Optical concentration measurement device and signal processing unit

Abstract

The invention provides an optical concentration measurement device and a signal processing unit. The optical concentration measurement device includes: a light source; a detection unit (21, 22) that detects a signal based on light emitted from the light source and outputs a detection signal; a signal processing unit (50) that acquires the detection signal and converts the detection signal into a digital signal; and a substrate (30) on which a detection unit and a signal processing unit are provided, the signal processing unit having a terminal array in which a plurality of signal terminals, which are input / output terminals of signal lines connected to the detection unit, are sandwiched between a plurality of voltage terminals for supplying a voltage not more than 0 V, and in a plan view in which the substrate is viewed from the front side, the voltage of the signal terminals is greater than 0 V. Wiring connecting the plurality of voltage terminals and the signal processing unit surround the signal line.

Description

Technical Field

[0001] The present disclosure relates to an optical concentration measuring device and a signal processing unit. Background Art

[0002] In recent years, the development of gas sensors (gas measuring devices) has been progressing. These sensors have a light source that emits infrared rays, are configured to transmit infrared rays through a gas containing a gas to be detected, and utilize the infrared absorption characteristics of the gas to be detected to detect the concentration of the gas to be detected. For example, an infrared sensor module has been proposed that includes an infrared sensor, an IC (Integrated Circuit) that processes the output signal of the infrared sensor, and a package that houses the infrared sensor and the IC. In small infrared sensor modules, the IC sometimes processes signals based on tiny currents in the nA range, and in order to improve detection accuracy, it is necessary to suppress leakage current. For example, Patent Document 1 discloses an output current detection IC for a diode-type sensor that reduces the effects of leakage current.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: International Publication No. 2015 / 105048 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] The technology in Patent Document 1 is designed to reduce leakage current in a protective circuit and is difficult to directly apply to typical gas sensor measurements. Furthermore, existing methods for suppressing leakage current in gas sensor substrates are known, employing a layout that surrounds the infrared sensor at a ground potential. However, this existing method has limited effectiveness in suppressing leakage current, and a more effective method is desired.

[0008] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide an optical concentration measurement device and a signal processing unit that have an enhanced effect of suppressing leakage current.

[0009] Means for solving problems

[0010] (1) An optical concentration measuring device according to one embodiment of the present disclosure includes:

[0011] a light source for emitting light toward a gas detection space into which a gas to be detected is introduced;

[0012] a detection unit that detects a signal based on at least a portion of the light emitted from the light source and passing through the detection target gas, and outputs a detection signal;

[0013] a signal processing unit, which acquires the detection signal and converts it into a digital signal; and

[0014] A substrate is provided with the detection unit and the signal processing unit,

[0015] The detection unit includes a first detection unit and a second detection unit.

[0016] The signal processing unit forms a terminal arrangement in which a plurality of signal terminals are sandwiched between a plurality of voltage terminals, the plurality of signal terminals being input and output terminals of a signal line electrically connected to the detection unit, the plurality of voltage terminals supplying a constant voltage other than 0V and being not electrically connected to the detection unit,

[0017] The plurality of voltage terminals include a first voltage terminal, a second voltage terminal, and a third voltage terminal.

[0018] In a top view of the substrate viewed from the front, the wiring connecting the first voltage terminal and the second voltage terminal and the signal processing unit surround the signal line connecting the first detection unit and the signal processing unit, and the wiring connecting the second voltage terminal and the third voltage terminal and the signal processing unit surround the signal line connecting the second detection unit and the signal processing unit.

[0019] (2) As one embodiment of the present disclosure, in (1),

[0020] The plurality of signal terminals include at least two signal terminals for connecting to the first detection unit and sandwiched between the first voltage terminal and the second voltage terminal, and at least two signal terminals for connecting to the second detection unit and sandwiched between the second voltage terminal and the third voltage terminal.

[0021] (3) As one embodiment of the present disclosure, in (2),

[0022] The plurality of signal terminals include two signal terminals connected to the first detection unit and sandwiched between the first voltage terminal and the second voltage terminal, and two signal terminals connected to the second detection unit and sandwiched between the second voltage terminal and the third voltage terminal.

[0023] (4) As one embodiment of the present disclosure, in any one of (1) to (3),

[0024] In a plan view of the substrate viewed from the front, all of the plurality of voltage terminals and the plurality of signal terminals are provided on one side of the rectangular signal processing portion.

[0025] (5) As one embodiment of the present disclosure, in any one of (1) to (4),

[0026] A portion of wiring connecting the first voltage terminal and the second voltage terminal is shared with a portion of wiring connecting the second voltage terminal and the third voltage terminal.

[0027] (6) As one embodiment of the present disclosure, in any one of (1) to (5),

[0028] The length of wiring from the signal processing unit to the first detection unit is shorter than the length of wiring from the signal processing unit to the second detection unit.

[0029] (7) As one embodiment of the present disclosure, in any one of (1) to (6),

[0030] The wiring has a cut portion at a portion thereof, and the length of the cut portion is 1 / 10 or less of the length of a signal line connecting the signal terminal to the detection unit.

[0031] (8) A signal processing unit according to one embodiment of the present disclosure is used in the optical concentration measuring device according to any one of (1) to (7).

[0032] Effects of the Invention

[0033] According to the present invention, it is possible to provide an optical concentration measuring device and a signal processing unit with an enhanced leakage current suppression effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a diagram showing a configuration example of a gas sensor according to one embodiment of the present disclosure.

[0035] Figure 2 This is a top view of the substrate viewed from the front. Figure 1 Figure 1 shows a portion of a gas sensor.

[0036] Label Description

[0037] 10Gas Sensors

[0038] 11 Light Source

[0039] 11a Luminous surface

[0040] 12 light source substrate

[0041] 20 Testing Department

[0042] 21 First Detection Department

[0043] 22 Second Detection Unit

[0044] 23 Sealing part

[0045] 30 substrates

[0046] 30a main surface

[0047] 40 air chambers

[0048] 42 Gas detection space

[0049] 43 holes

[0050] 50 Signal Processing Unit DETAILED DESCRIPTION

[0051] Hereinafter, a gas sensor 10 according to an embodiment of the present disclosure will be described with reference to the accompanying drawings (see FIG. Figure 1 ) and the signal processing unit 50 (refer to Figure 2 ).

[0052] (Gas sensor 10)

[0053] Figure 1 This figure shows the structure of a gas sensor 10 according to this embodiment. The gas sensor 10 measures the presence or concentration of a target gas in a gas. In this embodiment, the gas sensor 10 is described as a device for measuring the concentration of a target gas. In this embodiment, the gas sensor 10 employs an NDIR (non-dispersive infrared) method, but is not limited to this. For example, a photoacoustic method may also be employed. An NDIR gas sensor 10 uses an infrared light-receiving element that receives infrared light in an absorption band corresponding to the target gas and an infrared light-emitting element that emits infrared light in the same absorption band to measure the concentration of the target gas. When the gas sensor 10 employs a photoacoustic method, the concentration of the target gas is measured by using a high-performance microphone to pick up the vibrations of gas molecules that have absorbed light as sound (pressure changes). The gas sensor 10 according to this embodiment can be applied to various devices. For example, it can be used for environmental measurement in buildings, as a portable, small-sized measurement device mounted on portable communication devices such as smartphones, and for indoor gas detection in mobile units such as cars, trains, and airplanes.

[0054] According to the structure of the gas sensor 10 in this embodiment, it can be applied as a light-receiving and light-emitting device for purposes other than gas detection. That is, the disclosure content derived by replacing the "gas sensor 10" in the above description with "optical concentration measuring device", "optical physical quantity measuring device", "light-receiving and light-emitting device", "optical device", etc. is included in the scope of this disclosure. For example, it is possible to detect the state of the optical path space (as an example other than gas, the presence or concentration of a specific component of the fluid, etc.). For example, it can be used for a component detection device or a component concentration measurement device for a substance (such as water or body fluid) present in the optical path space between the light-emitting part and the light-receiving part. For example, when the substance present in the optical path space is blood, the component detection device or the component concentration measurement device can be used for measuring the glucose concentration in the blood, etc.

[0055] The component detection device or the component concentration measuring device can measure the glucose concentration in blood glucose by measuring the absorption of light with a wavelength of 1 to 10 μm. In the measurement of the glucose concentration in blood glucose, it is preferred to measure the absorption of light in the 1.6 μm band, the 2.0 μm band, and the 10.0 μm band. A small, high-precision, and highly reliable non-invasive glucose concentration meter can be realized. With such a glucose concentration meter, for example, a diabetic patient can accurately investigate the blood glucose level without causing damage to the skin that would be caused by an invasive method. In addition, based on the investigated blood glucose level, more accurate management of medication (such as insulin) can be achieved.

[0056] The gas sensor 10 includes a light source 11, a detection unit 20, and a signal processing unit 50 (see Figure 2 ) and a substrate 30. In this embodiment, the detection unit 20 is composed of a first detection unit 21 and a second detection unit 22. In addition, the gas sensor 10 includes a gas chamber 40. Here, the detection unit 20 detects a signal based on the light emitted from the light source 11 and outputs a detection signal. The signal detected by the detection unit 20 may be the light itself (the above-mentioned NDIR method) or may include the vibration of gas molecules that have absorbed the light (the above-mentioned photoacoustic method).

[0057] The gas chamber 40 has a hole 43 for gas (such as ambient air) to pass through, and gas is introduced into the gas detection space 42 from the hole 43. The gas sensor 10 measures the concentration of the gas to be detected in the introduced gas. The gas to be detected can be a combustible gas such as carbon dioxide, breath alcohol (ethanol, etc.), methane, propane, hydrogen, ethylene, MCH (methylcyclohexane), etc. In addition, the gas to be detected can be a toxic gas such as carbon monoxide, hydrogen sulfide, formaldehyde, ammonia, etc. Moreover, the gas to be detected can be a greenhouse gas such as nitric oxide, refrigerant gas (Freon, alternative Freon, R32, R1234y) used in air conditioners or refrigerators, etc. The gas sensor 10 measures the concentration of the gas to be detected in the gas introduced into the gas detection space 42, and outputs the measurement result.

[0058] The gas sensor 10 is configured to include a gas cell 40 on a main surface 30a of a substrate 30. The main surface 30a is one of the surfaces having the largest area among the surfaces of the substrate 30. Figure 1 As shown, the orthogonal coordinates are set in a manner that the xy plane is parallel to the main surface 30a of the substrate 30. The z-axis direction is a direction perpendicular to the main surface 30a of the substrate 30. The z-axis direction is sometimes referred to as the up-down direction. In this case, the positive direction of the z-axis corresponds to the upward direction. In addition, the top view is a manner of observing toward the negative direction of the z-axis (downward direction). In this embodiment, the light source 11, the detection unit 20 and the signal processing unit 50 are provided on the main surface 30a of the substrate 30, and are arranged inside the gas detection space 42 above the main surface 30a.

[0059] In this embodiment, the second detection unit 22 is integrated with the light source 11. Specifically, the light source 11 and the second detection unit 22 are sealed by the sealing unit 23 on one surface of the light source substrate 12. In other words, the light source substrate 12, the light source 11, the second detection unit 22, and the sealing unit 23 are integrated to form a light source module. Figure 1 1 is a cross-sectional view showing a cross section of the gas sensor 10 including these components. Here, regarding the first detection portion 21, a detection substrate may be present on the light incident side in a manner corresponding to the light source substrate 12, but for ease of observation, Figure 1 Not shown.

[0060] Figure 2 This is a top view of the substrate 30 viewed from the front. Figure 1 A diagram obtained by a portion of the gas sensor 10. In detail, Figure 2 This is a diagram obtained by looking down at the substrate 30 on which the detection unit 20 (the first detection unit 21 and the second detection unit 22) and the signal processing unit 50 are provided, through the gas chamber 40, the light source substrate 12, the light source 11, and the sealing portion 23. The following describes the details of the components of the gas sensor 10, and then Figure 2 The layout of the signal processing unit 50 and the substrate 30 shown in FIG.

[0061] (Substrate 30)

[0062] The substrate 30 holds the gas chamber 40, the light source module, the first detection unit 21, and the signal processing unit 50. In this embodiment, the substrate 30 is a printed circuit board (PCB), which mounts the light source module, the first detection unit 21, and the signal processing unit 50 and provides electrical connections between them. Materials such as paper, glass cloth, ceramic, polyimide, and liquid crystal polymer can be used for the substrate 30.

[0063] (Air chamber 40)

[0064] As described above, the gas chamber 40 has a gas detection space 42 for detecting the gas to be detected. The gas detection space 42 is an internal space surrounded by the outer wall of the gas chamber 40 and the substrate 30. The material of the outer wall of the gas chamber 40 can be, for example, metal, glass, resin, or a composite material thereof. The resin can be, for example, phenolic resin, epoxy resin, polyimide resin, bismaleimide triazine resin, fluororesin, polyphenylene ether resin, LCP (liquid crystal polymer), PP (polypropylene) or PEEK (polyether ether ketone). In addition, the resin can be PA (polyamide), PPE (polyphenylene ether), PC (polycarbonate), PPS (polyphenylene sulfide), PMMA (polymethyl methacrylate resin) or PAR (polyarylate resin). In addition, the resin can be a hard resin obtained by mixing two or more of these materials. In addition, in order to efficiently confine the light emitted from the light source 11 in the gas chamber 40, the gas chamber 40 is preferably composed of a material with a small light absorption coefficient and a high reflectivity. Specifically, the material of the air chamber 40 is preferably a coated resin shell containing an alloy of aluminum, gold, or silver, a dielectric, or a laminate thereof. From the perspective of high productivity and lightweight, the inner surface of the air chamber 40 is preferably formed by vapor deposition or plating on the resin shell. In addition, the air chamber 40 can be formed by cutting, but from the perspective of productivity, it is preferably formed by injection molding or stamping. In addition, the air chamber 40 and the substrate 30 can be mechanically joined using adhesives, screws, claws, fittings, grommets, welding, soldering, etc.

[0065] Here, if the gas cell 40 is formed of a conductive material such as metal and the substrate 30 and gas cell 40 are electrically connected by solder or the like, the gas cell 40 can be fixed to a reference potential. By fixing the gas cell 40 to the reference potential, the gas cell 40 functions as an electromagnetic shield, thereby improving the performance of the gas being detected. The reference potential is, for example, ground potential.

[0066] (Light source 11)

[0067] The light source 11 emits light containing a wavelength absorbed by the detected gas. The light source 11 is also called a light emitting portion. The light source 11 can be provided on the main surface 30a of the substrate 30 inside the gas detection space 42. In the present embodiment, the light is infrared. That is, the light source 11 is composed of a light emitting element that emits infrared. The light emitting element is preferably driven at high speed by a voltage pulse or a current pulse. The light emitting element may be, for example, an LED (Light Emitting Diode), a laser (Light Amplification by Stimulated Emission of Radiation), a MEMS (Micro Electro Mechanical System) heater, a lamp, or the like. LEDs include, for example, resonant light emitting diodes, etc. Lasers include, for example, vertical resonator surface emitting lasers, etc. In the present embodiment, the light source 11 is an LED (infrared LED) that emits infrared rays. In addition, the light source 11 is preferably a quantum-type infrared LED that uses electrons or holes in a semiconductor to emit infrared rays so that it can be driven at a high frequency.

[0068] Here, the gas sensor 10 may further include a driving source that outputs a driving signal to drive the light emitting element. In this embodiment, the driving source is included in the signal processing unit 50. That is, a part of the signal processing unit 50 functions as the driving source.

[0069] Furthermore, the light source 11 may include auxiliary components having auxiliary optical functions such as wavelength selection, focusing, scattering, wavelength conversion, etc. Specifically, the auxiliary components include wavelength selection filters, lenses, phosphors, diffraction gratings, and the like.

[0070] The light source 11 emits light from a light emitting surface 11a. The light emitting surface 11a is the surface of the light source 11 that contacts the light source substrate 12. The light emitting surface 11a corresponds to the surface of the light source 11 that has the largest area.

[0071] Here, the wavelength of infrared light can be 2 μm to 12 μm. The wavelength range of 2 μm to 12 μm contains a variety of absorption bands specific to various gases, making it a wavelength band particularly suitable for use in the gas sensor 10. For example, methane has an absorption band at a wavelength of 3.3 μm, carbon dioxide has an absorption band at a wavelength of 4.3 μm, and alcohol (ethanol) has an absorption band at a wavelength of 9.5 μm.

[0072] A portion of the light emitted by the light source 11 may be directed toward the gas detection space into which the target gas is introduced. Furthermore, the remaining portion of the light emitted by the light source 11 may not be directed toward the gas detection space into which the target gas is introduced. The light emitted by the light source 11 may be directed directly toward the gas detection space into which the target gas is introduced, or may be directed toward the gas detection space into which the target gas is introduced via a reflective portion (light guide) such as a reflector.

[0073] (Sealing portion 23)

[0074] The sealing portion 23 is formed of, for example, a molded resin, but is not limited thereto as long as it seals the light source 11 and the second detection portion 22. When the sealing portion 23 is formed of a molded resin, the light source 11 and the second detection portion 22 can be integrated with the light source substrate 12 while maintaining their positional relationship. Examples of the material for the molded resin include epoxy resin and phenolic resin.

[0075] (Light source substrate 12)

[0076] The light source substrate 12 may be, for example, a semiconductor substrate. Examples of such semiconductor substrates include Si substrates, InP substrates, and GaAs substrates. Furthermore, the light source substrate 12 may include auxiliary components that provide auxiliary optical functions such as wavelength selection, focusing, scattering, and wavelength conversion. Specific examples of these auxiliary components include wavelength selection filters, lenses, phosphors, and diffraction gratings.

[0077] (Second Detection Unit 22)

[0078] The second detection unit 22 functions as a light detector that detects the amount of light emitted by the light source 11. The second detection unit 22 can be configured to include a light-receiving element that is sensitive to the wavelength band of light emitted from the light source 11. As a specific example, the light-receiving element can be a quantum sensor such as a photodiode having a PIN structure. As another example, the light-receiving element can be a phototransistor, a thermopile, a pyroelectric sensor, a bolometer, or the like. In the present embodiment, the light-receiving element is a quantum infrared sensor. The second detection unit 22 is arranged at a position where light emitted from the light source 11, which is reflected by the surface of the light source substrate 12 that is in contact with the gas detection space 42 and passes through the interior of the light source substrate 12, is incident. By being arranged at such a position, the second detection unit 22 can detect the amount of light emitted by the light source 11 regardless of the usage environment.

[0079] Here, the gas sensor 10 includes an analog-to-digital converter that converts the analog signal (detection signal) output by the second detection unit 22 into a digital signal. Furthermore, the analog signal (detection signal) output by the first detection unit 21 is also converted into a digital signal. In this embodiment, the analog-to-digital converter is included in the signal processing unit 50. Specifically, the signal processing unit 50 has the function of acquiring the detection signal output by the detection unit 20 and converting it into a digital signal.

[0080] (First Detection Unit 21)

[0081] The first detection unit 21 detects changes corresponding to the amount of the detected gas present in the gas (air) within the gas detection space 42 when measuring the concentration of the detected gas. The first detection unit 21 is disposed on the main surface 30a of the substrate 30 within the gas detection space 42. In this embodiment, the first detection unit 21 can be configured to include a light-receiving element sensitive to the wavelength band of light emitted from the light source 11. As a specific example, the light-receiving element can be a quantum sensor such as a photodiode having a PIN structure. As another example, the light-receiving element can be a phototransistor, a thermopile, a pyroelectric sensor, a bolometer, or the like. In this embodiment, the light-receiving element is a quantum infrared sensor. The first detection unit 21 is disposed at a position where light emitted from the light source 11 that has passed through the gas detection space 42 is incident. A reflective portion (light guide) can be disposed within the gas detection space 42 to reflect the light emitted from the light source 11 and direct it toward the first detection unit 21. The reflective portion can be, for example, a concave mirror, and the reflective surface can be made of a metal with a high reflectivity, such as aluminum or gold.

[0082] The first detection unit 21 can receive light that has passed through the gas detection space into which the detection target gas is introduced, among the light emitted by the light source 11. The first detection unit 21 can receive both light that has passed through the gas detection space into which the detection target gas is introduced, and light that has not passed through the gas detection space into which the detection target gas is introduced, among the light emitted by the light source 11.

[0083] Here, as another example, when the gas sensor 10 is a photoacoustic type, the first detection unit 21 may be, for example, a microphone, an air pressure sensor, or a pressure sensor.

[0084] (Gas detection space 42)

[0085] The gas detection space 42 is partitioned by an outer wall and has a function of containing gas such as air in its inner space. The gas contained in the gas detection space 42 is replaced through the hole 43 .

[0086] (Hole 43)

[0087] Hole 43 is provided in a portion of the outer wall (side wall and top) of gas chamber 40 that defines gas detection space 42. Gas passes through hole 43, displacing the gas within gas detection space 42. Multiple holes 43 may be present. Hole 43 may be equipped with a dust filter for dust protection. The dust filter may be, for example, a nonwoven fabric or a Teflon (registered trademark) sheet.

[0088] (Signal Processing Unit 50)

[0089] The signal processing unit 50 can control the entire gas sensor 10. For example, the signal processing unit 50 can perform arithmetic processing for obtaining the concentration of the detected gas. That is, the signal processing unit 50 can calculate the concentration of the detected gas based on the detection signal from the detection unit 20. As described above, in this embodiment, the signal processing unit 50 has at least the function of acquiring the detection signal output from the detection unit 20 and converting it into a digital signal. In addition, in this embodiment, the signal processing unit 50 functions as a driving source for driving the light-emitting element. The signal processing unit 50 can be configured to include one or more processors. The processor is, for example, a general-purpose processor or a dedicated processor dedicated to specific processing, but is not limited thereto and can be any processor. The signal processing unit 50 can be a small signal processing device composed of an IC including one or more processors.

[0090] (Design of Gas Sensor 10)

[0091] Here, in the gas sensor 10 of this embodiment, in order to effectively suppress the leakage current and improve the measurement accuracy of the detected gas, Figure 2 The layout of the signal processing unit 50 and the substrate 30 is as shown.

[0092] First, the signal processing unit 50 has a plurality of voltage terminals for supplying voltage, and a signal line ( Figure 2 The input and output terminals (thin solid lines) are arranged as a plurality of signal terminals. The voltage supplied by the plurality of voltage terminals may be a constant voltage other than 0V. Here, the so-called constant voltage includes the case where it is considered to be approximately constant, taking into account errors such as voltage fluctuations caused by the operation of peripheral circuits, voltage fluctuations caused by component deviations, and voltage fluctuations caused by temperature characteristics. Figure 2 In the example, the plurality of voltage terminals are composed of a first voltage terminal TP1, a second voltage terminal TP2, and a third voltage terminal TP3. In this embodiment, the plurality of voltage terminals are not supplied with a ground potential (not 0V), but with an analog reference voltage used in an analog signal processing circuit. The analog signal processing circuit amplifies the detection signal as an analog signal or reduces noise. In addition, Figure 2In the example, the plurality of signal terminals are composed of two signal terminals (TS1, TS2) for connecting to the first detection unit 21 and two signal terminals (TS3, TS4) for connecting to the second detection unit 22. The two signal terminals (TS1, TS2) are clamped by the first voltage terminal (TP1) and the second voltage terminal (TP2). In addition, the two signal terminals (TS3, TS4) are clamped by the second voltage terminal (TP2) and the third voltage terminal (TP3). Here, the number of signal terminals clamped by the first voltage terminal (TP1) and the second voltage terminal (TP2) is at least two, for example, it can be three or more. Similarly, the number of signal terminals clamped by the second voltage terminal (TP2) and the third voltage terminal (TP3) is at least two, for example, it can be three or more.

[0093] In addition, in the gas sensor 10, the wiring ( Figure 2 The thick solid line) and the signal processing unit 50 surround the signal line ( Figure 2 That is, as the wiring layout of the substrate 30, the signal line ( Figure 2 Thin solid line) is simulated reference voltage wiring ( Figure 2 The thick solid line) shield. Figure 2 In the example shown in FIG1 , when viewed from above, the wiring connecting the first voltage terminal (TP1) and the second voltage terminal (TP2) and the signal processing unit 50 surround the signal line connecting the first detection unit 21 and the signal processing unit 50. In addition, the wiring connecting the second voltage terminal (TP2) and the third voltage terminal (TP3) and the signal processing unit 50 surround the signal line connecting the second detection unit 22 and the signal processing unit 50. Here, “surrounding” does not require that the wiring connecting multiple voltage terminals ( Figure 2 The thick solid line) completely surrounds the signal line ( Figure 2 "Surrounding" means using wiring that connects multiple voltage terminals ( Figure 2 The thick solid line) and the signal processing unit 50 surround the signal line ( Figure 2 In addition, the wiring surrounding the signal line and connecting multiple voltage terminals may have a cut-off portion in part. The cut-off portion is the portion where the wiring is not connected (the interrupted portion). However, in order to effectively suppress leakage current and improve the measurement accuracy of the detected gas, the length of the cut-off portion is preferably less than 1 / 10 of the length of the signal line connecting the signal terminal to the detection unit 20. Figure 2 In the wiring that connects multiple voltage terminals ( Figure 2The portion of the wiring (shown as a thick solid line) that overlaps with the first detection portion 21 or the second detection portion 22 is indicated by a dotted line. The wiring in the dotted line portion means that it passes below (in the negative z-axis direction) the first detection portion 21 or the second detection portion 22 in a top view of the substrate 30 from the front. As another example, the wiring connecting the multiple voltage terminals may extend in the xy plane direction by passing around the first detection portion 21 or the second detection portion 22, rather than passing below (in the negative z-axis direction) the first detection portion 21 or the second detection portion 22.

[0094] Here, assuming that the voltage of the signal line connecting the detection unit 20 and the signal processing unit 50 is Vsig and the analog reference voltage is Vref, leakage current is likely to flow when the difference between Vsig and Vref is large. Figure 2 R is the insulation resistance of substrate 30. Leakage current is given by |Vref - Vsig| / R. R is generally on the order of gigaohms, but the wiring on substrate 30 is not completely insulated. During operation of gas sensor 10 (i.e., during measurement of the detected gas), the value of Vsig (i.e., the level of the detection signal output by detection unit 20) is closer to Vref than to 0V. Therefore, in the structure of gas sensor 10 of this embodiment, |Vref - Vsig| is close to zero during operation of gas sensor 10, thereby suppressing leakage current during operation of gas sensor 10.

[0095] For example, in conventional technology, the detection unit 20 is surrounded by a ground potential. In such conventional technology, leakage current due to Vsig / R occurs during the operation of the gas sensor 10. Therefore, the gas sensor 10 of this embodiment can effectively suppress leakage current compared to conventional technology.

[0096] Here, in Figure 2 In the example, the signal processing unit 50 is rectangular when viewed from above, and all of the multiple voltage terminals and the multiple signal terminals are provided on one side of the signal processing unit 50. However, the signal processing unit 50 may also be a structure in which a portion of the multiple voltage terminals and the multiple signal terminals are provided on other sides. In addition, depending on the arrangement of the multiple voltage terminals and the multiple signal terminals, it is sometimes difficult to make the distance from the signal processing unit 50 to the first detection unit 21 and the distance from the signal processing unit 50 to the second detection unit 22 the same. In this case, for example, Figure 2 As shown, the first detection unit 21, which is directly related to the concentration measurement of the detected gas, is preferably arranged closer to the signal processing unit 50 than the second detection unit 22. In other words, the wiring length from the signal processing unit 50 to the first detection unit 21 is preferably shorter than the wiring length from the signal processing unit 50 to the second detection unit 22. This is to minimize the influence of noise on the detection signal from the first detection unit 21.

[0097] In order to miniaturize the gas sensor 10, it is preferable that a portion of the wiring connecting the first voltage terminal (TP1) and the second voltage terminal (TP2) is shared with a portion of the wiring connecting the second voltage terminal (TP2) and the third voltage terminal (TP3).

[0098] As described above, the optical concentration measuring device and the signal processing unit 50 of this embodiment can enhance the effect of suppressing leakage current during measurement by virtue of the above configuration.

[0099] While the embodiments of the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art may easily make various modifications or alterations based on the present disclosure. Therefore, it should be noted that such modifications or alterations are within the scope of the present disclosure.

[0100] In the above embodiment, the structure in which the detection unit 20 is two is described, but the detection unit 20 may be only one (first detection unit 21) or may be three or more. In addition, in the above embodiment, when the detection unit 20 is a plurality of structures, there is a common voltage terminal (i.e., TP2) sandwiched between the signal terminals for connection to each of them, but it may also be a structure in which there is no common voltage terminal. That is, in the above embodiment, the signal processing unit 50 has a terminal arrangement of 7 terminals (TP1, TS1, TS2, TP2, TS3, TS4, TP3). Here, TP2 may be separated into two terminals (TP2A, TP2B), and the signal processing unit 50 may have a terminal arrangement of eight terminals (TP1, TS1, TS2, TP2A, TP2B, TS3, TS4, TP3).

Claims

1. An optical concentration measuring device, wherein: The optical concentration measuring device comprises: a light source for emitting light toward a gas detection space into which a gas to be detected is introduced; a detection unit that detects a signal based on at least a portion of the light emitted from the light source and passing through the detection target gas, and outputs a detection signal; A signal processing unit, which obtains the detection signal and converts it into a digital signal; as well as A substrate is provided with the detection unit and the signal processing unit, The detection unit includes a first detection unit and a second detection unit. The signal processing unit forms a terminal arrangement in which a plurality of signal terminals are sandwiched between a plurality of voltage terminals, the plurality of signal terminals being input and output terminals of a signal line electrically connected to the detection unit, the plurality of voltage terminals supplying a constant voltage other than 0V and being not electrically connected to the detection unit, The plurality of voltage terminals include a first voltage terminal, a second voltage terminal, and a third voltage terminal. In a top view of the substrate viewed from the front, the wiring connecting the first voltage terminal and the second voltage terminal and the signal processing unit surround the signal line connecting the first detection unit and the signal processing unit, and the wiring connecting the second voltage terminal and the third voltage terminal and the signal processing unit surround the signal line connecting the second detection unit and the signal processing unit.

2. The optical concentration measuring device according to claim 1, wherein The plurality of signal terminals include at least two signal terminals for connecting to the first detection unit and sandwiched between the first voltage terminal and the second voltage terminal, and at least two signal terminals for connecting to the second detection unit and sandwiched between the second voltage terminal and the third voltage terminal.

3. The optical concentration measuring device according to claim 2, wherein: The plurality of signal terminals include two signal terminals connected to the first detection unit and sandwiched between the first voltage terminal and the second voltage terminal, and two signal terminals connected to the second detection unit and sandwiched between the second voltage terminal and the third voltage terminal.

4. The optical concentration measuring device according to any one of claims 1 to 3, wherein In a plan view of the substrate viewed from the front, all of the plurality of voltage terminals and the plurality of signal terminals are provided on one side of the rectangular signal processing portion.

5. The optical concentration measuring device according to any one of claims 1 to 3, wherein A portion of wiring connecting the first voltage terminal and the second voltage terminal is shared with a portion of wiring connecting the second voltage terminal and the third voltage terminal.

6. The optical concentration measuring device according to any one of claims 1 to 3, wherein: The length of wiring from the signal processing unit to the first detection unit is shorter than the length of wiring from the signal processing unit to the second detection unit.

7. The optical concentration measuring device according to any one of claims 1 to 3, wherein The wiring has a cut portion at a portion thereof, and the length of the cut portion is 1 / 10 or less of the length of a signal line connecting the signal terminal to the detection unit. 8 . A signal processing unit used in the optical concentration measuring device according to claim 1 .

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