Sensing sensor and sensing device

Abstract

To make a sensing device which senses a material to be sensed contained in ambient gas around a piezoelectric vibrator on the basis of a change of an oscillation frequency of the piezoelectric vibrator, have a simple device constitution and be usable in various temperature circumstances.SOLUTION: A sensing device includes an oscillation circuit which makes a piezoelectric vibrator capable of attachment and detachment of a material to be sensed vibrate, a temperature detection part provided along with a case enclosing the piezoelectric vibrator and the oscillation circuit for detecting the ambient temperature, a first temperature control mechanism for controlling the temperature of the piezoelectric vibrator to a temperature within a first temperature range, a second temperature control mechanism for controlling the temperature of the piezoelectric vibrator to a temperature within a second temperature range different from the temperature within the first temperature range, and a selection part which selects one of the first temperature control mechanism and the second temperature control mechanism to control the temperature of the piezoelectric vibrator by the selected temperature control mechanism and supplies electric power from a power supply part to the selected temperature control mechanism.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a sensor and a sensing device that senses a substance to be sensed by changing the frequency of a piezoelectric vibrator. [Background technology]

[0002] One known sensing device for detecting substances contained in gases is a quartz crystal microbalance (QCM), which utilizes the change in the oscillation frequency of a quartz crystal oscillator due to the adhesion of the substance. The temperature of the quartz crystal oscillator can be changed to allow the substance to adhere to and desorb from the quartz crystal oscillator. Types of QCMs include cryogenic QCMs (CQCMs), which use liquid nitrogen to cool the quartz crystal oscillator to a low temperature of approximately -190°C, and thermoelectric QCMs (TQCMs), which use a Peltier element to heat and cool the quartz crystal oscillator. The sensing device is configured to be able to detect substances using either a CQCM or a TQCM.

[0003] The sensing device comprises a sensing sensor including a quartz crystal oscillator and a measuring unit that measures frequency, with the sensing sensor for a CQCM device and the sensing sensor for a TQCM device having different configurations. The sensing sensor for a CQCM device includes a heater for raising the temperature of the quartz crystal oscillator from the low temperature described above, while the sensing sensor for a TQCM device includes the Peltier element described above, and is capable of adjusting the temperature of the quartz crystal oscillator to within a range of, for example, -80°C to 125°C. Patent Document 1 describes a technique for sharing a measuring unit to which the sensing sensor for a CQCM device and the sensing sensor for a TQCM device are connected. Patent Document 2 describes a technique for controlling the heating and cooling of a quartz crystal oscillator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 6894397 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-064599 Summary of the Invention [Problem to be solved by the invention]

[0005] Although the quartz crystal unit of the CQCM sensing device can be cooled to a relatively low temperature as described above, the use of liquid nitrogen results in a large-scale device configuration. For TQCM sensing devices, this large-scale device configuration can be avoided. However, Peltier elements are made of semiconductors whose insulating properties increase as the temperature decreases, for example, from -113°C (160K), and therefore do not function properly at such low temperatures. Therefore, the temperature of the quartz crystal unit of a TQCM sensing device cannot be lowered compared to a CQCM sensing device, and the temperature range in which the sensor can be placed is limited.

[0006] However, it is desirable to simplify the device configuration while enabling the crystal oscillator temperature to be varied over a wide range. For example, the use of a sensing device for experiments on water detection in the lunar environment is being considered. In this case, due to significant constraints on transportation from Earth to the lunar surface, the sensing device must be compact and have fewer components. Furthermore, temperatures on the lunar surface vary greatly depending on location and time of day, as can be seen from temperatures of approximately -233°C in the permanent shadow on the moon and temperatures ranging from approximately +117°C to -163°C in the equatorial region where sunlight alternates between daylight and darkness. Even on such a lunar surface, water can be detected by attaching water to the sensing device's crystal oscillator at a temperature where water undergoes a phase transition. However, the temperature range of the sensing sensor for TQCM is limited, as mentioned above, which limits the locations and time periods in which experiments can be conducted, making it inconvenient.

[0007] The sensing device of Patent Document 1 has a large-scale configuration because it is equipped with a main body that can be used to selectively use both a CQCM sensor and a TQCM sensor. Patent Document 2 does not disclose a method for solving this problem.

[0008] The present invention has been made under these circumstances, and its purpose is to provide a technology for a sensing device that senses a substance to be sensed contained in a gas surrounding a piezoelectric vibrator based on changes in the oscillation frequency of the piezoelectric vibrator, which can have a simple device configuration and can be used in a variety of temperature environments. [Means for solving the problem]

[0009] A sensing device according to the present invention senses a substance to be sensed contained in a gas surrounding a piezoelectric vibrator based on a change in the oscillation frequency of the piezoelectric vibrator, comprising: the piezoelectric vibrator to which the substance to be sensed can be attached and detached; an oscillation circuit that oscillates the piezoelectric vibrator; a case that encloses the piezoelectric vibrator and the oscillation circuit; a temperature detection unit attached to the case for detecting an ambient temperature; a first temperature adjustment mechanism for adjusting the temperature of the piezoelectric vibrator to a temperature within a first temperature range; a second temperature adjustment mechanism for adjusting the temperature of the piezoelectric vibrator to a temperature within a second temperature range different from the temperature within the first temperature range; a selection unit that selects one of the first temperature adjustment mechanism and the second temperature adjustment mechanism to adjust the temperature of the piezoelectric vibrator using the selected one and supplies power from a power supply unit; Equipped with. [Effects of the Invention]

[0010] According to the sensing sensor of the present invention, a sensing device that senses a substance to be sensed contained in a gas surrounding a piezoelectric vibrator based on changes in the oscillation frequency of the piezoelectric vibrator can be configured simply and can be used in a variety of temperature environments. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a longitudinal sectional side view of the sensing device according to the embodiment. [Figure 2] FIG. 2 is a block diagram showing the electrical configuration of the sensing device. [Figure 3] FIG. 2 is an overall configuration diagram showing the sensing device. [Figure 4] FIG. 2 is a configuration diagram showing an amplifier circuit. [Figure 5] FIG. 10 is an explanatory diagram showing the operation of the switch. [Figure 6] FIG. 10 is an explanatory diagram showing the operation of the switch. DETAILED DESCRIPTION OF THE INVENTION

[0012] The overall configuration of a sensing device 1 according to the present invention will be described with reference to Figs. 1 and 2. Fig. 1 is a longitudinal side view showing the sensing device 1. Fig. 2 is a block diagram showing the electrical configuration of the sensing device 1. The sensing device 1 comprises a measurement unit 2, a sensing sensor 3 arranged apart from the measurement unit 2 and electrically connected to the measurement unit 2, and a cooling unit 7 configured to mount the sensing sensor 3 and to cool it. The measurement unit 2 supplies power to the sensing sensor 3, and controls the temperature of a quartz oscillator 4 provided in the sensing sensor 3 and measures its oscillation frequency.

[0013] The cooling unit 7 is composed of a flow path 71, and a cooling medium such as water whose temperature is adjusted by a chiller (not shown) flows through a circulation path including the flow path 71. Hereinafter, the direction from the cooling unit 7 toward the detection sensor 3 will be referred to as "upward," and the opposite direction will be referred to as "downward." However, because the measurement unit 2 and the detection sensor 3 can be used in any orientation, the up-down direction does not necessarily coincide with the vertical direction. The cooling unit 7 has a through-hole 72 formed through the center of the top surface on which the detection sensor 3 is placed. This cooling unit 7 provides a heat dissipation path from the Peltier element that cools the quartz oscillator 4. In this example, the detection sensor 3 is placed in an experimental space with a temperature environment at or near room temperature, and the cooling unit 7 is provided as described above. However, depending on the temperature environment in which the detection sensor 3 is placed, the cooling unit 7 may not be provided. The detection sensor 3 is detachable from the cooling unit 7 and the measurement unit 2.

[0014] The sensing sensor 3 is used to detect a vaporized substance to be sensed in the experimental space. The sensing sensor 3 includes a quartz oscillator 4 and a temperature control mechanism 5, and is configured to attach and detach the substance to be sensed to the quartz oscillator 4, whose temperature is controlled by the temperature control mechanism 5 or the experimental space, and to detect the substance to be sensed by the measuring unit 2. The temperature of the quartz oscillator 4 is controlled by a cooling operation and a heating operation, and in parallel with this temperature control, the sensing device 1 measures the oscillation frequency, which is a detection operation.

[0015] The overall configuration of the detection sensor 3 will be described. As shown in Fig. 1, the detection sensor 3 includes a cylindrical lid 31 that is open at the bottom, a base 32 that closes the bottom of the lid 31, and a circuit board 40 and a sensor board 50 that are disposed in the internal space defined by the base 32 and the lid 31. The lid 31 and the base 32 form a case 30 that defines the internal space.

[0016] The base 32 is configured to be attached to the cooling unit 7 and is configured to be cooled from its underside, which contacts the upper surface of the cooling unit 7. The base 32 is formed, for example, from nickel-plated copper, and is composed of a base main body 33 and a lid 34. The base main body 33 is configured as a block that is circular in plan view, and has a circular protrusion 35 that protrudes upward in the center of the upper surface and a lower hole 36 that is recessed upward in the center of the lower surface. The lower hole 36 is formed, for example, in a disk shape, and a lower hole 36a that is further recessed upward is formed in the center of the bottom of the lower hole 36. The bottom of the lower hole 36a forms the central portion of the upper surface 35a of the protrusion 35, and multiple cylindrical through holes 37 are formed around the periphery of the bottom of the lower hole 36a. A conductive pin 65 is provided in the through hole 37 so as to penetrate vertically and extend upward from the upper surface 35a of the protrusion 35.

[0017] The lid 34 is attached to the lower opening of the lower hole 36 so as to fit along the lower surface of the base body 33. A through hole extending in the vertical direction is formed in the center of the lid 34, and a cable 61 (described below) extending vertically is disposed in the through hole. An annular protrusion 34a protruding upward is formed on the upper surface of the lid 34 so as to surround the through hole of the lid 34, and the circuit board 40 is placed on the annular protrusion 34a via a spacer. The spacer is a heat insulating member that suppresses heat transfer from the annular protrusion 34a to the circuit board 40.

[0018] The circuit board 40 includes a plate-shaped substrate body 41, an integrated circuit chip 4A configured with multiple silicon semiconductor elements and provided in the center of the upper surface of the substrate body 41, and a wiring pattern (not shown) connected to the integrated circuit chip 4A. The integrated circuit chip 4A includes semiconductor elements such as oscillation circuits 42 and 43 connected to the crystal oscillator 4 for oscillating the crystal oscillator 4, and a heater (not shown) for heating the oscillation circuits 42 and 43. A plurality of cables 61 are connected to the circuit board 40 so as to be connected to the wiring pattern. The cables 61 form conductive paths that electrically connect the wiring pattern provided on the substrate body 41 to connection terminals provided on a pair of connectors 62 provided on the lower side of the base 32. The pair of connectors 62 are electrically connected to the measurement unit 2 via the connection terminals, which are electrically connected by fitting together, and the cable on the measurement unit 2 side. The detection sensor 3 is electrically connected to the measurement unit 2 in a detachable manner via this pair of connectors 62.

[0019] A plurality of cylindrical sockets 63 extending vertically are arranged along the front-rear direction on the left and right ends of the upper surface of the substrate body 41. These sockets 63 are disposed between the bottoms of the pilot holes 36a and the substrate body 41. Conductive connection members are provided in the internal holes of the sockets 63, and these connection members are connected to the respective wiring patterns of the circuit board 40 and electrically connected to the integrated circuit chip 4A. Each socket 63 is disposed so that a corresponding pin 65 is inserted into the connection member of the socket 63. Holes are drilled in the thickness direction of the substrate body 41 at positions overlapping the holes of the sockets 63, and the lower ends of the pins 65 inserted into the sockets 63 are positioned in the holes and penetrate the substrate body 41. The upper ends of the pins 65 extending upward from the through holes 37 are positioned so as to penetrate the sensor board 50 and are connected to the respective wiring patterns (not shown) of the sensor board 50. The circuit board 40 and the sensor board 50 are electrically connected by the conductive paths formed thereby.

[0020] The sensor substrate 50 has a wiring pattern and a recess 56 formed on its upper surface, and an electric heater 51, which constitutes the temperature control mechanism 5, is embedded in it. The electric heater 51 is a heating resistor provided to heat the quartz crystal unit 4 via the sensor substrate 50. The quartz crystal unit 4 is disposed on the sensor substrate 50 so as to cover the opening of the recess 56 so as not to interfere with its oscillation. It includes a disk-shaped quartz crystal blank 4a, e.g., an AT-cut piezoelectric piece. As shown in FIG. 2 , the upper and lower surfaces of the quartz crystal blank 4a are respectively formed with a pair of first excitation electrodes (reaction electrodes) 4b, 4c, a pair of second excitation electrodes (reference electrodes) 4d, 4e, and wiring patterns (not shown) connected to these electrodes, each made of gold (Au). Therefore, the peripheral edge of the lower surface (one side) of the quartz crystal blank 4a is supported by the edge of the opening of the recess 56, and the excitation electrodes 4c, 4e face the space defined by the recess 56. A first oscillation circuit 42 is connected to the first excitation electrodes 4b and 4c, and a second oscillation circuit 43 is connected to the second excitation electrodes 4d and 4e.

[0021] In the crystal blank 4a, the region sandwiched between the first excitation electrodes 4b and 4c is the first vibration region 40A, and the region sandwiched between the second excitation electrodes 4d and 4e is the second vibration region 40B. Furthermore, a temperature detection unit 57 for detecting the temperature of the crystal unit 4 is provided on the top surface of the crystal blank 4a. The temperature detection unit 57 is, for example, a resistance temperature sensor whose resistance value changes with temperature. Therefore, when a preset voltage is applied, the current that flows is output as a temperature information value, and the temperature is measured from this current value.

[0022] The above-mentioned lid 31 covers the quartz crystal unit 4 and the sensor substrate 50 from above, and is arranged to surround the periphery of the protrusion 35 of the base 32, so as to engage with the base 32. A cone-shaped opening 31a is formed in the upper surface of the lid 31. The first excitation electrode 4b on the upper surface of the quartz crystal unit 4 faces the opening 31a, and the second excitation electrode 4d is isolated from the external space of the detection sensor 3. The lower end of the opening 31a is spaced 0.5 mm from the surface of the quartz crystal unit 4.

[0023] The temperature adjustment mechanism 5 is composed of, for example, a Peltier element unit 52 and the electric heater 51 described above. The Peltier element unit 52 is sandwiched between the sensor substrate 50 and the protrusion 35 and is composed of two stacked Peltier elements 52a and 52b. Specifically, a thermally conductive sheet 66, an upper Peltier element 52a, a lower Peltier element 52b, and a thermally conductive sheet 67 are stacked in this order between the sensor substrate 50 and the protrusion 35. The lower surface of the upper Peltier element 52a and the upper surface of the lower Peltier element 52b are in close contact with each other. The thermally conductive sheet 66 is in close contact with the lower surface of the sensor substrate 50 and the upper surface of the upper Peltier element 52a, respectively, and the thermally conductive sheet 67 is in close contact with the upper surface of the protrusion 35 and the lower surface of the lower Peltier element 52b, respectively. The thermally conductive sheets 66 and 67 have relatively high thermal conductivity in the vertical direction and are composed of, for example, graphite sheets.

[0024] The temperatures of the upper and lower surfaces of the Peltier elements 52a and 52b are changed by the supply of power. That is, one of the upper and lower surfaces of the Peltier elements 52a and 52b serves as a heat dissipation surface and the other as a heat absorption surface, and the heat dissipation and heat absorption surfaces are switched back and forth by switching the direction of the supplied current. Specifically, when cooling the sensor substrate 50, the upper surfaces of the Peltier elements 52a and 52b serve as heat absorption surfaces and the lower surfaces serve as heat dissipation surfaces, respectively. When heating the sensor substrate 50, the upper surfaces of the Peltier elements 52a and 52b serve as heat dissipation surfaces and the lower surfaces serve as heat absorption surfaces. In this way, the Peltier element unit 52 can appropriately heat and cool the crystal resonator 4 via the sensor substrate 50, and high cooling performance is achieved by stacking the Peltier elements 52a and 52b on top of each other. For example, if the temperature of the experimental space is room temperature, the Peltier element unit 52 is configured to adjust the temperature of the crystal oscillator 4 between -80°C and +125°C.

[0025] On the other hand, the excitation electrodes 4b to 4e, the electric heater 51, and the temperature detection unit 57 are each electrically connected to the wiring pattern of the circuit board 40 via the wiring pattern, pins 65, and sockets 63 formed on the sensor board 50, and are further connected to the measurement unit 2 via conductive paths such as cables 61 and connectors 62. By forming the conductive paths as described above, power is supplied from the measurement unit 2 to each circuit element such as the oscillation circuit 42 and the oscillation circuit 43, the electric heater 51, the Peltier element unit 52, and the temperature detection unit 57, and the measurement unit 2 can acquire oscillation frequency signals from the oscillation circuits 42 and 43 and temperature information values ​​from the temperature detection unit 57.

[0026] The measurement unit 2 will be described below with reference to the already mentioned Fig. 2. In this example, the measurement unit 2 is installed in a space isolated from the experimental space, but it may be installed in any location as long as it does not interfere with the measurement. The measurement unit 2 includes a data processing unit 21 and a switch 22. The switch 22 connects the data processing unit 21 to either the first or second oscillation circuit 42 or 43. The first frequency signal of the first vibration area 40A and the second frequency signal of the second vibration area 40B are input in a time-division manner by switching the switch 22. The data processing unit 21 performs digital processing on the time-division first and second frequency signals to acquire time-series data of the first oscillation frequency "F1" of the first vibration area 40A and time-series data of the second oscillation frequency "F2" of the second vibration area 40B. Although not shown, the measurement unit 2 also includes a display unit that displays the oscillation frequencies F1 and F2, and an operation unit such as a button that commands the user to execute a predetermined operation.

[0027] The measurement unit 2 is also provided with a CPU 20, a voltage adjustment unit 23, a temperature conversion unit 24, and an EEPROM 25. The temperature conversion unit 24 generates a voltage (referred to as a temperature detection voltage Va) within a range of 0V to 10V, for example, corresponding to the temperature T detected by the temperature detection unit 57, based on the current value from the temperature detection unit 57, and supplies the voltage adjustment unit 23. The CPU 20 also calculates the detected temperature T from the current value. Note that the temperature detection unit 57 is provided in the crystal unit 4, and therefore the detected temperature T is the temperature of the crystal unit 4.

[0028] The voltage adjustment unit 23 applies a voltage to one of the Peltier element unit 52 and the electric heater 51 according to the difference between the detected temperature T and the target temperature of the crystal oscillator 4, thereby adjusting the temperature of the crystal oscillator 4. Therefore, the power supply destination is switched to either the Peltier element unit 52 or the electric heater 51. A reference temperature T0 is stored in the EEPROM 25, and the CPU 20 compares this reference temperature T0 with the detected temperature T and controls the operation of switches 26a and 26b, which will be described later, so that the power supply destination is switched based on the result of the comparison.

[0029] To explain the switching of the power supply destination in more detail, the Peltier element unit 52 (Peltier elements 52a, 52b) is highly convenient because it can heat and cool the crystal oscillator 4 without requiring the flow of a fluid that is difficult to handle, such as liquid nitrogen. However, as described in the section on the solution to be solved by the invention, if the temperature of the environment in which the detection sensor is placed is relatively low, the Peltier element unit 52 cannot operate. Therefore, when controlling the temperature of the crystal oscillator 4, if the detected temperature T is higher than the reference temperature T0, the Peltier element unit 52 is used, and the power supply destination is set to the Peltier element unit 52. On the other hand, if the detected temperature T is equal to or lower than the reference temperature T0, the power supply destination is set to the electric heater 51.

[0030] When the detected temperature T is equal to or lower than the reference temperature T0, it means that the temperature of the environment in which the sensor 3 is placed is relatively low. Therefore, the cooling effect on the crystal unit 4 depends on this environmental temperature, and the temperature of the crystal unit 4 is controlled by balancing the cooling at this environmental temperature with the action of the electric heater 51. By configuring the sensor to switch the power supply in this way, the environmental temperature range in which the temperature of the crystal unit 4 can be controlled is expanded compared to a sensor configuration that includes only the Peltier unit 52 out of the Peltier unit 52 and the electric heater 51. In order to expand the temperature range in this way, the reference temperature T0 stored in the EEPROM 25 is set to a relatively low temperature within the range in which the temperature of the crystal unit 4 can be controlled by the Peltier unit 52, specifically, −80° C. or lower. The temperature range higher than the reference temperature T0 in which the temperature is controlled by the Peltier unit 52 is the first temperature range, and the temperature range lower than the reference temperature T0 in which the temperature is controlled by the electric heater 51 is the second temperature range.

[0031] Next, the description of the measurement unit 2 will continue with reference to the block diagram of Figure 3, which shows the voltage adjustment unit 23 in detail. The voltage adjustment unit 23 is composed of a temperature adjustment unit 2A, an amplifier circuit 29, a variable regulator 28, a constant voltage regulator 27, and switches 26a and 26b. The temperature adjustment unit 2A, the amplifier circuit 29, the variable regulator 28, and the constant voltage regulator 27 form a power supply unit common to the Peltier element unit 52 and the heater 51, and the switches 26a and 26b form a selection unit that selects the destination of power supply from the power supply unit. A voltage of, for example, 24 V is applied to the temperature adjustment unit 2A, the variable regulator 28, and the constant voltage regulator 27 from a power supply (not shown).

[0032] The temperature conversion unit 24 described in FIG. 2 applies a temperature detection voltage Va to the temperature adjustment unit 2A. Then, the temperature adjustment unit 2A supplies a voltage (hereinafter referred to as a temperature adjustment voltage Vb) to an amplifier circuit 29, which is a control voltage supply unit. This temperature adjustment voltage Vb changes according to the difference between the temperature detection voltage Va input to the temperature adjustment unit 2A and a voltage corresponding to the target temperature of the crystal resonator 4, and is set to a value calculated by the CPU 20 through a predetermined calculation. The temperature adjustment voltage Vb is input to the amplifier circuit 29, and a control voltage Vc corresponding to the temperature adjustment voltage Vb is applied to the control terminal ADJ of the variable regulator 28. The variable regulator 28 outputs a voltage V1 corresponding to this control voltage Vc.

[0033] A switch 26a is provided downstream of the variable regulator 28, and the destination of the voltage V1 is switched between the terminal A1 of the Peltier elements 52a and 52b and the terminal A3 of the electric heater 51. As will be described later, the range of the voltage V1 that can be applied to the Peltier elements 52a and 52b is different from the range of the voltage V1 that can be applied to the electric heater 51.

[0034] A switch 26b is provided in the subsequent stage of the constant voltage regulator 27. The output voltage V2 of the constant voltage regulator 27 is, for example, 10 V, and the destination of application of the voltage V2 is switched between the terminals A2 of the Peltier elements 52a and 52b and the terminal A4 of the electric heater 51 via the switch 26b.

[0035] 3 shows only Peltier element 52a out of Peltier elements 52a and 52b. As shown in FIGS. 5 and 6, Peltier elements 52a and 52b are provided in parallel with switches 26a and 26b after switches 26a and 26b, respectively. Therefore, the application and stop of voltages V1 and V2 to the terminals of Peltier elements 52a and 52b from variable regulator 28 and constant voltage regulator 27 are performed simultaneously and in the same way between Peltier elements 52a and 52b.

[0036] The switching of switches 26a and 26b is controlled by CPU 20. Switches 26a and 26b switch between a state in which voltages V1 and V2 are applied to terminals A1 and A2, respectively, and the temperature of crystal unit 4 is controlled by Peltier element unit 52, and a state in which voltages V1 and V2 are applied to terminals A3 and A4, respectively, and the temperature of crystal unit 4 is controlled by electric heater 51. Terminals A2 and A3 are grounded. The two-dot chain arrows in the figure indicate switching signals output from CPU 20 for switching switches 26a and 26b and switch SW (described later) of amplifier circuit 29.

[0037] The amplifier circuit 29 will be described with reference to the circuit diagram in Figure 4. Specifically, the amplifier circuit 29 is configured as a non-inverting amplifier circuit using an operational amplifier 29a, and is configured to feed back from the output side of the operational amplifier 29a to the negative input side via a resistor R1. Resistors R2 and R3 are also provided in parallel with each other on the negative input side of the operational amplifier 29a, and the connection on the resistor R2 side is configured to be switched by a switch SW. As described above, the switching of the switch SW is controlled by the CPU 20.

[0038] The amplification factor of amplifier circuit 29 is expressed as 1 + (Rf / RS), where RS is the combined resistance of resistors R2 and R3, and Rf is the resistance of resistor R1. When switch SW is off, RS increases and the amplification factor of amplifier circuit 29 decreases compared to when switch SW is on, resulting in a relatively small amplification of temperature adjustment voltage Vb and a small control voltage Vc. Switch SW operates in synchronization with switches 26a and 26b, and is on while switches 26a and 26b are connected to terminals A1 and A2, and is off while switches 26a and 26b are connected to terminals A3 and A4.

[0039] The voltage V1 output from variable regulator 28 is, for example, 0V to 10V while switch SW is off, and 0V to 20V while switch SW is on. Therefore, while switches 26a and 26b are connected to terminals A1 and A2, the potential difference between terminals A1 and A2 of Peltier elements 52a and 52b can be changed within a range of +10V to -10V. This makes it possible to change the direction and amount of current flowing between terminals A1 and A2, and to change the temperature of crystal unit 4 within the above range. Note that when current flows from terminal A1 to terminal A2, the top surfaces of Peltier elements 52a and 52b act as heat dissipation surfaces, and when current flows in the opposite direction, these top surfaces act as heat absorption surfaces.

[0040] Furthermore, while switches 26a and 26b are connected to terminals A3 and A4, the potential difference between terminals A3 and A4 can be changed within a range of 0 V to 10 V, thereby changing the amount of heat generated by electric heater 51. The range of voltage V1 that can be output is changed by turning switch SW on and off so that the voltages applied to Peltier element unit 52 and electric heater 51 do not exceed their rated values.

[0041] The operation of the sensing device 1 configured as described above will now be described. The user performs a predetermined operation on the operation unit of the measurement unit 2 to instruct the device to start operating. The first vibration area 40A and the second vibration area 40B of the quartz crystal resonator 4 oscillate, and the measurement unit 2 begins monitoring the first oscillation frequency F1 and the second oscillation frequency F2. These first oscillation frequency F1 and second oscillation frequency F2 are then displayed on the screen. Meanwhile, the temperature detection unit 57 measures current to obtain the detected temperature T, which is then compared with the reference temperature T0. If the comparison results in the detected temperature T being higher than the reference temperature T0, the switches 26a and 26b connect the variable regulator 28 to the terminals A1 of the Peltier elements 52a and 52b, and the constant voltage regulator 27 to the terminals A2 of the Peltier elements 52a and 52b, as shown in FIG. 5. Meanwhile, the switch SW of the amplifier circuit 29 is turned on. A control voltage Vc is output to the variable regulator 28 so that the output voltage V1 becomes a value corresponding to the difference between a preset target temperature of the crystal resonator 4 and the detected temperature T, and the detected temperature T is controlled to become the target temperature.

[0042] 5, switches 26a and 26b connect variable regulator 28 to terminal A3 of electric heater 51, and constant voltage regulator 27 to terminal A4 of electric heater 51. Meanwhile, switch SW of amplifier circuit 29 is turned off. Then, control voltage Vc is output to variable regulator 28 so that output voltage V1 becomes a value corresponding to the difference between a preset target temperature of crystal resonator 4 and detected temperature T, and detected temperature T is controlled to become the target temperature.

[0043] While the temperature of the crystal unit 4 is being controlled in this manner, the first oscillation frequency F1 and the second oscillation frequency F2 are continuously monitored. Note that the target temperature of the crystal unit 4 does not necessarily have to be constant during this monitoring, but may be varied over time. Specifically, for example, the target temperature may be gradually increased from an arbitrary first temperature to reach the second temperature. In other words, the temperature of the crystal unit 4 may be gradually increased to measure the first oscillation frequency F1 and the second oscillation frequency F2. Note that this target temperature control is also performed by the CPU 20.

[0044] From the difference between the first oscillation frequency F1 and the second oscillation frequency F2, the user can obtain information regarding the adhesion and desorption of the target substance contained in the gas in the experimental space to the first excitation electrode 4b. For example, the target substance can be identified and the amount of adhesion can be calculated. Furthermore, by changing the target temperature in this way, the detection temperature T is continuously acquired and compared with the reference temperature T0 while the temperature of the quartz crystal resonator 4 is being changed, and the switches 26a, 26b, and SW are switched depending on the comparison result.

[0045] According to the sensing device 1 described above, the sensing sensor 3 can control the temperature of the quartz crystal oscillator 4 over a relatively wide range. Therefore, there is no need to prepare multiple different types of sensing sensors, each including a quartz crystal oscillator 4, as in Patent Document 1. Therefore, the sensing device 1 is highly convenient as it is possible to control the temperature of the quartz crystal oscillator 4 in various temperature environments as described above, while reducing the number of components and simplifying the device configuration. Therefore, it is possible to sense moisture on the lunar surface as described in the section on the problem to be solved by the invention, and the burden of transporting the sensing device to the lunar surface is also reduced.

[0046] Incidentally, the switches 26a and 26b do not necessarily have to be provided in the measurement unit 2, but may also be provided in the sensing sensor 3. Specifically, the switches 26a and 26b may be incorporated in the integrated circuit chip 4A. The reference temperature T0 stored in the EEPROM 25 described above may be rewritable by a user operating the operation unit of the measurement unit 2. Furthermore, the switches 26a, 26b, and SW are not necessarily switched by the CPU 20. The detected temperature T may be displayed on a screen of the measurement unit 2, and the user, viewing this screen display, may perform a predetermined operation on the operation unit to switch each switch.

[0047] The temperature detection unit 57 may be provided on the sensor substrate 50 instead of on the crystal unit 4. Furthermore, a temperature detection unit for judgment, which serves as a criterion for determining whether to switch each switch, may be provided on the sensing sensor 3, separate from the temperature detection unit 57 on the crystal unit 4. That is, the switching of the switches may be performed based on a comparison between the detected temperature T acquired from the dedicated temperature detection unit and the reference temperature T0, and the temperature control for adjusting the crystal unit 4 to the target temperature may be performed based on the detection result of the temperature detection unit 57 on the crystal unit 4, as in the above embodiment. In this way, the temperature detection unit for judgment only needs to be able to detect the temperature around the sensing sensor 3, and may be provided on, for example, the surface of the case 30 consisting of the lid 31 and the base 32.

[0048] The temperature sensor for determining whether to switch the switch in this way need only be attached to the case 30 so as to be able to detect the temperature of the environment in which the detection sensor 3 is placed, and is not limited to being attached to the crystal unit 4. Here, "attached to the case 30" means that the sensor moves with the case 30 when the case is moved, and therefore specifically means being provided inside the case 30 or being provided on the case 30 itself.

[0049] The electric heater 51 only needs to be able to heat the crystal resonator 4. Therefore, it is not limited to being provided on the sensor substrate 50, and may be provided on the wall surface of the case 30, for example, but it is preferable to provide it on the sensor substrate 50 in order to increase the heat transfer efficiency.

[0050] It should be noted that the embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects, and various omissions, substitutions, modifications, and combinations may be made to the above-described embodiments without departing from the scope and spirit of the appended claims. [Explanation of symbols]

[0051] 1 Sensing device 26a Switch 26b Switch 27 Constant voltage regulator 28 Variable Regulator 29 Amplification circuit 30 cases 4 crystal oscillator 42, 43 Oscillator circuit 51 Electric heater 52 Peltier element unit 57 Temperature detection unit

Claims

1. 1. A sensing device that senses a substance to be sensed contained in a gas surrounding a piezoelectric vibrator based on a change in the oscillation frequency of the piezoelectric vibrator, the piezoelectric vibrator to which the substance to be sensed can be attached and detached; an oscillation circuit that oscillates the piezoelectric vibrator; a case that encloses the piezoelectric vibrator and the oscillation circuit; a temperature detection unit attached to the case for detecting an ambient temperature; a first temperature adjustment mechanism for adjusting the temperature of the piezoelectric vibrator to a temperature within a first temperature range; a second temperature adjustment mechanism for adjusting the temperature of the piezoelectric vibrator to a temperature within a second temperature range different from the temperature within the first temperature range; a selection unit that selects one of the first temperature adjustment mechanism and the second temperature adjustment mechanism to adjust the temperature of the piezoelectric vibrator using the selected one and supplies power from a power supply unit; A sensing device comprising:

2. the first temperature adjustment mechanism is a Peltier element, 2. The sensing device according to claim 1, wherein the second temperature control mechanism is a heating resistor.

3. 3. The sensing device according to claim 2, further comprising a control section for controlling the operation of said selection section based on the temperature detection result by said temperature detection section.

4. the power supply unit includes a variable regulator; the selection unit includes a switch that switches the destination of the voltage from the variable regulator between the Peltier element and the heating resistor, 4. The sensing device according to claim 3, further comprising a control voltage supply unit that applies a control voltage to the variable regulator so that the range of voltage that can be applied to the Peltier element and the range of voltage that can be applied to the heating resistor are different.

5. a support member that supports the piezoelectric vibrator from one surface side of the piezoelectric vibrator and forms a space on the one surface side where an excitation electrode of the piezoelectric vibrator faces; 5. The sensing device according to claim 4, wherein the heating resistor is provided on the support member.

6. 6. The sensing device according to claim 5, wherein the temperature detection unit is provided on the piezoelectric vibrator, and the temperature of the piezoelectric vibrator is detected as the ambient temperature.

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