The types of detectors currently used are: electrode type, photoelectric water level type and cable type.
(1) Active Electrode Detector
Active electrode detectors use the physical properties of non-pure water to conduct the monitoring task. Between the detection electrodes of the detector, when it is not immersed in water, its resistance is larger. After the DC voltage is applied to the detection circuit, there is a certain positive and negative potential difference between the two electrodes. Once the two electrodes are immersed in water, the electrodes The resistance is close to zero and the potential difference between the two poles is also zero. By using a change in the potential difference between the two electrodes formed before and after the immersion in the resistance value between the two electrodes, it is possible to accurately detect the occurrence of water leakage near the two electrodes. Since this type of electrode detector must detect water leakage when both electrodes are simultaneously immersed in water, the distance between the two electrodes must be very close (1.7 mm}} to the right, and the number of probe points for the same electrode must be large (38 More than one), the total width of the electrodes is wider (llmm l right). In addition, the two metal electrodes adjacent to each other have positive and negative voltages of the opposite polarity, and due to the electrochemical effect, the electrodes must have anti-corrosion treatment measures and require regular cleaning during long-term use.
The characteristics of this detector are: large detection area, simple structure, electrodes need to be cleaned regularly, and pure water cannot be detected.
(2) Active photoelectric level detector
An active photoelectricity level detector uses a light emitting diode as an emission source for a photoelectric detection point at one end, and uses a photodiode as a receiving source for a photoelectric detection point at the other end, and directly contacts non-pure water or pure water as an optical transmission medium. It is also a contact-type test form. Before the reflector is flooded, the light emitted from one end of the light-emitting diode can reach the photodetector diode at the other end after two total reflections. However, once the reflector is immersed in water, the light emitted from the emitting source will inevitably refract, and it cannot form twice the total reflection of the optical path, then the ray can not reach the photoelectric receiving diode smoothly. We use this kind of refraction of the optical path. With the different physical characteristics of the reflection, the water leakage near the monitoring point is better completed.
The characteristics of this detector are: small detection area, complex structure, and need to set up a special power supply. The total reflection reflective cover needs regular cleaning, but it can detect non-pure water and pure water.
(3) Active cable leak detector
Active cable leak detectors work in the same way as electrode-type detectors, except that the distance between two electrodes is increased in parallel, which increases the monitoring area and is particularly applicable to strip-shaped spaces, cable trenches, tunnels, and culverts. If it can be combined with a distance measuring device, the distance from the leaking point to the detecting point can be accurately detected.
(4) Active Detector Monitor Controller
The monitoring controller is used to monitor the detector's alarm condition, offline condition, fault condition and power supply of the detector's power supply. The receiver function is to transmit the monitored condition to the interface circuit in the form of switch quantity. The work feature is that the leakage monitoring system is convenient The upper addressing and monitoring system is connected, which is a method to improve the reliability of the leakage monitoring system. Because, alarm, off-line, fault and power supply are situations where the upper system needs continuous monitoring. In addition, the working method of the active electrode detector is touch detection, and the electrode is charged at the same time, the corrosiveness is severe. Therefore, each electrode must be thoroughly cleaned after each alarm or it will affect the next alarm. The photoelectricity level detector must also thoroughly clean the electrodes after each alarm, otherwise it will affect the next alarm. If it is not cleaned and maintained in time, leak detectors will fail, and it will be difficult for the eyes of the human eye to directly detect them. At the same time, once the power supply has become a cow problem, it will definitely affect the work of the detector. Therefore, the monitoring of the power supply is also an essential function of the monitor.
(5) Passive Probe Detector
If the system uses a passive probe, no power supply is needed at all. The upper system only needs to monitor the leak alarm function, including the alarm condition, off-line condition and fault condition of the leak detector. At this point, the leaking monitor can be directly connected to the interface circuit with addressing function of the upper system, and no special monitor is required, and the purpose necessary for improving the reliability of this system can also be achieved.
(6) Interface connection circuit
The interface connection circuit is a monitoring module that can be identified in the addressing alarm system. It can establish an address single-element in the system itself, and can accurately display the specific location (image) of the small detector installation on the interface of the human-machine dialogue. The text address is convenient for on-duty personnel to check and search, and can be connected to leak detectors or power supply + monitoring controllers.
(7) Paging alarm system
The paging alarm system may be a monitoring signal of a building automation system or a monitoring signal of an automatic fire alarm system. Using the bus-based addressing method, it is appropriate to complete the search for the address area of ​​the monitoring point.
(1) Active Electrode Detector
Active electrode detectors use the physical properties of non-pure water to conduct the monitoring task. Between the detection electrodes of the detector, when it is not immersed in water, its resistance is larger. After the DC voltage is applied to the detection circuit, there is a certain positive and negative potential difference between the two electrodes. Once the two electrodes are immersed in water, the electrodes The resistance is close to zero and the potential difference between the two poles is also zero. By using a change in the potential difference between the two electrodes formed before and after the immersion in the resistance value between the two electrodes, it is possible to accurately detect the occurrence of water leakage near the two electrodes. Since this type of electrode detector must detect water leakage when both electrodes are simultaneously immersed in water, the distance between the two electrodes must be very close (1.7 mm}} to the right, and the number of probe points for the same electrode must be large (38 More than one), the total width of the electrodes is wider (llmm l right). In addition, the two metal electrodes adjacent to each other have positive and negative voltages of the opposite polarity, and due to the electrochemical effect, the electrodes must have anti-corrosion treatment measures and require regular cleaning during long-term use.
The characteristics of this detector are: large detection area, simple structure, electrodes need to be cleaned regularly, and pure water cannot be detected.
(2) Active photoelectric level detector
An active photoelectricity level detector uses a light emitting diode as an emission source for a photoelectric detection point at one end, and uses a photodiode as a receiving source for a photoelectric detection point at the other end, and directly contacts non-pure water or pure water as an optical transmission medium. It is also a contact-type test form. Before the reflector is flooded, the light emitted from one end of the light-emitting diode can reach the photodetector diode at the other end after two total reflections. However, once the reflector is immersed in water, the light emitted from the emitting source will inevitably refract, and it cannot form twice the total reflection of the optical path, then the ray can not reach the photoelectric receiving diode smoothly. We use this kind of refraction of the optical path. With the different physical characteristics of the reflection, the water leakage near the monitoring point is better completed.
The characteristics of this detector are: small detection area, complex structure, and need to set up a special power supply. The total reflection reflective cover needs regular cleaning, but it can detect non-pure water and pure water.
(3) Active cable leak detector
Active cable leak detectors work in the same way as electrode-type detectors, except that the distance between two electrodes is increased in parallel, which increases the monitoring area and is particularly applicable to strip-shaped spaces, cable trenches, tunnels, and culverts. If it can be combined with a distance measuring device, the distance from the leaking point to the detecting point can be accurately detected.
(4) Active Detector Monitor Controller
The monitoring controller is used to monitor the detector's alarm condition, offline condition, fault condition and power supply of the detector's power supply. The receiver function is to transmit the monitored condition to the interface circuit in the form of switch quantity. The work feature is that the leakage monitoring system is convenient The upper addressing and monitoring system is connected, which is a method to improve the reliability of the leakage monitoring system. Because, alarm, off-line, fault and power supply are situations where the upper system needs continuous monitoring. In addition, the working method of the active electrode detector is touch detection, and the electrode is charged at the same time, the corrosiveness is severe. Therefore, each electrode must be thoroughly cleaned after each alarm or it will affect the next alarm. The photoelectricity level detector must also thoroughly clean the electrodes after each alarm, otherwise it will affect the next alarm. If it is not cleaned and maintained in time, leak detectors will fail, and it will be difficult for the eyes of the human eye to directly detect them. At the same time, once the power supply has become a cow problem, it will definitely affect the work of the detector. Therefore, the monitoring of the power supply is also an essential function of the monitor.
(5) Passive Probe Detector
If the system uses a passive probe, no power supply is needed at all. The upper system only needs to monitor the leak alarm function, including the alarm condition, off-line condition and fault condition of the leak detector. At this point, the leaking monitor can be directly connected to the interface circuit with addressing function of the upper system, and no special monitor is required, and the purpose necessary for improving the reliability of this system can also be achieved.
(6) Interface connection circuit
The interface connection circuit is a monitoring module that can be identified in the addressing alarm system. It can establish an address single-element in the system itself, and can accurately display the specific location (image) of the small detector installation on the interface of the human-machine dialogue. The text address is convenient for on-duty personnel to check and search, and can be connected to leak detectors or power supply + monitoring controllers.
(7) Paging alarm system
The paging alarm system may be a monitoring signal of a building automation system or a monitoring signal of an automatic fire alarm system. Using the bus-based addressing method, it is appropriate to complete the search for the address area of ​​the monitoring point.
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