Sensing device

Abstract

To make a piezoelectric vibrator stably vibrate and measure a frequency in a sensing device for sensing a material to be sensed which attaches to the piezoelectric vibrator and is contained in gas.SOLUTION: A sensing device for sensing a material to be sensed which is contained in ambient gas around a piezoelectric vibrator and attaches to the piezoelectric vibrator, on the basis of a change of an oscillation frequency of the piezoelectric vibrator, includes a piezoelectric vibrator which is cooled so that the material to be sensed is attached to the piezoelectric vibrator, a temperature change part for changing the temperature of the piezoelectric vibrator, a substrate provided with an integrated circuit chip including an oscillation circuit which makes the piezoelectric vibrator vibrate, a frequency measurement part which receives a frequency signal output from the oscillation circuit and measures the oscillation frequency of the piezoelectric vibrator, a heater provided separately from the temperature change part to heat the integrated circuit chip, and a power supply part which can change electric power supplied to the heater.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] For example, a device that uses a quartz crystal microbalance (QCM) with a quartz oscillator is known as a sensing device for detecting substances contained in gas. In this sensing device, the quartz oscillator is cooled to an extremely low temperature, for example, around -190°C, causing gas to adhere to the oscillator. The temperature of the quartz oscillator is then gradually increased, causing the gas to desorb from the oscillator. From the change in oscillation frequency due to this desorption and the temperature at which the change in oscillation frequency occurs, it is possible to perform analyses such as identifying the gas components and detecting the amount of gas attached.

[0003] Patent Document 1 describes a technique for increasing the sensitivity of a sensor by cooling a quartz oscillator, and Patent Document 2 describes a technique for cooling a substrate on which an IC chip is mounted. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-203007 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-220454 Summary of the Invention [Problem to be solved by the invention]

[0005] The sensing device described above includes a sensing sensor that is placed in the environment where the measurement is to be performed. For example, the sensing sensor is provided with an integrated circuit chip in addition to the quartz crystal oscillator. To prevent the oscillation from becoming unstable due to the relatively large distance from the quartz crystal oscillator, the oscillation circuit that oscillates the quartz crystal oscillator is incorporated into the integrated circuit chip and provided within the sensing sensor.

[0006] When semiconductors such as silicon that make up integrated circuit chips are cooled excessively, the carrier density decreases, increasing their insulating properties. Therefore, when cooling a quartz crystal unit to attach a substance to be sensed, it is necessary to prevent the integrated circuit chip from being cooled excessively, causing the circuit elements to stop functioning and preventing the quartz crystal unit from oscillating. On the other hand, in a relatively high temperature environment, the negative resistance of the oscillator circuit decreases, reducing the oscillation margin. This can cause the oscillator circuit to operate unstable or even become inoperable.

[0007] However, studies have been conducted to measure the oscillation frequency by changing the temperature of a quartz crystal unit within various ranges to allow gas to adhere and desorb. Specifically, studies have been conducted to obtain the oscillation frequency by changing the temperature of the quartz crystal unit within a range whose lower limit is lower than the aforementioned temperature of about -190°C, and by changing the temperature of the quartz crystal unit within a range whose lower limit is higher than -190°C. Therefore, the ambient temperature of the oscillation circuit provided together with the quartz crystal unit in the sensor may change each time the sensor is used.

[0008] In light of the above, there is a need for a sensing device that can stably oscillate a quartz crystal oscillator and measure frequency even when the ambient temperature of the oscillation circuit varies. The above-mentioned Patent Documents 1 and 2 do not disclose a method for solving this problem.

[0009] The present invention has been made under these circumstances, and its purpose is to provide a technology that can stably oscillate a piezoelectric vibrator and measure the frequency in a sensing device for sensing a substance to be sensed contained in a gas that adheres to a piezoelectric vibrator. [Means for solving the problem]

[0010] A sensing device according to the present invention is a sensing device for sensing a substance to be sensed that is contained in a gas surrounding a piezoelectric vibrator and adheres to the piezoelectric vibrator, based on a change in the oscillation frequency of the piezoelectric vibrator, comprising: a piezoelectric vibrator to which the substance to be sensed adheres when cooled; a temperature change unit for changing the temperature of the piezoelectric vibrator; a substrate on which an integrated circuit chip including an oscillation circuit that causes the piezoelectric vibrator to oscillate is provided; a frequency measurement unit that receives a frequency signal output from the oscillation circuit and measures an oscillation frequency of the piezoelectric vibrator; a heater provided separately from the temperature changing unit for heating the integrated circuit chip; a power supply unit capable of changing the power supplied to the heater; Equipped with. [Effects of the Invention]

[0011] According to the sensing device of the present invention, in a sensing device for sensing a substance to be sensed contained in a gas that adheres to a piezoelectric vibrator, it is possible to stably oscillate the piezoelectric vibrator and measure the frequency. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a longitudinal sectional side view of an experimental device using a sensing device according to an embodiment. [Figure 2] FIG. 2 is a block diagram illustrating the sensing device. [Figure 3] 4 is a flowchart showing a temperature adjustment operation of the sensing device. DETAILED DESCRIPTION OF THE INVENTION

[0013] 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 an example of experimental equipment for detecting a substance to be sensed contained in a gas, and the sensing device 1 used in the experimental equipment. Fig. 2 is a block diagram showing the sensing device 1. The sensing device 1 comprises a main body 2 and a sensing sensor 3 configured to be connectable to the main body 2. The main body 2 supplies power to the sensing sensor 3 and measures the oscillation frequency of a quartz oscillator 4 provided in the sensing sensor 3.

[0014] The sensing sensor 3 is provided in a vacuum vessel 70 that constitutes an experimental device. The vacuum vessel 70 is capable of cooling the sensing sensor 3, and is configured to enable an experiment to be performed by attaching and desorbing, as a sensed substance, gas generated from a sample 77 in the vacuum vessel 70 to the quartz oscillator 4. In the experiment, as a measurement operation of the sensing device 1, measurement of the oscillation frequency is performed in parallel with temperature control of the quartz oscillator 4 to perform this attachment and desorption.

[0015] In the following explanation, an XYZ Cartesian coordinate system is used, and the side of the base body 32 described below of the detection sensor 3 installed in the experimental device is described as the downward direction, and the direction of the Z axis is described as the up-down direction. However, the detection sensor 3 can be used in any orientation and is not limited to the orientation described below.

[0016] The following describes the overall configuration of the detection sensor 3. As shown in Fig. 1, the detection sensor 3 includes a cylindrical lid portion 31 that is open at the bottom, a base body 32 that closes the bottom of the lid portion 31, and a substrate 40 and a sensor substrate 50 that are attached to the base body 32.

[0017] The base body 32 is formed in a disk shape from, for example, nickel-plated copper, and has a mounting portion 33 that is attached so that it can be cooled to extremely low temperatures by experimental equipment, and a circular protrusion 34 in a planar shape at the center of the upper surface of the mounting portion 33. A recess 35 that is rectangular in plan view is formed in the protrusion 34, and the center of the recess 35 is further recessed to form a recess 36. The peripheral edge of the recess 36 is supported by a plate-shaped spacer 37, which is a heat insulating member. Integrated circuit chips (IC chips) 41 to 43 and a heater 47 are mounted on the substrate 40.

[0018] Furthermore, holes 36a are formed in the bottom of the recess 36, and multiple cables 62 are inserted through the holes 36a. The cables 62 form conductive paths that electrically connect the wiring pattern provided on the substrate 40 to connection terminals provided on a connector 61 provided on the lower side of the base body 32. The connector 61 is inserted into a connecting member (not shown). The connection terminals of the connector 61 are electrically connected to connection terminals of the main body 2 provided outside the vacuum vessel 70 via the conductive paths provided on this connecting member. Since the connector 61 is inserted in this way and electrically connected to the main body 2, the detection sensor 3 can be freely attached to and detached from the main body 2.

[0019] Sockets 64 are provided on the left and right edge portions of the upper surface of the substrate 40. A plate-shaped cover 65 is provided on the sockets 64, covering the IC chips 41 to 43 and the heater 47. A plurality of pins 66 are provided that are inserted into the sockets 64 and extend in the Z direction, and the sensor substrate 50 is supported in a horizontal position above the cover 65 by the pins 66. The lower ends of the pins 66 pass through the substrate 40 and the spacer 37 and are connected to the base body 32. The pins 66 are supporting members that support the sensor substrate 50 and are also conductive members.

[0020] A recess 52 is formed on the upper surface of the sensor substrate 50. A heater 54 composed of a heating resistor for heating the quartz crystal oscillator 4 is embedded in the sensor substrate 50. The quartz crystal oscillator 4, which is a piezoelectric oscillator, is provided on the sensor substrate 50 so as to cover the opening of the recess 52, and includes a disk-shaped quartz crystal piece 4a, which is, for example, an AT-cut piezoelectric piece. As shown in FIG. 2, a pair of first excitation electrodes (reaction electrodes) 4b, 4c and a pair of second excitation electrodes (reference electrodes) 4d, 4e are formed on the upper and lower surfaces of the quartz crystal piece 4a, respectively, and wiring patterns (not shown) connected to these electrodes are formed of, for example, gold (Au).

[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. This crystal unit 4 is cooled by heat transfer via the pins 66 and the sensor substrate 50 when the base body 32 is cooled. Meanwhile, the crystal unit 4 is heated by heat transfer from the sensor substrate 50 when the heater 54, which is a temperature change unit, is heated. Furthermore, a temperature sensor 55 is provided on the top surface of the crystal blank 4a to detect the temperature of the crystal unit 4, and the main body 2 detects the temperature based on the detection signal output from this temperature sensor 55.

[0022] The lid 31 described above covers the quartz crystal unit 4 and the sensor substrate 50 from above, and is disposed so as to surround the periphery of the protrusion 34 of the base body 32, thereby engaging the lid 31 with the base body 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 excitation electrodes 4b to 4e, heater 54, and temperature sensor 55 are each electrically connected to the wiring pattern of the substrate 40 via a conductive path consisting of the wiring pattern, pins 66, and socket 64 formed on the sensor substrate 50. By forming a conductive path in this manner and electrically connecting the wiring pattern of the substrate 40 to the connection terminals of the main body 2 via the cable 62 as described above, it is possible to supply power from the main body 2 to the circuit elements included in the IC chips 41 to 43, the heater 47, and the temperature sensor 55, to electrically connect the excitation electrodes 4b to 4e to the oscillation circuit 44 described below, to cause the crystal unit 4 to oscillate, and to extract a frequency signal from the oscillation circuit 44 and a detection signal from the temperature sensor 55 to the main body 2.

[0024] The IC chips 41 to 43 will now be described in detail. The IC chip 41 is made of a semiconductor, such as silicon. For example, an oscillation circuit 44 is formed on the IC chip 41, a regulator 45 is formed on the IC chip 42, and two switches 48 and 49 are formed on the IC chip 43. The regulator 45 adjusts the voltage supplied from the main body 2 to the oscillation circuit 44.

[0025] The heater 47 on the substrate 40 is a heat generating resistor of, for example, about 300 Ω at room temperature, and heats each circuit element provided on the IC chips 41 to 43 to ensure operation in a relatively low temperature environment. One end of the heater 47 is connected to a conductive path connecting the main body 2 and the regulator 45, and the other end of the heater 47 is grounded. Therefore, the regulator 45 and the heater 47 are each connected in parallel to the main body 2, and the same voltage is applied to them. In addition, a voltage of, for example, 3 V is applied to the oscillator circuit 44 from the regulator 45.

[0026] The switch 48 connects either one of the excitation electrodes 4b and 4d to the oscillation circuit 44, and the switch 49 connects either one of the excitation electrodes 4c and 4e to the oscillation circuit 44. The operations of the switches 48 and 49 are synchronized with each other, and a state in which the excitation electrodes 4b and 4c are connected to the oscillation circuit 44 and a state in which the excitation electrodes 4d and 4e are connected to the oscillation circuit 44 are switched in a time-division manner, causing the first vibration area 40A and the second vibration area 40B to vibrate, respectively.

[0027] Next, the main body 2, which constitutes the power supply unit, will be described. The main body 2 includes a control unit 20, a power supply unit 21, a frequency measurement unit 22, a temperature detection unit 23, an operation unit, and a display unit. The power supply unit 21 is configured as a voltage change unit equipped with, for example, a variable voltage regulator, and outputs a voltage to the heater 47 and the regulator 45, and this output voltage is changeable. Therefore, the power supplied to the heater 47 and the amount of heat generated by the heater 47 change.

[0028] The regulator 45 also generates heat according to the difference between the output voltage (3V) to the oscillator circuit 44 and the output voltage to the regulator 45. The IC chip 42 on which the regulator 45 is formed, together with the heater 47, heats the IC chips 41 and 43, and plays a role in ensuring the operation of the oscillator circuit 44 and the switches 48 and 49 in a low-temperature environment. In the following explanation, the output voltage from the power supply unit 21 to the heater 47 and the regulator 45 is designated as V1.

[0029] The frequency measurement unit 22 detects whether a frequency signal is output from the oscillation circuit 44, and if a frequency signal is output, measures the frequency. That is, the first oscillation frequency F1 in the first vibration area 40A on the reaction electrode side and the second oscillation frequency F2 in the second vibration area 40B on the reference electrode side are measured by the frequency measurement unit 22. The temperature detection unit 23 detects the temperature of the quartz crystal oscillator 4 from the detection signal output from the temperature sensor 55.

[0030] As described in the section on the solution to the problem solved by the invention, it is preferable to set the oscillator circuit 44 at a lower temperature within its operable temperature range in order to stably oscillate the crystal oscillator 4. The control unit 20 includes a program for automatically setting the output voltage V1 so that the oscillator circuit 44 reaches such a temperature when performing a measurement operation of the sensing device 1. As will be described in detail later, the control unit 20 increases the output voltage V1 in steps from the initial voltage V0 in predetermined increments, and determines the value during the measurement operation based on whether or not a frequency signal is detected during the increase.

[0031] Data on the initial voltage V0 and the incremental voltage α, which is the step amount, are stored in a memory unit (not shown) of the main body unit 2. The initial voltage V0 is set to the lowest voltage at which the oscillator circuit 44 can stably operate, for example, given the configuration of the sensing sensor 3. As an example, the initial voltage V0 is 5V, and the incremental voltage α is 0.5V. The memory unit also stores data on the lower limit temperature (referred to as the operable temperature T°C) of the range in which the IC chips 41-43 can operate, and the upper limit voltage Vh, which is the upper limit of the output voltage V1, used for automatically setting the output voltage V1. T°C is set to, for example, approximately -160°C. The upper limit voltage Vh is set to, for example, the lowest value among the rated voltage of the regulator 45, the rated voltage of the heater 47, and the voltage that the power supply unit 21 can output, for example, 12V.

[0032] The display unit provided on the main body 2 is composed of lamps, an LCD screen, etc., and displays the first oscillation frequency F1, the second oscillation frequency F2, and the temperature detected by the temperature sensor 55. Furthermore, if the setting of the output voltage V1 cannot be performed in the setting flow described below, the display unit will display a message to that effect. The operation unit on the main body 2 is composed of switches and buttons operated by the user, and the output voltage V1 can be automatically set by performing a predetermined operation on this operation unit.

[0033] The experimental apparatus will be further described. The side of the vacuum vessel 70 constituting the experimental apparatus is configured as a cooling section 71 for cooling the detection sensor 3. The cooling section 71 is formed so that a portion facing the center of the bottom of the base body 32 is penetrated and the connector 61 of the main body 2 can be placed therein when the detection sensor 3 is installed. The cooling section 71 also has a flow path 71a through which a cooling medium such as liquid nitrogen (N) flows, and cools the base body 32 to approximately -190°C. The quartz crystal resonator 4 can also be cooled to a similar temperature by heat conduction via the pins 66 and the like.

[0034] Inside the vacuum vessel 70, a stage 73 for supporting a sample 77 is provided at a position opposite the opening 31a of the sensing sensor 3. This stage 73 is designed so that the sample 77 can be heated to a predetermined temperature by a heating mechanism 74. The vacuum vessel 70 is connected to a vacuum exhaust mechanism 76 via an exhaust path 75, and is configured so as to be evacuated to a predetermined vacuum level.

[0035] Before performing the measurement operation of the sensing device 1 (i.e., before starting the experiment), the output voltage V1 is automatically set. FIG. 3 is a flowchart of this automatic setting, which is executed by the control unit 20. The experimenter first confirms that the temperature detected by the temperature sensor 55 is approximately −190°C, which is the temperature of the environment in which the sensing sensor 3 is installed, and then performs a predetermined operation to start the automatic setting on the operation unit of the main unit 2. The power supply unit 21 applies an initial voltage V0, for example, 5 V, as the output voltage V1 to the regulator 45 and the heater 47 (step S1). Then, after a predetermined time has elapsed since the start of application, it is determined whether a frequency signal is being output from the oscillator circuit 44 to the main unit 2 (step S2).

[0036] If it is determined in step S2 that a frequency signal is not being output, it is determined whether the temperature detected by the temperature sensor 55 is equal to or higher than the operable temperature T°C (step S3). If it is determined in step S3 that the detected temperature is equal to or higher than the operable temperature T°C, it is determined that measurement is not possible due to a malfunction of the sensing device 1, and a message to that effect is displayed (step S4), and the automatic setting is terminated.

[0037] If it is determined in step S3 that the detected temperature is below the operable temperature T°C, it is determined whether the output voltage V1 + the increased voltage α is higher than the upper limit voltage Vh (step S5). If it is determined in step S5 that the output voltage V1 + the increased voltage α is higher than the upper limit voltage Vh, it is determined that measurement is not possible due to a malfunction of the sensing device 1, and a message to that effect is displayed (step S6), and the automatic setting is terminated.

[0038] If it is determined in step S5 that the sum of the output voltage V1 and the increased voltage α is equal to or less than the upper limit voltage Vh, the output voltage V1 is increased by α from its previous voltage. That is, the output voltage V1 is changed so that it becomes the voltage compared with the upper limit voltage Vh in step S5 (step S7). This increases the temperatures of the regulator 45 and the heater 47, thereby increasing the temperatures of the IC chips 41 and 43. Then, the flow from step S1 onwards is executed again.

[0039] If it is determined in step S2 that a frequency signal is being output from the predetermined oscillation circuit 44 to the main body 2, the output voltage V1 at this time is determined to be the one to be used during the measurement operation (step S8), the automatic setting is completed, and this output voltage V1 is maintained. In addition, the first oscillation frequency F1 and the second oscillation frequency F2 are measured from the acquired frequency signal and displayed on the display unit.

[0040] Then, for example, the vacuum chamber 70 is evacuated to a predetermined vacuum level, and the base 73 is heated by the heating mechanism 74. During the automatic setting, the quartz crystal oscillator 4 is cooled. When the base 73 is heated, gas generated from the sample 77 enters the sensing sensor 3 through the opening 31a and is adsorbed onto the first excitation electrode 4b. Then, when the experimenter performs a predetermined operation on the operation unit of the main body 2, the measurement operation begins. For example, the power supply to the heater 54 of the sensor substrate 50 is controlled so that the detected temperature of the quartz crystal oscillator 4 increases at a rate of, for example, 1°C / minute. The temperature of the quartz crystal oscillator 4 continues to increase in this manner until the detected temperature reaches a predetermined temperature. While the temperature of the quartz crystal oscillator 4 is being controlled in this manner, the first oscillation frequency F1 and the second oscillation frequency F2 are monitored by the main body. When the detected temperature reaches the predetermined temperature, the temperature increase and frequency monitoring stop, and the measurement operation of the sensing device 1 ends.

[0041] Then, for example, an experimenter acquires data on the change over time in the difference value between the first oscillation frequency F1 and the second oscillation frequency F2, and uses this data to identify the substance to be sensed and calculate the amount of adsorption, etc. While the first oscillation frequency F1 and the second oscillation frequency F2 are being acquired, the output voltage V1 is maintained at the value determined in step S8 of the above-mentioned flow. Note that the power supply to the heater 54 is also controlled by the program of the control unit 20.

[0042] In the above example, the detection sensor 3 is placed inside the vacuum vessel 70 of the experimental equipment. However, the detection sensor 3 is not limited to being placed inside the vacuum vessel 70 and can be placed in various environments. When placing the detection sensor 3 in such various environments, the main body 2 changes the output voltage V1 to maintain a temperature at which the oscillation circuit 44 and the switches 48 and 49 can operate while preventing the oscillation circuit 44 from becoming excessively hot. Therefore, the crystal resonator 4 can oscillate stably to measure the first oscillation frequency F1 and the second oscillation frequency F2. As a result, the accuracy of the experiment can be improved.

[0043] Assume that multiple detection sensors 3 are installed in the same relatively low-temperature environment, the output voltage V1 is unchangeable, and the same output voltage V1 is supplied to each detection sensor 3. Even in this case, due to individual differences between the detection sensors 3, a situation may arise in which one detection sensor 3 can measure frequency while another cannot. In other words, even detection sensors 3 installed in the same environment may have different appropriate output voltages V1. Therefore, if the output voltage V1 is unchangeable, it would be necessary to set an appropriate output voltage V1 for each detection sensor 3. This could complicate the manufacturing process of the device. The sensing device 1 with a variable output voltage V1 can supply an appropriate output voltage V1 to each detection sensor 3 while preventing such a complicated manufacturing process.

[0044] As described in FIG. 3, the output voltage V1 is automatically set, reducing the burden on the device user. This automatic setting increases the output voltage V1 stepwise, and each time the output voltage V1 is increased, a determination is made as to whether the output voltage V1 is appropriate based on whether or not a frequency signal is output. This prevents the output voltage V1 from being set to a relatively large value. This more reliably stabilizes the oscillation of the crystal unit 4. Furthermore, since the thermal influence of the heater 47 and regulator 45 on the crystal unit 4 is reduced, the crystal unit 4 can be cooled to a relatively low temperature, thereby broadening the applicability of the sensing device 1 for experiments. The increased voltage α does not need to be constant for a single measurement operation, but may be varied as the series of determination steps from step S1 onward are repeated. For example, the increased voltage α may decrease as the number of repetitions increases.

[0045] Furthermore, as described above, when heating the IC chips 41 and 43, the regulator 45 and the heater 47 are each connected in parallel to the main body 2, and generate heat when the output voltage V1 is applied to each of them from the main body 2. Therefore, while reducing the power supplied to the detection sensor 3, the IC chips 41 and 43 can increase the amount of heat generated, enabling the main body 2 to acquire a frequency signal, thereby reducing the operating costs of the detection device 1.

[0046] Although the oscillator circuit 44, regulator 45, and switches 48 and 49 are shown as being included in separate IC chips, they may be included in a common IC chip. The heater 47 does not necessarily have to be provided separately from the IC chip, but may be incorporated into the IC chip.

[0047] The detection sensor is not limited to one having the same structure as the detection sensor 3, and may have, for example, a different thermal insulation structure of the oscillation circuit 44. Furthermore, the experimental device in which the detection sensor 3 is installed may be configured to cool the detection sensor 3 by supplying liquid helium, which is lower in temperature than liquid nitrogen, instead of liquid nitrogen.

[0048] Although it has been explained that the output voltage V1 is set based on whether or not a frequency signal is output from the oscillator circuit 44 to the main body 2, the level of this frequency signal may be detected, and if it is below a predetermined level, it may be determined that heating of the oscillator circuit 44, etc. is insufficient, and the output voltage V1 may be increased. That is, in step S2 of the above flow, it is determined whether or not the level of the detected frequency signal is below a reference value. In this way, the output state of the frequency signal from the oscillator circuit 44, which serves as a criterion for determining the output voltage V1, is not limited to the presence or absence of a frequency signal.

[0049] Furthermore, the output voltage V1 does not necessarily have to be automatically set to determine its value during measurement by the sensing device 1. The main body 2 may be configured so that it can be changed by a user's operation from the operation unit, and the value during measurement may be determined by the user operating the operation unit while checking whether the first oscillation frequency F1 and the second oscillation frequency F2 have been acquired by looking at the display unit.

[0050] Although an example in which the temperature of the quartz crystal oscillator 4 is gradually increased during the measurement operation has been shown, the temperature control is not limited to this. For example, the quartz crystal oscillator 4 may be kept at a predetermined temperature in order to observe the transition of the amount of the substance to be sensed in the environment in which the sensing sensor 3 is installed.

[0051] Furthermore, in order to efficiently heat the IC chips 41 and 43, the heater 47 is preferably provided on the substrate 40 on which the IC chips 41 and 43 are mounted, but this configuration is not limiting. For example, the heater 47 may be provided on a substrate provided above and adjacent to the substrate 40. In this way, the heater 47 may be provided separately from the heater 54 of the sensor substrate 50 and may heat the IC chip 41. While it is preferable to acquire both the first oscillation frequency F1 and the second oscillation frequency F2, it is also possible to acquire only the first oscillation frequency F1, and therefore the configuration may not include the switches 48 and 49. Therefore, the heater 47 may be provided to heat at least the IC chip 41 including the oscillation circuit 44.

[0052] Furthermore, the heater 47 is not limited to being connected to a conductive path connecting the regulator 45 and the main body 2, but may be configured to be supplied with power independently of the regulator 45 and to have the power adjustable.

[0053] In this embodiment, the cooling medium flow path 71a is formed in the vacuum vessel 70 of the experimental apparatus and is not provided in the detection sensor 3. However, it may be provided in, for example, the base body 32 of the detection sensor 3. It may be arranged to cool a portion of the detection sensor 3 other than the base body 32, as long as it can cool the quartz oscillator 4 to the desired cryogenic temperature. Furthermore, the detection sensor 3 is not limited to a configuration in which the quartz oscillator 4 is cooled externally. A mechanism for cooling the quartz oscillator 4, such as a Peltier element, may be incorporated within the detection sensor 3. This Peltier element may be provided in contact with the underside of the sensor substrate 50 so that the quartz oscillator 4 can be cooled via the sensor substrate 50. The Peltier element may also be used to heat the quartz oscillator 4. In this case, the Peltier element corresponds to the temperature change unit. Furthermore, the quartz oscillator 4 is not limited to being cooled by the action of the Peltier element or the cooling medium flow path 71a. It may also be cooled by the temperature of the natural environment in which the detection sensor 3 is located. This natural environment includes outer space. Therefore, when using the sensing device 1, a mechanism for cooling the crystal oscillator 4 is not necessary.

[0054] 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]

[0055] 1 Sensing device 21 power supply unit 22 frequency measurement unit 4 crystal oscillator 40 boards 41 IC chip 43 Oscillator Circuit 47 Heater 54 Heater

Claims

1. 1. A sensing device for sensing a substance to be sensed that is contained in a gas surrounding a piezoelectric vibrator and that is attached to the piezoelectric vibrator, based on a change in the oscillation frequency of the piezoelectric vibrator, comprising: a piezoelectric vibrator to which the substance to be sensed adheres when cooled; a temperature change unit for changing the temperature of the piezoelectric vibrator; a substrate on which an integrated circuit chip including an oscillation circuit that causes the piezoelectric vibrator to oscillate is provided; a frequency measurement unit that receives a frequency signal output from the oscillation circuit and measures an oscillation frequency of the piezoelectric vibrator; a heater provided separately from the temperature changing unit for heating the integrated circuit chip; a power supply unit capable of changing the power supplied to the heater; A sensing device comprising:

2. The sensing device according to claim 1 , wherein the power supply unit is a voltage change unit that changes the power by changing a voltage supplied to the heater.

3. the voltage change unit supplies a voltage to the oscillation circuit via a regulator provided on the substrate; 3. The sensing device of claim 2, wherein the voltages supplied to the regulator and the heater are both varied.

4. 4. The sensing device of claim 3, wherein the heater is mounted on the substrate.

5. 5. The sensing device according to claim 2, further comprising a control section for changing the voltage supplied to said heater in accordance with the output state of said frequency signal to said frequency measuring section.

6. the output state of the frequency signal is whether or not the frequency signal is output to the frequency measurement unit; 6. The sensing device according to claim 5, wherein the control unit determines the voltage to be supplied to the heater based on the presence or absence of the frequency signal when the voltage applied to the heater is increased from a preset initial value.

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