Composite linear thermal detector

Abstract

The utility model provides a composite linear thermal detector. The composite linear thermal detector comprises a control host, a resistance detection loop and an optical fiber detection loop, wherein the resistance detection loop comprises a temperature sensing cable, and a resistance detection unit and a terminal resistor which are respectively connected with two ends of the temperature sensing cable; the optical fiber detection loop comprises a pulse laser, an optical transmitting / receiving unit, an optical fiber arranged in parallel with the temperature sensing cable, and a signal processing unit. According to the utility model, the optical fiber OTDR technology and the NTC special temperature-sensitive cable detection technology are organically combined together, and the composite linear temperature-sensitive detector which can give sensitive alarm to small-size fire disasters and can rapidly position the fire disasters is provided. Through data fusion of the detection resistance and the detection light intensity, the reliability, the stability and the sensitivity of fire detection are greatly improved. In addition, compared with a linear detector adopting a DTS distributed optical fiber temperature sensing system in the prior art, the linear detector provided by the utility model is simpler, more economical and more reliable.

Description

Technical Field

[0001] The utility model belongs to the technical field of fire detection, and relates to a composite linear temperature sensing detector, in particular to a composite linear temperature sensing detector based on optical fiber and temperature sensing cable. Background Art

[0002] In the prior art, the linear temperature detector includes a temperature sensing cable and a resistance detection unit and a terminal resistor connected to its two ends, wherein the temperature sensing cable includes two parallel detection conductors and an NTC (negative temperature coefficient) characteristic barrier layer arranged between them. When the temperature sensing cable is heated, as the temperature rises, the resistance of the NTC characteristic barrier layer arranged between the two detection conductors in the temperature sensing cable decreases; the resistance detection unit detects the resistance change between the two detection conductors to generate a fire alarm. In this way, the use length of the temperature sensing cable is generally around 100m to 200m. Therefore, any point of the temperature sensing cable in the linear temperature sensing detector in the prior art will cause a resistance change between the two detection conductors, which is particularly sensitive to small-sized fire detection alarms, but it is impossible to confirm the specific heated position and heated temperature value of the temperature sensing cable when a fire occurs.

[0003] In the prior art, the DTS (Distributed Temperature Sensing) distributed fiber temperature sensing system includes a pulse laser, an optical transmitting / receiving unit, an optical fiber, a signal processing unit, and a data management and display unit. Based on the temperature effect of optical time-domain reflectometer (OTDR) and fiber Raman scattering of the optical fiber, the temperature changes at different positions along the optical fiber are detected to achieve truly distributed temperature measurement. However, since the light intensity of fiber Raman scattering is relatively weak, single-point temperature sampling or multi-point temperature sampling usually requires averaging for many seconds or even minutes to obtain a reasonable temperature measurement result, or multi-point temperature sampling is required, and the average value of several complete interval sampling length temperature samples is required to calibrate the temperature measurement result. Therefore, the DTS distributed fiber temperature sensing system is inaccurate for temperature measurement of small-sized fires (such as cigarette butts, welding slag, etc.) and may even lose high temperature information, that is, there is a problem of insensitivity to small-sized fires. Utility Model Content

[0004] The utility model aims to provide a composite linear temperature-sensing detector which has both the function of sensitive alarm for small-sized fires and the function of rapid fire positioning, comprising a control host and its resistance detection circuit and an optical fiber detection circuit; wherein the resistance detection circuit comprises a temperature-sensing cable and a resistance detection unit and a terminal resistor respectively connected at both ends thereof; the optical fiber detection circuit comprises a pulse laser, an optical transmitting / receiving unit, an optical fiber arranged in parallel with the temperature-sensing cable, and a signal processing unit; the temperature-sensing cable is a parallel NTC characteristic temperature-sensing cable, and the outer periphery of the optical fiber is coated with a protective layer.

[0005] Preferably, the parallel NTC characteristic temperature sensing cable includes two detection conductors arranged in parallel and an NTC characteristic barrier layer arranged therebetween.

[0006] Preferably, the parallel NTC characteristic temperature sensing cable includes two detection conductors and an NTC characteristic barrier layer and a fusible insulation layer arranged between them, at least one of the two detection conductors is an elastic conductor, the two detection conductors are twisted together, and the softening or melting temperature of the fusible insulation layer is greater than the laying environment temperature of the temperature sensing cable.

[0007] Preferably, the protective layer is made of a conductive or non-conductive material.

[0008] Preferably, the conductor material is a conductive tape, which is wound or woven around the periphery of the optical fiber to form the protective layer.

[0009] Preferably, the non-conductive material is an insulating tape, which is wound or woven around the periphery of the optical fiber to form the protective layer.

[0010] Preferably, the non-conductive material is a plastic insulating layer, which is coated on the periphery of the optical fiber by an extruder to form the protective layer.

[0011] The utility model organically combines the optical fiber OTDR technology and the NTC characteristic temperature sensing cable temperature detection technology to provide a composite linear temperature sensing detector that has both sensitive alarm for small-sized fires and rapid fire positioning; by fusing the data of the detection resistance and the detection light intensity, the reliability, stability and sensitivity of fire detection are greatly improved. In addition, the present invention only uses the OTDR technology in the existing DTS distributed optical fiber temperature sensing system, making the detector simpler, more economical and more reliable. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 A schematic diagram of the structural principle of a composite linear temperature sensing detector system provided in Example 1;

[0013] Figure 2 A schematic diagram of the structural principle of a composite linear temperature sensing detector system provided in Example 2;

[0014] Unified description of the numbers in the accompanying drawings:

[0015] 1. Control host; 2. Resistance detection circuit; 21. Resistance detection unit; 22. Terminal resistance; 23 / 23', temperature sensing cable; 23-1, detection conductor; 23-2, NTC characteristic barrier layer; 23-3, fusible insulation layer; 3. Optical fiber detection circuit; 31, pulse laser; 32, optical transmitting / receiving unit; 33, optical fiber; 34, signal processing unit. DETAILED DESCRIPTION

[0016] A composite linear temperature sensing detector provided by the utility model is described in detail below in conjunction with the accompanying drawings and specific embodiments. Example 1

[0017] like Figure 1 As shown, it is a schematic diagram of the structural principle of a composite linear temperature sensing detector system provided in this embodiment; the composite linear temperature sensing detector includes a control host 1 and its resistance detection circuit 2 and optical fiber detection circuit 3; wherein the resistance detection circuit 2 includes a temperature sensing cable 23 and a resistance detection unit 21 and a terminal resistor 22 connected at both ends thereof; the optical fiber detection circuit 3 includes a pulse laser 31, an optical transmitting / receiving unit 32, an optical fiber 33 arranged in parallel with the temperature sensing cable, and a signal processing unit 34; the temperature sensing cable 23 includes two detection conductors 23-1 arranged in parallel and an NTC characteristic barrier layer 23-2 arranged between them.

[0018] In order to prevent the optical fiber 33 from being damaged during production and processing, a protective layer is wrapped around it. The protective layer can be a conductor or a non-conductor material. If the protective layer is a conductor, it can be used as a detection conductor in the temperature sensing cable.

[0019] The parallel arrangement of the temperature sensing cable and the optical fiber can be in parallel or in a twisted manner.

[0020] The two detection conductors may be arranged in parallel or in a twisted or coaxial manner.

[0021] The temperature sensing cable is arranged in parallel with the optical fiber, and the outermost layer is covered with an outer sheath.

[0022] The working principle of the composite linear temperature sensing detector provided in this embodiment is:

[0023] During normal operation (when no fire occurs), the resistance detection unit detects the change in resistance between the two detection conductors 23-1 in the temperature sensing cable in real time; the optical fiber detection loop 3 controls the pulse laser 31 to emit laser pulses into the optical fiber 33 by the optical transmitting / receiving unit 32, and the laser pulses propagate from the incident end to the tail end in the optical fiber 33. At the same time, backscattered light at each point is reflected back to the transmitting end and received by the optical transmitting / receiving unit 32 and converted into an electrical signal to the signal processing unit 34. The signal processing unit 34 calculates the change in light intensity along the optical fiber 33 by the time of receiving the scattered light and the time of emitting the pulsed laser.

[0024] When a fire occurs, as the temperature of the heated part of the temperature-sensitive cable increases, the resistance value of the NTC characteristic material layer 3 in the temperature-sensitive cable decreases, and the resistance detection unit detects the change in the resistance between the two detection conductors 23-1; at the same time, when the optical transmitting / receiving unit 32 controls the pulse laser 31 to emit laser pulses into the optical fiber 33, the laser pulses propagate from the incident end to the tail end in the optical fiber 33, and the backscattered light of the heated part of the optical fiber 33 (because the temperature-sensitive cable 23 and the optical fiber 33 are arranged in parallel, the light transmission performance of the optical fiber 33 at the heated part will change with the increase of the heated temperature) is reflected back to the transmitting end and received by the optical transmitting / receiving unit 32 and converted into an electrical signal to the signal processing unit 34. The signal processing unit 34 calculates the position information of the heated part of the optical fiber 33 and its light intensity change by the time of receiving the backscattered light of the heated part and the time of emitting the pulsed laser. When the resistance detection unit 21 detects that the resistance drops to its pre-set threshold, it outputs a fire alarm signal to the control host; the control host 1 receives the fire alarm signal output by the resistance detection unit 21 and the position information of the heated part output by the signal processing unit 34 and outputs it or / and digitally displays it to the outside at the same time.

[0025] The location information of the heated part of the optical fiber (i.e. the heated part when the temperature-sensitive cable is on fire) is calculated by the following formula:

[0026] d = (c × t) / 2 (IOR)

[0027] in:

[0028] t is the difference between the time when the light source emits the light pulse and the time when the scattered light is returned from the heated part, and its unit is s (seconds);

[0029] c is the speed of light in vacuum, which is 299792458 m / s (about 3x10 8 m / s);

[0030] IOR (Index of Refraction) is the refractive index of the optical fiber 33 and is determined by the specific optical fiber selected.

[0031] The terminal resistor 22 is used to detect the on-off status between the two detection conductors. When the two detection conductors 23-1 are short-circuited or open-circuited, the resistance detection unit detects that the resistance value between the two detection conductors 23-1 is not within the normal operating range, determines it as a fault and outputs it to the control host. The signal processing unit determines the state of the optical fiber 33 by measuring the comparison between the longest return time of the optical pulse and its set threshold. When the longest return time is less than its set threshold, it outputs the optical fiber fault and outputs it to the control host. Example 2

[0032] like Figure 2 As shown, it is a schematic diagram of the structure principle of a composite linear temperature sensing detector system provided by this embodiment; this embodiment is a further improvement on the basis of embodiment 1, and the difference is that: the temperature sensing cable 23' comprises two detection conductors 23-1 arranged in parallel and an NTC characteristic barrier layer 23-2 and a fusible insulation layer 23-3 arranged between them, at least one of the two detection conductors is an elastic conductor, and the two detection conductors are twisted together. The rest is the same as embodiment 1.

[0033] When a fire occurs, as the temperature of the heated part of the temperature sensing cable rises to the softening temperature of the meltable insulation layer in the temperature sensing cable, under the action of the elastic force between the two detection conductors, there is only one NTC characteristic barrier layer 23-2 between the two detection conductors at the heated part of the temperature sensing cable, and as the heated temperature continues to rise, the resistance detection unit detects the change in the resistance between the two detection conductors 23-1. The remaining working principles are the same as those of the corresponding parts of Example 1.

[0034] In this embodiment, the softening or melting temperature of the meltable insulating layer is greater than the laying environment temperature of the temperature sensing cable.

[0035] The above embodiments are examples of preferred implementations of the utility model, and are not limitations on the device. The components in the above embodiments can be combined, interchanged, or replaced according to actual needs without affecting the essence of the utility model, and will not affect its use effect.

[0036] The implementation methods of the present invention are not limited to the above-mentioned embodiments, and any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be considered as equivalent replacement methods and shall be included in the protection scope of the present invention.

Claims

1. A composite linear temperature detector, characterized in that: It includes a control host and its resistance detection circuit and an optical fiber detection circuit; wherein the resistance detection circuit includes a temperature-sensing cable and a resistance detection unit and a terminal resistor respectively connected at both ends thereof; the optical fiber detection circuit includes a pulse laser, an optical transmitting / receiving unit, an optical fiber arranged in parallel with the temperature-sensing cable, and a signal processing unit; the temperature-sensing cable is a parallel NTC characteristic temperature-sensing cable, and the optical fiber is coated with a protective layer.

2. The composite linear temperature detector according to claim 1, characterized in that: The parallel NTC characteristic temperature sensing cable comprises two detection conductors arranged in parallel and an NTC characteristic barrier layer arranged between them.

3. The composite linear temperature detector according to claim 1, characterized in that: The parallel NTC characteristic temperature sensing cable includes two detection conductors and an NTC characteristic barrier layer and a fusible insulation layer arranged between them. At least one of the two detection conductors is an elastic conductor. The two detection conductors are twisted together. The softening or melting temperature of the fusible insulation layer is greater than the laying environment temperature of the temperature sensing cable.

4. The composite linear temperature detector according to claim 1, 2 or 3, characterized in that: The protective layer is made of a conductive or non-conductive material.

5. The composite linear temperature detector according to claim 4, characterized in that: The conductor material is a conductive tape, which is wound or woven around the outer periphery of the optical fiber to form the protective layer.

6. The composite linear temperature detector according to claim 4, characterized in that: The non-conductive material is an insulating tape, which is wound or woven around the outer periphery of the optical fiber to form the protective layer.

7. The composite linear temperature detector according to claim 4, characterized in that: The non-conductive material is a plastic insulating layer, which is coated on the periphery of the optical fiber by an extruder to form a protective layer.

Images