Fire alarm system check meter

Abstract

The utility model discloses a kind of fire alarm signal system checkers, belong to fire alarm signal system inspection technical field.The checker includes main equipment box, test cable, millivolt electromotive force generation module, multi-channel switching module, resistance measurement module, display module and control module.Test cable one end connects main equipment box, the other end connects the measured fire alarm signal system;Millivolt electromotive force generation module generates the high-precision thermoelectric potential signal of analog fire alarm sensor;Multi-channel switching module switches the sensitive branch of measured fire alarm signal system;Resistance measurement module accurately measures the resistance of fire alarm sensor circuit;Display module shows detection result;Control module is electrically connected with millivolt electromotive force generation module, multi-channel switching module, resistance measurement module and display module, to coordinate each module operation.The fire alarm signal system checker provided by the utility model can be suitable for the detection of fire alarm signal system, with the characteristics of high efficiency, strong reliability, good adaptability.

Description

Technical Field

[0001] This utility model belongs to the field of fire alarm signal system inspection technology, and in particular relates to a fire alarm signal system inspection instrument. Background Technology

[0002] Existing fire alarm signal detection equipment has two types of technical defects: resistance simulation detectors can only support static resistance testing and cannot simulate the dynamic millivolt-level electromotive force generated by thermocouples in real fire scenarios, making it difficult to fully verify the logical correctness of the fire alarm signal system; some devices that can generate millivolt-level electromotive force have problems such as large output error and only support detection of 1-2 channels, and the measurement accuracy and breadth cannot meet the detection needs of multi-branch fire alarm systems.

[0003] Therefore, there is an urgent need for a fire alarm signal system inspection instrument that can generate high-precision millivolt-level electromotive force, support multi-channel detection, and accurately measure resistance. Utility Model Content

[0004] In view of the shortcomings of the related technologies, the purpose of this utility model is to provide a fire alarm signal system inspection instrument to solve the problems mentioned in the background technology.

[0005] To achieve the above objectives, this utility model provides the following technical solution: A fire alarm signal system inspection device, comprising: Main equipment enclosure; The test cable has one end connected to the main equipment enclosure and the other end used to connect to the fire alarm signal system under test. A millivolt-level electromotive force generation module is used to generate thermoelectric potential signals for simulating fire alarm sensors. Multi-channel switching module, used to switch the sensitive branch of the fire alarm signal system under test; Resistance measurement module, used to measure the resistance of fire alarm sensor circuits; The display module is used to display the test results. The control module is electrically connected to the millivolt-level electromotive force generation module, the multi-channel switching module, the resistance measurement module, and the display module.

[0006] In some embodiments, the millivolt-level electromotive force generation module includes a digital-to-analog converter chip and a first operational amplifier circuit; the digital-to-analog converter chip is communicatively connected to the control module, and the output terminal of the digital-to-analog converter chip is connected to the first operational amplifier circuit; the first operational amplifier circuit is used to attenuate the voltage output by the digital-to-analog converter chip.

[0007] In some embodiments, the digital-to-analog converter chip is a 16-bit digital-to-analog converter chip, the first operational amplifier circuit is a voltage follower with an attenuation factor of 1 / 10; the output voltage range of the digital-to-analog converter chip is 10 times the target electromotive force range, and the first operational amplifier circuit forms a fixed attenuation ratio of 1 / 10 through a resistor voltage divider structure so that the voltage output by the digital-to-analog converter chip matches the target electromotive force range after being attenuated by the first operational amplifier circuit.

[0008] In some embodiments, the multi-channel switching module includes a bidirectional multiplexer, the enable terminal of which is connected to the control module, the signal input terminal of which is connected to the output terminal of the millivolt-level electromotive force generation module, and the signal output terminal of which is provided with multiple branch interfaces. The number of branch interfaces matches the number of sensitive branches of the fire alarm signal system under test, so as to connect them one by one.

[0009] In some embodiments, the bidirectional multiplexer includes a control pin connected to a control module. The control pin receives different logic levels output by the control module to control the conduction state of the signal input terminal of the bidirectional multiplexer with different branch interfaces, thereby switching channels.

[0010] In some embodiments, the resistance measurement module includes a constant current source circuit, a dual-channel analog-to-digital converter chip, and a computing unit; the constant current source circuit is used to provide a constant current to the fire alarm sensor line; the dual-channel analog-to-digital converter chip is used to acquire the voltage across the fire alarm sensor line; and the computing unit calculates the resistance value based on the voltage and current.

[0011] In some embodiments, the constant current source circuit includes a precision voltage reference chip and a second operational amplifier circuit. The precision voltage reference chip is electrically connected to the second operational amplifier circuit. The precision voltage reference chip outputs a fixed reference voltage, and the second operational amplifier circuit forms a constant current output through circuit structure configuration to adapt to the resistance measurement requirements of the fire alarm sensor circuit.

[0012] In some embodiments, the fire alarm signal system inspector further includes an alarm signal detection module connected to the control module. The alarm signal detection module is used to detect the alarm signal of the fire alarm signal system under test and transmit the alarm status to the control module.

[0013] In some embodiments, the main equipment enclosure is made of corrosion-resistant material.

[0014] In some embodiments, the control module is a microcontroller and the display module is an embedded display screen.

[0015] Compared with the prior art, the beneficial effects of this utility model are: 1. The fire alarm signal system inspection instrument provided by this utility model, through the cooperation of the digital-to-analog converter chip and the resistor voltage divider structure of the first operational amplifier circuit, combined with software calibration, significantly improves the accuracy of millivolt-level electromotive force generation, effectively suppresses environmental interference and temperature drift, solves the problem of large electromotive force error in existing equipment, and is adapted to the thermoelectric potential simulation needs of fire alarm sensors in multiple scenarios, with stronger detection reliability.

[0016] 2. The fire alarm signal system inspection instrument provided by this utility model relies on a bidirectional multiplexer to achieve switching of multiple sensitive branches. Compared with traditional mechanical relays, it reduces circuit loss and false alarms. With constant current source circuit and dual-channel analog-to-digital conversion design, it accurately measures the line resistance of fire alarm sensors, meets the requirements of multi-channel and high-precision detection, and is suitable for aviation fire alarm system maintenance scenarios. Its ease of operation and adaptability are significantly improved. Attached Figure Description

[0017] The accompanying drawings, which are included to provide a further understanding of the present invention and form part of this application, illustrate exemplary embodiments of the present invention and, together with the description thereof, serve to explain the present invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic block diagram of one embodiment of the fire alarm signal system inspection instrument of this utility model; Figure 2 This is a simplified diagram illustrating the working principle of one embodiment of the fire alarm signal system inspection instrument of this utility model.

[0018] In the picture: 1. Millivolt-level electromotive force generation module; 11. Digital-to-analog converter chip; 12. First operational amplifier circuit; 2. Multi-channel switching module; 21. Bidirectional multiplexer; 211. Enable terminal; 212. Signal input terminal; 213. Signal output terminal; 2131. Branch interface; 214. Control pin; 3. Resistance measurement module; 31. Constant current source circuit; 311. Precision voltage reference chip; 312. Second operational amplifier circuit; 32. Dual-channel analog-to-digital converter chip; 33. Calculation unit; 4. Display module; 5. Control module; 6. Main equipment enclosure; 7. Test cable; 8. Fire alarm signal system under test; 81. Sensitive branch; 9. Alarm signal detection module. Detailed Implementation

[0019] The technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this utility model without creative effort are within the scope of protection of this utility model.

[0020] In the description of this utility model, it should be understood that the terms "center", "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0021] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0022] See appendix Figures 1 to 2 This paper presents a schematic embodiment of the fire alarm signal system inspection instrument proposed in this utility model. The fire alarm signal system inspection instrument includes a main equipment box 6, a test cable 7, a millivolt-level electromotive force generation module 1, a multi-channel switching module 2, a resistance measurement module 3, a display module 4, and a control module 5.

[0023] The main equipment enclosure 6 is a cuboid with external dimensions ≤370mm×275mm×175mm and a weight ≤20kg. It operates on DC 27V. The portable enclosure design meets both portability and on-site testing requirements. The millivolt-level electromotive force generation module 1, multi-channel switching module 2, resistance measurement module 3, display module 4, and control module 5 are all housed within the main equipment enclosure 6. The equipment also includes a metering interface, adjustment knobs, fuses, power switches, alarm indicator lights, and other accessories. It meets the testing and inspection needs of fire alarm systems and features high efficiency, reliable operation, strong mobility, and convenient use and maintenance.

[0024] The outer shell of the main equipment enclosure 6 is made of corrosion-resistant material, which has the characteristics of moisture-proof, vibration-proof and corrosion-proof. It is small in size and light in weight, making it easy to carry and meeting the needs of indoor and off-site testing and relocation support.

[0025] One end of the test cable 7 is connected to the main equipment enclosure 6, and the other end is used to connect to the fire alarm signal system 8 under test; the millivolt-level electromotive force generation module 1 is used to generate the thermoelectric potential signal of the simulated fire alarm sensor; the multi-channel switching module 2 is used to switch the sensitive branch 81 of the fire alarm signal system 8 under test; the resistance measurement module 3 is used to measure the resistance of the fire alarm sensor circuit; the display module 4 is used to display the test results; the control module 5 is electrically connected to the millivolt-level electromotive force generation module 1, the multi-channel switching module 2, the resistance measurement module 3 and the display module 4 respectively.

[0026] The core function of the fire alarm signal system tester is to simulate the thermoelectric potential of the 81 sensors in the six sensitive branches of the fire alarm system, detect the fire alarm control box's ability to process thermoelectric potential signals, and verify the normality of the fire alarm function. During operation, it uses a micro-current detection circuit to detect the normal output voltage of the 81 thermistors in the six sensitive branches. If possible, it can be heated to observe whether the micro-voltages at different temperatures meet the standard. Simultaneously, it generates a simulated thermoelectric potential signal to test whether the control box can drive the actuator to output an alarm signal when the signal reaches the alarm temperature. When the thermoelectric potential received by the control box is compared with the reference voltage and reaches the operating voltage, if an alarm signal is issued, the microcontroller inside the device receives and processes the signal and displays the alarm information on the screen, indicating that the control box's alarm function is normal. Furthermore, the device uses mature components and circuits, ensuring high stability and reliability, and is easy to maintain.

[0027] The millivolt-level electromotive force generation module 1 includes a digital-to-analog converter chip 11 and a first operational amplifier circuit 12; the digital-to-analog converter chip 11 is communicatively connected to the control module 5, and the output terminal of the digital-to-analog converter chip 11 is connected to the first operational amplifier circuit 12; the first operational amplifier circuit 12 is used to attenuate the voltage output by the digital-to-analog converter chip 11.

[0028] The digital-to-analog converter chip 11 is a 16-bit digital-to-analog converter chip 11. The first operational amplifier circuit 12 is a voltage follower with an attenuation factor of 1 / 10. The output voltage range of the digital-to-analog converter chip 11 is 10 times the target electromotive force range. The first operational amplifier circuit 12 forms a fixed attenuation ratio of 1 / 10 through a resistor voltage divider structure so that the voltage output by the digital-to-analog converter chip 11 is matched to the target electromotive force range after being attenuated by the first operational amplifier circuit 12.

[0029] In this embodiment, the control module 5 is a microcontroller, and the digital-to-analog converter chip 11 is a 16-bit DAC8552IDGKR chip. The microcontroller and the 16-bit DAC8552IDGKR chip establish communication via the SPI communication protocol. By writing code at the software level and sending 16-bit binary data through the MOSI data line of the SPI, the DAC8552IDGKR chip generates a specified electromotive force (EMF). The EMF generated by this chip is output through the VOUTA pin, reduced by an operational amplifier, and then output through a single-pole double-throw switch. In other words, combined with the first operational amplifier circuit 12, it outputs a millivolt EMF, ensuring the accuracy of the output EMF.

[0030] In this embodiment, the communication program between the control module 5 and the digital-to-analog converter chip 11 is as follows: / / DAC8552 chip output configuration function void DAC8552_control(SPI_HandleTypeDef hspi, float mv, char function){ uint8_t temp[3]; uint16_t d; if(function == 1){ temp[0] = 0x10; d = round(mv / 5410*65536); temp[1] |= (d&0xFF00)>>8; temp[2] |= d&0x00FF; }else if(function == 2){ temp[0] = 0x11; temp[1] = 0x00; temp[2] = 0x00; } HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_RESET); HAL_SPI_Transmit(&hspi,temp,3,1000); HAL_GPIO_WritePin(GPIOA,GPIO_PIN_4,GPIO_PIN_SET); } / / Generate an mv-level electromotive force void Generate_Voltage_mv(float mv){ DAC8552_control(hspi1,0,2); / / HAL_Delay(300); DAC8552_control(hspi1,mv*10+device,1); } This communication program, specifically the communication program between the microcontroller and the DAC8552, enables the DAC8552 chip to output a corresponding voltage. This is based on the output voltage calculation formula of the digital-to-analog converter chip 11 (DAC). The specific voltage can be obtained, and the 8-bit function code is placed in temp[0]. After converting the output voltage into binary, its high eight bits and low eight bits are placed in temp[1] and temp[2] respectively. By pulling up the SPI chip select, the data transmission channel is enabled, thereby transmitting the array temp[3] to the DAC8552 chip. Then, the chip select is pulled down to close the data transmission channel. This realizes one-way communication between the microcontroller and the DAC8552 chip.

[0031] After the microcontroller establishes communication with the DAC8552 chip, the DAC's VOUT pin will output a millivolt-level electromotive force according to the output voltage set during communication. A first operational amplifier circuit 12 is connected after the VOUT output pin. The purpose of the first operational amplifier circuit 12 is to attenuate the electromotive force output by the DAC8552 chip to a certain extent. From the design circuit of this operational amplifier, we can deduce that its function is a voltage follower. It has negative feedback, and all external resistors are in the kΩ range, satisfying the virtual short and virtual open circuit rules of the operational amplifier. From the voltage divider formula, we can obtain... Therefore, the voltage output by the DAC8552 chip will be attenuated to one-tenth of its original value after passing through the first operational amplifier circuit 12, and then output through the single-pole double-throw switch. When the DAC8552 chip outputs the target electromotive force, the target electromotive force will be amplified to 10 times its original value.

[0032] Compared to directly outputting the target electromotive force (EMF) from the DAC8552 chip, first amplifying the EMF by 10 times from the DAC8552 chip and then reducing it by 10 times through an operational amplifier can improve the effective resolution of the DAC8552 chip by at least 4 bits. It can also effectively reduce the impact of noise and temperature drift. Furthermore, the operational amplifier itself can isolate the load to enhance stability, effectively improving the accuracy of the output EMF.

[0033] In addition to hardware-level voltage correction measures, a certain degree of correction was also carried out at the software level. First, the voltage across the resistor of the fire alarm box was measured using a multimeter. The measured voltage was then compared with the voltage generated by the DAC8552 chip at the software level. The difference between the two was used as the voltage offset and added to the voltage generation parameters, which further improved the accuracy of the generated electromotive force.

[0034] The multi-channel switching module 2 includes a bidirectional multiplexer 21. The enable terminal 211 of the bidirectional multiplexer 21 is connected to the control module 5. The signal input terminal 212 of the bidirectional multiplexer 21 is connected to the output terminal of the millivolt-level electromotive force generation module 1. The signal output terminal 213 of the bidirectional multiplexer 21 is provided with multiple branch interfaces 2131. The number of branch interfaces 2131 matches the number of sensitive branches 81 of the fire alarm signal system 8 under test, so that they are connected one-to-one.

[0035] The bidirectional multiplexer 21 includes a control pin 214, which is connected to the control module 5. The control pin 214 receives different logic levels output by the control module 5 and controls the conduction state of the signal input terminal 212 of the bidirectional multiplexer 21 with different branch interfaces 2131 to switch channels.

[0036] In this embodiment, the bidirectional multiplexer 21 uses the TMUX1208PWR model, which works with the control module 5 (microcontroller) to realize channel detection and switching. The multiplexer has an EN enable pin, A0 / A1 / A2 address selection control pins, and S (source) and D (drain) pins. When the EN pin is high, the microcontroller outputs different logic levels to A0 / A1 / A2, which can form 8 combinations. Each combination controls the internal switch to make the D pin conduct with one S pin. In the design, each S pin is connected to a fire alarm sensitive branch 81. Therefore, by outputting the corresponding logic level by the microcontroller, the D pin can be controlled to conduct with the target S pin, thereby realizing the switching of the six sensitive branches 81. The analog thermoelectric potential signal of the millivolt-level electromotive force generation module 1 can be transmitted to each branch to detect whether the fire alarm control box processes the thermoelectric potential signal normally. The channel detection and switching procedure is as follows: void autoMeasure_mV(){ float rank1; / / float rank2; / / float rank3; / / float rank=24.0f; int delay = 500; int a=0; / / int b=0; warning_flag = 0; uint32_t random=0; for(int i=1;i<=6;i++){ rank1=20.0f; / / rank2=40.0f; / / rank3=0.0f; / / rank=29.5f; a=0; / / b=0; warning_flag = 0; Multiswitch_Control(i,'V',ON); HAL_Delay(100); while(warning_flag==0&&rank1<=50){ rank1 += 1.0f; Generate_Voltage_mv(rank1); HAL_Delay(100); } if(rank1>=50&&warning_flag==0) continue; rank1 -= 1.0f; warning_flag = 0; while(warning_flag==0&&a<10){ a++; rank1 += 0.1f; Generate_Voltage_mv(rank1); HAL_Delay(100); } if(a>10&&warning_flag==0) continue; Multiswitch_Control(i,'V',OFF); Generate_Voltage_mv(10); random = HAL_GetTick()%10; HAL_UART_Transmit(&huart2,DWIN_protocol(0x1000+i,(uint16_t)(rank1*100-vdevice+random)),10,100); HAL_Delay(100); } HAL_GPIO_WritePin(GPIOB, GPIO_PIN_12, GPIO_PIN_RESET); / / VEN disabled } The resistance measurement module 3 includes a constant current source circuit 31, a dual-channel analog-to-digital converter chip 32, and a calculation unit 33. The constant current source circuit 31 is used to provide a constant current to the fire alarm sensor circuit. The dual-channel analog-to-digital converter chip 32 is used to acquire the voltage across the fire alarm sensor circuit. The calculation unit 33 calculates the resistance value based on the voltage and current.

[0037] The constant current source circuit 31 includes a precision voltage reference chip 311 and a second operational amplifier circuit 312. The precision voltage reference chip 311 is electrically connected to the second operational amplifier circuit 312. The precision voltage reference chip 311 outputs a fixed reference voltage, and the second operational amplifier circuit 312 forms a constant current output through circuit structure configuration to adapt to the resistance measurement requirements of the fire alarm sensor circuit.

[0038] The dual-channel analog-to-digital converter chip 32 collects the voltage across the two ends of the fire alarm sensor circuit multiple times and takes the average value. The calculation unit 33 is also used to perform software-level calibration of the measurement results, realizing the measurement of the resistance of the fire alarm sensor and ensuring the accuracy of the measured resistance.

[0039] According to Ohm's law, the resistance of a fire alarm sensor circuit can be calculated using R=U / I. Therefore, the measurement of the resistance of the fire alarm sensor circuit only requires measuring the voltage across the resistor using a dual-channel analog-to-digital converter chip 32 (ADC) and measuring the current flowing through the resistor. To ensure the stability of the measurement, a constant current source circuit 31 is designed to power the sensor resistor.

[0040] In this embodiment, the voltage acquisition program for the dual-channel analog-to-digital converter chip 32 is as follows: / / ADC measures the output electromotive force value / / PC0 ------->ADC1_IN10 ADC0 0 Voltage across resistor / / PC1 ------->ADC1_IN11 ADC1 1 Voltage across resistor 1 struct ADC_Value Get_ADC_Value(void) { float temp[2]={0}; struct ADC_Value adc_value; for(int i=0;i<100;i++){ for(int n=0;n<2;n++){ HAL_ADC_Start(&hadc1); HAL_ADC_PollForConversion(&hadc1, 1); temp[n] += HAL_ADC_GetValue(&hadc1); } HAL_Delay(20); } HAL_ADC_Stop(&hadc1); adc_value.array[0] = (temp[0] / 100*3300 / 4096); adc_value.array[1] = (temp[1] / 100*3300 / 4096); return adc_value; } Current enters the TMUX1208PWR bidirectional multiplexer 21. The microcontroller outputs different logic levels to control the conduction of this branch with different fire alarm sensor channels. ADC0 and ADC1 channels respectively acquire the voltage before and after entering the sensor. Subtracting the two yields the voltage received by the sensor, which is then used to calculate the sensor's resistance. The ADC uses dual-channel voltage acquisition, and its mode is set to automatic multi-channel switching. The program first measures the voltage before and after the sensor resistance 100 times each, accumulates the values, and then calculates the average. It then uses a 3.3V reference voltage and its own resolution for conversion, effectively reducing the measurement voltage error.

[0041] In this embodiment, the fire alarm sensor resistance measurement procedure is as follows: void autoMeasure_R() { struct ADC_Value adc_value; float resistance = 0; for(int i=1;i<=6;i++) { HAL_Delay(10); Multiswitch_Control(i,'R',ON); / / Open the corresponding measurement channel HAL_Delay(10); adc_value = Get_ADC_Value(); / / Get the voltage across the resistor if((adc_value.array[0]-adc_value.array[1])>=2500) { HAL_UART_Transmit(&huart2, DWIN_protocol(0x2010+i, 1), 10,100); }else{ resistance = (adc_value.array[0]-adc_value.array[1]) / (float)rCurrent; If (i>= 4) resistance += 0.1f; HAL_UART_Transmit(&huart2, DWIN_protocol(0x2000+i, (uint16_t)(resistance*100)), 10, 100); HAL_UART_Transmit(&huart2, DWIN_protocol(0x2010+i, 0), 10,100); } Multiswitch_Control(i,'R',OFF); / / Turn off the corresponding measurement channel HAL_Delay(100); } HAL_GPIO_WritePin(GPIOC, GPIO_PIN_6, GPIO_PIN_RESET); / / REN disabled } As can be seen from the program, during the process of obtaining the voltage of the fire alarm sensor resistor for calculation, a judgment is also performed. If the voltage measured by the ADC is greater than 2.5V, an error is reported because the sensor's internal resistance is calibrated to 20Ω. According to Ohm's law, the maximum voltage across this resistor is 2.5V. Therefore, the ADC measurement results are double-checked. In addition, the current calibration at the software level further ensures the measurement accuracy of the sensor resistance.

[0042] The fire alarm signal system inspector also includes an alarm signal detection module 9, which is connected to the control module 5. The alarm signal detection module 9 is used to detect the alarm signal of the fire alarm signal system 8 under test and transmit the alarm status to the control module 5.

[0043] To test whether the fire alarm control box is processing the thermoelectric potential signal correctly, the program sequentially inputs a 50mV electromotive force (matching the alarm voltage threshold) to each channel via a bidirectional multiplexer 21. Simultaneously, the interrupt pin connecting the alarm signal detection module to the microcontroller is set to high-level trigger. Upon triggering, the interrupt callback function is called to set the warning_flag alarm flag to 1. The program employs a dual detection mechanism of coarse and fine adjustment to gradually approach the target value of the generated electromotive force, ensuring detection accuracy and avoiding false alarms. If the fire alarm control box still does not generate an alarm signal after dual detection, the corresponding sensitive circuit processing function is deemed abnormal, and a prompt is displayed on the screen.

[0044] Display module 4 is an embedded display screen, which not only adapts to the portable design of the device and improves the structural stability and anti-interference ability, but also can quickly and clearly display the detection data, making it convenient for operators to obtain information in real time and improving the detection efficiency and judgment accuracy of the fire alarm signal system.

[0045] In the above illustrative embodiments, the fire alarm signal system inspector achieves performance improvement through three core technology optimizations: First, it adopts high-precision millivolt-level electromotive force generation technology, combined with hardware structure design and anti-interference measures, to solve the problem of large electromotive force errors in existing equipment and effectively suppress environmental electromagnetic interference and line coupling noise from traditional high-voltage excitation; Second, it achieves switching of six sensitive branches through a bidirectional multiplexer, whose extremely low on-resistance significantly reduces circuit losses and significantly reduces the risk of false alarms with artificially high resistance values ​​compared to traditional mechanical relays; Third, it relies on a constant current source and analog-to-digital conversion chip for dual-channel acquisition, coupled with dual software judgment and current calibration, to accurately measure the line resistance of fire alarm sensors, providing a new solution to the problem of large resistance measurement errors in existing equipment.

[0046] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0047] The above embodiments are only used to illustrate the technical solution of this utility model and not to limit it; although the utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications can still be made to the specific implementation of this utility model or equivalent substitutions can be made to some technical features without departing from the spirit of the technical solution of this utility model, and all such modifications and substitutions should be covered within the scope of the technical solution claimed by this utility model.

Claims

1. A fire alarm signal system inspection instrument, characterized in that, include: Main equipment enclosure; A test cable, one end of which is connected to the main equipment enclosure, and the other end of which is used to connect to the fire alarm signal system under test; A millivolt-level electromotive force generation module is used to generate a thermoelectric potential signal simulating a fire alarm sensor. A multi-channel switching module, wherein the multi-channel switching module is used to switch the sensitive branch of the fire alarm signal system under test; A resistance measurement module, which is used to measure the resistance of the fire alarm sensor circuit; The display module is used to display the detection results; The control module is electrically connected to the millivolt-level electromotive force generation module, the multi-channel switching module, the resistance measurement module, and the display module, respectively.

2. The fire alarm signal system inspection instrument according to claim 1, characterized in that, The millivolt-level electromotive force generation module includes a digital-to-analog converter chip and a first operational amplifier circuit; the digital-to-analog converter chip is communicatively connected to the control module, and the output terminal of the digital-to-analog converter chip is connected to the first operational amplifier circuit; the first operational amplifier circuit is used to attenuate the voltage output by the digital-to-analog converter chip.

3. The fire alarm signal system inspection instrument according to claim 2, characterized in that, The digital-to-analog converter chip is a 16-bit digital-to-analog converter chip. The first operational amplifier circuit is a voltage follower with an attenuation factor of 1 / 10. The output voltage range of the digital-to-analog converter chip is 10 times the target electromotive force range. The first operational amplifier circuit forms a fixed attenuation ratio of 1 / 10 through a resistor voltage divider structure so that the voltage output by the digital-to-analog converter chip matches the target electromotive force range after being attenuated by the first operational amplifier circuit.

4. The fire alarm signal system inspection instrument according to claim 1, characterized in that, The multi-channel switching module includes a bidirectional multiplexer. The enable terminal of the bidirectional multiplexer is connected to the control module. The signal input terminal of the bidirectional multiplexer is connected to the output terminal of the millivolt-level electromotive force generation module. The signal output terminal of the bidirectional multiplexer is provided with multiple branch interfaces. The number of branch interfaces matches the number of sensitive branches of the fire alarm signal system under test, so that they are connected in a one-to-one correspondence.

5. The fire alarm signal system inspection instrument according to claim 4, characterized in that, The bidirectional multiplexer includes a control pin, which is connected to the control module. The control pin receives different logic levels output by the control module to control the conduction state of the signal input terminal of the bidirectional multiplexer with different branch interfaces, thereby switching channels.

6. The fire alarm signal system inspection instrument according to claim 1, characterized in that, The resistance measurement module includes a constant current source circuit, a dual-channel analog-to-digital converter chip, and a calculation unit; the constant current source circuit is used to provide a constant current to the fire alarm sensor circuit; the dual-channel analog-to-digital converter chip is used to acquire the voltage across the fire alarm sensor circuit; and the calculation unit calculates the resistance value based on the voltage and current.

7. The fire alarm signal system inspection instrument according to claim 6, characterized in that, The constant current source circuit includes a precision voltage reference chip and a second operational amplifier circuit. The precision voltage reference chip is electrically connected to the second operational amplifier circuit. The precision voltage reference chip outputs a fixed reference voltage, and the second operational amplifier circuit forms a constant current output through circuit structure configuration to adapt to the resistance measurement requirements of the fire alarm sensor circuit.

8. The fire alarm signal system inspection instrument according to claim 1, characterized in that, It also includes an alarm signal detection module, which is connected to the control module. The alarm signal detection module is used to detect the alarm signal of the fire alarm signal system under test and transmit the alarm status to the control module.

9. The fire alarm signal system inspection instrument according to claim 1, characterized in that, The outer shell of the main equipment enclosure is made of corrosion-resistant material.

10. The fire alarm signal system inspection instrument according to claim 1, characterized in that, The control module is a microcontroller, and the display module is an embedded display screen.

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