JP2023130161A - Gas sensor module and gas sensor system - Google Patents

Abstract

To provide a gas sensor module capable of easily acquiring a gas detection signal while suppressing increase in electric power or space when the width of voltage range of a signal detecting gas is large.SOLUTION: A gas sensor module 10 includes: a gas sensor 110; an amplifier group 120 for amplifying a first analog signal outputted from the gas sensor 110 by a predetermined amount corresponding to the measurement results of an object to be measured to output a second analog signal; an AD converter 130 for converting the second analog signal into a digital signal; and a microcontroller 140 for acquiring the digital signal. The microcontroller 140 includes an offset control part 144 performing control for sliding the offset voltage of each amplifier of the amplifier group 120.SELECTED DRAWING: Figure 3

Description

The present disclosure relates to gas sensor modules and gas sensor systems.

Sensors are known that include a volume changeable body whose volume changes depending on the amount of an object (for example, molecules constituting a gas or liquid), and that detect stress that occurs as the volume of the volume change body changes. . Patent Document 1 discloses a sensor including a main body, a volume change body, and a detection section. The main body has a flat plate shape, has a first end supported in the first direction, and has a housing space that is open at at least one of both end faces in the thickness direction. The volume-changing body has a volume that changes depending on the amount of the object, and is supported by the main body so that at least a portion thereof is accommodated in the accommodation space. The detection section is connected to a second end of the main body section in the first direction, and detects stress that occurs due to a change in volume of the volume change body.

A gas sensor module using such a sensor can detect gas by amplifying the voltage of the analog signal of the gas detected by the sensor using an amplifier, converting it into a digital signal using an AD converter, and outputting the digital signal to a microcomputer. Get data.

International Publication No. 2019/188164

The analog signal output to the AD converter may exceed the voltage range that can be output by the AD converter. In this case, the microcomputer cannot acquire the gas detection signal. For example, in the case of a gas sensor that uses a sensitive film that detects gas by the stress generated by expanding or contracting in response to the gas, the gas may be detected as a voltage in a wide range including both positive and negative voltages. In such a case, the detected signal tends to exceed the voltage range that can be output by the AD converter. If the detected signal tends to exceed the voltage range that can be output by the AD converter, it will naturally be impossible to obtain the gas detection signal.

On the other hand, if we simply try to widen the voltage range that can be output by the AD converter in order to deal with this problem, we will have problems such as requiring a large amount of power and increasing the size of the AD converter. also occurs.

The present disclosure has been made in view of the above points, and when the voltage range of the gas detection signal is wide, it is easy to obtain the gas detection signal while suppressing an increase in power and space. The present invention aims to provide a gas sensor module and a gas sensor system.

According to one aspect of the present disclosure, a gas sensor, an amplifier that amplifies a first analog signal output from the gas sensor by a predetermined amount according to a measurement result of a measurement target and outputs a second analog signal, and A gas sensor module comprising: an AD converter that converts a signal into a digital signal; and a control section that acquires the digital signal; the control section includes an offset control section that controls sliding of an offset voltage of the amplifier; provided.

The offset control section may perform control to slide the input range of the AD converter based on a set value.

The control unit may further include a storage unit that stores the setting value.

The gas sensor module may further include a selection switch that selects the set value.

The offset control section may perform control to slide the offset voltage of the amplifier based on the slope of the digital signal over a predetermined time.

The control section may further include a gain control section that performs control to switch an amplification factor of the amplifier.

The gain control unit may control to reduce the amplification factor of the amplifier when the voltage of the second analog signal exceeds an input range of the AD converter.

The gain control section may perform control to switch an amplification factor of the amplifier based on a slope of the digital signal over a predetermined period of time.

The control unit may further include a correction unit that performs correction to match the output of the AD converter before and after sliding the offset voltage by the offset control unit or before and after switching the amplification factor of the amplifier by the gain control unit. good.

The gas sensor may include a sensitive film whose volume changes depending on the amount of gas to be detected, and a detection section that detects stress generated due to the change in volume of the sensitive film.

According to another aspect of the present disclosure, there is provided a gas sensor system including the gas sensor module and an information processing device that acquires the digital signal from the control unit and outputs information based on the digital signal.

According to the present disclosure, there is provided a gas sensor module and a gas sensor system that can easily acquire a gas detection signal while suppressing an increase in power and space even when the voltage range of the gas detection signal is wide. can do.

1 is a diagram showing a schematic configuration of a gas sensor system including a gas sensor module according to the present embodiment. It is a graph showing an example of an analog signal output from a sensor. It is a figure showing an example of composition of a gas sensor module. It is a graph showing an example of a time change of an analog signal output from an amplifier. It is a graph showing an example of a time change of an analog signal output from an amplifier. It is a figure which shows the example of correction of the digital signal which an AD converter outputs. It is a graph showing an example of a time change of an analog signal output from an amplifier.

An example of an embodiment of the present disclosure will be described below with reference to the drawings. In addition, the same reference numerals are given to the same or equivalent components and parts in each drawing. Furthermore, the dimensional ratios in the drawings are exaggerated for convenience of explanation and may differ from the actual ratios.

FIG. 1 is a diagram showing a schematic configuration of a gas sensor system including a gas sensor module according to this embodiment. The gas sensor system 1 shown in FIG. 1 includes a gas sensor module 10, a relay device 20, and an information processing device 30.

The gas sensor module 10 measures a measurement target. The measurement target is a gas, a liquid, or a molecule constituting a solid. For example, the measurement target is a molecule that constitutes a mixture of at least two of gas, liquid, and solid. The gas sensor module 10 includes a sensor inside. The sensor according to the present embodiment is a sensor that includes a volume changeable body whose volume changes depending on the amount of the object to be measured, and detects stress that occurs due to a change in the volume of the volume change body.

The relay device 20 acquires the measurement results of the measurement target by the gas sensor module 10 from the gas sensor module 10 . The gas sensor module 10 and the relay device 20 are connected by wire. The relay device 20 acquires the measurement results of the measurement target from the gas sensor module 10 and supplies power to the gas sensor module 10.

The relay device 20 then accumulates the measurement results of the measurement target obtained from the gas sensor module 10, and transmits the accumulated measurement results to the information processing device 30 at an arbitrary timing. Transmission from the relay device 20 to the information processing device 30 is performed using a predetermined communication protocol, for example, UDP (User Datagram Protocol). The transmission from the relay device 20 to the information processing device 30 may be wired transmission or wireless transmission. When the relay device 20 accumulates the measurement results, it accumulates them in a predetermined format, for example, a CSV (Comma Separated Value) format.

The information processing device 30 performs information processing on the measurement results measured by the gas sensor module 10 and transmitted from the relay device 20. For example, the information processing device 30 executes a process of displaying the measurement results measured by the gas sensor module 10 in a graph.

Note that in this embodiment, the gas sensor module 10 and the relay device 20 are separate devices, but the present disclosure is not limited to such an example. The gas sensor module 10 may be provided with the function of the relay device 20 and the measurement results may be directly transmitted from the gas sensor module 10 to the information processing device 30.

The gas sensor module 10 amplifies the output from the sensor with an amplifier, and converts the amplified analog signal into a digital signal with an AD converter, thereby obtaining a measurement result of the object to be measured by the sensor. Here, an AD converter cannot normally convert an input signal level of every signal level, and the convertible signal level is limited to the maximum voltage of the specification. If the range of the analog signal output from the sensor is known in advance, an AD converter with an input range that can cover that range may be prepared. However, if the range of the analog signal output from the sensor is undefined, the analog signal output from the sensor may not be correctly converted into a digital signal.

FIG. 2 is a graph showing an example of an analog signal output from a certain sensor. For example, when using an AD converter with an input range of 0V to 5V, analog signals in the range of 0V to 5V can be converted to digital signals. However, an analog signal exceeding the range of 0V to 5V will be clipped by an AD converter whose input range is 0V to 5V, and cannot be correctly converted into a digital signal.

Furthermore, the sensor used in this embodiment includes a volume-changing body whose volume changes depending on the amount of the object to be measured, and outputs a positive voltage value when it expands and a negative voltage value when it contracts. . Furthermore, since the waveform output by the sensor is determined by the measurement target and the functional membrane, it is not known what kind of waveform data the sensor will output when measuring a new measurement target.

Furthermore, since the analog signal output from the sensor is minute, it is amplified by an amplifier before being sent to the AD converter, but depending on the offset voltage of the amplifier, the range of the analog signal after passing through the amplifier may be is out of the input range. Therefore, it is also necessary to adjust the offset voltage of the amplifier, but the adjustment is required depending on the object to be measured, and furthermore, the offset voltage drifts depending on the ambient temperature and the passage of time.

In addition, assuming that an analog signal in a range exceeding the input range is input to the AD converter, it is possible to use an AD converter with a wide input range or an amplifier whose offset voltage does not drift. This leads to an increase in power consumption and an increase in the cost of the gas sensor module.

The gas sensor module according to this embodiment allows adjustment of the offset voltage of the amplifier and adjustment of the gain of the amplifier to be performed on the housing of the gas sensor module so that it can be used for various measurement targets without using parts that would lead to an increase in cost. It is characterized by being able to be performed without opening the body.

FIG. 3 is a diagram showing a configuration example of the gas sensor module 10 according to the present embodiment. The gas sensor module 10 includes a gas sensor 110, an amplifier group 120, an AD converter 130, a microcontroller 140, a DCDC converter 150, and a switch section 160.

The gas sensor 110 is a piezoresistive stress-responsive sensor that includes a functional film 111 whose volume changes depending on the amount of the object to be measured, and a detection section 112 that detects stress that occurs due to changes in the volume of a volume-changing object. be. For the gas sensor 110, for example, a sensor disclosed in International Publication No. 2019/188164 can be used. The gas sensor 110 according to this embodiment is a sensor manufactured using a MEMS (Micro Electro Mechanical Systems) process. The gas sensor 110 according to this embodiment outputs the measurement results of the measurement target through four channels. The analog signal output in response to the measurement of the measurement target by the gas sensor 110 is an example of the first analog signal of the present disclosure.

Amplifier group 120 amplifies the output of gas sensor 110 by a predetermined amount. The amplifier group 120 consists of amplifiers corresponding to the number of output channels of the gas sensor 110, and in this embodiment, the amplifier group 120 consists of four amplifiers 121, 122, 123, and 124. Each of the amplifiers 121 to 124 constituting the amplifier group 120 is an amplifier whose amplification factor (gain) and offset voltage can be switched from the outside. The analog signals output by each of the amplifiers 121 to 124 of the amplifier group 120 are an example of the second analog signal of the present disclosure.

The AD converter 130 converts analog signals output from each amplifier of the amplifier group 120 into digital signals. In this embodiment, the AD converter 130 converts each of the four channels of analog signal input into a digital signal, and outputs the digital signal to the microcontroller 140.

The microcontroller 140 is an example of a control unit according to the present disclosure, and is an integrated circuit including a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). A range control program is stored in the ROM of the microcontroller 140 by controlling the gains of each of the amplifiers 121 to 124 of the amplifier group 120. When the CPU of the microcontroller 140 reads and executes the gain control program stored in the ROM, the microcontroller 140 functions to include an offset control section 142, a gain control section 144, and a correction section 146.

The offset control unit 142 performs control to switch the offset voltage of each amplifier 121 to 124 of the amplifier group 120. The offset control unit 142 can adapt the output of the amplifier group 120 to the input range of the AD converter 130 by switching the offset voltages of the amplifiers 121 to 124.

The gain control unit 144 performs control to switch the gain (amplification factor) of each amplifier 121 to 124 in the amplifier group 120. The gain control unit 144 can adapt the output of the amplifier group 120 to the input range of the AD converter 130 by switching the gains of the amplifiers 121 to 124.

The offset control section 142 switches the offset voltages of the amplifiers 121 to 124 by referring to the setting values stored in the setting value storage section 148. Further, the gain control section 144 switches the gains of the amplifiers 121 to 124 by referring to the setting values stored in the setting value storage section 148. The setting values stored in the setting value storage unit 148 are, for example, such that several measurement targets are measured in advance, and the analog signal output by the gas sensor 110 as the measurement result of the measurement target matches the input range of the AD converter 130. The offset voltage and gain settings are such that

The setting values referred to by the offset control unit 142 and the gain control unit 144 may be switched, for example, by transmitting a command to switch the setting values from the relay device 20 or the information processing device 30 to the gas sensor module 10. By sending a command to change the set value from the relay device 20 or the information processing device 30 to the gas sensor module 10, the gas sensor 110 can be changed without having to open the casing of the gas sensor module 10 to adjust the offset voltage or change the gain. The analog signal output by the converter can be adapted to the input range of the AD converter 130.

FIG. 4 is a graph showing an example of a temporal change in an analog signal output from a certain amplifier in the amplifier group 120. For example, when the voltage value indicating the measurement result by the gas sensor 110 increases with time, it exceeds a predetermined threshold value at a certain time t. If the voltage value continues to rise, it will eventually reach the upper limit of the input range of the AD converter 130, and the AD converter 130 will no longer be able to correctly convert the voltage value representing the measurement result into a digital signal.

Therefore, when the digital signal output from the AD converter 130 exceeds a predetermined threshold, the offset control section 142 and the gain control section 144 switch the reference setting value and apply the switched setting value to the amplifier group 120. It may be set in each of the amplifiers 121 to 124. For example, when the value of a digital signal output from the AD converter 130 exceeds a predetermined threshold (in other words, when the voltage value of an analog signal output from a certain amplifier in the amplifier group 120 exceeds a predetermined threshold) , the gain control section 144 switches the reference destination of the setting values stored in the setting value storage section 148 and changes the gain set for each amplifier of the amplifier group 120.

FIG. 5 is a graph showing an example of a temporal change in an analog signal output from a certain amplifier in the amplifier group 120. In the example shown in FIG. 5, the gain of the amplifier was increased to 100 times until time t, but since the value of the digital signal output from the AD converter 130 exceeded a predetermined threshold at time t, after time t In this case, the gain control section 144 switches the gain of the amplifier to 50 times. Since the gain control unit 144 switches the gain of the amplifier to half at time t, even if the voltage value continues to rise, there is a margin until the upper limit of the input range of the AD converter 130 is reached.

If the offset control section 142 switches the offset voltage of the amplifier or the gain control section 144 switches the gain of the amplifier during measurement, the continuity of the analog signal output from the amplifier is lost. The microcontroller 140 may include a correction unit 146 that performs correction on the digital signal output from the AD converter 130 after the offset voltage or gain has been switched to match the offset voltage or gain before switching. In the example of FIG. 5, the correction unit 146 performs correction to double the digital signal output by the AD converter 130 after time t.

FIG. 6 is a diagram showing an example of correction of the digital signal output by the AD converter 130 by the correction unit 146. If the digital signal output by the AD converter 130 is not corrected after time t, the value shown by the broken line in FIG. Must not be. After time t, the correction unit 146 doubles the digital signal output by the AD converter 130, so that the gain matches the measurement result before time t and the measurement result after time t and before time t. It turns out.

In the example of FIG. 5, the gain control unit 144 switches the gain of the amplifier, but instead of or in addition to switching the gain of the amplifier, the offset control unit 142 switches the offset voltage of the amplifier. You may go.

FIG. 7 is a graph showing an example of a temporal change in an analog signal output from a certain amplifier in the amplifier group 120. In the example shown in FIG. 7, the offset voltage of the amplifier was set to the predetermined first voltage until time t, but at time t, the value of the digital signal output from the AD converter 130 exceeded the predetermined threshold. Therefore, after time t, the offset control unit 142 switches the offset voltage of the amplifier to a predetermined second voltage lower than the first voltage. At time t, the offset control unit 142 switches the offset voltage of the amplifier downward, so that even if the voltage value continues to rise, there is a margin until the upper limit of the input range of the AD converter 130 is reached.

Although FIG. 6 shows an example of correction when the gain of the amplifier is switched before and after time t, the correction unit 146 similarly corrects the digital signal even when the offset voltage is switched before and after time t. .

DCDC converter 150 performs DC voltage conversion. For example, the DCDC converter 150 converts the voltage of power supplied from the outside into an internal operating voltage and outputs it to each part. In this embodiment, the voltage of the power supplied from the relay device 20 is converted into an internal operating voltage and output.

The switch section 160 includes various switches for operating the gas sensor module 10. In this embodiment, the switch section 160 may be provided with a switch that switches setting values referenced by the offset control section 142 and the gain control section 144. Since the switch unit 160 is provided with a switch for changing the set value, the gas sensor module 10 does not require an external device to switch the set value referred to by the offset control unit 142 and the gain control unit 144.

By having the configuration shown in FIG. 3, the gas sensor module 10 according to the present embodiment can suppress an increase in power and space, compared to a configuration in which the gain and offset voltage are not switched from a microcontroller. , it becomes easier to obtain gas detection signals.

Note that the setting values stored in the setting value storage unit 148 may be modified from an external device such as the information processing device 30. Furthermore, setting values may be added to the setting value storage unit 148 from an external device such as the information processing device 30. By modifying or adding set values from outside the gas sensor module 10, it is possible to cope with an increase in the types of gases detected by the gas sensor module 10.

Further, in the above example, the correction unit 146 corrects the digital signal output from the AD converter 130 after the offset voltage or gain has been switched to match the offset voltage or gain before switching. However, the present disclosure is not limited to such examples. The correction unit 146 may perform correction on the digital signal output from the AD converter 130 before the offset voltage or gain is switched to match the offset voltage or gain after switching. Such correction by the correction unit 146 is suitable, for example, when noise is small and it is better to amplify the signal with respect to the digital signal before switching.

Furthermore, in the above example, the offset control section 142 and the gain control section 144 switched the gain and offset voltage of each amplifier 121 to 124 by referring to the setting values stored in the setting value storage section 148. , the present disclosure is not limited to such examples. For example, the offset control unit 142 or the gain control unit 144 determines, based on the slope of the digital signal over a predetermined period of time, whether the digital signal exceeds a predetermined threshold if the slope continues, and based on the determination result, Control may be performed to switch the gain or offset voltage of each amplifier 121 to 124. For example, the offset control section 142 or the gain control section 144 may perform control to switch the gain or offset voltage of each amplifier 121 to 124 based on the slope of the digital signal during a predetermined time from the start of measurement. By performing such control, the offset control section 142 or the gain control section 144 can switch the gain or offset voltage of each amplifier 121 to 124 in real time without referring to the set value.

Although the embodiments of the present disclosure have been described above in detail with reference to the accompanying drawings, the technical scope of the present disclosure is not limited to such examples. It is clear that a person with ordinary knowledge in the technical field of the present disclosure can come up with various changes or modifications within the scope of the technical idea described in the claims. It is understood that various changes or modifications naturally fall within the technical scope of the present disclosure.

1 Gas sensor system 10 Gas sensor module 20 Relay device 30 Information processing device 110 Gas sensor 120 Amplifier group 130 AD converter 140 Microcontroller 150 DCDC converter 160 Switch section

Claims (11)

gas sensor and
an amplifier that amplifies a first analog signal output from the gas sensor by a predetermined amount according to a measurement result of a measurement target and outputs a second analog signal;
an AD converter that converts the second analog signal into a digital signal;
a control unit that acquires the digital signal;
Equipped with
A gas sensor module, wherein the control section includes an offset control section that controls sliding of an offset voltage of the amplifier. The gas sensor module according to claim 1, wherein the offset control section performs control to slide the input range of the AD converter based on a set value. The gas sensor module according to claim 2, wherein the control section further includes a storage section that stores the set value. The gas sensor module according to claim 2, further comprising a selection switch for selecting the set value. The gas sensor module according to claim 1, wherein the offset control section performs control to slide the offset voltage of the amplifier based on the slope of the digital signal over a predetermined time. The gas sensor module according to any one of claims 1 to 5, wherein the control section further includes a gain control section that performs control to switch an amplification factor of the amplifier. The gas sensor module according to claim 6, wherein the gain control section controls the amplification factor of the amplifier to decrease when the voltage of the second analog signal exceeds the input range of the AD converter. The gas sensor module according to claim 6, wherein the gain control section performs control to switch the amplification factor of the amplifier based on the slope of the digital signal over a predetermined time. The control unit further includes a correction unit that performs correction to match the output of the AD converter before and after sliding the offset voltage by the offset control unit or before and after switching the amplification factor of the amplifier by the gain control unit. The gas sensor module according to any one of items 6 to 8. The gas sensor is
A sensitive membrane whose volume changes depending on the amount of gas to be detected,
a detection unit that detects stress generated due to a change in the volume of the sensitive film;
The gas sensor module according to any one of claims 1 to 9, comprising: The gas sensor module according to claim 1;
an information processing device that acquires the digital signal from the control unit and outputs information based on the digital signal;
A gas sensor system equipped with