, the second electrical conductor having a connection point (312) at the first end (306); Equipped with the sensor area (310) further comprises a strain sensitive portion between a first end (314) and a second end (313), the sensor area (310) being configured to change resistance in response to an applied mechanical strain of the metal object (301), the first end (314) of the strain sensitive portion being connected to the first electrical conductor (304) and the second end (313) of the strain sensitive portion being connected to the second electrical conductor (311); The sensor, characterized in that the contacts (305) are configured to sense a temperature of the strain sensitive portion.

2. The sensor (100, 300) of claim 1, characterized in that the contact (305) is formed on the strain sensitive portion.

3. The sensor (100, 300) according to claim 1 or 2, characterized in that the metal object is a metal tube or a metal strip.

4. The sensor (100, 300) according to any one of claims 1 to 3, characterized in that the electrically insulating film is a metal oxide or a metal nitride.

5. A sensor system (500) for sensing strain and temperature of a metal object, comprising: A sensor (300) according to any one of claims 1 to 4; a cold junction temperature detector (501) configured to detect an isothermal temperature of the connection point (308, 309) of the first electrical conductor and the metal object; a temperature circuit (502) connected to the first terminal (W0) and to the metal object terminal (W1) and configured to measure a temperature of the junction, the temperature circuit being further connected to the cold junction temperature detector to compensate for a cold junction temperature of the connection points (308, 309); a distortion circuit (503) connected to the first terminal (W0) and to the second terminal (W2) for determining a distortion based on a change in resistance of the distortion sensitive portion; a calculation circuit (504) connected to the temperature circuit (502) and to the strain circuit (503), the calculation circuit being configured to determine mechanical strain on the metal object and strain caused by temperature-induced strain of the metal object.

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