Reference junction compensator of thermocouple, and measuring instrument of temperature measurement device

Abstract

To provide a reference junction compensator of a thermocouple, capable of measuring a temperature of reference junction of the thermocouple with high accuracy and further reducing a thickness, and a measuring instrument of a temperature measurement device having the reference junction compensator.SOLUTION: A reference junction compensator 1 connectable between a thermocouple 23 and a processing unit 24, is configured by one print circuit board 5A obtained by laminating a metal foil 2, an insulation substrate 3, and a metal plate 4. The print circuit board 5A includes at least a pair of connecting wires 8 and one temperature measuring resistor wire 9, which are formed with the metal foil 2. Each of the pair of connecting wires 8 has one end 8a connected to the thermocouple 23 and the other end 8b connected to the processing unit 24. The temperature measuring resistor wire 9, including both ends 9a and 9b connected to the processing unit 24 and a middle section 9c composed of serpentine wiring 10, functions as a temperature measuring resistor having a prescribed electric resistance value at a prescribed temperature.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a thermocouple reference junction compensator and a measuring instrument for a temperature measuring device, and more particularly to a thermocouple reference junction compensator that can measure the temperature of the reference junction of a thermocouple with high accuracy and can be made thinner, and a measuring instrument for a temperature measuring device that has the reference junction compensator. [Background technology]

[0002] A reference junction compensator for a thermocouple has been proposed (see Patent Document 1), which includes a substrate made of a metal layer, an insulating layer, and a conductor layer, a fixed winding core protruding from the metal layer of the substrate, and a resistance thermometer sensor wound around the winding core. In the invention described in Patent Document 1, the resistance thermometer sensor wound around the winding core is heated uniformly by the metal layer of the substrate, so that the resistance thermometer measures the temperature of the reference junction of the thermocouple with high precision. However, in the invention of Patent Document 1, the winding core protruding from the substrate is an obstacle to achieving a thinner device. Therefore, there is room for improvement in order to achieve a thinner device with a configuration that can measure the temperature of the reference junction of a thermocouple with high precision. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-85690 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a thermocouple reference junction compensator that can measure the temperature of the reference junction of a thermocouple with high accuracy and can be made thinner, and a measuring instrument for a temperature measuring device that has the reference junction compensator. [Means for solving the problem]

[0005] The thermocouple reference junction compensator of the first aspect of the present invention, which achieves the above-mentioned object, is a thermocouple reference junction compensator that is connected to both a thermocouple and a computing device that calculates the temperature of the hot junction of the thermocouple and is used to measure the temperature of the reference junction of the thermocouple, and is characterized in that it is composed of a single printed circuit board on which metal foil, an insulating base material, and a metal plate are laminated, and the printed circuit board has at least a pair of connecting wires formed from the metal foil and one resistance thermometer wire, one end of each of the pair of connecting wires is connected to the thermocouple and the other end is connected to the computing device, and the resistance thermometer wire has both ends connected to the computing device and a middle portion formed of serpentine wiring, and functions as a resistance thermometer having a predetermined electrical resistance value at a predetermined temperature.

[0006] According to the reference junction compensator of the first invention, the printed circuit board having a metal plate has excellent thermal uniformity with respect to the ambient temperature, so that the electrical resistance value of the resistance temperature detector wiring made of metal foil accurately and stably represents the ambient temperature as the temperature of the reference junction of the thermocouple. This resistance temperature detector wiring is made of metal foil and is housed within a rigid board.

[0007] A thermocouple reference junction compensator according to a second aspect of the present invention is a thermocouple reference junction compensator that can be connected to a thermocouple and a computing device that calculates the temperature of the hot junction of the thermocouple and is used to measure the temperature of the reference junction of the thermocouple. The thermocouple reference junction compensator is made up of a printed circuit board on which a metal foil, an insulating base material, and a metal plate are laminated, and the printed circuit board has at least a pair of connection wires formed from the metal foil and one resistor wire formed from the metal foil and electrically connected at its midpoint via a temperature-sensitive resistor, and each of the pair of connection wires has one end connected to the thermocouple and the other end connected to the computing device, and both ends of the resistor wire are connected to the computing device.

[0008] According to the reference junction compensator of the second invention, the printed circuit board having a metal plate has excellent thermal uniformity with the ambient temperature, so the electrical resistance value of the temperature-sensitive resistor attached to the printed circuit board accurately and stably represents the ambient temperature as the temperature of the reference junction of the thermocouple. This temperature-sensitive resistor is a tiny electronic component that only protrudes from the component side of the printed circuit board when attached to the printed circuit board.

[0009] A thermocouple reference junction compensator according to a third aspect of the present invention is a thermocouple reference junction compensator that can be connected to a thermocouple and a computing device that calculates the temperature of the hot junction of the thermocouple and is used to measure the temperature of the reference junction of the thermocouple, and is characterized in that the thermocouple reference junction compensator is constructed as a flexible printed circuit board in which metal foil is laminated between insulating substrates, the printed circuit board has at least a pair of connecting wires formed from the metal foil and one resistance thermometer wire, one end of each of the pair of connecting wires is connected to the thermocouple and the other end is connected to the computing device, and the resistance thermometer wire has both ends connected to the computing device and a meandering wire in the middle, and functions as a resistance thermometer having a predetermined electrical resistance value at a predetermined temperature.

[0010] According to the reference junction compensator of the third aspect of the invention, the printed circuit board, which is a flexible substrate, is sufficiently thin and highly flexible, allowing it to be attached to any desired location. The resistance temperature detector wiring, formed of metal foil on the printed circuit board, has a small heat capacity and high responsiveness. Therefore, by attaching it to a component with high thermal uniformity, the electrical resistance value of the resistance temperature detector wiring accurately and stably represents the temperature of that component as the temperature of the reference junction of the thermocouple. This resistance temperature detector wiring is wiring formed of metal foil and contained within a flexible substrate.

[0011] A measuring instrument for a temperature measuring device according to the present invention is characterized by comprising the above-described thermocouple reference junction compensator and the above-described arithmetic unit. [Effects of the Invention]

[0012] The reference junction compensator of the present invention enables the temperature of the reference junction of a thermocouple to be measured with high accuracy and can be made thinner. Furthermore, the measuring instrument of the present invention makes it possible to reduce the thickness of the reference junction compensator, thereby reducing the installation space for the reference junction compensator. This allows the entire measuring instrument to be made smaller. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is an explanatory diagram illustrating an embodiment of a thermocouple reference junction compensator and a measuring instrument of a temperature measuring device. [Figure 2] 2 is an explanatory diagram illustrating a cross section taken along an arrow A in FIG. 1. [Figure 3] FIG. 10 is an explanatory diagram illustrating a part of a meandering wiring. [Figure 4] 10A and 10B are explanatory diagrams illustrating a reference junction compensator during the manufacturing process. [Figure 5] FIG. 10 is an explanatory diagram illustrating a reference junction compensator fixed to a computing device. [Figure 6] FIG. 10 is an explanatory diagram illustrating a modified example of the embodiment. [Figure 7] FIG. 10 is an explanatory diagram illustrating another embodiment. [Figure 8] 8 is an explanatory diagram illustrating a cross section taken along the arrow B in FIG. 7. [Figure 9] 10A and 10B are explanatory diagrams illustrating a reference junction compensator during the manufacturing process. [Figure 10] FIG. 10 is an explanatory diagram illustrating yet another embodiment. [Figure 11] 11 is an explanatory diagram illustrating a cross section taken along an arrow C in FIG. 10. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a thermocouple reference junction compensator and a measuring instrument for a temperature measuring device according to the present invention will be described based on the embodiments shown in the drawings.

[0015] Fig. 1 is an explanatory diagram showing an example of an embodiment of a thermocouple reference junction compensator according to the first aspect of the present invention. The temperature measuring device 20 shown in Fig. 1 includes a temperature sensor 21 and a measuring instrument 22. The temperature sensor 21 has a thermocouple 23, and the measuring instrument 22 has a reference junction compensator 1 and a computing device 24. The temperature measuring device 20 electrically connects the reference junction compensator 1, the thermocouple 23, and the computing device 24, and measures the temperature of the hot junction of the thermocouple 23 as the temperature of the object to be measured. In the present invention, the reference junction compensator 1 can be connected between the thermocouple 23 and the computing device 24, and is used to measure the temperature of the reference junction of the thermocouple 23.

[0016] The temperature measuring device 20 has a configuration in which the temperature sensor 21 and the measuring device 22 are integrated. The temperature measuring device 20 may also be configured with the temperature sensor 21 and the measuring device 22 as separate devices, as exemplified in Fig. 5 described later. The temperature measuring device 20 may include multiple temperature sensors 21, or may be configured with multiple temperature sensors 21 and one measuring device 22.

[0017] The reference junction compensator 1 is composed of a printed circuit board 5A, which has a pair of connection wires 8 and one resistance thermometer wire 9. The reference junction compensator 1 does not include a thermocouple 23 or a computing device 24. When the reference junction compensator 1 is incorporated into the temperature measuring device 20, it is connected to the thermocouple 23 and the computing device 24. Details of the reference junction compensator 1 will be described later.

[0018] Various known thermocouples can be used for thermocouple 23, such as Type K, which uses chromel for the positive electrode and alumel for the negative electrode, Type T, which uses copper for the positive electrode and constantan for the negative electrode, Type E, which uses chromel for the positive electrode and constantan for the negative electrode, and Type B, which uses a platinum-rhodium alloy (rhodium content 30%) for the positive electrode and a platinum-rhodium alloy (rhodium content 6%) for the negative electrode. Thermocouple 23 may be structured so that the hot junction is in direct contact with the object to be measured, or may be structured so that the hot junction is in contact with a contact plate or the like that is in direct contact with the object to be measured.

[0019] The arithmetic unit 24 is configured as a computer, and various data are input and stored therein, and this data is used to perform data processing to calculate the temperature of the hot junction of the thermocouple 23. Various known computers can be used as the arithmetic unit 24. The arithmetic unit 24 has a processing unit (CPU), a main storage unit (memory), an auxiliary storage unit (e.g., HDD), an input unit (keyboard), and an output unit (display).

[0020] The arithmetic unit 24 executes data processing to calculate the temperature of the hot junction of the thermocouple 23 (temperature of the object to be measured) based on the thermoelectromotive force Va [μV] of the thermocouple 23 and the compensation value Vc [μV] obtained using the reference junction compensator 1. The compensation value Vc corresponds to the temperature of the reference junction of the thermocouple 23, i.e., the ambient temperature of the reference junction compensator 1 (internal temperature of the measuring instrument 22), and is based on the electrical resistance value Rc [Ω] of the resistance thermometer wiring 9, which will be described later.

[0021] The reference junction compensator 1 is composed of a printed circuit board 5A on which a metal foil 2, an insulating substrate 3, and a metal plate 4 are laminated, as exemplified in FIG. 2 described later. This printed circuit board 5A is a rigid board. The reference junction compensator 1 has a pair of connection wires 8 formed from the metal foil 2 of the printed circuit board 5A and one resistance temperature detector wire 9. One end 8a of each connection wire 8 is connected to a thermocouple 23, and the other end 8b is connected to a computing device 24. The resistance temperature detector wire 9 has both ends 9a, 9b connected to the computing device 24, and its middle part 9c is composed of a meandering wire 10, and functions as a resistance temperature detector having a predetermined electrical resistance value at a predetermined temperature.

[0022] As illustrated in FIG. 2 , the printed circuit board 5A is a rigid board in which a metal foil 2, an insulating base material 3, and a metal plate 4 are laminated in this order from top to bottom in the figure. This printed circuit board 5A only needs to have the metal plate 4. It may be a metal-based board (metal heat dissipation board) prepared by pressing the insulating base material 3 and the metal foil 2 onto the metal plate 4, or it may be a rigid board in which the metal foil 2 and the insulating base material 3 are laminated, or a flexible board in which the metal plate 4 is bonded with an adhesive. The printed circuit board 5A may be a double-sided board in which the metal foil 2, the insulating base material 3, the metal plate 4, the insulating base material 3, and the metal foil 2 are laminated in this order, or it may be a multilayer board in which multiple sets of metal foils 2 and insulating base materials 3 are laminated on one side of a single metal plate 4. The printed circuit board 5A is preferably a single-sided board in which the metal foil 2, the insulating base material 3, and the metal plate 4 are laminated in this order, as this has the best thermal uniformity.

[0023] The metal foil 2 is a rolled foil or electrolytic foil of a metal (pure metal, metal oxide, or alloy such as a dilute alloy). For example, the metal foil 2 may be a rolled foil or electrolytic foil of platinum, nickel, or copper, which are commonly used to make resistance thermometer sensors. The electrical resistivity of these metals is lowest for copper, followed by nickel and platinum, in that order. Due to this low electrical resistivity, the wiring length of a resistance thermometer sensor made of copper is longer than that of a resistance thermometer sensor made of nickel or platinum, given the same thickness. The measurement ranges of resistance thermometer sensors made of each metal are 0°C to 180°C for copper, -50°C to +300°C for nickel, and -200°C to +600°C for platinum. The price of each metal per volume is highest for platinum, followed by nickel and copper, in that order.

[0024] The metal foil 2 can also be made of platinum or nickel, but is preferably made of copper. Specifically, copper is less expensive than platinum or nickel. Furthermore, copper has a relatively low electrical resistivity and high conductivity among metals, making it suitable for wiring the printed circuit board 5A. In addition, a resistance thermometer sensor made of copper requires a longer wiring length than a resistance thermometer sensor made of platinum or nickel, but the longer the wiring length, the more advantageous it is for achieving uniform temperature distribution with the ambient temperature. Note that the measurement range of a resistance thermometer sensor made of copper is narrower than that of a resistance thermometer sensor made of platinum or nickel, but this narrow range is acceptable because the ambient temperature of the reference junction compensator 1, i.e., the internal temperature of the measuring instrument 22, is generally within the range of 0°C to 40°C.

[0025] The thickness of the metal foil 2 varies depending on the metal that constitutes the metal foil 2. When the metal foil 2 is made of copper, the thickness is, for example, 18 μm or 17.5 μm (1 / 2 oz / ft 2 ), 35μm (1oz / ft 2 ) In the reference junction compensator 1, a specified current such as 0.5 mA, 1 mA, or 2 mA flows through the circuit pattern, so the thickness of the metal foil 2 can be 18 μm or less, and a thickness of 35 μm or more is not required for currents significantly greater than the specified current. In general metal-based substrates (metal heat dissipation substrates), the metal foil is 35 μm or more thick to suppress the temperature rise in the substrate caused by the flow of a large current and ensure heat dissipation. When the printed circuit board 5A of the present invention is constructed from a metal-based substrate, the thickness of the metal foil 2 should be approximately 18 μm.

[0026] The unexposed portions of the metal foil 2 and the gaps between the wirings are covered or filled with an insulating film 6 (e.g., solder resist). The exposed portions of the metal foil 2 that are not covered with the insulating film 6 are covered with a conductive coating film 7 formed by a known surface treatment such as water-soluble preflux (OSP), solder leveler, electroless plating, or electrolytic gold plating. The thickness of the conductive coating film 7 varies depending on the type of surface treatment, but is, for example, approximately 0.01 μm to 0.05 μm when electrolytic gold plating is used.

[0027] The insulating substrate 3 can be made of various known insulating substrates, such as a paper-based phenolic resin, a composite-based epoxy resin (CEM-3), a glass cloth-based epoxy resin (FR-4), an epoxy resin, a polyimide, or a fluororesin. Note that a separate adhesive may be used to bond the insulating substrate 3 to the metal plate 4, or the insulating substrate 3 to the metal foil 2. In some metal-based substrates, an insulating substrate 3 with a thermal conductivity of 3 W / mk or more is used. The thinner the insulating substrate 3, the better the thermal uniformity of the metal foil 2 but the lower the voltage resistance. The thicker the insulating substrate 3, the lower the thermal uniformity of the metal foil 2. The thickness of the insulating substrate 3 is set to a range of, for example, 100 μm to 150 μm, so as to improve the thermal uniformity of the metal foil 2 while still ensuring sufficient voltage resistance when the metal plate 4 is laminated.

[0028] The metal plate 4 is composed of a single plate of metal, metal oxide, or dilute alloy. The metal plate 4 is preferably a metal with a thermal conductivity greater than 200 [W / (m·K)], such as a single plate of aluminum or copper. The metal plate 4 is preferably a single plate of the same metal as the metal foil 2. For example, if the metal foil 2 is composed of copper, the metal plate 4 is a single plate of copper, and if the metal foil 2 is composed of aluminum, the metal plate 4 is a single plate of aluminum. By using the same metal for the metal foil 2 and the metal plate 4, the coefficients of thermal expansion of the metal foil 2 and the metal plate 4 are equal. This is advantageous for preventing peeling or damage of the metal foil 2 due to temperature changes. Furthermore, a thicker metal plate 4 is advantageous for improving the thermal uniformity of the metal foil 2. The thickness of the metal plate 4 is preferably at least 50% of the thickness of the printed circuit board 5A, and more preferably at least 80%. In the illustrated example, the thickness of the printed circuit board 5A is approximately 1.15 mm, and the thickness of the metal plate 4 is approximately 1.00 mm.

[0029] The circuit pattern (each wiring of the metal foil 2) is formed on the printed circuit board 5A using photolithography and chemical etching. Various known subtractive methods can be used to form the circuit pattern, and various known additive methods (full additive method, semi-additive method, etc.) can also be used. Portions of the circuit pattern of the printed circuit board 5A where the minimum pattern width / spacing is less than 100 μm may be formed using laser processing. A known laser processing machine can be used for the laser processing.

[0030] Next, details of each of the wires including the connection wires 8 and the resistance temperature detector wires 9 formed by the metal foil 2 will be described.

[0031] FIG. 1 shows an example of the component side (L1 side, A side) of a printed circuit board 5A. In plan view, the metal foil 2, insulating substrate 3, and metal plate 4 may have substantially the same external shape, and their shapes are not particularly limited. In FIG. 1, the shaded areas indicate solder s. Each wiring has an exposed portion covered with a conductive coating film 7 and an unexposed portion covered with an insulating film 6. The solid lines indicate the exposed portions of each wiring, the dashed-dotted lines indicate the unexposed portions of the connection wiring 8, and the dashed lines indicate the unexposed portions of the resistance thermometer wiring 9.

[0032] One end 8a of the pair of connecting wires 8 is directly connected to the thermocouple 23, and the other end 8b is connected to the computing device 24 via a conductor (lead wire) w. The conductor wire w is, for example, a vinyl wire, a tin-plated wire, or an enameled wire. Note that the pair of connecting wires 8 is not limited to one in which one end 8a is directly connected to the thermocouple 23, but may be connected to the thermocouple 23 via a compensation conductor (the same metal wire as the thermocouple wire that constitutes the thermocouple 23). The exposed portions of the pair of connecting wires 8 are the one end 8a and the other end 8b that are soldered, and the unexposed portions are the remaining portions. When multiple thermocouples 23 are connected to one computing device 24, multiple pairs of connecting wires 8 are formed.

[0033] The resistance temperature detector wiring 9 has both ends 9a and 9b connected to the arithmetic unit 24 via conductors w. The middle portion 9c of the resistance temperature detector wiring 9 is composed of serpentine wiring 10. The middle portion 9c extends between the left and right ends of the printed circuit board 5A. The serpentine wiring 10 meanders in the vertical direction of the printed circuit board 5A. The exposed portion of the resistance temperature detector wiring 9 is the portion to be soldered and the middle portion 9c where the serpentine wiring 10 is formed by laser processing, and the non-exposed portion is the rest. The soldered portions are the portions to which both ends 9a and 9b, the respective contacts of the adjustment unit 11 described below, and the condenser 12 (capacitor) are connected.

[0034] In the illustrated example, the resistance thermometer wiring 9 has two conductors w connected to both ends 9a, 9b, so it functions as a two-wire resistance thermometer. The resistance thermometer wiring 9 may have three or four conductors w connected to both ends 9a, 9b, so it may function as a three-wire or four-wire resistance thermometer. A three-wire or four-wire type requires the effort of making the conductor resistance values ​​of the conductors w the same, but is advantageous in eliminating the effect of the conductor resistance value of the conductors w on the function of the resistance thermometer.

[0035] Since the midpoint 9c of the resistance temperature detector wiring 9 is configured with the meandering wiring 10, the wiring length of the resistance temperature detector wiring 9 is increased, and the resistance temperature detector wiring 9 functions as a resistance temperature detector having a predetermined electrical resistance value at a predetermined temperature. While typical meandering wiring in a printed circuit board is used as equal-length wiring to match the delay times of signals between multiple wirings, the meandering wiring 10 of this embodiment does not function as equal-length wiring, but is used to make the resistance temperature detector wiring 9 function as a resistance temperature detector.

[0036] More specifically, for the resistance thermometer wiring 9 to function as a resistance thermometer sensor, the resistance thermometer wiring 9 must have a predetermined electrical resistance value at a predetermined temperature. For example, if the resistance thermometer wiring 9 is copper foil, the predetermined electrical resistance value is 108.5 Ω at a predetermined temperature of 20°C. The electrical resistance value is proportional to the wiring length and inversely proportional to the cross-sectional area of ​​the wiring. In other words, for the resistance thermometer wiring 9 to function as a resistance thermometer sensor, the wiring length must be a predetermined length based on the thickness of the metal foil 2. Therefore, serpentine wiring 10 is suitable for ensuring a wiring length sufficient for the resistance thermometer wiring 9 to function as a resistance thermometer sensor in a limited space such as the printed circuit board 5A.

[0037] The circuit pattern of the resistance thermometer sensor wiring 9 should be designed to minimize the loop area of ​​the resistance thermometer sensor wiring 9. When a specified current from the computing device 24 flows through the resistance thermometer sensor wiring 9, the larger the loop area of ​​the resistance thermometer sensor wiring 9, the greater the degree of magnetic force (noise) generated, and the smaller the loop area, the smaller the degree of magnetic force generated. In the illustrated example, the distance between both ends 9a, 9b, the distance between the wiring from both ends 9a, 9b to the midpoint 9c, and the distance between the part of the wiring from one end 9a to the midpoint 9c and the midpoint 9c are minimized. This layout reduces the loop area of ​​the resistance thermometer sensor wiring 9, which is advantageous for suppressing the generation of magnetic force.

[0038] In a plan view, the area occupied by the resistance temperature detector wiring 9 is preferably 40% to 60% of the area of ​​the component side of the printed circuit board 5A. If the area occupied by the resistance temperature detector wiring 9 is less than 40% of the area of ​​the component side, the thermal uniformity of the resistance temperature detector wiring 9 will be reduced, and if it exceeds 60%, it will be difficult to arrange other wiring such as the pair of connecting wires 8.

[0039] A metal foil 2 may be disposed around the periphery of the meandering wiring 10 so as to surround the periphery. This metal foil 2 may be a wiring other than the meandering wiring 10, or may be a wiring (reinforcement pattern) that does not function as a wiring. This type of wiring may be either the connection wiring 8 or the resistance temperature detector wiring 9. In the illustrated example, the wires 9d to 9g of the resistance temperature detector wiring 9 are disposed so as to surround the periphery of the meandering wiring 10. Wire 9d branches off from the upstream of the middle portion 9c of the resistance temperature detector wiring 9 and is disposed along the upper end of the meandering wiring 10. Wires 9e and 9f are disposed at both ends of the middle portion 9c, along the left and right ends of the meandering wiring 10. Wire 9g is disposed along the lower end of the meandering wiring 10. Disposing the wires 9d, 9e, 9f, and 9g so as to surround the periphery of the meandering wiring 10 is advantageous in ensuring uniform temperature distribution of the meandering wiring 10. Furthermore, the wirings 9d to 9g minimize steps between the meandering wiring 10 and the edge of the printed circuit board 5A, making the meandering wiring 10 less susceptible to shocks from external forces, etc. This is advantageous in improving the durability of the meandering wiring 10.

[0040] As illustrated in FIG. 3 , the wiring length of the meandering wiring 10 can be adjusted by parameters such as the wiring width (minimum pattern width) a of the meandering wiring 10, the distance (spacing) b between adjacent wirings, the meandering width c, and the number of bends (number of meanders) d. These parameters are set based on the area of ​​the printed circuit board 5A occupied by the meandering wiring 10 and the wiring length over which the resistance temperature detector wiring 9 functions as a resistance temperature detector. Even if the area occupied by the meandering wiring 10 is the same, the smaller the wiring width a or the distance b between the lines, the greater the number of bends d, resulting in a longer wiring length. On the other hand, the larger the wiring width a or the distance b between the lines, the fewer the number of bends d, resulting in a shorter wiring length. Furthermore, even if the wiring length of the meandering wiring 10 is the same, the smaller the wiring width a or the distance b between the lines, the smaller the area occupied by the meandering wiring 10, and the larger the wiring width a or the distance b between the lines, the larger the area occupied by the meandering wiring 10. Therefore, by adjusting these parameters, it is possible to reduce the area occupied by the serpentine wiring 10 within the range where the resistance thermometer wiring 9 functions as a resistance thermometer, which is advantageous for miniaturizing the reference junction compensator 1.

[0041] Furthermore, the shorter the line-to-line distance b, the greater the effect of impedance coupling between adjacent wires, resulting in a smaller delay in the resistance thermometer wire 9, while the longer the line-to-line distance b, the smaller the effect of impedance coupling, resulting in a larger delay. Therefore, while the line-to-line distance in meandering wiring on a typical printed circuit board is limited to a length of at least twice the wiring width, there is no such restriction in the meandering wiring 10. Therefore, the line-to-line distance b of the meandering wiring 10 may be equal to or less than the wiring width a. By setting the line-to-line distance b of the meandering wiring 10 to be equal to or less than the wiring width a, the area occupied by the meandering wiring 10 can be reduced.

[0042] Each parameter is set to an appropriate value depending on the area of ​​the component side of printed circuit board 5A, the circuit pattern, and the type and thickness of metal of metal foil 2. If the component side of printed circuit board 5A illustrated in Fig. 1 has a width of 20 mm in the left-right direction in the figure, a length of 25 mm in the up-down direction in the figure, and metal foil 2 is made of copper and has a thickness of 18 µm, then the wiring width (pattern width) a of meandering wiring 10 illustrated in Fig. 3 is 15 µm to 25 µm, and the line-to-line distance b is 15 µm to 25 µm.

[0043] As shown in FIG. 4, before the insulating film 6 is applied, a pair of connection wirings 8 and a single resistance thermometer wiring 9, in which the meandering wiring 10 is not formed in the midsection 9c, are formed on the printed circuit board 5A using photolithography and chemical etching. The meandering wiring 10 is formed by laser cutting alternating grooves in the midsection 9c. The width of the cut groove determines the inter-wire distance b. In the laser processing, the depth of the groove can be adjusted by adjusting the intensity of the laser light. The groove depth should be at least greater than the thickness of the metal foil 2, but not so deep as to cut into the metal plate 4. In the illustrated example, the shape of the midsection 9c, in which the meandering wiring 10 is not formed, is rectangular; however, depending on the layout, the shape of the midsection 9c may be a concave polygon, ellipse, or the like.

[0044] The manufacturing procedure for the reference junction compensator 1 differs depending on whether the printed circuit board 5A is a metal-based board or a rigid or flexible board bonded to the metal plate 4 with an adhesive. Furthermore, the meandering wiring 10 of the resistance temperature sensor wiring 9 is formed by laser processing after the printed circuit board 5A is created if the minimum pattern width / spacing is less than 100 μm for a metal-based or rigid board, or if the minimum pattern width / spacing is less than 30 μm for a flexible board. Note that if the meandering wiring 10 can be formed using photolithography and chemical etching, laser processing is not necessary.

[0045] In the procedure when the printed circuit board 5A is a metal-based board, first, the metal foil 2, insulating substrate 3, and metal plate 4 are pressed together, and then the wiring is formed using photolithography and chemical etching. On the printed circuit board 5A, a pair of connecting wires 8 and a single resistance thermometer wire 9, the midway portion 9c of which does not have the meandering wire 10, are formed. Next, an insulating film 6 is used to form exposed and unexposed portions on the metal foil 2. Next, the meandering wire 10 is formed in the midway portion 9c by laser processing.

[0046] When the printed circuit board 5A is a rigid or flexible board made by laminating a metal foil 2 and an insulating base material 3 to a metal plate 4 with an adhesive, the procedure is as follows: first, each wiring is formed on the rigid or flexible board using photolithography and chemical etching. On the rigid or flexible board, a pair of connection wirings 8 and a single resistance temperature sensor wiring 9, the midpoint 9c of which does not have the meandering wiring 10, are formed. Next, an insulating film 6 forms exposed and unexposed portions on the metal foil 2. Next, the rigid or flexible board and the metal plate 4 are bonded together with an adhesive to create the printed circuit board 5A. Next, the meandering wiring 10 is formed in the midpoint 9c by laser processing.

[0047] An example of a method for measuring the temperature of a measurement object using the reference junction compensator 1 will be described. This measurement method uses a publicly known standard resistance value table and standard thermoelectromotive force table. The standard resistance value table and standard thermoelectromotive force table are pre-stored in the auxiliary memory of the computing device 24. The standard resistance value table shows the relationship between the resistance value Rc [Ω] calculated from the voltage measured when a constant current is passed through the resistance thermometer wiring 9 and the temperature [°C]. The standard thermoelectromotive force table shows the relationship between the thermoelectromotive force Va [μV] of the thermocouple 23 and the temperature [°C].

[0048] In the procedure of this measurement method, first, the arithmetic unit 24 acquires the thermoelectromotive force Va [μV] of the thermocouple 23 in contact with the temperature of the object to be measured and the resistance value Rc [Ω] of the resistance thermometer wiring 9. Next, the arithmetic unit 24 executes data processing to calculate the compensation value Vc [μV] based on the resistance value Rc and a resistance value table. The resistance value Rc corresponds to the ambient temperature of the reference junction compensator 1. Next, the arithmetic unit 24 executes data processing to convert the value obtained by adding the thermoelectromotive force Va and the compensation value Vc into a temperature Ta [°C] using a standard thermoelectromotive force table corresponding to the type of thermocouple 23. The finally obtained temperature Ta is the temperature of the object to be measured.

[0049] As described above, according to this embodiment, the printed circuit board 5A, which is formed by laminating the metal foil 2, insulating base material 3, and metal plate 4, has excellent thermal uniformity with respect to the ambient temperature, and the resistance temperature detector wiring 9 formed on the printed circuit board 5A also sufficiently uniformly heats up to the ambient temperature on the component surface where the connection wiring 8 is located. Therefore, the electrical resistance value of the resistance temperature detector wiring 9 accurately represents the ambient temperature, which is the temperature of the reference junction of the thermocouple 23. Furthermore, because the resistance temperature detector wiring 9 is formed on the printed circuit board 5A, it is contained within the board without protruding outside the printed circuit board 5A. In this way, this embodiment can achieve a further reduction in thickness of the reference junction compensator 1 while providing a configuration that can measure the temperature of the reference junction of the thermocouple 23 with high precision.

[0050] By making the reference junction compensator 1 thinner, the installation space for the reference junction compensator 1 can be reduced, and the degree of freedom in the internal design of the measuring instrument 22 increases. This is advantageous for making the measuring instrument 22 smaller overall.

[0051] The metal-based substrate, rigid substrate, or flexible substrate that constitutes the printed circuit board 5A can be produced in multiple pieces at once by imposition. Furthermore, the meandering wiring 10 can also be produced with roughly the same quality by setting processing conditions, including parameters such as wiring width a, line-to-line distance b, and meandering width c, in a laser processing machine. As described above, this embodiment is suitable for mass production, allowing for more inexpensive manufacturing. In addition, as described in Patent Document 1, manufacturing requires less labor than the process of winding a resistance thermometer sensor around a winding core that protrudes from the board.

[0052] When the minimum pattern width / spacing of the meandering wiring 10 is fine, the portions other than the meandering wiring 10 are formed first, followed by the formation of the meandering wiring 10. For example, when the minimum pattern width / spacing of the meandering wiring 10 on a metal-based substrate or a rigid substrate is less than 100 μm, or when the minimum pattern width / spacing of the meandering wiring 10 on a flexible substrate is less than 30 μm, photolithography and chemical etching are used to form the portions other than the meandering wiring 10, and laser processing is used to form the meandering wiring 10. This allows for the formation of a finer meandering wiring 10 with high precision.

[0053] Even if the resistance thermometer wiring 9 is designed to have a predetermined electrical resistance value at a predetermined temperature, the actually formed resistance thermometer wiring 9 may have deviations in the electrical resistance value due to differences in lots, mechanical errors in the wiring formation process, soldering of the conductors w to both ends 9a, 9b, etc. It is desirable for the reference junction compensator 1 to be able to adjust the deviations in the electrical resistance value.

[0054] 1, the resistance temperature detector wiring 9 preferably has an adjustment unit 11 that adjusts the wiring length of the resistance temperature detector wiring 9. By having the adjustment unit 11 in the resistance temperature detector wiring 9, it becomes possible to adjust the wiring length of the resistance temperature detector wiring 9 so that the resistance temperature detector wiring 9 has a predetermined electrical resistance value at a predetermined temperature.

[0055] More specifically, the adjustment unit 11 is configured to be able to select a standard wiring length, a wiring length shorter than the standard, or a wiring length longer than the standard. That is, if the resistance thermometer wiring 9 for which the standard wiring length has been selected has an electrical resistance value smaller than a predetermined electrical resistance value at a predetermined temperature, the electrical resistance value can be finely adjusted by selecting a wiring length longer than the standard. Also, if the resistance thermometer wiring 9 for which the standard wiring length has been selected has an electrical resistance value larger than the predetermined electrical resistance value, the electrical resistance value can be finely adjusted by selecting a wiring length shorter than the standard.

[0056] The adjusting unit 11 may have a plurality of adjusting means. In the illustrated example, the adjusting unit 11 has circuit units (11a to 11c) and a processing unit 11d. The selectable wiring length in the circuit unit is fixed, allowing for easy fine adjustment. The processing unit 11d is capable of forming meandering wiring by cutting, allowing for greater adjustment than the circuit unit. The selectable wiring length in the circuit unit is not particularly limited as long as it is three or more, and in the illustrated example, five wiring lengths including a central reference wiring length are selectable. Since the uncut state of the processing unit 11d is the reference wiring length, the electrical resistance value can be adjusted only when the electrical resistance value is smaller than the reference value.

[0057] The circuit section includes a first circuit section 11a and a second circuit section 11b that are not electrically connected to each other. Each of the first circuit section 11a and the second circuit section 11b has three or more contacts. The first circuit section 11a is electrically connected to one of the two end sections 9a and 9b, and the second circuit section 11b is electrically connected to the other of the two end sections 9a and 9b. One of the circuit sections includes a meandering wiring 11c, on which three or more contacts are arranged. The meandering wiring 11c of the circuit section has a larger wiring width and spacing than the meandering wiring 10 described above and can be formed by known photolithography and chemical etching. The wiring length of the resistance thermometer wiring 9 is adjusted by connecting the contacts of each circuit section. Various known jumpers, such as jumper wires, jumper pins, and dip switches, can be used to connect the contacts. The adjusting section 11 is not essential, and can be omitted if the electrical resistance value in the circuit design and the electrical resistance value of the actually formed resistance temperature sensor wiring 9 can be considered to be roughly equivalent.

[0058] The adjustment of the wiring length by the adjustment unit 11 is performed with the thermocouple 23 and the arithmetic unit 24 electrically connected to the reference junction compensator 1. Specifically, the adjustment of the wiring length by the adjustment unit 11 is performed based on the electrical resistance value of the resistance thermometer wiring 9 when the reference junction compensator 1 is soaked to a predetermined temperature and a specified current is passed from the arithmetic unit 24.

[0059] The measuring instrument 22 incorporating the reference junction compensator 1 preferably has electromagnetic compatibility (EMC). Whether the measuring instrument 22 has electromagnetic compatibility can be confirmed using an electromagnetic compatibility test specified in JIS C61326-1:2022, JIS C61326-2-1:2022, etc. If the electromagnetic compatibility test shows that the measuring instrument 22 does not have electromagnetic compatibility, the impedance of the AC component of a specific frequency in the meandering wiring 10 is high. Therefore, it is preferable that a capacitor (condenser) 12 be connected to the resistance thermometer wiring 9.

[0060] The capacitor 12 has the property of blocking DC current flowing through the resistance thermometer wiring 9 and passing AC current, thereby reducing the impedance of AC components of a specific frequency. The frequency of the AC component at which the capacitor 12 reduces the impedance can be set arbitrarily, for example, between 80 MHz and 1000 MHz. The capacitor 12 is connected in parallel to the meandering wiring 10. In the illustrated example, one end of the capacitor 12 is connected to a wiring 9d branching from the upstream of the midpoint 9c, and the other end is connected to a wiring 9f downstream of the midpoint 9c. By connecting the capacitor 12 in parallel to the meandering wiring 10, AC components of a specific frequency bypass the meandering wiring 10. This reduces the impedance of the AC component of the specific frequency in the meandering wiring 10. This prevents the meandering wiring 10 from being a source of electromagnetic interference and is not subject to electromagnetic interference. The number of capacitors 12 is not limited to one, and multiple capacitors 12 may be used. The multiple capacitors 12 may target AC components of different frequencies. The capacitor 12 is not essential and can be omitted if the measuring instrument 22 incorporating the reference junction compensator 1 is deemed to have electromagnetic compatibility.

[0061] The respective portions (8b, 9a, 9b) of each wiring connected to the computing device 24 are preferably arranged near the edge of the printed circuit board 5. More preferably, the respective portions of each wiring connected to the computing device 24 are arranged near one edge of the printed circuit board 5 and are spaced apart along that edge. In the illustrated example, the respective portions (8b, 9a, 9b) are arranged near the lower edge of the printed circuit board 5 and are spaced apart in the left-right direction along that edge. This layout is advantageous for the routing of the conductors (w). A pin connector can also be constructed by configuring the conductors (w) as lead pins. Alternatively, an edge connector can be constructed by projecting the metal foil 2 and insulating base material 3 outward from the edge of the metal plate 4 in the planar direction, and arranging the other end 8b of the pair of connection wirings 8 and both ends 9a, 9b of the resistance temperature sensor wiring 9 on the projecting metal foil 2. This allows a pin connector or edge connector to be inserted into the connector socket (slot) of the arithmetic unit 24 to directly connect the pair of connection wires 8 and the resistance temperature detector wire 9 to the arithmetic unit 24 .

[0062] Reference holes 13a and 13b and an identification mark 14 are formed in the reference junction compensator 1. The reference holes 13a and 13b and the identification mark 14 are used in the manufacturing process of the printed circuit board 5A. The reference holes 13a and 13b penetrate the printed circuit board 5A, and the identification mark 14 is formed in the metal foil 2. The reference holes 13a and 13b and the identification mark 14 are not essential, but the reference holes 13a and 13b can also be used to fix the reference junction compensator 1 to the computing device 24.

[0063] As illustrated in FIG. 5, the reference junction compensator 1 is fixed to the printed circuit board of the computing device 24 with fasteners such as bolts and nuts. Bolts are inserted into the reference holes 13a. The component side of the printed circuit board 5A faces the printed circuit board of the computing device 24. The printed circuit board 5A is fixed to the printed circuit board of the computing device 24 with a predetermined distance between them. In this way, the reference holes 13a and 13b can be used to fix the reference junction compensator 1. The reference junction compensator 1 may be fixed to the computing device 24, but the fixing location is not particularly limited as long as it is inside the measuring instrument 22.

[0064] Next, a modification of this embodiment will be described.

[0065] 6 differs from the above-described temperature measuring device 20 in that the temperature sensor 21 and the measuring device 22A are configured separately. The measuring device 22A differs in that it has a reference junction compensator 1A, a terminal 25, and a computing device 24. The measuring device 22A may have multiple terminals 25, or may be configured with multiple terminals 25, one reference junction compensator 1A, and one computing device 24.

[0066] The reference junction compensator 1A differs from the above-described embodiment in that it includes a terminal thermocouple 15 whose hot junction contacts a terminal 25, the printed circuit board 5A has a pair of terminal connection wires 16, and one end 8a of each of the pair of connection wires 8 is connected to the thermocouple 23 via a conductor w and a terminal 25. When there are multiple terminals 25, there will be multiple terminal thermocouples 15, multiple pairs of terminal connection wires 16, and multiple pairs of connection wires 8.

[0067] As with thermocouple 23, various known thermocouples can be used for terminal thermocouple 15. A thermocouple with a relatively small heat capacity is desirable for terminal thermocouple 15, such as a type T thermocouple with copper for the positive electrode and constantan for the negative electrode. The hot junction of terminal thermocouple 15 is in contact with terminal 25, and measures the temperature of terminal 25.

[0068] One end 16a of the pair of terminal connection wires 16 is directly connected to the terminal thermocouple 15, and the other end 16b is connected to the computing device 24 via a conductor w. The terminal connection wires 16 are also formed using a method similar to that of the connection wires 8.

[0069] One end 8a of a pair of connecting wires 8 of the reference junction compensator 1A is electrically connected to the thermocouple 23 via a conductor w and a terminal 25. That is, the terminal 25 is the connection point between the thermocouple 23 and the conductor w, which are different metal wires. This connection point acts as a hot junction, and an electromotive force is generated according to the temperature of the terminal 25. The temperature of the terminal 25 is soaked to the temperature outside the measuring instrument 22A, i.e., the ambient temperature.

[0070] If the thermocouple 23 of the temperature sensor 21 connected to the terminal 25 is limited to a specific type (for example, Type K), the reference junction compensator 1 described above can be used by connecting the terminal 25 and the connection wiring 8 with a compensation conductor (the same metal wire as Type K). On the other hand, if the type of thermocouple 23 of the temperature sensor 21 connected to the terminal 25 is not limited, even if the terminal 25 and the connection wiring 8 are connected with a compensation conductor, the terminal 25 becomes a connection point between different metal wires, and a thermoelectromotive force corresponding to the ambient temperature is generated. Therefore, by providing a terminal thermocouple 15 that measures the temperature of the terminal 25, it is possible to correct the thermoelectromotive force.

[0071] An example of the procedure for measuring the temperature of the object to be measured in this modified example will be described below. First, the arithmetic unit 24 acquires the thermoelectromotive force Va [μV] of the thermocouple 23, the resistance value Rc [Ω] of the resistance temperature detector wiring 9, and the thermoelectromotive force Vb [μV] of the terminal thermocouple 15. Next, the arithmetic unit 24 executes data processing to calculate a compensation value Vd [μV] based on the resistance value Rc and the thermoelectromotive force Vb. The thermoelectromotive force Vb corresponds to the ambient temperature, which is the temperature outside the measuring instrument 22A, the resistance value Rc corresponds to the internal temperature of the measuring instrument 22A (the ambient temperature of the reference junction compensator 1A), and the compensation value Vd corresponds to the temperature obtained by subtracting the internal temperature from the ambient temperature.

[0072] Next, the arithmetic unit 24 executes data processing to calculate the temperature Ta [°C] based on the thermoelectromotive force Va of the thermocouple 23 in contact with the temperature of the object to be measured and the compensation value Vd. The finally obtained temperature Ta is the temperature of the object to be measured. Specifically, the arithmetic unit 24 executes data processing to convert the compensation value Vd into a conversion value Ve [μV]. This data processing uses a power conversion table, which is stored in advance in the auxiliary storage unit of the arithmetic unit 24 and shows the relationship between the thermoelectromotive force of the terminal thermocouple 15 and the thermoelectromotive force of the thermocouple 23, or a standard thermoelectromotive force table corresponding to the terminal thermocouple 15 and the thermocouple 23. The conversion value Ve is a value obtained by converting the compensation value Vd into the thermoelectromotive force of the thermocouple 23. Next, data processing is executed to convert the sum of the thermoelectromotive force Va and the conversion value Ve into the temperature Ta using a standard thermoelectromotive force table corresponding to the type of thermocouple 23.

[0073] As described above, the reference junction compensator 1A of the modified example includes a terminal thermocouple 15, which makes it possible to accurately acquire the temperature of terminal 25, i.e., the thermoelectromotive force generated in response to the environmental temperature outside measuring instrument 22A. This makes it possible to use various types of thermocouples 23 without limiting the type of thermocouple 23 connected to terminal 25. Measuring instrument 22A equipped with this reference junction compensator 1A makes it possible to select a temperature sensor 21 having an appropriate thermocouple 23 in accordance with the object to be measured and the environmental temperature. Furthermore, measuring instrument 22A can be made smaller as the reference junction compensator 1A is made thinner.

[0074] Next, another embodiment, that is, a second embodiment of the present invention will be described.

[0075] The reference junction compensator 1B illustrated in FIG. 7 differs from the first embodiment of the present invention in that the printed circuit board 5B is a flexible board and is in surface contact with the temperature equalizing member 26. Similar to the above-described embodiment, the reference junction compensator 1B is incorporated into the temperature measuring devices 20 and 20A, can be connected between the thermocouple 23 and the computing device 24, and is used to measure the temperature of the reference junction of the thermocouple 23. The temperature measuring devices 20 and 20A are generally similar to those in the above-described embodiment, and therefore are not shown and will not be described here. In practice, the reference junction compensator 1B is connected to both the thermocouple 23 and the computing device 24. Specifically, one end 8a of the connection wiring 8 is connected to the thermocouple 23, and the other end 8b is connected to the computing device 24, and both ends 9a and 9b of the resistance temperature detector wiring 9 are connected to the computing device 24.

[0076] The reference junction compensator 1B is configured from a single printed circuit board 5B in which metal foil 2 is laminated between insulating substrates 3, as exemplified in FIG. 8, which will be described later. This printed circuit board 5B is a flexible board. As in the above-described embodiment, the reference junction compensator 1B has a pair of connection wires 8 formed from metal foil 2 and one resistance temperature detector wire 9. Details of the reference junction compensator 1B will be described later.

[0077] Heat-equalizing member 26 may be any member that exists inside measuring instrument 22 and that sufficiently equalizes the temperature to the internal temperature of measuring instrument 22 (the ambient temperature of reference junction compensator 1B). Heat-equalizing member 26 is, for example, a printed circuit board or terminals 25 of computing device 24. As will be described later, printed circuit board 5B, which is a flexible board, has a thickness significantly smaller than that of printed circuit board 5A, which is a rigid board. Therefore, printed circuit board 5B has high responsiveness to temperature. In other words, reference junction compensator 1B, which is in surface-to-surface contact with heat-equalizing member 26, can measure the temperature of heat-equalizing member 26, i.e., the internal temperature of measuring instrument 22, with high accuracy. An adhesive may be used to bring printed circuit board 5B and heat-equalizing member 26 into surface contact.

[0078] As illustrated in FIG. 8 , the printed circuit board 5B is a flexible board in which an insulating substrate 3, a metal foil 2, and another insulating substrate 3 are laminated in this order from top to bottom in the figure. An adhesive layer may be interposed between the metal foil 2 and the insulating substrate 3; however, the presence of an adhesive layer reduces flexibility and responsiveness, so it is preferable not to interpose an adhesive layer. The metal foil 2 and the insulating substrate 3 can be laminated using known methods such as casting, laminating, and metallization. The printed circuit board 5B may be a double-sided board in which an insulating substrate 3, a metal foil 2, an insulating substrate 3, a metal foil 2, and an insulating substrate 3 are laminated in this order, or a multilayer board in which multiple sets of metal foils 2 and insulating substrates 3 are laminated on one side of a single insulating substrate 3. The printed circuit board 5B is preferably a single-sided board in which a metal foil 2 is laminated between each pair of insulating substrates 3, as this provides the best responsiveness and flexibility.

[0079] Copper or nickel is preferably used for the metal foil 2. The reasons for copper being preferred are the same as those in the first embodiment of the present invention. Nickel is more expensive than copper but less expensive than platinum. Furthermore, a resistance thermometer sensor made of nickel has a wider measurement range than a resistance thermometer sensor made of copper but a narrower measurement range than a resistance thermometer sensor made of platinum. However, the measurement range of a resistance thermometer sensor made of nickel is a general measurement range, excluding special environments such as extremely low temperatures below -50°C and extremely high temperatures above +300°C. Additionally, nickel has a higher electrical resistivity than copper but a lower electrical resistivity than platinum, making it more suitable for the circuit pattern of the printed circuit board 5B than platinum. Furthermore, because nickel has a high electrical resistivity, similar to platinum, it is suitable for reducing the thickness of the metal foil 2 and reducing its heat capacity.

[0080] The thickness of the metal foil 2 varies depending on the metal that constitutes the metal foil 2. The thinner the metal foil 2, the smaller the heat capacity, which is advantageous for the responsiveness of the resistance temperature sensor wiring 9, which will be described later, and the thicker the metal foil 2, the larger the heat capacity. For example, when the metal foil 2 is made of copper, the thickness of the metal foil 2 is 9 μm (1 / 4 oz / ft 2 ) or less. When the metal foil 2 is made of nickel, the thickness of the metal foil 2 is preferably 3 μm or more and 5 μm or less. If the thickness is less than 3 μm, it becomes difficult to form a circuit pattern using known photolithography and chemical etching, resulting in high manufacturing costs. If the thickness exceeds 5 μm, the heat capacity increases, and the responsiveness of the heat spreader 26 to temperature decreases.

[0081] Most of the surface of the metal foil 2 (the component side of the printed circuit board 5B) is covered with an insulating base material (coverlay) 3 arranged on the upper side in the figure, but both ends 8a, 8b of a pair of connection wires 8 and both ends 9a, 9b of a resistance temperature sensor wire 9 are not covered with the insulating base material 3. Therefore, it is advisable to cover these parts with a conductive coating film 7 obtained by a known surface treatment.

[0082] The insulating substrate 3 can be made of various known insulating materials such as polyimide, polyester, and liquid crystal polymer. The thickness of the insulating substrate 3 is approximately 12.5 μm or 25 μm, which is the thickness used in general flexible printed circuit boards. Each insulating substrate 3 may be made of a different insulating substrate, and each may have a different thickness. The insulating substrate 3 arranged on the component side of the printed circuit board 5B (upper side in the figure) is sometimes called a coverlay.

[0083] The thickness of the printed circuit board 5B is approximately 27 μm to 40 μm. As described above, the thickness of the printed circuit board 5B, which is a flexible board, is sufficiently smaller than the thickness of the printed circuit board 5A of the first embodiment of the present invention described above.

[0084] In the printed circuit board 5B, the circuit pattern (each wiring of the metal foil 2) is formed using photolithography and chemical etching, as in the first embodiment of the present invention described above. Note that the formation of the circuit pattern of the printed circuit board 5B is not limited to various known subtractive methods, and various known additive methods (full additive method, semi-additive method, etc.) can also be used.

[0085] Next, details of the reference junction compensator 1B that differ from the above-described first embodiment of the present invention will be described.

[0086] 7 and 9 show examples of the component side (L1 side, A side) of the printed circuit board 5B, with FIG. 7 showing a state in which the unexposed portion is covered with the insulating base material 3 and FIG. 9 showing a state in which the unexposed portion is not covered with the insulating base material 3. Note that the external shape of the printed circuit board 5B is not particularly limited in plan view. In FIG. 7, the double-dashed line indicates the reinforcing plate 17. Each wiring has an exposed portion and an unexposed portion covered with the insulating base material 3, with solid lines indicating the exposed portion of each wiring, one-dot-dashed lines indicating the unexposed portion of the connecting wiring 8, and dashed lines indicating the unexposed portion of the resistance temperature sensor wiring 9.

[0087] The printed circuit board 5B is prone to breaking due to its small thickness, particularly at the locations where portions where the metal foil 2 is not present overlap in the vertical and horizontal directions in the figure. Therefore, it is desirable that the printed circuit board 5B has a circuit pattern in which portions where the metal foil 2 is not present overlap as little as possible in the vertical and horizontal directions in the figure. In the illustrated example, the circuit pattern of the printed circuit board 5B is symmetrical in the horizontal direction in the figure, and there is a portion between a pair of connection wirings 8 where the metal foil 2 is not present. Therefore, by making the wiring width of the meandering wiring 10 in the horizontal center portion in the figure larger than the wiring width of other portions, the portion between the pair of connection wirings 8 is less likely to break.

[0088] Furthermore, it is preferable that the printed circuit board 5B has a metal foil 2 arranged along the edge of the printed circuit board 5B. This metal foil 2 may be wiring, or may not function as wiring (a reinforcing pattern). This wiring may be either the connection wiring 8 or the resistance temperature detector wiring 9. In the illustrated example, the wiring 9h and 9i of the resistance temperature detector wiring 9 are arranged along the edge of the printed circuit board 5B. When the printed circuit board 5B is rectangular, the wiring 9h and 9i form, for example, a wide rectangular loop. In this way, the wiring 9h and 9i made of the metal foil 2 reinforce the edge of the printed circuit board 5B.

[0089] When the capacitor 12 is connected to the resistance temperature detector wiring 9, one end of the wiring 9h is connected to one end 9a of the resistance temperature detector wiring 9. Furthermore, one end of the wiring 9i is connected to the other end 9b of the resistance temperature detector wiring 9. The other ends of the wirings 9h and 9i are electrically connected to each other via the capacitor 12. In this way, by connecting the capacitor 12 in parallel with the meandering wiring 10, the meandering wiring 10 does not become a source of electromagnetic interference and is not subject to electromagnetic interference. Note that the capacitor 12 is not essential and can be omitted if the reference junction compensator 1B is deemed to have electromagnetic compatibility.

[0090] Similar to the first embodiment of the present invention, the reference junction compensator 1B may have an adjustment unit 11. However, since it is not easy to form wiring by laser processing on the printed circuit board 5B made of a flexible substrate, the adjustment unit 11 is limited to one formed using known photolithography and chemical etching.

[0091] In the reference junction compensator 1B of this embodiment, the printed circuit board 5B, which is a flexible board, has a sufficiently small thickness and high flexibility, so that it can be attached to the soaking member 26. The resistance temperature detector wiring 9, which is formed from the metal foil 2 of the printed circuit board 5B, has a small heat capacity and a high response rate. Therefore, by being attached to the soaking member 26, the electrical resistance value of the resistance temperature detector wiring 9 accurately and stably represents the temperature of the reference junction of the thermocouple 23, which is the temperature of the soaking member 26. The resistance temperature detector wiring 9 is wiring that is formed from the metal foil 2 and is contained within the flexible board. Therefore, with this reference junction compensator 1B, it is possible to measure the temperature of the reference junction of the thermocouple 23 with high accuracy, and the thickness of the wiring can be reduced.

[0092] Although the manufacturing cost of printed circuit board 5B, which is a flexible board, is higher than that of printed circuit board 5A described above, it eliminates the need to use laser processing to form fine meandering wiring 10. Therefore, this reference junction compensator 1B is more suitable for mass production.

[0093] In the reference junction compensator 1B, it is not necessary for the entire printed circuit board 5B to be in surface contact with the temperature equalizing member 26, but it is sufficient that at least the entire meandering wiring 10 is in surface contact with the temperature equalizing member 26. Therefore, a reinforcing plate can be placed at the connection portion of the printed circuit board 5B.

[0094] Similar to the reference junction compensator 1A described above, the reference junction compensator 1B includes a terminal thermocouple 15 whose hot junction contacts a terminal 25, and the printed circuit board 5B has at least a pair of terminal connection wires 16, with one end 16a of each of the pair of terminal connection wires 16 connected to the terminal thermocouple 15 and the other end 16b connected to the computing device 24, and one end 8a of each of the pair of connection wires 8 connected to the terminal 25 via a conductor w. As a result, the reference junction compensator 1B makes it possible to use various types of thermocouples 23 without limiting the type of thermocouple 23 connected to the terminal 25.

[0095] Next, a further embodiment, that is, a third embodiment of the present invention will be described.

[0096] The reference junction compensator 1C illustrated in FIG. 10 differs from the first embodiment of the present invention in that it has a single resistor wiring 19 electrically connected to the midpoint 19c via a temperature sensitive resistor 18 instead of the resistance temperature detector wiring 9. That is, the reference junction compensator 1C uses the temperature sensitive resistor 18 to measure the temperature of the reference junction of the thermocouple 23. As in the above-described embodiments, the reference junction compensator 1C is incorporated into the temperature measuring devices 20, 20A, can be connected between the thermocouple 23 and the computing device 24, and is used to measure the temperature of the reference junction of the thermocouple 23. The temperature measuring devices 20, 20A are generally similar to those in the above-described embodiments, and therefore are not shown and will not be described here. In practice, the reference junction compensator 1C is connected to both the thermocouple 23 and the computing device 24. Specifically, one end 8a of the connection wiring 8 is connected to the thermocouple 23, the other end 8b is connected to the calculation device 24, and both ends 19a, 19b of the resistor wiring 19 are connected to the calculation device 24.

[0097] The reference junction compensator 1C is configured with a rigid printed circuit board 5A, similar to the above-described embodiment, as shown in Fig. 11 (described later). Similar to the above-described embodiment, the reference junction compensator 1C has a pair of connection wires 8 formed of metal foil 2. The reference junction compensator 1C also has one resistor wire 19 formed of metal foil 2, with a midpoint 19c electrically connected by a temperature-sensitive resistor 18.

[0098] The printed circuit board 5A shown in Fig. 11 is a rigid board, and is similar to the embodiment described above, so detailed description will be omitted. Temperature-sensitive resistors 18 are soldered to the middle portions 19c of the resistor wiring 19. The temperature-sensitive resistors 18 are attached to the component side of the printed circuit board 5A where the connection wiring 8 is present.

[0099] The temperature-sensitive resistor 18 is a square chip-type fixed resistor (thermistor). Various known fixed resistors, such as a surface-mount type or a lead type, can be used for the temperature-sensitive resistor 18. Examples of fixed resistors include an NTC thermistor, a PTC thermistor, and a CTR thermistor. The temperature-sensitive resistor 18 is a minute electronic component. "Minute" means that when attached to the printed circuit board 5A, its height from the component surface of the printed circuit board 5A is smaller than the height of the winding core described in Patent Document 1.

[0100] As described above, according to the reference junction compensator 1C, the printed circuit board 5A having the metal plate 4 has excellent thermal uniformity with respect to the ambient temperature, so the electrical resistance value of the temperature-sensitive resistor 18 attached to the printed circuit board 5A accurately represents the ambient temperature, which is the temperature of the reference junction of the thermocouple 23. Furthermore, because the temperature-sensitive resistor 18 is attached to the component side of the printed circuit board 5A where the connection wiring 8 is located, the ambient temperature on the component side can be measured with higher accuracy while achieving a thinner design than conventional devices.

[0101] Similar to the reference junction compensator 1A described above, the reference junction compensator 1C may be configured to include a terminal thermocouple 15 whose hot junction is in contact with a terminal 25, a printed circuit board 5B having at least a pair of terminal connection wires 16, one end 16a of each of the pair of terminal connection wires 16 connected to the terminal thermocouple 15 and the other end 16b connected to the computing device 24, and one end 8a of each of the pair of connection wires 8 connected to the terminal 25 via a conductor w. As a result, the reference junction compensator 1C does not limit the type of thermocouple 23 connected to the terminal 25, and various types of thermocouples 23 can be used.

[0102] The present invention is not limited to a specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention. [Explanation of symbols]

[0103] 1, 1A, 1B, 1C reference junction compensator 2. Metal foil 3. Insulating substrate 4 metal plate 5A, 5B printed circuit board 6. Insulating film 7 Conductive coating film 8 Connection wiring 9 Resistance temperature sensor wiring 10 Serpentine wiring 11 Adjustment part 12 Capacitor 13a, 13b Reference holes 14 Recognition Mark 15-Terminal Thermocouple 16 Terminal connection wiring 18 Temperature sensitive resistor 19 Resistor wiring 20, 20A temperature measuring device 21 Temperature sensor 22, 22A Metering Instruments 23 Thermocouple 24 Arithmetic unit 25 terminals 26 Heat-equalizing member

Claims

1. A thermocouple reference junction compensator connectable to a thermocouple and a computing device that computes a temperature of a hot junction of the thermocouple, and used to measure a temperature of a reference junction of the thermocouple, comprising: It is composed of a printed circuit board in which metal foil, an insulating substrate, and a metal plate are laminated, the printed circuit board has at least one pair of connection wires and one resistance temperature sensor wire formed of the metal foil, each of the pair of connection wires has one end connected to the thermocouple and the other end connected to the computing device; The resistance thermometer wiring has both ends connected to the computing device, and the middle part is made up of serpentine wiring, and functions as a resistance thermometer having a predetermined electrical resistance value at a predetermined temperature. This is a reference junction compensator for a thermocouple.

2. A thermocouple reference junction compensator connectable to a thermocouple and a computing device that computes a temperature of a hot junction of the thermocouple, and used to measure a temperature of a reference junction of the thermocouple, comprising: It is composed of a printed circuit board in which metal foil, an insulating substrate, and a metal plate are laminated, the printed circuit board has at least one pair of connection wirings formed of the metal foil, and one resistor wiring formed of the metal foil and electrically connected at its midpoint via a temperature-sensitive resistor; each of the pair of connection wires has one end connected to the thermocouple and the other end connected to the computing device; A thermocouple reference junction compensator, wherein both ends of the resistor wiring are connected to the computing device.

3. 3. The thermocouple reference junction compensator according to claim 1, wherein the metal foil and the metal plate are made of the same metal.

4. 3. The thermocouple reference junction compensator according to claim 1, wherein the metal foil is made of copper.

5. 2. The thermocouple reference junction compensator according to claim 1, wherein the resistance temperature detector wiring has an adjusting section for adjusting the wiring length.

6. A thermocouple reference junction compensator connectable to a thermocouple and a computing device that computes a temperature of a hot junction of the thermocouple, and used to measure a temperature of a reference junction of the thermocouple, comprising: It is a flexible printed circuit board with metal foil laminated between insulating substrates. the printed circuit board has at least one pair of connection wires and one resistance temperature sensor wire formed of the metal foil, each of the pair of connection wires has one end connected to the thermocouple and the other end connected to the computing device; The resistance thermometer wiring has both ends connected to the computing device, and the middle part is made up of serpentine wiring, and functions as a resistance thermometer having a predetermined electrical resistance value at a predetermined temperature. This is a reference junction compensator for a thermocouple.

7. 7. The thermocouple reference junction compensator of claim 6, wherein the metal foil is made of copper or nickel.

8. 7. The thermocouple reference junction compensator according to claim 1, wherein a capacitor is connected to the resistance temperature detector wiring.

9. the thermocouple is connected to a terminal of a measurement unit that houses the arithmetic unit; a terminal thermocouple having a hot junction in contact with the terminal; the printed circuit board has a pair of terminal connection wires formed from the metal foil, one end of each of the terminal connection wires is connected to the terminal thermocouple and the other end is connected to the arithmetic device; 7. The thermocouple reference junction compensator according to claim 1, wherein one end of each of the pair of connection wires is connected to the terminal via a conductor.

10. A measuring instrument for a temperature measuring device, comprising the reference junction compensator for a thermocouple according to claim 1, 2 or 6, and the arithmetic unit.

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