Smoke sensor

Abstract

To reduce the inconvenience that a smoke detector that generates log data indicating the measurement value of a flow meter generates useless log data indicating substantially the same value. [Solution] A flow meter 115 measures the flow rate of air flowing into the detection area of ​​the smoke detector from an external space. A flow signal acquisition means 1183 included in a control unit 118 provided in the smoke detector acquires a flow rate signal indicating the measurement value of the flow meter 115, and a storage means 1180 temporarily stores the flow rate signal in a flow rate temporary storage table. When a log generation means 1184 determines that the rate of change of the measurement value of the flow rate stored in the flow rate temporary storage table has reached a set airflow change step value, the log generation means 1184 generates log data indicating the measurement value of the flow rate at that time, and the storage means 1180 adds the log data to the flow rate log table. A threshold change means 1187 changes the set airflow change step value in response to a predetermined operation performed by a user on a button 116.

Description

[Technical Field]

[0001] The present invention relates to smoke sensing technology. [Background technology]

[0002] 2. Description of the Related Art There are smoke detectors that detect the generation of smoke in an external space by detecting particles contained in the air that flows into a detection area from the external space.

[0003] For example, a smoke detector known as a photoelectric smoke detector emits light from a light-emitting element into a sensing area, and the scattered light that is scattered by particles in the air within the sensing area is received by a light-receiving element.Based on the intensity of the light received and measured by the light-receiving element, the detector detects particles contained in the air flowing into the sensing area from the external space, thereby detecting the generation of smoke in the external space.

[0004] Patent Document 1 is an example of a patent document disclosing technology related to photoelectric smoke detectors. The photoelectric smoke detector described in Patent Document 1 focuses on the fact that the way the output signal from the light receiving element changes over time differs between when particles other than smoke, such as steam, flow into the smoke detection space (detection area) and when smoke flows into the smoke detection space, and proposes an invention that delays the output signal output from the light receiving element by a predetermined delay time, thereby avoiding the inconvenience of falsely detecting smoke due to the generation of steam, etc. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2019-61423 Summary of the Invention [Problem to be solved by the invention]

[0006] Many smoke detectors (hereafter simply referred to as "smoke detectors"), such as photoelectric smoke detectors, detect smoke in the exterior space by detecting particles contained in the air flowing into the detection area from the exterior space. To prevent dust particles, which are larger than smoke particles, from flowing into the detection area and adhering to the light-emitting element, light-receiving element, etc. as dirt, they are equipped with a filter in the airflow path from the exterior space to the detection area that is coarse enough to allow smoke to pass through but not dust. If this filter becomes clogged or damaged for any reason, the photoelectric smoke detector will not be able to properly detect smoke occurring in the exterior space. Furthermore, dust particles may adhere to the inner walls of the pipes or other devices that form the airflow path from the exterior space to the detection area, obstructing the airflow. In this case, the photoelectric smoke detector will also not be able to properly detect smoke occurring in the exterior space.

[0007] In order to detect the occurrence of such abnormalities, a flow meter that measures the flow rate of air flowing into the sensing area from the outside space can be installed, and a system can be considered that monitors whether the air flow rate measured by the flow meter is within an appropriate range. In such a system, data indicating the measurement results of the flow meter is stored as log data, and by analyzing changes in the air flow rate over time, it is possible to estimate the cause when the air flow rate falls outside the appropriate range, and to estimate the time when the air flow rate will fall outside the appropriate range.

[0008] For example, if the measurement results of a flow meter are stored as log data at predetermined intervals, log data showing substantially the same values ​​will be generated unnecessarily during periods when the air flow rate hardly changes. For example, when log data is stored in a smoke detector, it is undesirable to store unnecessary log data in a memory area with limited capacity. Furthermore, when log data is transmitted from a smoke detector to a host system and stored in the host system, it is undesirable to increase the amount of data communication due to unnecessary log data. Furthermore, when maintenance personnel or the like check log data, if there is a large amount of log data showing substantially the same values, the review process becomes unnecessarily time-consuming and undesirable.

[0009] Therefore, by generating new log data every time the rate of change of the flow rate measured by the flow meter (the absolute value of the amount of change from the flow rate when the last log data was generated divided by the flow rate when the last log data was generated) reaches a predetermined threshold, the inconvenience of generating unnecessary log data can be reduced. Hereinafter, the threshold value of the rate of change of the flow rate used as a condition for generating log data will be referred to as the "airflow change step value."

[0010] The rate of change of the airflow rate flowing into the detection area of ​​a smoke detector from the outside space often differs depending on whether the flow rate is low or high. For example, the lower the flow rate, the larger the rate of change even for a small change in flow rate. Therefore, when the flow rate is low, the rate of change frequently reaches the airflow change step value, resulting in the generation of unnecessary log data.

[0011] In view of these circumstances, the present invention provides a means for reducing the inconvenience of a smoke detector generating log data indicating the measurement value of a flow meter generating useless log data indicating substantially the same value. [Means for solving the problem]

[0012] In order to solve the above problems, the present invention proposes a smoke detector that detects the generation of smoke in an external space by detecting particles contained in the air flowing from the external space into a sensing area, the smoke detector comprising: a flow measurement means for measuring the flow rate of air; a log generation means for generating log data indicating the measurement value when the rate of change of the measurement value of the flow measurement means reaches a threshold value; and a threshold change means for changing the threshold value. [Effects of the Invention]

[0013] According to the present invention, by changing the airflow change step value to an appropriate value according to the flow rate of air flowing into the sensing area from the external space, log data showing the measurements of the flow rate measuring means are generated at an appropriate frequency, thereby reducing the inconvenience of generating unnecessary log data showing substantially the same values. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a diagram showing the configuration of a smoke detection system according to an embodiment; [Figure 2] 1 is a diagram illustrating a configuration of a smoke detector according to an embodiment; [Figure 3] FIG. 2 is a diagram showing the configuration of a computer employed as hardware of a control unit according to an embodiment. [Figure 4] FIG. 2 is a diagram showing the functional configuration of a control unit according to an embodiment. [Figure 5] FIG. 10 is a diagram illustrating the configuration of an airflow change step value table according to an embodiment. [Figure 6] FIG. 10 is a diagram illustrating the configuration of a flow rate temporary storage table according to an embodiment. [Figure 7] FIG. 10 is a diagram illustrating the configuration of a flow rate log table according to an embodiment. [Figure 8] FIG. 10 is a diagram illustrating the configuration of an airflow change step value table according to a modified example.

[0015] [Embodiment] A smoke detection system 1 according to one embodiment of the present invention will be described below. Fig. 1 is a diagram showing the configuration of the smoke detection system 1. The smoke detection system 1 includes a smoke detector 11 and a host system 12.

[0016] The smoke detector 11 is a device that is placed in a space to be monitored for smoke generation (hereinafter referred to as the "monitored space"), takes in the air in the monitored space, detects smoke if it is contained in the air that has been taken in, and if it detects smoke, sends an alarm of smoke generation to the upper system 12.

[0017] In FIG. 1, the smoke detection system 1 includes one smoke detector 11, but the number of smoke detectors 11 included in the smoke detection system 1 varies depending on the number and size of monitored spaces.

[0018] The host system 12 may be a monitoring terminal device, a smoke alarm panel, a central monitoring system, etc. The host system 12 and the smoke detector 11 are connected via a wired, wireless, or mixed communication medium, and are capable of data communication with each other.

[0019] The host system 12 is similar to a host system according to the prior art, and therefore a description thereof will be omitted.

[0020] 2 is a diagram showing a schematic configuration of the smoke detector 11. The smoke detector 11 includes a housing 110, a light-emitting unit 111, a light-receiving unit 112, a fan 113, a filter 114, a flow meter 115, a button 116, a light-emitting unit 117, and a control unit 118.

[0021] The housing 110 is a container that forms a space inside. The housing 110 has an intake port P, which is an opening that functions as an inlet for air to flow from the external space into the internal space, and an exhaust port Q, which is an opening that functions as an outlet for air to flow from the internal space to the external space.

[0022] The housing 110 also has a wall 1101 for forming a sensing area S, which is an area for sensing smoke within the internal space, a pipe 1102 for forming an air flow path from the intake port P to the sensing area S, and a pipe 1103 for forming an air flow path from the sensing area S to the exhaust port Q.

[0023] The light-emitting unit 111 has, for example, an LED, and emits light from the LED to the sensing area S. The light-receiving unit 112 is disposed at a position not facing the light-emitting unit 111 so that the light emitted from the light-emitting unit 111 does not directly enter the sensing area S, but rather scattered light scattered by particles in the air within the sensing area S enters the sensing area S. The light-receiving unit 112 has, for example, a photodiode, receives a portion of the scattered light within the sensing area S, and outputs a light intensity signal indicating the intensity of the received light.

[0024] The fan 113 is disposed on the air flow path formed by the pipe 1102, and serves to generate a flow of air from the external space toward the sensing area S by means of rotating blades.

[0025] The filter 114 is disposed on the air flow path formed by the pipe 1102, and captures dust contained in the air flowing from the external space toward the sensing area S, thereby preventing the dust from entering the sensing area S.

[0026] The flow meter 115 (an example of a flow rate measuring means) is a sensor that measures the flow rate of air flowing from the external space into the sensing area S due to the operation of the fan 113. The flow meter 115 includes, for example, a thermistor, and identifies the air flow rate based on the resistance value of the thermistor, which changes in accordance with the air flow rate. However, the method by which the flow meter 115 measures the air flow rate is not limited to this, and various known types of flow meters may be adopted as the flow meter 115.

[0027] The button 116 (an example of an operation receiving means) is an operator that receives an operation from a user (for example, an administrator of the smoke detection system 1). The button 116 is operated when the user changes the set airflow change step value (an example of a threshold value).

[0028] Light emitting unit 117 is a component that serves to notify the user that the user's operation on button 116 has been accepted. Light emitting unit 117 has, for example, an LED, and notifies the user of the set value by emitting light in different modes according to the set value of the airflow change step value in response to the user's operation on button 116, such as once when the airflow change step value is set to 10%, twice when set to 20%, and three times when set to 30%.

[0029] 2, button 116 and light-emitting unit 117 are arranged on the outer surface of housing 110, but the arrangement positions of button 116 and light-emitting unit 117 are not limited to this. For example, if housing 110 has an openable cover, button 116 may be arranged in a position within the interior space of housing 110 that the user can press when the cover is open, and light-emitting unit 117 may be arranged in a position within the interior space of housing 110 that the user can see when the cover is open. In this case, the inconvenience of the set value of the airflow change step value being changed by an unintended operation by the user can be avoided.

[0030] The control unit 118 is a device that controls the operation of the smoke detector 11. The hardware of the control unit 118 is, for example, a computer, and the control unit 118 is realized by the computer performing processing in accordance with a program for the control unit 118.

[0031] 3 is a diagram showing the configuration of a computer 10 employed as hardware for the control unit 118. The computer 10 includes a processor 101 that performs various types of data processing, a memory 102 that stores various types of data, an input / output interface 103 that exchanges signals with components such as the light-emitting unit 111 of the smoke detector 11, and a communication interface 104 that exchanges data with an external device (in this case, the host system 12).

[0032] Fig. 4 is a diagram showing the functional configuration of control unit 118. That is, control unit 118 including the components shown in Fig. 4 is realized by computer 10 performing processing in accordance with a program for control unit 118. The functional components of control unit 118 are described below.

[0033] The storage means 1180 stores various data. The data stored in the storage means 1180 includes the following: (1) A table showing options for airflow change step values ​​and airflow change step values ​​selected and set from among those options (hereinafter referred to as the "airflow change step value table"). (2) A table that temporarily stores the measured values ​​of the flow meter 115 together with time information indicating the time at which the measured values ​​were measured (hereinafter referred to as a "flow rate temporary storage table"). (3) A table (hereinafter referred to as the "flow log table") that stores, among the measurement values ​​stored in the flow temporary storage table, the measurement value when the rate of change reaches the set airflow change step value, along with time information indicating the time when the measurement value was measured. (4) A threshold value for determining whether or not there is a flow rate abnormality. (5) Threshold for determining whether or not smoke is present.

[0034] Fig. 5 is a diagram illustrating the configuration of an airflow change step value table. The data in the airflow change step value table illustrated in Fig. 5 indicates that of the three airflow change step value options of 10%, 20%, and 30%, 20% is the currently selected and set airflow change step value.

[0035] Fig. 6 is a diagram illustrating the configuration of a flow rate temporary storage table. The flow rate temporary storage table has a "time" column that stores time information indicating the time when the flow rate measurement value was measured, and a "flow rate" column that stores the flow rate measurement value measured at that time. The flow rate temporary storage table stores only two records.

[0036] The data in the first row of the flow rate temporary storage table indicates the data most recently added to the flow rate log table. The data in the second row of the flow rate temporary storage table is a measurement value indicating the flow rate last measured by the flow meter 115 and the time at which that measurement value was measured. Hereinafter, the measurement value stored in the "Flow Rate" column in the first row of the flow rate temporary storage table will be referred to as f(1), and the measurement value stored in the "Flow Rate" column in the second row of the flow rate temporary storage table will be referred to as f(2).

[0037] In this embodiment, the rate of change (%) of flow rate compared with the set airflow change step value is represented by R in Equation 1 below. R=|f(2)-f(1)| / f(1)×100...(Formula 1) Note that |X| indicates the absolute value of X.

[0038] When the rate of change R reaches the set airflow change step value, the data in the second row of the flow rate temporary storage table is added to the bottom row of the flow rate log table, and the data in the first row of the flow rate temporary storage table is deleted, and the data in the second row becomes the data in the new first row. After that, the second row is sequentially overwritten with data indicating the latest measurement value of the flow meter 115 and the time of measurement.

[0039] 7 is a diagram illustrating the configuration of a flow rate log table. The flow rate log table has a "time" column that stores time information indicating the time at which the flow rate measurement value was measured, and a "flow rate" column that stores the flow rate measurement value measured at that time. The flow rate log table sequentially stores data indicating the flow rate measurement value when the rate of change R of the air flow measured by flow meter 115 reaches a set airflow change step value and the time at which that measurement value was measured.

[0040] 4, the functional configuration of the control unit 118 will be further described. The light emission instruction means 1181 instructs the light emitter 111 to emit light. The light intensity signal acquisition means 1182 acquires a light intensity signal indicating the intensity of light received by the light receiver 112. The light intensity signal acquired by the light intensity signal acquisition means 1182 is used by the smoke determination means 1186.

[0041] The flow signal acquiring means 1183 acquires a flow signal indicating a measurement value of the flow meter 115. The measurement value indicated by the flow signal acquired by the flow signal acquiring means 1183 is temporarily stored in a flow temporary storage table of the storage means 1180 together with the time of acquisition.

[0042] The log generation means 1184 generates log data indicating the measurement value when the rate of change of the measurement value of the flowmeter 115 reaches a threshold. Specifically, the log generation means 1184 calculates the rate of change R according to the above-mentioned formula 1 based on two measurement values ​​(f(1) and f(2)) stored in the flow rate temporary storage table of the storage means 1180, determines whether the calculated rate of change R reaches the airflow change step value selected in the airflow change step value table, and if the rate of change R reaches the selected airflow change step value, generates a copy of the data in the second row of the flow rate temporary storage table as new log data and adds this log data to the bottom row of the flow rate log table. Furthermore, when adding new log data to the flow rate log table as described above, the log generation means 1184 deletes the data in the first row of the flow rate temporary storage table and makes the data in the second row the data in the new first row.

[0043] The flow rate abnormality determination means 1185 determines whether the measurement value stored in the "flow rate" column of the second row of the flow rate temporary storage table reaches the threshold value for determining flow rate abnormality stored in the storage means 1180, and if the measurement value reaches the threshold value for determining flow rate abnormality, generates flow rate abnormality notification data that notifies of a flow rate abnormality. The flow rate abnormality notification data generated by the flow rate abnormality determination means 1185 is transmitted to the upper system 12 by the communication means 1189.

[0044] The smoke determination means 1186 determines whether the light intensity indicated by the light intensity signal acquired from the light emitter 111 by the light intensity signal acquisition means 1182 reaches a threshold value for determining the presence or absence of smoke stored in the storage means 1180, and if the intensity reaches the threshold value for determining the presence or absence of smoke, generates smoke generation notification data notifying that smoke has been generated. The smoke generation notification data generated by the smoke determination means 1186 is transmitted to the upper system 12 by the communication means 1189.

[0045] The threshold value changing means 1187 changes the set airflow change step value. Specifically, the threshold value changing means 1187 receives an operation signal output from the button 116 in response to a user operation, and based on the received operation signal, changes the records in the airflow change step value table in the storage means 1180 that have a "○" stored in the "selection" column. For example, each time the user presses and holds the button 116, the records in the airflow change step value table that have a "○" stored in the "selection" column are changed in a cyclical manner, such as the first record, the second record, the third record, the first record, ...

[0046] Every time the record in which "○" is stored in the "selection" column of the airflow change step value table changes, the light emission instruction means 1188 instructs the light emitting unit 117 to emit light in a manner corresponding to the record number storing the changed "○" (i.e., the newly set airflow change step value). Examples of the manner in which the light emitting unit 117 emits light in accordance with the light emission instruction means 1188 are as described above.

[0047] The communication means 1189 (an example of a transmitting means and a receiving means) transmits and receives various data to and from the host system 12. Specifically, as described above, when flow rate abnormality notification data is generated by the flow rate abnormality determination means 1185, the communication means 1189 transmits the flow rate abnormality notification data to the host system 12. Also, as described above, when smoke occurrence notification data is generated by the smoke determination means 1186, the communication means 1189 transmits the smoke occurrence notification data to the host system 12.

[0048] Furthermore, the communication means 1189 receives, for example, a request to send a flow rate log table from the host system 12, and in response to the request, sends a copy of the flow rate log table to the host system 12. The host system 12 or a user of the host system 12 can, for example, analyze changes in the air flow rate over time based on the data stored in the flow rate log table that the host system 12 received from the smoke detector 11, thereby estimating the cause when the air flow rate falls outside the appropriate range, or estimating the time when the air flow rate will fall outside the appropriate range before the air flow rate falls outside the appropriate range.

[0049] The timekeeping means 1190 continuously measures the current time and generates time information indicating the measured current time. The time information generated by the timekeeping means 1190 is used, for example, as time information stored in the "time" column of the flow rate temporary storage table.

[0050] According to the smoke detection system 1 described above, if a user views the log data stored in the flow rate log table and determines that log data is being added to the flow rate log table at an unnecessarily high frequency, the user can increase the set airflow change step value by operating button 116. As a result, the inconvenience of unnecessary log data being stored in the flow rate log table thereafter is reduced, and the storage capacity of storage means 1180 is used efficiently.

[0051] Furthermore, according to the above-described smoke detection system 1, if a user views the log data stored in the flow rate log table and determines that the frequency at which log data is added to the flow rate log table is too low, the user can decrease the set airflow change step value by operating button 116. As a result, log data is then stored in the flow rate log table at an appropriate frequency, and the user can easily estimate the cause of the above-described flow rate abnormality based on the log data.

[0052] [Variations] The above-described embodiment is a specific example of the present invention, and various modifications are possible within the scope of the technical concept of the present invention. Examples of such modifications are shown below. Note that two or more of the following modifications may be combined as appropriate.

[0053] (1) In the above-described embodiment, the operation acceptance means for accepting user operations on the smoke detector 11 is the button 116, but the form of the operation acceptance means provided in the smoke detector 11 is not limited to a button. For example, a physical operator different from a button, such as a slider or a switch, may be employed as the operation acceptance means of the smoke detector 11. Also, a touch screen may be employed as the operation acceptance means of the smoke detector 11. In this case, the operation acceptance means displays a virtual operator on the screen and accepts touch operations performed by the user on the virtual operator.

[0054] (2) In the above-described embodiment, the threshold value changing means 1187 changes the set airflow change step value in response to a user operation received by an operation receiving means exemplified by the button 116. Alternatively or in addition to this, the threshold value changing means 1187 may change the set airflow change step value in response to data received by the communication means 1189 (an example of a receiving means) from the host system 12 (an example of an external device).

[0055] For example, when a user performs a specified operation on the host system 12, the host system 12 requests the smoke detector 11 to send an airflow change step value table, and in response to the request, the smoke detector 11 sends a copy of the airflow change step value table to the host system 12.

[0056] The host system 12 displays the airflow change step value table received from the smoke detector 11. When the user operates the host system 12 to change the airflow change step value selected in the displayed airflow change step value table, the host system 12 generates an airflow change step value table in which a "○" is stored in the "Selection" column of the record for the changed airflow change step value, and transmits the airflow change step value table to the smoke detector 11.

[0057] The smoke detector 11 overwrites the airflow change step value table stored in the storage means 1180 with the airflow change step value table received from the host system 12. As a result, the airflow change step value selected by the user who operated the host system 12 is newly set in the smoke detector 11.

[0058] In this modified example, the user can change the airflow change step value used in the smoke detector 11 without directly operating the smoke detector 11.

[0059] (3) In the above-described embodiment, the threshold value changing means 1187 changes the set airflow change step value in response to an operation by a user. Alternatively, the threshold value changing means 1187 may change the set airflow change step value based on a measurement value of the flow meter 115 (an example of a flow measurement means).

[0060] In this modification, the storage means 1180 stores an airflow change step value table having the configuration shown in Fig. 8, instead of the airflow change step value table having the configuration shown in Fig. 5. A "flow rate range" column is added to each record of the airflow change step value table in this modification.

[0061] The threshold change means 1187, for example, determines which range shown in the "Flow rate range" column of the airflow change step value table the measurement value stored in the "Flow rate" column of the second row of the flow rate temporary storage table, i.e., the air flow rate last measured by the flow meter 115, falls within, and updates the airflow change step value table so that "○" is stored in the "Selection" column of the record corresponding to the determined range.

[0062] According to this modification, for example, in the case where the lower the air flow rate, the larger the value of the rate of change R of flow rate even for a small change in flow rate, by storing a high flow rate range in the "Flow Rate Range" column of a record in which a small value is stored in the "Airflow Change Step Value" column, and storing a low flow rate range in the "Flow Rate Range" column of a record in which a large value is stored in the "Airflow Change Step Value" column, an appropriate airflow change step value can be automatically selected and used without manual intervention depending on the current flow rate, thereby saving the user the trouble of selecting an appropriate airflow change step value.

[0063] In this modified example, instead of the airflow change step value table, a relational expression showing the correspondence between the flow rate range and the airflow change step value may be stored in the storage means 1180, and the threshold value changing means 1187 may calculate the airflow change step value corresponding to the current flow rate according to the relational expression and set the calculated airflow change step value.

[0064] (4) In the above-described embodiment, the selectable airflow change step values ​​are discrete values ​​such as 10%, 20%, and 30%, but the number of selectable airflow change step values ​​may be increased so that an airflow change step value selected from a substantially continuous range of values ​​can be set.

[0065] (5) In the above-described embodiment, the log data of the air flow rate generated in the smoke detector 11 is stored in a flow rate log table in the smoke detector 11. Alternatively, or in addition, the log data may be transmitted from the smoke detector 11 to an external device (e.g., the host system 12) and stored in the external device.

[0066] (6) In the above-described embodiment, the hardware of the control unit 118 is a computer. However, the control unit 118 may be configured as a dedicated device having an integrated circuit such as an ASIC or FPGA. [Explanation of symbols]

[0067] 1...Smoke detection system, 10...Computer, 11...Smoke detector, 12...Host system, 101...Processor, 102...Memory, 103...Input / output interface, 104...Communication interface, 110...Housing, 111...Light emitting unit, 112...Light receiving unit, 113...Fan, 114...Filter, 115...Flow meter, 116...Button, 117...Light emitting unit, 118...Control unit, 1101...Wall body, 1102...Pipe, 1103...Pipe, 1180...Memory means, 1181...Light emitting instruction means, 1182...Light intensity signal acquisition means, 1183...Flow rate signal acquisition means, 1184...Log generation means, 1185...Flow rate abnormality determination means, 1186...Smoke determination means, 1187...Threshold value change means, 1188...Light emitting instruction means, 1189...Communication means, 1190...Timekeeping means.

Claims

1. a flow rate measuring means for measuring the flow rate of air; a log generating means for generating log data indicating measurements by the flow rate measuring means; a storage means for sequentially storing the log data generated by the log generating means; Equipped with The log generating means generates log data indicating the latest value only when the rate of change of the latest value relative to the reference value reaches a predetermined threshold value, where the measurement value indicated by the most recently stored log data in the storage means is used as a reference value and the latest measurement value by the flow rate measuring means is used as the latest value. Smoke detector.

2. the storage means has only two records, a first area for storing the reference value and a second area for storing the latest value; when the rate of change reaches the threshold, the log generation means records the data stored in the second area as log data and stores the data in the second area as a new reference value in the first area; If the rate of change does not reach the threshold, the next measurement value by the flow rate measuring means is overwritten in the second area.

10. The smoke detector of claim 1.

Images