Point heat detector based on surface-mounted thermistor

Abstract

Described herein are apparatuses, systems, and methods for providing a surface mount thermistor based point heat detector. One circuit board for a point heat detector of a fire sensing system includes a circuit board body having a plurality of corners, at least one hole disposed in the circuit board body proximate one of the corners, and a surface mount thermistor mounted on the at least one corner.

Description

Technical Field

[0001] This disclosure relates to apparatus, systems, and methods for providing point thermal detectors based on surface-mount thermistors. Background Technology

[0002] Facilities (e.g., buildings) (such as commercial facilities, office buildings, hospitals, etc.) may have fire detection systems that can be triggered during emergencies (e.g., fire) to warn occupants to evacuate. For example, a fire detection system may include a fire alarm control panel within the building and multiple point thermal detectors located throughout the facility (e.g., on different floors and / or in different rooms of the facility) that can sense thermal conditions indicating a fire occurring in the facility and provide thermal condition notifications to occupants and / or building monitoring personnel via alarms or other mechanisms.

[0003] Point-temperature detectors used in fire detection systems are currently based on leaded temperature sensors, which have two leads separating the sensor from the surface of the printed circuit board (PCB) to which it is mounted. The ability to achieve a fast response time for airflow temperature measurements is related to the fact that the sensing element (a packaged thermistor chip) is separated above the PCB surface by two leads (e.g., a commercial PSB-S3 type thermistor). This allows the thermistor to detect air temperature with very little influence from heat residing on the PCB (known as PCB thermal inertia).

[0004] The process of mounting these temperature sensors spaced apart above the circuit board surface (thus creating an air gap between the sensor and the board surface) is manual and has several drawbacks. For example, the mounting process is expensive because it requires human operators at the soldering station. This typically results in the need for a separate production area where fire detectors with thermal detection are manufactured, which comes with additional human error and inconsistencies, as well as the complexity and cost associated with such manufacturing processes.

[0005] Additionally, because these leaded temperature sensors need to be positioned above the surface of the PCB to isolate the sensing element from the PCB, this structure occupies more space, which may be undesirable in some implementations. For example, because the sensor is mounted away from the surface of the circuit board, this high profile limits the designer's ability to reduce the height profile of the thermal detector device on which the circuit board is placed. Attached Figure Description

[0006] Figure 1A This is an example of the front side of a printed circuit board for a point thermal detector for a fire alarm system according to one or more embodiments of this disclosure.

[0007] Figure 1BThis is an example of the back side of a printed circuit board for a point thermal detector for a fire alarm system according to one or more embodiments of this disclosure.

[0008] Figure 1C This is an example of the front side of a circular printed circuit board for a point thermal detector for a fire alarm system according to one or more embodiments of this disclosure.

[0009] Figure 2A This is an example of the front of a corner of a printed circuit board for a point thermal detector for a fire alarm system having a surface-mount thermistor thereon, according to one or more embodiments of this disclosure.

[0010] Figure 2B This is an example of the back side of a corner of a printed circuit board for a point thermal detector for a fire alarm system having a surface-mount thermistor thereon, according to one or more embodiments of this disclosure.

[0011] Figure 3 It is a printed circuit board panel having nine printed circuit boards printed together on a panel, according to one or more embodiments of this disclosure.

[0012] Figure 4 This is an inclined bottom view of the cover of a point heat detector according to one or more embodiments of this disclosure.

[0013] Figure 5 This is an oblique side view of a point thermal detector according to one or more embodiments of the present disclosure, showing a corner of a printed circuit board having a surface-mount thermistor disposed therein.

[0014] Figure 6 This is a side view of a point thermal detector according to one or more embodiments of the present disclosure, showing a corner of a printed circuit board having a surface-mount thermistor disposed therein.

[0015] Figure 7 This is a bottom view of a point thermal detector according to one or more embodiments of the present disclosure, wherein the outer cover and detector cover are removed, and the bottom view shows a corner of a printed circuit board having a surface-mount thermistor disposed therein.

[0016] Figure 8 It is a graph illustrating the estimation process for determining the temperature within a space monitored by a point thermal detector, according to one or more embodiments of this disclosure.

[0017] Figure 9 It is a graph showing the response of a thermistor to airflow according to one or more embodiments of the present disclosure, and a related illustration showing the direction of airflow blowing toward the detector.

[0018] Figure 10 This is another graph showing the response of a thermistor to airflow according to one or more embodiments of the present disclosure, and a related illustration showing the direction of airflow blowing toward the detector.

[0019] Figure 11 This is a diagram illustrating the possible direction selection of a heat flow direction algorithm according to one or more embodiments of this disclosure.

[0020] Figure 12 This is a diagram illustrating another set of possible direction selections for the heat flow direction algorithm according to one or more embodiments of this disclosure. Detailed Implementation

[0021] This article describes apparatus, systems, and methods for providing point thermal detectors based on surface-mount thermistors.

[0022] As disclosed in this article, surface-mount thermistor-based solutions offer excellent sensing performance and overcome the problems of existing designs. This is possible in part because surface-mount thermistors are less expensive than leaded temperature sensors. Furthermore, since surface-mount thermistors can be mounted during PCB manufacturing, the manufacturing process is simplified, eliminating the separate manufacturing steps and problems discussed above.

[0023] Furthermore, some embodiments disclosed herein position the surface-mount thermistors in such a way that they do not require mounting with space between the surface-mount thermistor and the PCB surface. This arrangement allows for greater design flexibility and a more compact design compared to previous form factors.

[0024] In addition, this paper teaches a novel implementation scheme for directional processes and temperature estimation techniques.

[0025] An example of an embodiment of the point thermal detector disclosed herein includes a point thermal detector device having a point-type thermal detector that uses surface-mount thermistors, such as four surface-mount NTC (negative temperature coefficient) thermistors placed (e.g., spaced 90° apart) at the corners of a polygonal PCB or on a circular PCB. In various embodiments, the sensors may be angularly spaced around the center point of the board at intervals (e.g., regular intervals such as every 90 degrees, every 45 degrees, etc.). As used herein, these locations are referred to as corners because they represent the corners of a polygon. When used on a circular board, the circumference of the circle can be defined by the positions of the spaced sensors at the corners of the polygon formed within the circle.

[0026] This design avoids the directionality problems found in thermal detectors, and offers other benefits. This is because having thermistors spaced apart and / or angled to each other allows airflow to be sensed from different locations and / or directions, thus enabling the inference of directionality. For example, if a first thermistor senses a change in airflow, and then a second thermistor at another location senses the same change, the direction from which the airflow change originates can be inferred.

[0027] Furthermore, if the thermistor senses airflow entering the device housing from different directions, the sensing of the heated airflow by one thermistor instead of another can indicate the direction of the heat source.

[0028] In addition, the PCB has one or more openings located between the central portion of the PCB and the surface-mount thermistor in order to reduce the effect of the PCB's thermal inertia on the thermistor.

[0029] Any residual thermal inertia can be offset by an observer process, such as a proportional-integral observer (PIO) process. Specifically, PIO can be used to estimate the airflow temperature using a model of the airflow-thermal detector system with temperature measured by a thermistor.

[0030] Due to the low profile of the embodiments of this disclosure, the PCB with the surface mount system can be placed in a low-profile housing. Figures 4 to 6 As shown in the diagram, the mechanical configuration of this low-profile housing is designed to efficiently direct airflow towards the surface-mount thermistor. Utilizing the surface-mount thermistor-based embodiments disclosed herein, fire detector devices can be manufactured with integrated thermal detection, including, for example, thermal detectors, photothermal detectors, and multi-standard (e.g., COPTIR) detectors, which have a lower profile (and therefore better aesthetics) and lower cost. The COPTIR device combines four separate sensing elements into a single unit:

[0031] 1. Electrochemical cell technology for monitoring carbon monoxide (CO) produced in smoldering fires;

[0032] 2. A photoelectric (P) chamber is used to sense airborne particles for smoke detection;

[0033] 3. Thermal (T) detection to monitor temperature; and

[0034] 4. Infrared (IR) sensing measures ambient light levels and flame characteristics.

[0035] This cost reduction includes component costs, as one leaded thermistor costs more than four surface-mount thermistors. Manufacturing costs are also lower because the complete surface-mount mounting process can be achieved through a unique production unit that can produce various detector types for light detectors, thermal detectors, and photothermal fire detectors. Additionally, see below regarding... Figure 3 In more detail, multiple PCBs can be manufactured simultaneously, which further reduces the time required for device fabrication and lowers manufacturing costs.

[0036] The device disclosed herein can also reduce device size and the number and size of packaged components. For example, the device can affect the reduction of plastic parts because new low-profile detector covers for photodetectors, thermal detectors, and photothermal detectors can be used, and current plastic elements used to compensate for orientation in some photothermal detectors can be eliminated.

[0037] In some proposed embodiments, the proposed mechanical solution integrates four surface-mount thermistors within a rectangular PCB, with specific mechanical features within the detector cap (e.g., to guide airflow, protect the thermistors, and drain water therefrom). Furthermore, in some embodiments, dedicated software (e.g., stored in memory on the detector device and executable by a controller such as a microcontroller) compensates for system thermal inertia that cannot be overcome by physical design. These features are not feasible in the prior art.

[0038] In one embodiment, the proposed surface-mount solution for thermal detection in a fire sensor comprises four surface-mount thermistors (e.g., 0603NTC thermistors) mounted near the edge of a square or rectangular PCB at its corners. In some embodiments, the square / rectangular shape of the PCB provides a compact and therefore inexpensive PCB panel layout with a suitable orifice pattern between the four surface-mount thermistors and the rest of the PCB to minimize the PCB's influence on the surface-mount thermistors in terms of thermal inertia. Using four thermistors can be advantageous, for example, by avoiding the directionality issues of the thermal detector due to providing a thermistor for each corner.

[0039] Furthermore, in some implementations, the mechanical configuration of the plastic components (cover and base) of the fire detector can be configured with a surface mount configuration on the PCB to effectively direct airflow to the surface mount thermistor and ensure a certain level of protection for the circuit board and the thermistor.

[0040] As discussed above, the implementation scheme may also include dedicated software to correct the measured thermistor temperature based on an airflow temperature model. This functionality is used to compensate for the thermal inertia of the surface mount configuration.

[0041] The airflow temperature model can be implemented, for example, using measurements of the actual airflow temperature (input) of a real system and the thermistor output. Dedicated software calculates the airflow temperature to feed into the system model in order to minimize the difference between the effectively measured temperature and the thermistor temperature estimate (e.g., using a proportional-integral observer (PIO) process). The model's parameters can be stored in the device's on-device memory.

[0042] The data type obtained by dedicated software can be volatile integer data representing ambient temperature. Alternatively, this data can be stored in random access memory (RAM) for fire alarm generation, or stored at the application level in non-volatile RAM (NVRAM) for diagnostic purposes using different types of algorithms (e.g., averaging, patterning, etc.) to assess ambient temperature. This layer can, for example, be provided to a fire system control panel.

[0043] In this detailed description, reference is made to the accompanying drawings, which form a part thereof. The drawings illustrate, by way of example, how one or more embodiments of this disclosure can be practiced.

[0044] These embodiments are described in sufficient detail to enable one or more embodiments of this disclosure to be practiced by a person skilled in the art. It should be understood that other embodiments may be utilized and process, electrical and / or structural changes may be made without departing from the scope of this disclosure.

[0045] It should be understood that elements shown in the various embodiments herein may be added, exchanged, combined, and / or eliminated to provide multiple additional embodiments of this disclosure. The scale and relative dimensions of the elements provided in the accompanying drawings are intended to illustrate embodiments of this disclosure and should not be construed as limiting.

[0046] The figures in this document follow the following numbering convention: one or more first digits correspond to the figure number, while the remaining digits identify elements or parts in the figure. Similar elements or parts between different figures may be identified by using similar digits. For example, 102 may refer to element "02" in Figure 1, and a similar element in Figure 2 may be referred to as 202.

[0047] As used in this article, "one" or "several" can refer to one or more such things, while "multiple" can refer to more than one such thing. For example, "numerous components" can refer to one or more components, while "multiple components" can refer to more than one component.

[0048] Figure 1A This is an example of the front side of a printed circuit board for a point thermal detector for a fire alarm system according to one or more embodiments of this disclosure. Figure 1BThis is an example of the back side of a printed circuit board for a point thermal detector for a fire alarm system according to one or more embodiments of this disclosure.

[0049] Thermal detectors are important components in some types of fire detection systems. Similarly, a controller is also important, providing detection analysis, alarm functions, and communication capabilities with other fire system devices. A printed circuit board 100 designed according to embodiments of this disclosure can provide these functions in a single integrated circuit board.

[0050] exist Figure 1A and Figure 1B In the illustrated embodiment, the surface-mount thermistor 102 is disposed at a corner defined by the edge 103 of the printed circuit board 100. This reduces cost, shortens manufacturing time, and decreases complexity, among other benefits. The embodiment shows apertures formed near the corner. These apertures provide thermal inertia insulation between the thermistor and the rest of the circuit board. This is important because the thermistor is sensing temperature, and the circuit board is generating heat that could produce erroneous readings at the thermistor.

[0051] Any number of orifices can be provided. Figure 1A and Figure 1B There are two openings with a bridge between them, allowing circuitry to cross the bridge and connect the thermistor to other circuitry on the board.

[0052] Figure 1C This is an example of the front side of a circular printed circuit board for a point thermal detector for a fire alarm system according to one or more embodiments of this disclosure. As shown in this embodiment, the sensors can be angularly spaced around the center point of the circuit board at regular intervals (e.g., at regular intervals such as every 90 degrees, every 45 degrees, etc.). As used herein, these locations are referred to as corners. When used on a circular circuit board, the circumference of the circle can be defined by the positions of the spaced sensors at the corners of the polygon formed within the circle.

[0053] Figure 2A This is an example of the front of a corner of a printed circuit board for a point thermal detector for a fire alarm system having a surface-mount thermistor thereon, according to one or more embodiments of this disclosure. Figure 2B This is an example of the back side of a corner of a printed circuit board for a point thermal detector for a fire alarm system having a surface-mount thermistor thereon, according to one or more embodiments of this disclosure.

[0054] Such as about Figure 1A and Figure 1BThe corner region 202 discussed includes a corner 210 formed by the two sides of the edge 203 of the circuit board. The corner region includes a thermistor 204 mounted to the circuit board and positioned between the edge 203 and a plurality of apertures 206 (this embodiment shows two apertures 206-1 and 206-2, but any suitable number of apertures can be used). The thermistor 204 is electrically connected to other circuitry 208 of the circuit board via a bridge circuit 209 positioned between the apertures 206.

[0055] Figure 3 This is a printed circuit board wafer according to one or more embodiments of the present disclosure, having nine printed circuit boards printed together on a wafer. As can be determined by the layout of the circuit boards 300-1 to 300-9 on the wafer 320, because the corners are formed to be adjacent to each other, the formation of associated thermistor circuits can be conveniently fabricated. This was not possible in previous wired designs.

[0056] Figure 4 It is an inclined bottom view of a point thermal detector according to one or more embodiments of this disclosure. Figure 4 The implementation scheme includes a plurality of airflow orifices 434 formed in the bottom surface 432 of the housing 430. Figure 4 The location of the orifices shown in the implementation scheme allows condensation or moisture to drain from the detector. These orifices also facilitate airflow around the thermistor. Figure 4 In the configuration shown, the position of the orifice on the bottom surface of the detector allows airflow to be detected by the thermistor directly below the detector. This is advantageous because the detector is typically mounted on the ceiling of the room to be monitored.

[0057] The housing 430 also includes cutouts in the side surface 436 to allow corners of the circuit board to protrude from the housing. In this way, the thermistor can be exposed to airflow in the area to be monitored, rather than the air inside the housing.

[0058] The housing 430 also has a tamper-proof structure 435 located in the cut-out portion to prevent objects from entering the thermistor sensing area. This reduces the possibility that the thermistor may be damaged by tampering or other actions.

[0059] Figure 5 This is an oblique side view of a point thermal detector according to one or more embodiments of the present disclosure, showing a corner of a printed circuit board having a surface-mount thermistor disposed therein.

[0060] In some implementations, the size of the cutout can be set to limit the ability of a tamper to insert an item into the cutout of the housing to approach the thermistor 504 or the circuit board 520. Figure 5The image illustrates such a specific implementation, in which the size of the small cutout 538 in the sidewall 536 is set to restrict the access of a tamper's fingertip, such as... Figure 5 As shown. Furthermore, although the orifices 534 are formed in the bottom surface 532, they are small enough that they cannot be tampered with with a finger or other object of similar size.

[0061] Figure 6 This is a side view of a point thermal detector according to one or more embodiments of the present disclosure, showing a corner of a printed circuit board having a surface-mount thermistor disposed therein. Figure 6 As shown, side surface 636 has a cutout that allows corner 610 of the circuit board to protrude from the interior of the housing. Orifice 634 provides additional channels for air to flow in and out of the area surrounding the thermistor 604, and tamper-proof structure 635 restricts access to the thermistor and circuit board through the cutout.

[0062] Additionally, in some embodiments, the cut-out portion has a sloping surface (on each side of the cut-out orifice), which is closer to the corner 610 as the surface approaches the corner through which the orifice protrudes. This allows air to be directed toward the thermistor 604. Preferably, the sloping surfaces adjacent to the orifice are symmetrical to provide uniform airflow to the thermistor 604 in both directions along the sloping surfaces.

[0063] Figure 7 This is a bottom view of a point thermal detector according to one or more embodiments of the present disclosure, with the outer housing removed. The bottom view shows a corner of a printed circuit board having a surface-mount thermistor disposed therein. Such embodiments can be used to provide directionality for the detection of heat sources by the thermistor.

[0064] For example, Figure 7 The system shown has four surface-mount thermistors mounted near the edges of a circuit board, with a cover 750 mounted on the board. Because the surface-mount thermistors are mounted at the corners 702 of the rectangular circuit board, the angle difference between adjacent thermistors is 90°, and the thermistors report their data to a microcontroller to measure the air temperature in four equidistant directions.

[0065] To further optimize directional detection, some implementations may include a digital compass integrated into the hotspot detector (e.g., the Honeywell 1-axis low-cost magnetoresistive sensor HMC1051) to provide a unique reference system (e.g., the direction of the Earth's magnetic field) for all installed detectors, regardless of their installation orientation. The novel dedicated software described herein can then be used to determine the direction of airflow based on measurements from four thermistors and the indication of the Earth's magnetic field direction from the digital compass. Further details will follow. Figures 9 to 12 Let's discuss this directional concept in more detail.

[0066] Figure 8 It is a graph illustrating the estimation process for determining the temperature within a space monitored by a point thermal detector, according to one or more embodiments of this disclosure. Figure 4 and Figure 5 The aperture 206 and the implementation scheme reduce thermal inertia caused by the plastic components of the circuit board and detector; however, the temperature measured by the thermistor may still be affected by residual thermal inertia. To increase the accuracy of temperature measurement, processes based on control system theory (e.g., unknown inputs and state observers) have been created to estimate the temperature of the monitored space.

[0067] Figure 8 The graph shows the actual temperature at 840, the estimated temperature at 842 based on the algorithm and process described in this paper, and the sensed temperature at 844 as measured by a thermistor.

[0068] exist Figure 8 In the illustrated implementation, the alarm threshold is met when: the estimated temperature value at any time is greater than or equal to a temperature threshold (S-point thermal detector) or when the function of the rate of temperature rise is greater than or equal to a certain value (R-point thermal detector). Therefore, in this implementation, there are several ways to quantify whether an alarm should be triggered.

[0069] Airflow temperature measurement considers several phenomena, namely nonlinear convection resistance (attributed to factors such as air velocity and temperature difference), thermal conduction resistance, and thermal capacitance due to the thermistor and other components of the system. The goal is to estimate the airflow temperature by eliminating other components that affect the results due to system conditions. This can be achieved using mathematical models and system control theory. This can be an iterative process where each estimate is compared to the measured thermistor temperature until the difference between the measured and estimated thermistor temperatures is very small.

[0070] Figure 9 This is a graph showing the response of a thermistor to airflow according to one or more embodiments of the present disclosure, and a related illustration showing the direction of the airflow blowing toward the detector. In this example, the heated airflow comes from the east and reaches the thermistor 2 (TH2) directly.

[0071] Therefore, on the graph, thermistor 2 shows a rapid increase in temperature, but thermistors 1, 3, and 4 do not show a significant increase in temperature. The point heat detector analyzes this information to determine the direction of the likely location of the heat source (fire), which can be used to guide emergency personnel and / or determine evacuation strategies, among other uses. In this example, the data indicates that the heat source is located to the east of the detector.

[0072] Figure 10 This is another graph illustrating the response of a thermistor to airflow according to one or more embodiments of the present disclosure, and a related illustration showing the direction of the airflow blowing towards the detector. In this example, the direction of the heating airflow is from the southeast of the detector. Since the airflow direction is between the two thermistors, this graph shows the heating airflow detected at thermistor 2 and thermistor 4 (east and south, respectively). Therefore, the detector can analyze this data and determine that the heat source is located in the southeast direction of the detector.

[0073] Furthermore, in some implementations, the detector's controller can determine the slope difference between the two sets of data from thermistors 2 and 4, and use this information to determine a more accurate direction of the heat source. For example, on the graph, there is more heat near thermistor 2 (the slope is greater than that of the thermistor 4's data), and this data can be used to determine that the heat source is closer to the thermistor facing east. This information can be used to determine how close the heat source is to the east.

[0074] Figure 11 This is a diagram illustrating possible direction selections for a heat flow direction algorithm according to one or more embodiments of this disclosure. The heat flow direction process using mathematical algorithms can be very helpful in determining the location of a heat source.

[0075] One such process reads the temperature sensed at each of thermistors 1, 2, 3, and 4. This heat flow direction process then calculates the heat flow direction based on the balance and thermal readings between two thermistors, for example, initially down to 45 degrees. For further precise positioning, the controller can determine a correction factor based on the temperature slope difference between adjacent thermistors. The detector then combines these values ​​to calculate a more accurate direction.

[0076] In some implementations, digital compass data may also be used. Here, the digital compass data is determined, and then the non-compass direction data is rotated to correlate with the digital compass reference direction information (e.g., correlated with a true north digital compass reading).

[0077] for Figure 11The device shown can have the direction of the heat source accurate to 45 degrees (midway between two thermistors at a 90-degree angle to each other). For example, if thermistors 3 and 4 record elevated temperature readings, the controller can determine whether the heat source is located in direction C, D, or DC, depending on whether one or both of the sensed temperatures meet a threshold indicating that the heat source is close to the thermistor. Alternatively, the evaluation can be based on whether one or both of the slopes of the temperature data meet a threshold indicating that the heat source is close to the thermistor. In some embodiments, the analysis may include determining that the temperature change is above a threshold when comparing the elevated temperature to the temperature of a thermistor that has not risen or has also risen, but not to the level of the thermistor with the higher temperature.

[0078] Figure 12 This is an illustration of another set of possible direction selections for the heat flow direction algorithm according to one or more embodiments of this disclosure. As briefly described above, in this embodiment, the detector can calculate a correction factor via a controller, which can further refine the direction determined by the analysis of the detector.

[0079] For example, evaluating the difference between the temperature slopes (ROR: the rate of rise of the outputs of the four thermistors) using the function DifROR(T1, T2, T3, T4) allows the calculation of a correction factor β, which is added to α (based on the direction determined by the sensed temperature data, which determines which thermistors have rising readings) to obtain a more accurate assessment of the direction of heat flow (α' = α + β).

[0080] The digital compass provides a unique reference system (Earth's magnetic field direction) for the installed detector (regardless of its installation orientation): this generates an angle between the Earth's magnetic field direction and the reference orientation of the circuit board. The corresponding digital values ​​(e.g., along the axis between thermistors th1 and th4). Finally, the rotation of the reference system is applied. In order to calculate the base point CP (the most accurate determination of the heat flow direction). Therefore, the possible values ​​of CP are: unknown direction, N, S, E, W, NE, NW, SE, SW.

[0081] As discussed, by using embodiments of this disclosure, point heat detectors can be manufactured more compactly, more easily, and more cost-effectively, with greater consistency and fewer chances of human error among manufactured units, and can be more accurate in detecting airflow temperature and determining the direction of heat sources. Such features can be highly beneficial in detecting fires in their early stages and warning emergency personnel and building occupants, among other benefits.

[0082] Although specific embodiments have been illustrated and described herein, those skilled in the art will understand that any arrangement calculated to achieve the same technology may replace the specific embodiments shown. This disclosure is intended to cover any and all modifications or variations of the various embodiments of this disclosure.

[0083] It should be understood that the above description is given in an illustrative rather than restrictive manner. Combinations of the above embodiments, as well as other embodiments not specifically described herein, will be apparent to those skilled in the art upon reading the above description.

[0084] The scope of the various embodiments of this disclosure includes any other application using the structures and methods described above. Therefore, the scope of the various embodiments of this disclosure should be determined with reference to the appended claims and the full scope of their equivalents.

[0085] In the above specific embodiments, for the purpose of simplifying this disclosure, various features are combined in the example embodiments shown in the drawings. This disclosure method should not be construed as reflecting an intention to require more features than expressly recited in each claim.

[0086] Instead, as reflected in the following claims, the subject matter of the invention lies in fewer than all the features of a single disclosed embodiment. Therefore, the following claims are incorporated herein by reference, wherein each claim exists independently as a separate embodiment.

Claims

1. A circuit board (100) for a point thermal detector in a fire sensing system, comprising: The circuit board body has multiple corners (202). At least one aperture (206) is provided in the circuit board body near one of the corners (202); and A surface-mount thermistor (204) is mounted on at least one corner (202); The circuit board body has an edge (203) at its periphery, and the surface-mount thermistor (204) is positioned at the corner having an opening adjacent thereto and between the edge (203) and the at least one opening (206). The circuit board body includes at least two openings (206) near one of the corners (202), and the circuit board body includes a bridging member having circuitry (209) thereon between at least two of the openings (206) to connect the surface-mount thermistor (204) to another part (208) of the circuit board body.

2. The circuit board (100) for a point thermal detector in a fire sensing system according to claim 1, wherein, The circuit board includes a detector housing (430) having at least one aperture in a side surface (536) of the detector housing, thereby allowing at least one corner (202) of the surface-mount thermistor (204) thereon to protrude through the aperture.

3. The circuit board (100) for a point thermal detector in a fire sensing system according to claim 1, wherein, The circuit board body is positioned inside the detector housing (430), and wherein the detector housing includes at least one cutout portion (538) to allow at least one corner (202) having the surface-mount thermistor (204) thereon to protrude through the at least one cutout portion (538).

4. The circuit board (100) for a point thermal detector in a fire sensing system according to claim 3, wherein, The at least one cutout portion (538) has an opening that allows at least one corner (202) on which the surface-mount thermistor (204) protrudes through the opening of the at least one cutout portion (538).

5. The circuit board (100) for a point thermal detector in a fire sensing system according to claim 4, wherein, The at least one cutout portion has an inclined portion that is inclined toward the opening of the at least one cutout portion (538).

6. The circuit board (100) for a point thermal detector in a fire sensing system according to claim 4, wherein, The detector housing (430) has a bottom surface (432), wherein the bottom surface (432) has at least one aperture near the surface-mounted thermistor (204).

7. The circuit board (100) for a point thermal detector in a fire sensing system according to claim 4, wherein, The circuit board has surface-mount thermistors (204) mounted at each corner (202) of the circuit board body.

8. The circuit board (100) for a point thermal detector in a fire sensing system according to claim 7, wherein, Each corner (202) of the circuit board body has a plurality of openings (206) formed therein.

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