Gas detector

Abstract

To provide a gas detector that increases reliability in detection result of detection object gas for a user.SOLUTION: A gas detector 1 comprises: a measurement unit 2 that is configured to detect detection object gas and measure a peripheral environmental condition; and a control unit 3. The control unit 3 is configured to: determine whether a peripheral environment of a measurement object changes from a peripheral environment at a prescribed timing on the basis of a detection result of the detection object gas and measurement result of the peripheral environmental condition obtained in a peripheral environment of a measurement object, and a reference detection result of the detection object gas and a reference measurement result of the peripheral environmental condition obtained in the peripheral environment at the prescribed timing; and, when determining that the peripheral environment changes, notify a user of the gas detector 1 of the change in the peripheral environment.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a gas detector.

Background Art

[0002] Conventionally, in order to detect a gas to be detected contained in the surrounding environment, a gas detector as disclosed in Patent Document 1, for example, has been used. In such a gas detector, generally, there is a problem that the output value of the gas detection unit contained in the gas detector does not stabilize for some time after the power is turned on and the drive is started. Therefore, in the gas detector, after the drive of the gas detector is started, a period (so-called warm-up period) during which the detection operation of the gas to be detected is not performed is provided until the output value of the gas detection unit stabilizes. And at the stage where the output value of the gas detection unit stabilizes, the indication value indicating the gas concentration calculated from the output value of the gas detection unit is adjusted to be the zero indication value, and then, in the surrounding environment where the gas to be detected may be contained, the detection operation of the gas to be detected is performed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, when the gas detector performs the detection operation of the gas to be detected, after the indicated value of the gas detector is zero-adjusted, the surrounding environment of the gas detector may change. For example, if the gas detector is portable, the surrounding environment of the gas detector changes when the gas detector is carried from the environment where the zero-adjustment of the indicated value is performed to a different environment. Thus, when the surrounding environment changes from the time when the zero-adjustment of the indicated value is performed to the time when actually trying to detect the gas to be detected, the indicated value of the gas to be detected may change beyond the zero indicated value. As this factor, there may be cases due to the actual inclusion of the gas to be detected in the surrounding environment, or cases due to changes in the surrounding environment other than the presence of the gas to be detected. For example, when using a gas thermal conductivity type gas sensor as the gas detection unit, because the detection principle of detecting the gas to be detected based on the difference in the thermal conductivity between the gas to be detected and the standard gas is adopted, the indicated value may be affected by changes in the temperature and humidity of the surrounding environment of the gas detector. Even if the indicated value changes in this way, the user of the gas detector cannot determine the cause of the change in the indicated value just by looking at the indicated value. Therefore, the reliability of the indicated value displayed on the gas detector is low.

[0005] The present invention has been made in view of the above problems, and an object thereof is to provide a gas detector capable of confirming whether or not the surrounding environmental state that can affect the detection result of the gas to be detected has changed when the detection result of the gas to be detected has changed, thereby improving the reliability of the detection result of the gas to be detected for the user.

Means for Solving the Problems

[0006] The gas detector of the present invention is a gas detector for detecting a gas to be detected contained in the surrounding environment, and includes a measurement unit configured to detect the gas to be detected and measure the surrounding environmental state, a control unit configured to determine a change in the surrounding environment based on a detection result of the gas to be detected and a measurement result of the surrounding environmental state, and a storage unit configured to store information regarding the gas to be detected and information regarding the surrounding environmental state. The control unit is configured to store, in the storage unit, the detection result of the gas to be detected and the measurement result of the surrounding environmental state obtained in the surrounding environment at a predetermined timing during a driving period of the gas detector, as a reference detection result of the gas to be detected and a reference measurement result of the surrounding environmental state, respectively. The control unit is configured to determine whether the surrounding environment of the measurement target has changed from the surrounding environment at the predetermined timing based on the detection result of the gas to be detected and the measurement result of the surrounding environmental state obtained in the surrounding environment of the measurement target, and the reference detection result of the gas to be detected and the reference measurement result of the surrounding environmental state obtained in the surrounding environment at the predetermined timing. The control unit is configured to notify a user of the gas detector that the surrounding environment has changed when it is determined that the surrounding environment has changed.

[0007] Further, the detection result of the gas to be detected preferably includes an indication value indicating the concentration of the gas to be detected calculated by the control unit based on an output value obtained by detecting the gas to be detected by the measurement unit, and the reference detection result of the gas to be detected preferably includes an indication value after zero adjustment is performed on the indication value obtained in the surrounding environment at the predetermined timing.

[0008] Further, it is preferable that the measurement unit includes a first measurement unit for detecting the gas to be detected and a second measurement unit for measuring the surrounding environmental state.

[0009] Further, it is preferable that the first measurement unit includes a thermal conductivity type gas sensor, and the second measurement unit includes a temperature sensor for measuring temperature and / or a humidity sensor for measuring humidity.

[0010] Further, it is preferable that the control unit is configured to correct an indication value indicating the concentration of the gas to be detected by using the temperature measured by the temperature sensor and / or the humidity measured by the humidity sensor.

[0011] Further, the control unit is configured to notify the user of a warning when the indication value indicating the concentration of the gas to be detected exceeds a predetermined threshold value, and it is preferable that the control unit is configured to be able to simultaneously notify the user of the change in the surrounding environment and the warning.

[0012] Further, while the control unit is notifying the user that the surrounding environment is changing, when the difference between the detection result of the gas to be detected obtained in the surrounding environment of the measurement target and the reference detection result of the gas to be detected becomes less than a predetermined threshold value, it is preferable that the control unit is configured to stop notifying the user that the surrounding environment is changing.

[0013] Further, it is preferable that the control unit continues to determine whether the surrounding environment of the measurement target has changed from the surrounding environment at the predetermined timing, and based on the determination result, notify the user that the surrounding environment has changed, throughout the driving period of the gas detector.

Advantages of the Invention

[0014] According to the present invention, when the detection result of the gas to be detected changes, it is possible to confirm whether the surrounding environmental state that can affect the detection result of the gas to be detected has changed, thereby providing a gas detector that improves the reliability of the detection result of the gas to be detected for the user.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Mode for Carrying Out the Invention

[0016] Hereinafter, a gas detector according to an embodiment of the present invention will be described with reference to the accompanying drawings. However, the embodiment shown below is only an example, and the gas detector of the present invention is not limited to the following example.

[0017] The gas detector 1 of the present embodiment is used, for example, to detect a gas to be detected contained in the surrounding environment such as the atmosphere. The gas to be detected that the gas detector 1 detects is not particularly limited, and examples include combustible gases such as hydrogen, methane, propane, butane, isobutane, and ethylene, and oxygen, carbon monoxide, carbon dioxide, sulfur dioxide, hydrogen sulfide, and hydrogen fluoride. In the present embodiment, the gas detector 1 is a portable gas detector that can be carried. By the user carrying the gas detector 1, the gas to be detected can be detected in a plurality of different environments. However, the gas detector 1 is not limited to being portable and may be a stationary type installed at a specific location.

[0018] FIG. 1 is a schematic front view showing the appearance of the gas detector 1 according to the present embodiment. In the present embodiment, as shown in FIG. 1, the gas detector 1 includes a detector main body DB that houses components to be described later, a display panel DP that forms part of a notification unit 5 to be described later, a gas introduction unit GI that guides a measurement target gas (ambient atmosphere gas) including a gas to be detected to the detector main body DB, and an operation panel OP for a user to operate the gas detector 1. The display panel DP includes indication value display areas DP1 and DP2 for displaying indication values indicating the concentrations of two types of gases to be detected, and an ambient environment change display area DP3 for notifying changes in the ambient environment. Further, the detector main body DB is provided with a through hole TH that communicates a second measurement unit 22 (temperature sensor and / or humidity sensor) to be described later with the ambient environment. The gas detector 1 guides the measurement target gas to the detector main body DB through the gas introduction unit GI by a pump (not shown) provided in the detector main body DB, and detects the gas to be detected by a first measurement unit 21 (thermal conductivity gas sensor) to be described later provided in the detector main body DB. However, the appearance of the gas detector 1 shown in FIG. 1 is merely an example, and the gas detector 1 is not limited to the illustrated example and can be modified as appropriate.

[0019] FIG. 2 is a block diagram showing the configuration of the gas detector 1 according to the present embodiment. As shown in FIG. 2, the gas detector 1 is configured to detect a gas to be detected and measure the ambient environmental state, and includes a measurement unit 2, a control unit 3 that performs arithmetic processing, and a storage unit 4 that stores information on the gas to be detected and information on the ambient environmental state. Further, in the present embodiment, the gas detector 1 includes a notification unit 5 that notifies the user of information on the gas to be detected and changes in the ambient environment, and a power supply 6 that supplies power to each component.

[0020] The measurement unit 2 is configured to detect a gas to be detected included in the ambient environment and outputs an output value corresponding to the concentration of the gas to be detected in the ambient environment. Further, the measurement unit 2 is configured to measure the ambient environmental state around the gas detector 1 and outputs the measurement result of the ambient environmental state. As shown in FIG. 2, the measurement unit 2 is communicably connected to the control unit 3, is operationally controlled by the control unit 3, and transmits the output value and the measurement result output to the control unit 3. In the present embodiment, the measurement unit 2 includes a first measurement unit 21 for detecting the gas to be detected and a second measurement unit 22 for measuring the ambient environmental state. By including the first and second measurement units 21 and 22 that are separate from each other, the measurement unit 2 can simultaneously perform the detection operation of the gas to be detected and the measurement operation of the ambient environmental state. However, the measurement unit 2 does not necessarily have to include two different types of measurement units. For example, it may be configured to detect the gas to be detected and measure the ambient environmental state by changing the detection / measurement conditions according to the detection / measurement target with one measurement unit.

[0021] The first measurement unit 21 detects a gas to be detected and outputs an output value corresponding to the concentration of the gas to be detected. The output value output by the first measurement unit 21 is used to examine the presence or absence of the gas to be detected in the ambient environment and to determine the concentration of the gas to be detected in the ambient environment. In the present embodiment, the first measurement unit 21 includes a gas thermal conductivity type gas sensor (hereinafter also referred to as the gas thermal conductivity type gas sensor 21). The gas thermal conductivity type gas sensor 21 detects the difference in the thermal conductivity of the measurement target gas (ambient atmosphere gas) including the gas to be detected and the standard gas by detecting the signal intensity caused by the difference in the thermal conductivity of the measurement target gas and the standard gas. Then, the gas thermal conductivity type gas sensor 21 detects the gas to be detected contained in the measurement target gas based on the difference in the thermal conductivity of the measurement target gas and the standard gas. By including a gas thermal conductivity type gas sensor, the first measurement unit 21 can detect the gas to be detected over a high concentration range. However, the first measurement unit 21 may include different types of gas sensors according to the type of the gas to be detected. The first measurement unit 21 is not limited to a gas thermal conductivity type gas sensor, and may include other gas sensors such as a known catalytic combustion type gas sensor, a semiconductor type gas sensor, and a constant potential electrolysis type gas sensor. Further, the first measurement unit 21 is not limited to one gas sensor, and may include a plurality of gas sensors of the same type or a plurality of gas sensors of different types.

[0022] As shown in FIG. 3, the gas thermal conductivity type gas sensor 21 includes a detection element 211, a compensation element 212, two fixed resistance elements 213 and 214, a circuit power supply 215, and a potentiometer 216, and constitutes a Wheatstone bridge circuit. In the gas thermal conductivity type gas sensor 21, due to the difference in the thermal conductivity of the gas to be measured and the standard gas, a difference occurs in the resistance values of the detection element 211 and the compensation element 212 in the circuit, and accordingly, a potential difference caused by the difference in the thermal conductivity of the gas to be measured and the standard gas is generated. The gas thermal conductivity type gas sensor 21 outputs the potential difference generated due to the difference in the thermal conductivity of the gas to be measured and the standard gas as an output value corresponding to the concentration of the gas to be detected. Note that the circuit power supply 215 is separately provided independently of the power supply 6 of the gas detector 1 in the present embodiment, but may be shared with the power supply 6 of the gas detector 1.

[0023] The detection element 211 is an element in which the gas to be measured flows through (natural diffusion), and the resistance value changes due to the heat balance with the gas to be measured. As shown in FIG. 3, the detection element 211 includes a first variable resistor 211a whose resistance value changes due to the heat balance with the gas to be measured, and a detection container 211b that houses the first variable resistor 211a and through which the gas to be measured can flow. Since the heat balance of the first variable resistor 211a with the gas to be measured is affected by the thermal conductivity of the gas to be measured, the resistance value changes according to the thermal conductivity of the gas to be measured. The first variable resistor 211a is not particularly limited as long as it is configured to change its resistance value according to the change in the thermal conductivity of the gas to be measured. For example, a known platinum resistor can be used. As shown in FIG. 3, the detection container 211b is provided with a through hole H through which the gas to be measured can flow, and is configured to allow the gas to be measured to flow through.

[0024] The compensating element 212 is an element in which a reference standard gas is filled for the gas to be measured, and the resistance value changes due to the heat balance with the standard gas. As shown in FIG. 3, the compensating element 212 includes a second variable resistor 212a that is thermally equivalent to the first variable resistor 211a, and a compensating container 212b that houses the second variable resistor 212a and is filled with the standard gas. Since the heat balance of the second variable resistor 212a with the standard gas is affected by the thermal conductivity of the standard gas, the resistance value changes according to the thermal conductivity of the standard gas. The second variable resistor 212a is not particularly limited as long as it is thermally equivalent to the first variable resistor 211a. For example, one having the same configuration as the first variable resistor 211a can be used. The compensating container 212b is configured to be filled with the standard gas so that no other gas flows in. The compensating container 212b is configured to maintain the filled standard gas in a predetermined state and expose the second variable resistor 212a to the standard gas. The standard gas is not particularly limited as long as it is a reference gas for the gas to be measured. For example, air, helium gas, nitrogen gas, etc. can be used.

[0025] In the gas thermal conductivity type gas sensor 21, when the thermal conductivity of the gas to be measured is different from the thermal conductivity of the standard gas, the heat balance between each of the first variable resistor 211a and the second variable resistor 212a and each of the gas to be measured and the standard gas is different. Therefore, a difference occurs in the resistance values of the first variable resistor 211a and the second variable resistor 212a, and thereby a potential difference occurs in the detection circuit. The gas thermal conductivity type gas sensor 21 can detect the potential difference caused by the difference in the thermal conductivity of the gas to be measured and the standard gas by measuring the potential difference generated in the detection circuit with the potentiometer 216. The gas thermal conductivity type gas sensor 21 outputs the potential difference detected by the potentiometer 216 as an output value.

[0026] The second measurement unit 22 measures the ambient environmental state around the gas detector 1 and outputs the measurement result of the ambient environmental state. The ambient environmental state to be measured by the second measurement unit 22 is a parameter representing the state of the ambient environment of the gas detector 1 that can affect the detection result of the gas to be detected by the first measurement unit 21. The ambient environmental state is not particularly limited as long as it is a parameter that may affect the detection result of the gas to be detected, and examples include the temperature, humidity, atmospheric pressure, and concentration of gases other than the gas to be detected in the ambient environment of the gas detector 1. In the present embodiment, the ambient environmental state is the temperature and / or humidity around the gas detector 1, and the second measurement unit 22 includes a temperature sensor for measuring temperature and / or a humidity sensor for measuring humidity. The temperature sensor and the humidity sensor are not particularly limited, and a known thermistor or the like, and a known polymer resistance type or polymer capacitance type sensor can be used respectively. Note that when the second measurement unit 22 includes both a temperature sensor and a humidity sensor, they may be provided separately, or may be provided as an integrated temperature and humidity sensor. Further, the second measurement unit 22 may include a gas sensor for the purpose of measuring the concentration of gases other than the gas to be detected.

[0027] The temperature and / or humidity measured by the temperature sensor and / or humidity sensor which is the second measurement unit 22 is used to determine whether the ambient environment of the gas detector 1 has changed as described later, and may also be used to correct the indication value indicating the concentration of the gas to be detected. When a gas thermal conductivity type gas sensor is used as the first measurement unit 21, when detecting the difference in thermal conductivity between the gas to be measured and the standard gas as described above, the difference in thermal conductivity is affected by the temperature and humidity of the ambient environment in which the gas to be measured is included. Therefore, by correcting the indication value with the temperature and / or humidity measured by the second measurement unit 22, a more accurate indication value can be obtained. Further, by using the same second measurement unit 22 for both the purpose of determining the ambient environment change and correcting the indication value, the gas detector 1 can be miniaturized.

[0028] The control unit 3 is configured to calculate an indication value indicating the concentration of the gas to be detected based on the output value obtained by detecting the gas to be detected by the measurement unit 2 (the first measurement unit 21). Further, as described above, the control unit 3 may be configured to correct the indication value indicating the concentration of the gas to be detected by using the temperature measured by the temperature sensor and / or the humidity measured by the humidity sensor. The indication value calculated by the control unit 3 indicates the concentration of the gas to be detected expressed in units such as ppm, vol%, %LEL, etc. The indication value is notified to the user of the gas detector 1 via the notification unit 5 of the gas detector 1. The control unit 3 uses, for example, a relational expression (calibration curve) between the output value of the measurement unit 2 (the first measurement unit 21) obtained in advance and the indication value indicating the concentration of the gas to be detected to calculate an indication value indicating the gas concentration of the gas to be detected from the output value obtained by the measurement unit 2 (the first measurement unit 21). In addition to calculating the indication value, the control unit 3 has an arithmetic processing function for performing the processes described below. Details of other functions of the control unit 3 will be described later.

[0029] As shown in FIG. 2, the control unit 3 is communicably connected to the measurement unit 2, controls the operation of the measurement unit 2, and receives the output value and the measurement result obtained by the measurement unit 2. Further, the control unit 3 is communicably connected to the storage unit 4 and the notification unit 5, controls the operation of each component, and is configured to be able to transmit and receive information. The control unit 3 can be configured by using, for example, a known central processing unit (CPU) or the like.

[0030] The storage unit 4 stores information regarding the gas to be detected and information regarding the ambient environmental conditions. As shown in FIG. 2, the storage unit 4 is communicably connected to the control unit 3 and is configured to communicate information regarding the gas to be detected and the ambient environmental conditions with the control unit 3. The information regarding the gas to be detected includes, for example, the output value corresponding to the gas to be detected obtained by the measurement unit 2 (the first measurement unit 21), the relational expression (calibration curve) between the output value corresponding to the gas to be detected of the measurement unit 2 obtained in advance and the indicated value indicating the concentration of the gas to be detected, the indicated value of the gas to be detected calculated by the control unit 3, the threshold value for the output value and the indicated value, and the like. Further, the information regarding the ambient environmental conditions includes, for example, the measurement result of the ambient environmental conditions obtained by the measurement unit 2 (the second measurement unit 22), the threshold value for the measurement result, and the like. Further, the storage unit 4 may be configured to store a program capable of executing the functions of the control unit 3 described in this specification. The storage unit 4 is not particularly limited and can be configured by a known volatile memory such as a RAM, or a known non-volatile memory such as a hard disk or a flash memory.

[0031] The notification unit 5 notifies the user of the gas detector 1 of information regarding the gas to be detected. Further, the notification unit 5 notifies the user of the gas detector 1 of information regarding changes in the surrounding environment of the gas detector 1. As shown in FIG. 2, the notification unit 5 is communicably connected to the control unit 3, receives information regarding the gas to be detected and information regarding changes in the surrounding environment from the control unit 3, and notifies the user of the information regarding the gas to be detected and the information regarding changes in the surrounding environment. The information regarding the gas to be detected herein includes, for example, an indication value indicating the concentration of the gas to be detected and information indicating that the indication value exceeds a predetermined threshold. Further, the information regarding changes in the surrounding environment includes, for example, information indicating that the surrounding environment of the measurement target has changed from the surrounding environment at a predetermined timing. The notification unit 5 is embodied by, for example, visual notification means such as a display or auditory notification means such as a speaker. For example, the visual notification means displays an indication value indicating the concentration of the gas to be detected (see the indication value display areas DP1 and DP2 in FIG. 1), displays warning information indicating that the indication value exceeds a predetermined threshold, and displays cautionary information indicating that the surrounding environment has changed (see the surrounding environment change display area DP3 in FIG. 1), etc., and notifies the user of information that can be visually recognized. Further, the auditory notification means emits a warning sound indicating that the indication value exceeds a predetermined threshold and emits a cautionary sound indicating that the surrounding environment has changed, etc., and emits information that can be aurally recognized by the user. In the present embodiment, the notification unit 5 is provided inside the gas detector 1, but may also be provided outside the gas detector 1.

[0032] The power supply 6 supplies power to the components of the gas detector 1. In the present embodiment, as shown in FIG. 2, the power supply 6 is connected to the control unit 3 and is configured to supply power to other components via the control unit 3. However, the power supply 6 may be directly connected to other components and configured to directly supply power to other components. In the present embodiment, the power supply 6 is embodied as a battery provided inside the gas detector 1, but may also be embodied as an external power supply provided outside the gas detector 1.

[0033] Next, while explaining the operation of the gas detector 1, further functions of the control unit 3 will be described. When the power supply 6 is turned on, the gas detector 1 starts to operate. The gas detector 1 is provided with a warm-up period during which it does not perform the detection operation of the gas to be detected until the output value of the measurement unit 2 (the first measurement unit 21) stabilizes at the initial stage of driving. Here, not performing the detection operation of the gas to be detected means that although the measurement unit 2 is driven and the control unit 3 calculates an instruction value from the output value obtained by the measurement unit 2, the instruction value is not notified to the user of the gas detector 1 as indicating at least the concentration of the gas to be detected contained in the ambient environment. In the gas detector 1, at the elapsed time when the warm-up period ends, the instruction value calculated from the output value obtained by the measurement unit 2 is adjusted to be the zero instruction value (zero adjustment of the instruction value). Here, the zero instruction value is an instruction value indicating the concentration of the gas to be detected assumed in a sound ambient environment. For example, when the gas to be detected is a combustible gas such as methane, it is assumed that it does not exist in a sound ambient environment, so the zero instruction value can be set to 0 vol%. Also, when the gas to be detected is oxygen, it is assumed that 20.9 vol% exists in the atmosphere, which is a sound ambient environment, so the zero instruction value can be set to 20.9 vol%. Such zero adjustment of the instruction value can be automatically performed by the control unit 3 or can be performed by the user's operation. When the zero adjustment of the instruction value is completed, the gas detector 1 starts the detection operation of the gas to be detected. However, the zero adjustment of the instruction value is not limited to the end of the warm-up period and can be performed at any timing during the driving period of the gas detector 1. Also, the zero adjustment of the instruction value does not necessarily have to be performed if the instruction value already indicates the zero instruction value, etc. Further, the gas detector 1 does not necessarily need to be provided with a warm-up period if the output value of the measurement unit 2 (the first measurement unit 21) is stable immediately after the start of driving.

[0034] When the control unit 3 starts the detection operation of the gas to be detected, it notifies the user of the gas detector 1 of the indicated value calculated based on the output value obtained by the measurement unit 2 (the first control unit 21) as indicating the concentration of the gas to be detected contained in the ambient environment. The detection of the gas to be detected, the calculation and notification of the indicated value are continuously performed at predetermined time intervals, such as 1 second, throughout the driving period until the driving of the gas detector 1 ends. At that time, when the difference between the indicated value and the zero indicated value is less than a predetermined threshold value (a predetermined threshold value regarding the detection result of the gas to be detected described later, for example, 0.3 vol%), the indicated value may be automatically adjusted to the zero indicated value and notified to the user. The notification of the indicated value is performed by the notification unit 5. In this embodiment, as shown in FIG. 1, it is performed by displaying a numerical value in the indicated value display areas DP1 and DP2 of the display panel DP provided on the detector main body DB. In the illustrated example, the indicated values of two types of gases to be detected are displayed in the two indicated value display areas DP1 and DP2. The user of the gas detector 1 can recognize the concentration of the gas to be detected contained in the ambient environment by the notification of the indicated value.

[0035] Furthermore, the control unit 3 may be configured to notify the user of a warning when the indicated value indicating the concentration of the gas to be detected exceeds a predetermined threshold value (a threshold value different from the predetermined threshold value regarding the detection result of the gas to be detected described later). The predetermined threshold value here is a value appropriately set within the range of the concentration of the gas to be detected that may affect the ambient environment and the human body, such as explosion and poisoning. The notification of the warning is performed, for example, by the notification unit 5 emitting a warning sound. The user of the gas detector 1 can recognize that there may be a dangerous state in the ambient environment by the notification of the warning.

[0036] Here, in the gas detector 1, after zero-adjusting the indicated value of the gas to be detected, if the environment around the gas detector 1 changes, the indicated value of the gas to be detected may change. In particular, when the gas thermal conductivity type gas sensor 21 is adopted to detect the gas to be detected as in the present embodiment, as can be understood from the above-described detection principle, when the temperature and humidity of the surrounding environment change, the possibility that the indicated value of the gas to be detected changes becomes high. The change in the environment around the gas detector 1 can occur during the driving period from the start to the end of driving. For example, if the gas detector 1 has its power turned on in the morning and the driving continues until the afternoon on the same day, the temperature and humidity of the surrounding environment may change. Alternatively, when the gas detector 1 is configured as a portable type, the temperature and humidity of the surrounding environment may change by moving from the environment where the driving is started to the environment where the gas to be detected is actually to be detected. Not limited to temperature and humidity, the atmospheric pressure and the concentration of gases other than the gas to be detected may also change. For example, if the surrounding environment where the gas to be detected is to be detected changes from the surrounding environment at the timing when the zero-adjustment of the indicated value of the gas to be detected is performed, the indicated value may change from the zero indicated value. When the indicated value changes beyond the zero indicated value, the user of the gas detector 1 cannot determine whether this change in the indicated value is due to the actual presence of the gas to be detected in the surrounding environment or due to a change in the surrounding environment other than the presence of the gas to be detected just by looking at the indicated value. Therefore, in the gas detector 1, in order to improve the reliability of the indicated value, it is important to determine whether the surrounding environment surrounding the gas detector 1 has changed.

[0037] In the gas detector 1, for the purpose of determining whether the surrounding environment surrounding the gas detector 1 has changed, the control unit 3 is configured to determine the change in the surrounding environment based on the detection result of the gas to be detected and the measurement result of the surrounding environmental state. More specifically, the control unit 3 first stores, in the storage unit 4, the detection result of the gas to be detected and the measurement result of the surrounding environmental state obtained in the surrounding environment (hereinafter, also referred to as the "reference surrounding environment") at a predetermined timing during the driving period of the gas detector 1, respectively, as the reference detection result of the gas to be detected and the reference measurement result of the surrounding environmental state. The predetermined timing referred to here is, in the present embodiment, the timing at which the zero adjustment of the indicated value of the gas to be detected is performed or the period including that timing. However, the predetermined timing is not limited to the timing at which the zero adjustment of the indicated value is performed, as long as it is the timing at which the gas detector 1 exists in the surrounding environment that can be compared with the surrounding environment (hereinafter, also referred to as the "target surrounding environment") where the gas to be detected is actually to be detected. It may be the timing at which the indicated value of the gas to be detected shows the zero indicated value regardless of the zero adjustment of the indicated value, or it may be the timing at which the zero adjustment of the indicated value is not performed.

[0038] The detection results of the gas to be detected described above include an indication value indicating the concentration of the gas to be detected calculated by the control unit 3 based on the output value obtained by detecting the gas to be detected by the measurement unit 2 (the first measurement unit 21). And the indication value of the gas to be detected obtained at a predetermined timing is zero-adjusted before being stored in the storage unit 4 as the reference detection result of the gas to be detected. That is, the reference detection result of the gas to be detected includes the indication value (that is, the zero indication value) after zero-adjustment is performed on the indication value obtained in the surrounding environment (reference surrounding environment) at a predetermined timing. However, the reference detection result of the gas to be detected does not necessarily have to be the indication value after zero-adjustment as long as it can be compared with the indication value of the target surrounding environment, and it may be the indication value before zero-adjustment. Also, the detection result of the gas to be detected is not limited to the indication value of the gas to be detected as long as it is a detection result comparable between the reference surrounding environment and the target surrounding environment. For example, it may be the output value obtained by detecting the gas to be detected.

[0039] In addition, the measurement results of the surrounding environmental conditions described above include the temperature and / or humidity of the surrounding environment measured by the measurement unit 2 (the second measurement unit 22). However, the measured surrounding environmental conditions are not limited to temperature and / or humidity as long as they are parameters indicating the state of the surrounding environment that can affect the detection results of the gas to be detected, and may be atmospheric pressure, the concentration of gases other than the gas to be detected, and the like.

[0040] Next, the control unit 3 is configured to determine whether the ambient environment (target ambient environment) of the measurement target has changed from the ambient environment (reference ambient environment) at a predetermined timing based on the detection result of the detection target gas obtained in the ambient environment (target ambient environment) of the measurement target and the measurement result of the ambient environmental state, and the reference detection result of the detection target gas and the reference measurement result of the ambient environmental state obtained in the ambient environment (reference ambient environment) at the above-described predetermined timing. The control unit 3 configured in this way determines, for example, that the target ambient environment has changed from the reference ambient environment when both conditions are satisfied: that the difference between the detection result of the detection target gas obtained in the target ambient environment and the reference detection result of the detection target gas obtained in the reference ambient environment is equal to or greater than a predetermined threshold value for the detection result of the detection target gas, and that the difference between the measurement result of the ambient environmental state obtained in the target ambient environment and the reference measurement result of the ambient environmental state obtained in the reference ambient environment is equal to or greater than a predetermined threshold value for the measurement result of the ambient environmental state. Note that the predetermined threshold value for the detection result of the detection target gas described above is a value that can be appropriately set in the boundary region between the range that can be recognized as a detection error and the range that can be recognized as a significant difference. Also, the predetermined threshold value for the measurement result of the ambient environmental state described above is a value that can be appropriately set within the range that can affect the detection result of the detection target gas.

[0041] For example, in the present embodiment, when the difference between the indication value, which is the detection result of the detection target gas obtained in the target ambient environment, and the zero indication value, which is the reference detection result obtained in the reference ambient environment, is 0.3 vol% or more, which is a predetermined threshold value, and the difference between the temperature and / or humidity, which are the measurement results of the ambient environmental state obtained in the target ambient environment, and the temperature and / or humidity, which are the reference measurement results obtained in the reference ambient environment, is 5°C and / or 10%RH or more, which are predetermined threshold values, it is determined that the target ambient environment has changed from the ambient environment (reference ambient environment) at the timing when the zero adjustment of the indication value was performed. When the zero adjustment of the indication value is performed multiple times and there are multiple reference ambient environments, the reference ambient environment for comparison with the target ambient environment may be the reference ambient environment at any timing before or after the measurement timing in the target ambient environment. However, in the present embodiment, the reference ambient environment measured immediately before the measurement in the target ambient environment is selected.

[0042] Here, in the present embodiment where the indication value of the detection target gas is adopted as the detection result of the detection target gas, the control unit 3 may be configured not to determine a change in the ambient environment when the indication value obtained in the target ambient environment is less than the zero indication value, and more specifically, when the indication value is a negative value. Since the concentration of the detection target gas is not assumed to be a negative value, when the indication value is a negative value, there may be a possibility that the gas detector 1 is malfunctioning or has failed. In such a case, the control unit 3 may notify the user of a warning indicating that there may be a possibility that the gas detector 1 is malfunctioning or has failed.

[0043] When the control unit 3 subsequently determines that the ambient environment has changed, it is configured to notify the user of the gas detector 1 that the ambient environment has changed. Further, when the control unit 3 determines that the ambient environment has not changed, it is configured not to notify that the ambient environment has changed. The notification that the ambient environment has changed is performed by the notification unit 5. In this embodiment, as shown in FIG. 1, in the ambient environment change display area DP3 of the display panel DP provided on the detector main body DB, it is performed by lighting a lamp. Note that the notification of the ambient environment change is not limited to lighting the lamp, and it may be performed by displaying an icon in the ambient environment change display area DP3 of the display panel DP. By the notification of the ambient environment change, the user of the gas detector 1 can recognize whether the target ambient environment has changed from the reference ambient environment.

[0044] For example, when the user recognizes that the ambient environment has not changed and the indicated value of the gas to be detected changes beyond the zero indicated value, the user can recognize that the indicated value shown is a more reliable indicated value that is not affected by the change in the ambient environment, and can determine that the gas to be detected exists in the target ambient environment. Also, when the user recognizes that the ambient environment has changed and the indicated value of the gas to be detected changes beyond the zero indicated value, it can be estimated that the change in the indicated value of the gas to be detected may be caused by the change in the ambient environment. In that case, the user can cancel the possible change in the indicated value due to the change in the ambient environment by readjusting the indicated value of the gas to be detected to zero again in the ambient environment where it is assumed that the gas to be detected does not exist in a state close to the target ambient environment, and can make the gas detector 1 in a state where a more accurate indicated value of the gas to be detected can be obtained. Therefore, in the gas detector 1, by notifying the user that the usage environment has changed, the reliability of the indicated value for the user is improved.

[0045] While the control unit 3 determines that the ambient environment is changing, it is configured to continue notifying that the ambient environment is changing. Then, while the control unit 3 is notifying the user that the ambient environment is changing, when the difference between the detection result of the detection target gas obtained in the target ambient environment and the reference detection result of the detection target gas obtained in the reference ambient environment is less than a predetermined threshold value regarding the detection result of the detection target gas described above, it is configured to stop notifying that the ambient environment is changing. For example, in the present embodiment, when the difference between the indicated value which is the detection result of the detection target gas obtained in the target ambient environment and the zero indicated value which is the reference detection result obtained in the reference ambient environment is less than 0.3 vol% which is the predetermined threshold value, the notification that the ambient environment is changing is stopped. In the gas detector 1, when the detection result of the detection target gas satisfies a predetermined condition, the notification that the ambient environment is changing is stopped without being continued. Therefore, the user can recognize that it is not necessary to consider the influence of the change in the ambient environment in the target ambient environment. However, once the notification that the ambient environment is changing is made, it may be continued regardless of subsequent conditions.

[0046] The control unit 3 is configured to continue determining whether the ambient environment (target ambient environment) of the measurement target has changed from the ambient environment (reference ambient environment) at a predetermined timing, and based on the determination result, notifying that the ambient environment has changed, throughout the driving period (strictly excluding the warm-up period) of the gas detector 1. In the gas detector 1, by continuing the determination and notification of the ambient environment change throughout the driving period, the reliability of the indicated value for the user can be improved throughout the driving period. However, the determination and notification of the ambient environment change may be performed only within a specific period during the driving period.

[0047] The control unit 3 is configured to be able to simultaneously notify that the surrounding environment has changed and issue a warning indicating that the indicated value exceeds a predetermined threshold (a threshold different from the predetermined threshold for the detection result of the gas to be detected). As a result, when the user is notified of a warning indicating that the indicated value exceeds the predetermined threshold, if no notification of the change in the surrounding environment is given, the user can recognize that the warning is a more reliable warning that is not affected by the change in the surrounding environment. Also, when the user is notified of a warning indicating that the indicated value exceeds the predetermined threshold and at the same time the change in the surrounding environment is also notified, it can be presumed that the increase in the indicated value may be affected by the change in the surrounding environment. In that case, the user can perform zero adjustment of the indicated value of the gas to be detected again in a surrounding environment close to the target surrounding environment and where it is assumed that the gas to be detected does not exist, and then perform the detection operation of the gas to be detected again in the target surrounding environment, thereby obtaining a more reliable indicated value and more accurately determining the danger level of the target surrounding environment. However, the notification of the change in the surrounding environment and the warning notification indicating that the indicated value exceeds the predetermined threshold may be performed at different timings.

Description of Signs

[0048] 1 Gas detector 2 Measuring unit 21 First measuring unit (thermal conductivity gas sensor) 211 Detection element 211a First variable resistor 211b Detection container 212 Compensation element 212a Second variable resistor 212b Compensation container 213, 214 Fixed resistor elements 215 Circuit power supply 216 Potentiometer 22 Second measuring unit (temperature sensor and / or humidity sensor) 3 Control unit 4 Storage unit 5 Notification unit 6 Power supply DB detector body DP display panel DP1 and DP2 indicated value display areas DP3 ambient environment change display area GI gas introduction part H through-hole OP operation panel TH through-hole

Claims

1. A gas detector for detecting a gas to be detected contained in the surrounding environment, comprising: a measurement unit configured to detect the gas to be detected and measure the surrounding environmental state; a control unit configured to determine a change in the surrounding environment based on a detection result of the gas to be detected and a measurement result of the surrounding environmental state; a storage unit that stores information on the gas to be detected and information on the surrounding environmental state; wherein the control unit is configured to store, in the storage unit, as a reference detection result of the gas to be detected and a reference measurement result of the surrounding environmental state, respectively, the detection result of the gas to be detected and the measurement result of the surrounding environmental state obtained in the surrounding environment at a predetermined timing during a driving period of the gas detector; the control unit is configured to determine whether the surrounding environment of the measurement target has changed from the surrounding environment at the predetermined timing based on the detection result of the gas to be detected and the measurement result of the surrounding environmental state obtained in the surrounding environment of the measurement target and the reference detection result of the gas to be detected and the reference measurement result of the surrounding environmental state obtained in the surrounding environment at the predetermined timing; the control unit is configured to notify a user of the gas detector that the surrounding environment has changed when it is determined that the surrounding environment has changed; a gas detector.

2. The control unit is configured to determine that the surrounding environment of the measurement target has changed from the surrounding environment at the predetermined timing when both conditions are satisfied: that a difference between the detection result of the gas to be detected obtained in the surrounding environment of the measurement target and the reference detection result of the gas to be detected is equal to or greater than a predetermined threshold value related to the detection result of the gas to be detected, and that a difference between the measurement result of the surrounding environmental state obtained in the surrounding environment of the measurement target and the reference measurement result of the surrounding environmental state is equal to or greater than a predetermined threshold value related to the measurement result of the surrounding environmental state. The gas detector according to claim 1.

3. The detection result of the gas to be detected includes an indication value indicating the concentration of the gas to be detected calculated by the control unit based on an output value obtained by detecting the gas to be detected by the measurement unit. The reference detection result of the gas to be detected includes the indication value after zero adjustment is performed on the indication value obtained in the surrounding environment at the predetermined timing. The gas detector according to claim 1 or 2.

4. The measurement unit includes a first measurement unit for detecting the gas to be detected and a second measurement unit for measuring the surrounding environmental state. The gas detector according to any one of claims 1 to 3.

5. The first measurement unit includes a gas thermal conductivity type gas sensor, and the second measurement unit includes a temperature sensor for measuring temperature and / or a humidity sensor for measuring humidity. The gas detector according to claim 4.

6. The control unit is configured to correct an indication value indicating the concentration of the gas to be detected by using the temperature measured by the temperature sensor and / or the humidity measured by the humidity sensor. The gas detector according to claim 5.

7. The control unit is configured to notify the user of a warning when the indication value indicating the concentration of the gas to be detected exceeds a predetermined threshold value. The control unit is configured to be able to simultaneously notify the user of the change in the surrounding environment and the warning. The gas detector according to any one of claims 1 to 6.

8. While the control unit is notifying the user that the surrounding environment is changing, when the difference between the detection result of the gas to be detected obtained in the surrounding environment of the measurement target and the reference detection result of the gas to be detected becomes less than a predetermined threshold value regarding the detection result of the gas to be detected, the control unit is configured to stop notifying that the surrounding environment is changing. The gas detector according to any one of claims 1 to 7.

9. The control unit is configured to continue determining whether the surrounding environment of the measurement target has changed from the surrounding environment at the predetermined timing and, based on the determination result, notifying the user that the surrounding environment has changed throughout the driving period of the gas detector. The gas detector according to any one of claims 1 to 8.

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