Fire detection system with tamper detection capability and method thereof

Abstract

A fire detection system having a plurality of fire detectors in a loop, at least one of the fire detectors including a tamper detection circuit having a reactance, and a controller connected to the detection circuit. The controller includes a processor capable of accessing a memory storing instructions executable by the processor, which causes the controller to measure a time taken for a voltage applied across the detection circuit or a current flowing through the detection circuit to reach a predefined value, measure a time constant of the detection circuit based on the measured time taken, and determine a time constant of the detection circuit based on the measured time taken. It is detected whether the measured time constant exceeds a predefined threshold, and in response to a positive detection, tampering in the fire detector is detected.

Description

[0001] Cross-reference to related applications

[0002] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 669,780, filed July 11, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments described herein relate to the field of tamper detection systems, and more specifically, to fire detection systems with tamper detection capabilities, and methods for detecting such tampering. Summary of the Invention

[0004] This document describes a fire detection system having multiple fire detectors in a ring, wherein at least one of the fire detectors includes a tamper detection circuit with reactance and a controller connected to the detection circuit. The controller includes a processor capable of accessing a memory storing instructions that can be executed by the processor. These instructions cause the controller to measure the time required for a voltage applied across the detection circuit or a current flowing through the detection circuit to reach a predefined value, measure a time constant of the detection circuit based on the measured time, detect whether the measured time constant exceeds a predefined threshold, and, in response to a positive detection, detect tampering in the fire detector.

[0005] In one or more embodiments, the controller is configured to monitor the time constant in response to a negative detection and / or in the absence of detection.

[0006] In one or more embodiments, the controller is configured to monitor and detect tampering in the detection circuit at predetermined intervals or in real time.

[0007] In one or more embodiments, the controller is configured to issue a detection signal to turn on or off the power supply to the detection circuit, and to measure the time constant of the detection circuit when the power supply to the detection circuit is turned on or off.

[0008] In one or more embodiments, the controller is configured to issue a detection signal to turn on the power supply to the detection circuit, measure the time delay of the voltage or current supply to the detection circuit when the power supply is turned on, and accordingly measure the time it takes for the capacitor associated with the detection circuit to be charged to a steady state, and determine the time constant of the detection circuit based on the time it takes for the capacitor to be charged to a steady state.

[0009] In one or more embodiments, the controller is configured to issue a detection signal to shut off the power supply to the detection circuit, measure the time delay at which the supply of voltage or current to the detection circuit is prohibited when the power supply is shut off, and accordingly measure the time required for the capacitor associated with the detection circuit to fully discharge, and determine the time constant of the detection circuit based on the measured time required for the capacitor to fully discharge.

[0010] In one or more embodiments, the controller is configured to issue a detection signal to turn on the power supply to the detection circuit, monitor the magnitude of the voltage or current associated with the power supplied to the detection circuit and the time delay of supplying the voltage or current to the detection circuit when the power supply is turned on, and determine and record the time constant of the detection circuit based on the monitored voltage or current and the monitored time delay.

[0011] In one or more embodiments, the controller is configured to issue a detection signal to shut off the power supply to the detector circuit, monitor the magnitude of the voltage or current associated with the power supplied to the detection circuit and the time delay in prohibiting the supply of voltage or current to the detection circuit when the power supply is shut off, and determine and record the RC time constant of the detection circuit based on the monitored voltage or current and the monitored time delay.

[0012] In one or more embodiments, the controller includes a comparator configured to compare a measured time constant with a predefined threshold range.

[0013] In one or more embodiments, the controller includes a digital-to-analog converter (DAC) configured to: convert a first digital signal associated with a measured time constant into a first analog signal for a comparator, and / or convert a second digital signal associated with the time taken to measure the voltage and the time delay of the measurement into an analog signal for a comparator.

[0014] In one or more embodiments, the controller is a control panel associated with the fire detection system.

[0015] This document also describes a method for detecting tampering in a fire detection system having multiple fire detectors in a loop. The method includes the following steps: providing a tamper detection circuit with reactance in at least one of the fire detectors; measuring, by a controller, the time taken for a voltage applied to the detection circuit or a current flowing through the detection circuit to reach a predefined value; measuring, by the controller, a time constant of the detection circuit based on the measured time; and detecting tampering in the fire detector when the measured RC time constant is detected to exceed a predefined threshold range.

[0016] In one or more embodiments, the method includes the step of having a controller monitor and detect tampering in the circuitry at predetermined intervals or in real time.

[0017] In one or more embodiments, the method includes the steps of: issuing a detection signal by a controller to turn on a power supply to a detector circuit; measuring a time delay in the supply of voltage or current to the detection circuit when the power supply is turned on, and accordingly measuring the time taken for a capacitor associated with the detection circuit to be charged to a steady state; and determining a time constant of the detection circuit based on the time taken for the capacitor to be charged to a steady state.

[0018] In one or more embodiments, the method includes the steps of: issuing a detection signal by a controller to shut off the power supply to a detection circuit; measuring by the controller the time delay in which the supply of voltage or current to the detection circuit is prohibited when the power supply is shut off, and accordingly measuring the time required for a capacitor associated with the detection circuit to fully discharge; and determining a time constant of the detection circuit by the controller based on the measured time required for the capacitor to fully discharge.

[0019] In one or more embodiments, the method includes the steps of: issuing a detection signal by a controller to turn on power supply to a detection circuit; monitoring by the controller the magnitude of a voltage or current associated with the power supplied to the detection circuit and the time delay in supplying the voltage or current to the detection circuit when the power supply is turned on; and determining and recording a time constant of the detection circuit by the controller based on the monitored voltage or current and the monitored time delay.

[0020] In one or more embodiments, the method includes the steps of: issuing a detection signal by a controller to shut off the power supply to a detector circuit; monitoring the magnitude of a voltage or current associated with the power supplied to the detection circuit and a time delay in prohibiting the supply of voltage or current to the detection circuit when the power supply is shut off; and determining and recording the RC time constant of the detection circuit based on the monitored voltage or current and the monitored time delay.

[0021] In one or more embodiments, the method includes the step of generating an alarm signal when tampering in a fire detector is detected.

[0022] In one or more embodiments, the controller is a control panel associated with the fire detection circuitry.

[0023] The foregoing overview is illustrative only and is not intended to be limiting in any way. Other aspects, embodiments, features, and techniques of this disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in addition to the illustrative aspects, embodiments, features, and techniques described above. Attached Figure Description

[0024] The accompanying drawings are included to provide a further understanding of this disclosure, and these drawings are incorporated in and form a part of this specification. The drawings illustrate exemplary embodiments of this disclosure and, together with the description, serve to explain the principles of this disclosure.

[0025] In the accompanying drawings, similar components and / or features may have the same reference numerals. Additionally, components of the same type may be distinguished by a second reference numeral following the reference numeral, which distinguishes similar components. If only the first reference numeral is used in the specification, the description applies to any of the similar components having the same first reference numeral, regardless of the second reference numeral.

[0026] Figure 1 An exemplary representation of a fire detection system having multiple fire detectors in a ring is shown, wherein at least one of the fire detectors is configured with a tamper detection circuit according to one or more embodiments of the present disclosure.

[0027] Figure 2A An exemplary block diagram is shown depicting a single fire detector having a tamper detection circuit connected to a control panel associated with a fire detection system according to one or more embodiments of the present disclosure.

[0028] Figure 2B One or more embodiments according to this disclosure are shown. Figure 2A An exemplary circuit diagram of the system.

[0029] Figure 3 A schematic flowchart of a method for detecting tampering in a fire detection system having multiple fire detectors in a ring, according to an embodiment of the present disclosure, is shown.

[0030] Figure 4A and 4B An exemplary graph according to an embodiment of the present disclosure is shown, which depicts the alteration of the voltage distribution across the detection circuit when the power supply to the detection circuit is turned on and off. Detailed Implementation

[0031] The following is a detailed description of embodiments of the present disclosure depicted in the accompanying drawings. These embodiments are sufficient to clearly convey the present disclosure. However, the amount of detail provided is not intended to limit the contemplation of the embodiments; rather, it is intended to cover all modifications, equivalents, and alternatives that fall within the spirit and scope of the present disclosure as defined by the appended claims.

[0032] Various terms are used herein. Where a term used in the claims is not within the scope defined below, it shall be given the broadest definition that a person skilled in the art has assigned to the term, as reflected in the printed publications at the time of filing and in the granted patents.

[0033] In this specification, reference may be made to the spatial relationships between the various components and the spatial orientation of various aspects of the components, as the device is depicted in the accompanying drawings. However, as those skilled in the art will recognize upon fully reading this disclosure, the components of the invention described herein can be positioned in any desired orientation. Therefore, the use of terms such as “above,” “below,” “upper,” “lower,” “first,” “second,” or other similar terms to describe the spatial relationships between the various components or to describe the spatial orientation of various aspects of such components should be understood as describing the relative relationships between the components or the spatial orientation of various aspects of such components.

[0034] Fire detection and alarm systems are used to ensure the safety of occupants in residential, commercial, and industrial buildings. These systems are designed to detect signs of fire, such as smoke, heat, or flame, and quickly alert occupants and emergency services to initiate evacuation and firefighting measures. A typical fire detection and alarm system may include multiple fire detectors connected via cables to a central control panel in a loop. The integrity and functionality of these detectors are critical to the effective and reliable operation of the system.

[0035] In traditional fire detection and alarm systems, the connection between each fire detector and the control panel consists of a pair of wires. These wires can transmit detection signals indicating the presence of fire-related conditions, as well as tampering signals that further warn the control panel of tampering or interference with the detectors. To facilitate the encoding of these signals, a resistor can be attached to the cable at the detector end. This resistor ensures that the control panel can verify the correct connection and function of each detector.

[0036] However, this design may contain a security vulnerability. If an individual gains access to the fire detector's wiring, they could disable the detector without triggering an alarm. This can be achieved by attaching a resistor of an appropriate value to the cable and then cutting the wire leading to the actual detector. By doing so, an individual can replicate the expected resistance value that the control panel would anticipate during normal operation, thus deceiving the system into believing that the detector is still operational and connected, even though it has been rendered inactive.

[0037] Determining the appropriate resistor value is a simple process that may involve measuring the voltage drop across the detection cable entering and leaving the detector. This measurement can be passive, meaning it may not involve any active interference or signal generation that could be detected by fire detection and alarm systems.

[0038] Therefore, the system may remain unaware that the detectors have been tampered with and disabled, posing a serious risk to home security. Given this weakness, there is a need to improve fire detection and alarm systems to prevent such undetectable tampering. This invention aims to address these weaknesses and provide a more secure fire detection and alarm system that can detect and prevent unauthorized tampering with detectors.

[0039] refer to Figures 1 to 2B A fire detection system with multiple fire detectors is disclosed, wherein the fire detectors are configured with tamper detection circuitry. The fire detection system 100 (hereinafter also referred to as system 100) may include multiple fire detectors 102-1 to 102-N (collectively referred to herein as fire detector 102), which are connected to a control panel 104 via field device cables in a loop. Furthermore, system 100 may also include one or more alarm units 106, which may include speakers, audible devices, lights, and / or indicators, and may also be connected to the control panel 104 via cables. The control panel 104 may be configured to connect the fire detectors 102 and alarm units 104 to a power supply 108 and further monitor and control the operation of the fire detection system 100. In one or more embodiments, the power supply 108 may be associated with an area of ​​interest (AOI), such as, but not limited to, a building, vehicle, or house in which the fire detection system is installed. However, the power supply 108 may also be an external power source (electric grid) or a dedicated power source (battery pack) for the fire detection system 100.

[0040] In one or more embodiments, the fire detector 102 may include, but is not limited to, a smoke detector, a heat or temperature detector, a flame detector, and one or more gas sensors. The smoke detector may include, but is not limited to, an ionization detector and a photoelectric detector. Furthermore, the heat detector may include, but is not limited to, a fixed temperature detector triggered at a set temperature, and a rate-of-rise detector responding to a rapid temperature increase. Furthermore, the flame detector may include, but is not limited to, infrared and ultraviolet type flame detectors to sense the light emitted by a flame. Furthermore, the gas sensors may include, but are not limited to, a carbon monoxide detector capable of identifying fire-related CO emissions, a carbon dioxide (CO2) detector capable of identifying fire-related CO2 emissions, and a non-volatile emission sensor capable of identifying fire-related non-volatile particulate emissions.

[0041] Furthermore, at least one of the fire detectors 102 may include a tamper detection circuit 204 with reactance. In one or more embodiments, the detection circuit 204 may include a resistor (R) with predefined resistance and a capacitor (C) with predefined capacitance. Additionally, in some embodiments, the detection circuit 204 may further include a predefined inductor (not shown). Therefore, the detection circuit 204 may have an effective predefined reactance, which may be a function of one or more of the resistance R, capacitance C, and inductance associated with the detection circuit 204. In one or more embodiments, in addition to the internal resistance Rin of the detection circuit (…),… Figure 2B In addition to the predefined resistor R, predefined capacitor C, and / or predefined inductor (not shown), the predefined resistor R, predefined capacitor C, and / or predefined inductor (not shown) may be additionally configured in the detection circuit 204. However, in other embodiments, the predefined resistor R, predefined capacitor C, and / or predefined inductor (not shown) may also be the effective internal resistance, internal capacitance, and internal inductor of the detection circuit, respectively. Furthermore, in one or more embodiments, a cable with capacitor Cc may also be part of the tamper detection circuit 204, wherein the effective capacitance of the tamper detection circuit 204 may be a function of the cable capacitance Cc, the predefined resistor R, the predefined capacitor C, and / or the predefined inductor.

[0042] It should be understood that although various embodiments and figures for detecting tampering in fire detectors 102 associated with fire detection system 100 have been described herein, the teachings of this disclosure can also be implemented for detecting tampering in sensors associated with intrusion detection or monitoring systems, which may include motion detectors, occupancy sensors, glass breakage detectors, vibration sensors, video surveillance systems, fence and perimeter alarms, earthquake detectors, vibration detectors, door and window opening sensors, etc., and all such embodiments are fully within the scope of this disclosure.

[0043] In one or more embodiments, system 100 may further include a controller 202 connected to detection circuitry 204 and fire detector 102. Controller 202 may include processor 202-1, which can access memory 202-2 storing instructions that can be executed by processor 202-1, causing controller 202 to perform one or more specified operations. In one or more embodiments, controller 202 may be associated with control panel 104. However, controller may also be connected to control panel 104 of fire detection system 100 to control operation of control panel 104.

[0044] In one or more embodiments, the controller 202 may be configured to operate the fire detection system 100 in tamper detection mode at predetermined intervals or in real time to monitor for tampering in the detection circuit 204 or the fire alarm system 100. During the tamper detection mode, the controller 202 may be configured to issue a detection signal to switch on or off the power supply from the power supply 108 to the detection circuit 204 of the fire detector 102. Furthermore, the controller 202 may measure the time it takes for the voltage applied across the detection circuit 204 or the current flowing through the detection circuit 204 to reach a predefined value when the power supply to the detection circuit 204 is switched on or off. Additionally, the controller 202 may measure the time constant of the detection circuit 204 based on the measured time it takes for the applied voltage or flowing current to reach the predefined value.

[0045] Therefore, if the measured time constant exceeds a predefined threshold, the controller 202 may detect tampering in the corresponding fire detector 102 and / or cable. Furthermore, the controller 202 can activate the alarm unit 106 by issuing an alarm signal upon detecting tampering in the fire detector 102. Additionally, if the measured time constant is equal to the predefined threshold, the controller 202 can identify the detection circuit 204 as tamper-free and maintain monitoring of tampering in the detection circuit 204 at predetermined intervals or in real-time. Furthermore, when no detection occurs due to pending calculations or an error detected at the controller 202, the controller 202 can be configured to maintain monitoring of tampering in the detection circuit 204 at predetermined intervals or in real-time.

[0046] Therefore, when an individual near the wiring of fire detector 102 attempts to disable detector 102 (without triggering an alarm) by attaching a new resistor of appropriate value (the same resistor as the predefined resistor R provided in the circuit of detector 102) to the cable and subsequently cutting off the wire leading to fire detector 102, the individual may still be unaware that a capacitor (or reactance) with its capacitance value (C) has been added to detection circuit 204. As a result, when the individual adds the new resistor (after tampering), the effective time constant of fire detector 102 may remain different from the effective time constant of the untampered fire detector 102, thereby enabling system 100 to detect the tampering in fire detection system 100 and further generate an alarm.

[0047] In one or more embodiments, the predefined threshold may be a function of a predefined reactance associated with the detection circuit 204, which may be determined and stored in the memory 202-2 of the controller 202 when a registered operator or administrator debugs or updates the detection circuit 204. For example, in one or more embodiments, the detector 102 circuit may include a resistor R with a predefined resistance and a capacitor C with a predefined capacitance, such as... Figure 2A and 2BAs shown. In such an embodiment, the detection circuit 204 may have a predefined threshold RC constant, which may be a function of a predefined resistance R and a predefined capacitance C (which may be set by a registered operator or administrator when debugging or updating the detection circuit 204). Therefore, during tamper monitoring mode, the controller 202 may be configured to measure the RC time constant of the detection circuit 204 and compare the measured RC time constant with the predefined threshold RC constant to identify tampering in the corresponding detection circuit 204 or fire detector 102. In one or more embodiments, if the measured RC time constant exceeds the predefined threshold RC constant, the controller 202 may detect tampering in the corresponding fire detector 102. Furthermore, if the measured time constant is detected to be equal to the predefined threshold RC constant, the controller 202 may identify that the detection circuit 204 or fire detector 102 has not been tampered with.

[0048] In one or more embodiments, during tamper monitoring mode, controller 202 can be configured to issue a detection signal to turn on the power supply from power source 108 to detection circuit 204. Furthermore, controller 202 can measure the time delay in supplying voltage or current to detection circuit 204 when the power supply is turned on, and accordingly determine the time taken for capacitor C associated with detection circuit 204 to charge to a steady state (63.2% or 100% of the voltage level of power source 108, but not limited to this) using the power received from power source 108. Additionally, controller 202 can determine the time constant of detection circuit 204 based on the measured time taken for capacitor C to charge to a steady state.

[0049] Furthermore, in one or more embodiments, during tamper monitoring mode, controller 202 can be configured to issue a detection signal to shut off the power supply to detection circuit 204. Additionally, controller 202 can measure the time delay before the power supply to detection circuit 204 is interrupted, and accordingly determine the time required for capacitor C associated with detection circuit 204 to fully discharge or discharge to a steady state (36.8% of the voltage level of power supply 108). Furthermore, controller 202 can determine the time constant of detection circuit 204 based on the measured time required for capacitor C to fully discharge or discharge to a steady state.

[0050] In one or more embodiments, during tamper monitoring mode, controller 202 may be configured to issue a detection signal to turn on power supply to detection circuit 204. Controller 202 may further monitor the magnitude of the voltage or current associated with the power supplied to detection circuit 204, and the time delay in supplying voltage or current to detection circuit 204 when power supply is turned on. Furthermore, controller 202 may determine and record the time constant of detection circuit 204 based on the monitored voltage or current and the monitored time delay.

[0051] Furthermore, in one or more embodiments, during tamper monitoring mode, controller 202 can be configured to issue a detection signal to shut off the power supply to detection circuit 204. Controller 202 can further monitor the magnitude of the voltage or current associated with the power supplied to detection circuit 204, and the time delay before the power supply is shut off, thus preventing the supply of voltage or current to detection circuit 204. Additionally, controller 202 can determine and record the time constant of detection circuit 204 based on the monitored voltage or current and the monitored time delay.

[0052] refer to Figure 2B In one or more embodiments, controller 202 may include a voltmeter or ammeter 202-3 to monitor the voltage across an RC circuit or the current flowing through the RC circuit. Additionally, controller 202 may include a comparator 202-4, which may be configured to compare a measured time constant with a predefined threshold range. Furthermore, in one or more embodiments, controller 202 may include a timer 202-5 to measure time while monitoring voltage and current. Additionally, controller 202 may include a digital-to-analog converter (DAC) 202-6, which may be configured to convert a first digital signal associated with the time constant measured by controller 202 into a first analog signal for comparator 202-4. Furthermore, DAC 202-6 may also convert a second digital signal associated with the time taken for the measured voltage and the measured time delay into an analog signal for comparator 202-4.

[0053] In one or more embodiments, comparator 202-4, timer 202-5, and DAC 202-6 may be integrated components of controller 202 (e.g., in the case of microcontroller 202, etc.). However, in other embodiments, comparator 202-4, timer 202-5, and DAC 202-6 may also be additionally configured with controller 202 (e.g., when control panel 104 is used as controller 202).

[0054] It should be understood that the time constant (τ) of the RC circuit associated with the detection circuit 204 of the fire detector 102 (or, typically) indicates how quickly the voltage across the capacitor of the detection circuit 204 charges or discharges to its steady-state value. The time constant can be defined as the product of the resistance (R) and capacitance (C) in the detection circuit 204.

[0055] In one or more embodiments, when using the charging method, controller 202 may issue a detection signal to close switch 206 associated with power supply 108 (connecting power supply 108 to detection circuit 204), thereby turning on the power supply to detection circuit 204. This can apply a step voltage from power supply 108 to detection circuit 204 (RC circuit), thereby initiating the charging process of capacitor C associated with detection circuit 204. Controller 202 can then use voltmeter 202-3 to measure the voltage across detection circuit 204. Furthermore, in one or more embodiments, when using the discharging method, capacitor C of detection circuit 204 (RC circuit) can initially be fully charged by connecting it to power supply 108. Additionally, controller 202 may issue a detection signal to open switch 206, thereby disconnecting power supply 108 from detection circuit 204 and allowing capacitor C of detection circuit 204 to discharge through a resistor in the same detection circuit 204 or a resistor associated with the cable or control panel 104 connected to detection circuit 204. Furthermore, the controller 202 can use a voltmeter 202-3 to measure the voltage across the detection circuit 204 at regular intervals.

[0056] Furthermore, for both the charging and discharging methods, the voltage across capacitor C or the detection circuit 204 (RC circuit) can be monitored and recorded at different time intervals. The controller 202 can then analyze the voltage data using the exponential charging formula VC(t) = V(1 - et / τ) or the exponential discharging formula VC(t) = Ve-t / τ to generate the following formulas respectively: Figure 4A and 4B The graph shown is a voltage versus time curve. (As shown) Figure 4A As shown, when the capacitor in the detection circuit 204 is charged, the voltage curve may rise exponentially toward the voltage level supplied by the power supply 108. Furthermore, as... Figure 4B As shown, when dealing with a discharge capacitor, the voltage curve can decrease exponentially toward zero.

[0057] Furthermore, to determine the time constant of the detection circuit 204, the controller 202 can monitor the time (using timer 202-5) during which the voltage curve may reach approximately 63.2% of its final value (during charging) or decrease to approximately 36.8% of its initial value (during discharging) when the power supply to the detection circuit 204 is turned on or off. This monitoring time can correspond to the time constant (τ) of the detection circuit 204 (RC circuit).

[0058] For example, in a non-limiting example, when the detection circuit 204 is initially undisturbed during debugging, if the detection circuit 204 has a 10kΩ (predefined resistance) resistor and a 100μF (predefined capacitance) capacitor, the time constant (predefined threshold) of the detection circuit 204 is measured to be 1 second (τ = RC = 1 second). These values ​​of the predefined resistance, predefined capacitance, and measured time constant (predefined threshold) of the detection circuit 204 in the undisturbed state can be stored in the memory 202-2 of the controller 202 or control panel 104 during debugging.

[0059] Later, during the tamper detection mode, the voltage amplitude across the detection circuit 204 can be monitored when the power supply to the detection circuit 204 is turned on or off to detect tampering in the detector 102 circuit or the fire detector 102. For example, in a non-limiting example, during the charging method, if a 5V power supply is applied across the detection circuit 204, and the voltage across the capacitor is measured to be approximately 3.16V (63.2% of 5V) one second after the power supply to the detection circuit 204 is turned on, the controller 202 can identify that the detection circuit 204 or the fire detector 102 has not been tampered with. Furthermore, during the discharging method, if the capacitor is initially fully charged to 5V, then allowed to discharge through a resistor, and the voltage across the capacitor is measured to be approximately 1.84V (36.8% of 5V) one second after the power supply to the detection circuit 204 is turned off, the controller 202 can identify that the detection circuit 204 or the fire detector 102 has not been tampered with.

[0060] Similarly, in a non-limiting example, during the charging method, if a 5V power supply is applied across the detection circuit 204, and one second after the power supply to the detection circuit 204 is turned on, the voltage across the capacitor does not reach or exceed 3.16V (63.2% of 5V), the controller 202 can identify that the detection circuit 204 or the fire detector 102 has been tampered with. Furthermore, during the discharging method, if the capacitor is initially fully charged to 5V, then allowed to discharge through a resistor, and one second after the power supply to the detection circuit 204 is turned off, the voltage across the capacitor does not reach or exceed approximately 1.84V (36.8% of 5V), the controller 202 can identify that the detection circuit 204 or the fire detector 102 is in a tampered state.

[0061] It should be understood that, for the sake of brevity, the above embodiments and examples describe the fire detector circuit 204 as an RC circuit, wherein known values ​​of capacitance C and resistance R are added to or may be part of the detection circuit 204 for the purpose of detecting tampering in the fire detector 102. Similarly, the detector circuit 204 may also include reactance to enable the detection of tampering in the fire detector without any limitation, and all such embodiments are fully within the scope of this disclosure. Furthermore, although various embodiments and examples for detecting tampering in fire detectors have been described herein, the system can also detect tampering in the cable connecting the fire detector to the control panel, and all such embodiments are fully within the scope of this disclosure.

[0062] refer to Figure 3 A method 300 for detecting tampering in a fire detection system having multiple fire detectors arranged in a ring is disclosed. Method 300 may relate to... Figures 1 to 2B The system is associated with tamper detection circuitry, controllers, comparators, voltmeters, and DACs.

[0063] Method 300 may include step 302 of providing a tamper detection circuit with reactance in at least one of the fire detectors. Method 300 may further include step 304, whereby the controller measures the time taken for the voltage applied across the detection circuit or the current flowing through the detection circuit to reach a predefined value, followed by another step 306, whereby the controller measures the time constant of the detection circuit based on the measured time taken. Therefore, method 300 may include step 308, whereby the controller detects tampering in the fire detector when the measured RC time constant is detected to exceed a predefined threshold range. Furthermore, when the measured RC time constant is detected to be within the predefined threshold range, the controller may identify and mark the fire detector as being in an untampered state.

[0064] In one or more embodiments, at step 304, method 300 may include the step of the controller issuing a detection signal to turn on the power supply to the detector circuit. At step 304, method 300 may further include the step of the controller measuring the time delay of supplying voltage or current to the detection circuit when the power supply is turned on, and accordingly measuring the time taken for a capacitor associated with the detection circuit to charge to a steady state. Furthermore, at step 306, method 300 may include the step of the controller determining a time constant of the detection circuit based on the time taken for the capacitor to charge to a steady state.

[0065] In one or more embodiments, at step 304, method 300 may include the step of the controller issuing a detection signal to shut off the power supply to the detection circuit. At step 304, method 300 may further include the steps of the controller measuring the time delay by which the supply of voltage or current to the detection circuit is prohibited when the power supply is shut off, and accordingly measuring the time required for the capacitor associated with the detection circuit to fully discharge. Furthermore, at step 306, method 300 may include the step of the controller determining a time constant of the detection circuit based on the measured time required for the capacitor to fully discharge.

[0066] In one or more embodiments, at step 304, method 300 may include the step of the controller issuing a detection signal to turn on the power supply to the detection circuit. At step 304, method 300 may further include the steps of the controller monitoring the amplitude of a voltage or current associated with the power supplied to the detection circuit, and the time delay in supplying the voltage or current to the detection circuit when the power supply is turned on. Furthermore, at step 306, method 300 may include the step of determining and recording the time constant of the detection circuit based on the monitored voltage or current and the monitored time delay.

[0067] In one or more embodiments, at step 304, method 300 may include the step of the controller issuing a detection signal to shut off the power supply to the detector circuit. At step 304, method 300 may further include the steps of the controller monitoring the magnitude of a voltage or current associated with the power supplied to the detection circuit, and a time delay for prohibiting the supply of voltage or current to the detection circuit when the power supply is shut off. Furthermore, at step 306, method 300 may include the step of the controller determining and recording the RC time constant of the detection circuit based on the monitored voltage or current and the monitored time delay.

[0068] Therefore, the present invention provides a solution to the limitations and drawbacks associated with existing tamper detection systems used in fire detectors by providing an improved, safe, and reliable fire detection and alarm system and method that detects and prevents unauthorized tampering of fire detectors by employing an additional capacitor and monitoring a time constant.

[0069] Although this disclosure has been described with reference to exemplary embodiments, those skilled in the art will understand that various changes can be made and equivalents can be substituted for elements therein without departing from the scope of this disclosure as defined by the appended claims. Modifications can be made to employ particular situations or materials for the teachings of this disclosure without departing from its scope. Therefore, this disclosure is intended to be limited to the specific embodiments disclosed, but rather to include all embodiments falling within the scope of this disclosure as defined by the appended claims.

[0070] In interpreting the specification, all terms shall be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprising” and “including” shall be interpreted as referring to an element, component, or step in a non-exclusive manner, indicating that the mentioned element, component, or step may be present, utilized, or combined with other elements, components, or steps not expressly mentioned. When a claim in the specification refers to at least one thing selected from the group consisting of A, B, C, ... and N, the text shall be interpreted as requiring only one element from that group, rather than A plus N, or B plus N, etc.

Claims

1. A fire detection system having a plurality of fire detectors arranged in a ring, wherein at least one of the fire detectors comprises: A tamper detection circuit with reactance; and A controller connected to the detection circuit includes a processor capable of accessing a memory containing stored instructions, which can be executed by the processor, enabling the controller to: The time it takes for the voltage applied across the detection circuit or the current flowing through the detection circuit to reach a predefined value; The time constant of the detection circuit is measured based on the time taken. Detect whether the measured time constant exceeds a predefined threshold; and In response to the positive detection, tampering was detected in the fire detector.

2. The system of claim 1, wherein the controller is configured to monitor the time constant in response to a negative detection and / or in the absence of a detection.

3. The system of claim 1, wherein the controller is configured to monitor and detect tampering in the detection circuit at predetermined intervals or in real time.

4. The system of claim 1, wherein the controller is configured to: Sending a detection signal to turn the power supply to the detection circuit on or off; and The time constant of the detection circuit is measured when the power supply to the detection circuit is turned on or off.

5. The system of claim 1, wherein the controller is configured to: Send a detection signal to connect the power supply to the detection circuit; The time delay of supplying voltage or current to the detection circuit when power is turned on is measured, and correspondingly, the time it takes for the capacitor associated with the detection circuit to charge to a steady state is measured; and The time constant of the detection circuit is determined based on the time it takes for the capacitor to charge to a steady state.

6. The system of claim 1, wherein the controller is configured to: Send a detection signal to cut off the power supply to the detection circuit; The measurement covers the time delay required to prevent the supply of voltage or current to the detection circuit when the power supply is turned off, and correspondingly measures the time required for the capacitor associated with the detection circuit to fully discharge; and The time constant of the detection circuit is determined based on the time required for the measured capacitor to fully discharge.

7. The system of claim 1, wherein the controller is configured to: Send a detection signal to connect the power supply to the detection circuit; Monitoring the magnitude of the voltage or current associated with the power supplied to the detection circuit, and the time delay in supplying the voltage or current to the detection circuit when the power supply is turned on; and Based on the monitored voltage or current and the monitoring time delay, the time constant of the detection circuit is determined and recorded.

8. The system of claim 1, wherein the controller is configured to: A detection signal is sent to cut off the power supply to the detector circuit; Monitoring the magnitude of the voltage or current associated with the power supplied to the detection circuit, and the time delay before supplying voltage or current to the detection circuit is prohibited when the power supply is turned off; and Based on the monitored voltage or current and the monitoring time delay, the RC time constant of the detection circuit is determined and recorded.

9. The system of claim 1, wherein the controller includes a comparator configured to compare the measured time constant with the predefined threshold range.

10. The system of claim 9, wherein the controller includes a digital-to-analog converter (DAC) configured to: The first digital signal associated with the measured time constant is converted into a first analog signal for use by the comparator; and / or The second digital signal, which is associated with the time taken to measure the voltage and the time delay of the measurement, is converted into an analog signal for use by the comparator.

11. The system of claim 1, wherein the controller is a control panel associated with the fire detection system.

12. A method for detecting tampering in a fire detection system having multiple fire detectors in a ring, the method comprising: At least one of the fire detectors provides a tamper detection circuit with reactance; The time taken for the voltage applied across the detection circuit or the current flowing through the detection circuit to reach a predefined value, as measured by the controller; The controller measures the time constant of the detection circuit based on the measured time taken. and When the measured RC time constant is detected to exceed a predefined threshold range, the controller detects tampering in the fire detector.

13. The method of claim 12, wherein the method comprises the following steps: The controller monitors and detects tampering in the circuit at predetermined intervals or in real time.

14. The method of claim 12, wherein the method comprises the following steps: The controller sends a detection signal to connect the power supply to the detector circuit; The controller measures the time delay of supplying voltage or current to the detection circuit when power is supplied, and accordingly measures the time it takes for the capacitor associated with the detection circuit to be charged to a steady state; and The controller determines the time constant of the detection circuit based on the time it takes for the capacitor to be charged to a steady state.

15. The method of claim 12, wherein the method comprises the following steps: The controller sends a detection signal to cut off the power supply to the detection circuit; The controller measures the time delay by which voltage or current is prohibited from being supplied to the detection circuit when the power supply is turned off, and accordingly measures the time required for the capacitor associated with the detection circuit to fully discharge; and The time constant of the detection circuit is determined by the controller based on the time required for the measured capacitor to fully discharge.

16. The method of claim 12, wherein the method comprises the following steps: The controller sends a detection signal to connect the power supply to the detection circuit; The controller monitors the magnitude of the voltage or current associated with the power supplied to the detection circuit, as well as the time delay in supplying voltage or current to the detection circuit when the power supply is turned on; and The controller determines and records the time constant of the detection circuit based on the monitored voltage or current and the monitored time delay.

17. The method of claim 12, wherein the method comprises the following steps: The controller sends a detection signal to cut off the power supply to the detector circuit; The controller monitors the magnitude of the voltage or current associated with the power supplied to the detection circuit and the time delay for prohibiting the supply of voltage or current to the detection circuit when the power supply is turned off; and The controller determines and records the RC time constant of the detection circuit based on the monitored voltage or current and the monitored time delay.

18. The method of claim 12, wherein the method includes the step of generating an alarm signal when tampering in a fire detector is detected.

19. The method of claim 12, wherein the controller is a control panel associated with the fire detection circuit.

Images