Shop Best Fiber Testing Equipment in NOYAFA

After a fault occurs in an underground cable, it is generally necessary to make a preliminary judgment on the nature of the fault. Then, according to the fault type, the appropriate fault location method is adopted to preliminarily locate the fault point; Finally, along the direction of the buried cable, carefully detect the fixed point before and after the position until the accurate position of the fault point is found, so as to realize the fault maintenance of the buried cable. Today, let's learn about the fault finding method of buried cables in rural areas. 1、 Analysis and judgment method before finding the fault of rural buried cable, it is generally necessary to understand the relevant situation of the fault, then conduct comprehensive analysis, find out the cause of the fault, and then find and eliminate it pertinently. For example, finding informed parties such as constructors, wire users and other relevant personnel to understand the situation in detail may often eliminate the fault in the shortest time at a small cost. The advantages of analysis and judgment are simple and easy, no complex instruments are required, and some faults can be eliminated in time. Therefore, it is difficult to eliminate it quickly by this method. For buried wires with a length of more than 100 meters, the fault can be found by human analysis and judgment without instruments. Sometimes, it takes more than a dozen times to excavate, and it is difficult to find the fault point in more than ten days. Sometimes, it will damage other wires in the same trench and cause new faults. This method is generally not used alone, but in combination with other instrument detection methods. The failure of buried wires is caused by the following reasons: 1. External force damage: it is the main cause of the failure. For example, repeated construction above buried lines, laying water pipes, building canals, planting trees, building buildings, etc. are often very easy to damage the buried wire insulation layer, resulting in wire breaking fault or grounding fault. 2. Joint failure: due to the nonstandard joint process during construction, it is very easy to cause mechanical damage at the joint. Or there are problems such as large contact resistance and poor insulation at the joint. After the wire runs under load for a period of time, the hidden danger at the joint often causes wire breakage or grounding fault 3. Nonstandard laying: there shall be strict process requirements when laying buried wires. However, due to the large workload, wide range and shortage of personnel in rural power network transformation, there are often some non-standard construction behaviors in some areas in the construction of buried lines. For example, when the trench is backfilled, the spinning soil is not used, and the soil block containing gravel is directly backfilled, which is very easy to damage the insulating layer. 2、 The simple ground fault tester is used to test faults. At present, many brands of ground fault testers on the market have similar working principles and test methods. Its working principle is: a fixed voltage signal is applied to the grounding wire, and an electric field is formed on the ground around the grounding point. The closer it is to the fault point, the greater the potential difference between the same distance, and vice versa. According to this principle, the ground fault point can be found. The market price of this kind of test instrument is hundreds to thousands of yuan. The buried wire fault with very small grounding resistance can achieve the test purpose. The fault finding method of rural buried cable is introduced here. I hope you can use it in your work.

We all know that the cable needs to pass the test when it is officially put into the mall. However, the functions and methods of different cable tests are also different. The test method of high-voltage power cable is flicker method. Flicker method includes impulse flash and direct flash. Impulse flash method is also the most commonly used test method. Due to the high precision of impulse flash test, its operation is simple, safe and reliable. The equipment of flicker method is composed of two parts. The high-voltage attack equipment is used to generate DC high voltage or impulse high voltage, which will be applied to the faulty high-voltage power cable. The discharge at the fault point will produce a reflected signal. The current pulse meter is used to pick up the fault interval of the reflected signal, measure some faults such as open circuit, short circuit or low resistance. Fault resistance is also the place where faults are most likely to occur. Based on this measurement method. (1) When the resistance at the fault point is immeasurable, the open circuit fault can be quickly found by measuring with low-voltage pulse method. Simple open circuit faults are not often seen. Open circuit faults are phase to ground or phase to phase high resistance faults, and phase to phase or phase to phase low resistance faults exist together. (2) When the resistance of the defect point is greater than zero and less than 150 kiloohm, the cause of the low resistance problem can be found at will by measuring with the low-voltage pulse method. (3) When the resistance at the fault point is equal to zero, the defect of measuring short circuit by low-voltage pulse method can be found, but this problem is rarely encountered. (4) Flashover defects can be measured by direct flashover method. This problem is usually caused by questionable joints. When the resistance of the fault point is greater than 150 kiloohm, the value changes greatly, so it is very uncertain during measurement. The measured interval is the interval from the fault point to the cable test end; Otherwise, it is the interval from the fault point to the opposite end of the cable test. (5) With the progress of high-voltage power cable fault test skills, different methods should be used for different power cables. We should constantly improve skills and equipment. This allows the safe use of high-voltage cable power for a long time.

If you are writing content for a specific niche, it might be useful to use wire tracker. With this tool you can track the key words in your content. So you can find out what keywords and phrases people are using to find your content.If I download torrents while using a VPN, how do trackers know my real IP?The short answer is "Assuming the VPN is correctly set up, they can not ". If the IP address assigned to you by your ISP is being leaked, the traffic is not going across the VPN, which could happen for one of 3 reasons - The VPN does not have a default gateway set, the VPN is down and the system is falling back to the systems regular IP or the computer has been set up to allow some routes to bypass the VPN (which is unlikely but possible).Of-course, there is more to downloading torrents then just downloading them - if your system has been compromised (eg you ran untrusted software) this could be finding your route table, and even conceivably your ISP assigned IP address and sending it back outside the Bittorrent program/protocol. From a conceptual point of view a VPN provides an IP address to your computer, and this IP address takes precedence over your ISP provided IP address (except for to the VPN endpoint). Thus when Bittorrent clients/trackers are communicating with the VPN it does so exactly as it would if it were your routers provided IPIs it possible to detect cardiac arrhythmia with activity trackers?The physics of the situation also argues against it. A "short vector" ECG is particularly sensitive to motion artifact, as well as being a non-traditional ECG vector, that being placed by a lay person, will be inconsistent from application to application.AFib might be detectable, but consistent detection would be difficult. Noise and placement will often mask the atrial components of the ECG. Consistent blocks may be detectable by R to R patterns, but P-R and ST intervals and elevation measurements wo not be consistent or necessarily available.My understanding is that a device like fitbit relies on optically sensing blood flow. That probably makes any real arrhythmia detection impossible. Timing of pulse relative to electrical activity changes with peripheral circulatory changes, as well as being affected by artifact, anything but gross average changes in R-R (like rate) will be unreliable.Remember there is a huge difference between possible in one in the lab, versus possible in most or all normal use.What is a torrent? (leech, seeds, trackers - those words)?um its just a hosting service, i talked to a friend and he recommended Bittornado. You type in what you want, from games to songs to movies and download. the problem is, they are not always what they say they are so you want to look at the ratings.10 Best Sleep Trackers 2021 | MumsnetStress, screen time and work can all contribute to sleep issues, with one in three of us suffering from poor sleep. Over time, this can have a serious effect on our health, putting us more at risk of conditions such as obesity and heart disease. A sleep tracker can help you work out how much rest you are getting and how to take steps to improve it. It can also help monitor health conditions like sleep apnoea, which is when your breathing stops and starts while you sleep. Trackers come in a variety of forms including apps on your phone, fitness bands, smartwatches and sleep monitors that go under your mattress. Most devices track movement and sleep duration while others provide detailed reports about your heart rate, blood oxygen saturation level (SpO2), and even the temperature and sounds in the room. Whatever product you go for, having this kind of information can be really useful to help you feel more rested. Here are the best sleep trackers to suit all needs and budgets. "Withings do an excellent sleep monitor that measures sleep, apnoea, snoring etc. It's not a wearable so wo not disturb and you would not know it's there." A pad that goes under your mattress, the Withings Sleep Analyzer is a clinically approved sleep tracker that gives useful sleep insight to help you achieve a good night's rest. Along with the usual data, such as heart rate and movement, it tracks your sleep cycles, and detects snoring and signs of sleep apnoea. Connect the tracker to the Health Mate app on your phone and, in the morning, you will get a full report with a sleep score rating. You can also generate a PDF to show your doctor if you need to. A great option if you do not want to wear a sleep tracker or are concerned about more serious sleep conditions. Can be connected to Amazon Alexa May not be compatible with all mattresses App: Yes - Withings Health Mate (on Android and iOS) Buy now from Amazon A great option if you do not want to wear a sleep tracker or are concerned about more serious sleep conditions. "I would highly recommend the Honor Band 5 which both me and my partner use at the moment, or any of the Huawei ones. They are comfortable, affordable, waterproof, and monitor sleep, heart rate, oxygen levels, steps, distance, menstrual cycle and calories. Plus, you can program different workouts on them like swimming, cycling, walking and running." Sleep trackers can be pricey but most fitness bands, like the Honor Band 5, track sleep too and can be much more budget-friendly. As the watch tracks your movements throughout the day, detecting changes in heart rate, blood oxygen levels, physical activity and calories burnt, the Honor Band 5 can help you spot any lifestyle factors that could be affecting your sleep. Turn on the TruSleep technology and, at night, it monitors your heart rate and records sleep cycles, duration and quality - and can identify six common sleep disorders. It offers over 200 tips to help you improve your sleep and the full colour touch screen is a nice feature too. Offers over 200 tips for better sleep Battery life: 6 days (with TruSleep and heart rate tracking turned on) Buy now from Amazon Price: From 214.14 | Buy now from Amazon Another product from Withings, the ScanWatch is a fitness watch that uses a medical-grade ECG and an oximeter to monitor your heart rate and oxygen levels, and lets you know when there are any irregularities. While it's a more traditional-looking design, like all smartwatches the ScanWatch tracks your workouts and physical activity. At night, it can detect any breathing issues that may be associated with sleep conditions such as sleep apnoea. It delivers a report to the Health Mate app on your phone, including data based on sleep cycles, when you go to bed and wake, and gives an overall score with advice on how to sleep better. There's also a silent, vibrating alarm, which can wake you at the best time in your sleep cycle. This is done by tracking changes to your heart rate variability and breathing to help you identify any issues that might be affecting your sleep. While it can help anyone looking to get more insight into their sleep, it's very useful for people who exercise regularly as it identifies if you have recovered properly from a training session and when the best time to exercise is. As the sensor stays under your mattress, you simply go to bed and the Emfit QS provides detailed stats on your physical recovery, stress levels and sleep quality, which can be found on the web app. Buy now from Think Sport Price: From 252 | Buy now from Amazon "I've had Fitbit trackers for about three or four years and really enjoy their features, I've worn one every day in that time. I bought their newest smartwatch, Sense, as I need to lose my lockdown weight and I love it so much." Fitbit is probably the most well known brand of fitness and health trackers. We particularly like the Fitbit Sense as it looks at your wellness as a whole. It comes with the usual Fitbit features for tracking fitness - such as a pedometer and calories burnt - but the best thing about this watch is that it detects a rise in stress levels to help you try and manage it better, which in turn could help you sleep more soundly. The watch comes with a heart rate and temperature sensor. The Sense also tracks your blood oxygen levels and gives a detailed report about your sleep quality, with personalised recommendations to help improve it. This tracker is not cheap, but you do get a free six-month Fitbit premium trial. Buy now from Amazon If you do not fancy forking out for an expensive sleep monitor or watch, the Sleep Cycle app offers many of the same features and is free to download. There's nothing to wear or put under your bed - you simply download the app onto your phone, tablet or smartwatch (available on iPhone, Android and Huawei), put the device next to your bed at night and turn on Sleep Cycle. It uses the microphone to detect sounds, such as snoring and talking, and tracks your movements. One of the big selling points is the app's smart alarm, which tracks your sleep patterns and wakes you when you are in your lightest sleep. You get a detailed sleep analysis with graphs and a score, but you can upgrade to premium (38.99 per year) for extra features, including a heart rate monitor through the device's camera and sound recordings. Alarm wakes you when you are in light sleep Not as accurate as wearable trackers View now on the App Store The Apple Watch Series 6 comes with a host of great features for maintaining a healthy lifestyle, including helping identify sleep trends for a better night's sleep. The watch has built-in sleep software which tracks your movements, with a heart sensor to monitor your heart rate and an ECG. You can also create bedtime schedules and an alarm will gently wake you up in the morning. The sleep report is not as detailed as other trackers so if you want more in-depth information you can pair it with other sleep apps (such as the Sleep Cycle above). The battery life is short compared to other devices, but it will remind you to charge if the watch gets less than 30% before bed. Other features include measuring blood oxygen levels, tracking 80 different types of exercise and built-in GPS. Set sleep goals and alarm gently wakes you in the morning Buy now from Amazon If getting to sleep is your problem, the MUSE S is a brain sensing headband that not only tracks your sleep but how well you focus and relax at night. Through meditation, relaxation techniques and soothing sounds, the band helps calm your mind and guide you into sleep. The band will even tell you when you've become distracted to help you refocus. The MUSE S monitors your heart rate and breathing and is made of a soft, breathable fabric to make it more comfortable to wear at night. In the morning, check your sleep insights, such as how deep you slept, positions and a sleep score. The app is free, but you can upgrade to premium from 11.99 a month and get access to over 500 meditations. Tracks how well you relax before sleep Feedback to help you refocus App: Yes - Muse: Meditation and Sleep (iOS 11, Android 5 or higher; Huawei devices not supported) Buy now from Amazon 9. Best fitness and sleep tracker for under 100: Garmin Vivosmart 4 Price: From 82.47 | Buy now from Amazon "I have a Garmin Vivosmart. I like it so much better than the Fitbit I used to have." When your blood oxygen level drops in your sleep, it could be a sign that something more serious is going on. So the Garmin Vivosmart 4 comes with a pulse oximeter to let you know if you are not getting enough oxygen at night. A slim fitness band, you can track your exercise throughout the day to help you get a bigger picture of your health. It monitors your heart rate, stress levels in the day and, at night, checks your blood oxygen levels, and monitors your movement and sleep cycles to give you a report of how well you slept. Other features also include a relaxation breathing timer and GPS tracking - all for less than 100. Buy now from Amazon Price: From 44.50 | Buy now from Amazon "Our nearly nine-year-old has the Garmin Vivofit, and he's not taken it off once since he got it for his seventh birthday. It's great for him because it does not need charging. We've asked him if he wants to change to a Fitbit, but he does not ." "The Garmin Vvofit Junior is great. Different designs are available and they collect tokens for doing chores/active minutes. It also tracks their sleep and is waterproof for swimming." We all know children can play up at bedtime so, because poor sleep can affect their health and schoolwork, it may be helpful to see what is going on at night. The Garmin Vivofit Jr 2 is an activity tracker that also helps you see how well your child is sleeping. It's waterproof and comes in a host of fun designs, including Spiderman, Disney Princess and Star Wars. It tracks steps and 60 minutes of daily exercise and kids can earn rewards through chores and activity, and play games on the parent-controlled app. There's no heart rate monitor so you wo not get the same level of sleep insight as other trackers, but the watch monitors your child's movement to identify sleep patterns. The battery lasts for over a year and kids will love the personalised screen. Suitable from children aged four and above. Buy now from Amazon These are the main features to consider when choosing a sleep tracker: Wearable: these can be worn on your body, such as smart watches, rings, fitness bands and headbands. They can track your movement, heart rate, breathing as well as physical activity. Sensors/non-wearable: This is a sleep monitor which you place under your mattress to track your movement and heart rate as you sleep. Others can also monitor sounds, temperature and light. Bedside monitor: you can also get bedside monitors, including home hubs like Google Nest, which can track your sleep. You can also use sleep apps on your phone from the side of your bed. Most devices use an app to report the data so make sure you have a phone or tablet that's compatible. While all sleep trackers will give you data on your sleep length and movement, others may track your sleep cycles (when you are in REM, lighter and deeper stages) and environmental factors such as how light, hot and humid your room is. Trackers can also monitor your lifestyle such as physical activity, exercise and stress levels to give you a bigger picture of your health. Sleep trackers that feature a heart rate sensor are really useful, especially if it checks your pulse rate throughout the day as you get a better idea of your overall health. Trackers can also check your blood oxygen and stress levels which can help to identify what is keeping you awake. If you wake feeling groggy, a tracker with a smart alarm that wakes you at the optimum time in your sleep could help. Wearable trackers like smartwatches and fitness bands also tend to have pedometers to count steps and monitor exercise as well as tracking calories burnt. While most sleep trackers give you a sleep report, an overall score can be helpful for comparing different nights. One that offers tips for a better night's sleep is really useful too. Also check how long the battery lasts as some sleep trackers may need charging every day. You can pick up a decent sleep and fitness tracker for under 50, but smartwatches and dedicated sleep monitors can go up to around 300. Sleep tracker apps are the cheaper option as they can be downloaded for free, but you may need to pay a subscription for extra benefits. What is the best sleep tracker? We think the Withings Sleep Analyzer is the best sleep tracker. There's no need to worry about wearing anything on your wrist or finger - the sensor mat goes under your mattress to track your heart rate, movement, snoring and signs of sleep apnoea, and gives you a full report every morning. How we chose our recommendations Most of our recommendations for sleep trackers came from Mumsnet users themselves. We searched the Mumsnet forums for posts about which sleep trackers Mumsnetters really rated. We also researched various review sites to find out which sleep trackers performed well across the board. Why you should trust us We work hard to provide unbiased, independent advice you can trust. We do sometimes earn revenue through affiliate (click-to-buy) links in our articles. This helps us fund more helpful articles like this one.

At NOYAFA, there are numerous options for delivering prototype model. When determining the form of transportation, the cost, the urgency of the shipment, the value of the goods being shipped as well as the volume and weight of the goods need to be evaluated. Air freight is a critical mode of transport. It serves markets and supply chains that demand speed. Land shipping, probably one of the earliest forms of transporting cargo, can transport goods of almost any size. Rails and trucks are usually the vehicles used to transport the goods. Ocean freight is less expensive and the most popular method of shipping goods. It is suitable for a wide range of products with long lead times. We will prioritize your needs and choose the best method of transport.SHENZHEN NOYAFA ELECTRONIC CO.,LIMITED is a company which has achieved a great success in the design and production of prototype model. This kind of prototype model is produced with the latest technology. We will provide drawings and clear installation guide for prototype model to make it more convenient and effective.Our goal and mission is simple: 'make and sell a superior prototype model.' Get an offer!· Related Questions：1. Does NOYAFA have forwarder?At NOYAFA, we work closely with logistics partners so that we can deliver your products promptly. We have built stable partnerships with reliable and experienced logistics companies. Whether it is sea freight or air transport, we can meet your requirements and ensure the accurate, safe, and on-time delivery of your products. Our long-term cooperation relationships with logistics companies also allow us to get more favorable freight. Of course, if you have your own freight forwarder, we can deliver the products to the designated location. ——————— 2. Can our logo or company name be printed on prototype model?The definition of customization is that business activities are dominated by the needs of customers, and enterprises should provide products and services completely in accordance with the needs of customers. NOYAFA will formulate detailed plans for our specific customers according to their requirements, and discuss and optimize the plan before our manufacturing of prototype model. On the basis of an agreement of two parties, we shall carry out our further producing. The goal of future business activities, or the ultimate goal, is to pursue the goal of customization. We are confident that we can provide customers with a fine solution and never make the customer lose their reliance on us. ——————— 3. What are NOYAFA shipping modes?The mode of transportation is an important consideration when planning the shipment process. NOYAFA provides several shipping methods for customers by working with several international logistics companies. In the current market, there are mainly three kinds of transportation modes which are respectively air freight, ocean freight, and rail/road freight. You may choose any of the three different modes of transport depending on several factors such as budget, time, and types of goods being transported. Normally, shipping by sea has been practiced for thousands of years and remains pivotal to today's global trade. 90% of all international trade is accomplished through maritime transportation. However, if the order is urgent, you may choose air freight which may cost more. ——————— 4. How to pay for prototype model?There are different payment methods provided for prototype model at NOYAFA. Customers can get the whole picture of the payment from our official website. Credit cards, PayPal, UnionPay, etc. are all accepted to meet customers' requirements from different countries and regions. There is no doubt that payment efficiency is highly guaranteed through the adoption of different kinds of payment ways. Customers should pay attention to the cash flow turnover time to prevent delay payment for the orders. If you have any problems, contact us.

Optical fiber communication is a communication mode with optical wave as carrier and optical fiber as transmission medium. Optical fiber communication has become the main means of information transmission and the cornerstone of "information highway" because of its long transmission distance, large information capacity and high communication quality. Optical fiber testing technology is the most extensive and basic special technology in the field of optical fiber applications. OTDR is the main instrument in the field of optical fiber testing technology. It is widely used in the maintenance and construction of optical fiber lines. It can measure the length of optical fiber, transmission attenuation of optical fiber, joint attenuation and fault location. OTDR has the advantages of short test time, fast test speed and high test accuracy.1. Two basic formulas supporting OTDR TechnologyOTDR (optical time domain reflectometer) is a high-tech and high-precision photoelectric integrated instrument made by using Rayleigh scattering and Fresnel reflection when optical pulse is transmitted in optical fiber. The semiconductor light source (LED or LD) outputs light pulses modulated by the driving circuit, which are injected into the tested optical cable line through the directional optical coupler and movable connector to become incident light pulses.When the incident light pulse is transmitted in the line, Rayleigh scattered light and Fresnel reflected light will be generated along the way. Most of the Rayleigh scattered light will be refracted into the cladding and attenuated. The back Rayleigh scattered light opposite to the propagation direction of the light pulse will be transmitted to the light inlet port of the line along the optical fiber, and will be transmitted to the photodetector through directional coupling shunt and converted into electrical signals, After low-noise amplification and digital averaging, the processed electrical signal is scanned synchronously with the trigger signal emitted from the back of the light source and becomes a reflected light pulse on the oscilloscope.The returned useful information is measured by the OTDR detector, and they are regarded as time or curve segments at different positions in the measured optical fiber. According to the time from transmitting signal to returning signal, and then determine the speed of light in quartz material, the distance (fiber length) l (unit: m) can be calculated, as shown in formula (1).In formula (1), n is the average refractive index and â–³ t is the transmission delay. The attenuation a (unit: dB / km) can be calculated by using the power level corresponding to the incident light pulse and the reflected light pulse and the length of the measured optical fiber, as shown in formula (2):2. Five parameter settings to ensure OTDR accuracy2.1 test wavelength selectionSince OTDR serves optical fiber communication, the test wavelength shall be selected before optical fiber test, and only 1310 nm or 1550 nm shall be selected for single-mode optical fiber. Since the influence of 1550 nm wavelength on the bending loss of optical fiber is much more sensitive than 1310 nm wavelength, 1550 nm wavelength is generally used to test the whole process optical fiber backscattering signal curve of an optical cable or an optical fiber transmission link, whether it is optical cable line construction, optical cable line maintenance or experiment and teaching.The shapes of the test curves at 1310nm and 1550nm are the same, and the measured fiber connector loss values are basically the same. If no problem is found in the 1550 nm wavelength test, the 1310 nm wavelength test is certainly no problem.If the 1550 nm wavelength is selected for testing, it is easy to find out whether there is excessive bending in the whole process of the optical fiber. If a large loss step is found somewhere on the curve, retest with 1310 nm wavelength. If the loss step disappears at 1310 nm wavelength, it indicates that there is excessive bending at this place, which needs to be further found and eliminated. If the loss step is also large at 1310 nm wavelength, there may be other problems in the optical fiber, which need to be found and eliminated. In the test of single-mode optical fiber line, 1550 nm wavelength should be selected as far as possible, so the test effect will be better.2.2 optical fiber refractive index selectionThe refractive index of the single-mode optical fiber used now is basically in the range of 1.4600 1.4800, which should be accurately selected according to the actual value provided by the optical cable or optical fiber manufacturer. For G.652 single-mode fiber, if 1310 nm wavelength is used in actual test, the refractive index is generally 1.4680; If 1550 nm wavelength is used, the refractive index is generally 1.468 5. Incorrect selection of refractive index will affect the test length.In equation (1), if the refractive index error is 0.001, an error of about 35 m will be generated in the relay section of 50000 M. Small mistakes in optical cable maintenance and troubleshooting will bring obvious errors, which must be paid enough attention during testing.2.3 selection of test pulse widthIf the set light pulse width is too wide, strong Fresnel reflection will be generated, which will increase the blind area. Although the narrow test light pulse has a small blind area, the test light pulse is too narrow, the power must be too weak, the corresponding backscattering signal is also weak, the backscattering signal curve will fluctuate, and the test error is large. The set optical pulse width shall not only ensure that there is no strong blind spot effect, but also ensure that the backscattering signal curve has sufficient resolution and can see each point along the optical fiber.Generally, an appropriate test pulse width is selected according to the length of the measured optical fiber, and an optimal value is determined after one or two trials. When the distance of the measured optical fiber is short (less than 5000 m), the blind area can be less than 10 m; When the distance of the measured optical fiber is long (less than 50000 m), the blind area can be less than 200 m; When the distance of the measured optical fiber is very long (less than 2500 000 m), the blind area can be up to more than 2000 m.In the single disk test, the blind area can be less than 10 m by properly selecting the optical pulse width (50 nm). If the average value is obtained through two-way test or multiple tests, the impact of blind area will be less.2.4 selection of test rangeThe range of OTDR refers to the maximum distance that the abscissa of OTDR can reach. During the test, the measuring range shall be selected according to the length of the measured optical fiber, and it is better that the measuring range is 1.5 times the length of the measured optical fiber. If the range selection is too small, it can not be seen comprehensively on the display screen of the optical time domain reflectometer; When the range selection is too large, the abscissa compression on the display screen of the optical time domain reflectometer can not be seen clearly.According to the practical experience of engineers and technicians, the selection of test range can make the backscatter curve account for about 70% of the OTDR display screen, whether it is length test or loss test, better direct viewing effect and accurate test results can be obtained.In the test of optical fiber communication system, the link length is hundreds to thousands of kilometers, the relay section length is 40 60 km, and the single optical cable length is 2 4km. Good test results can be obtained by selecting the range of OTDR.2.5 selection of averaging timeBecause the backscattered light signal is extremely weak, the method of multiple statistical average is generally used to improve the signal-to-noise ratio. OTDR test curve samples the reflected signal after each output pulse, and averages the multiple samples to eliminate random events. The longer the averaging time is, the closer the noise level is to the minimum value, and the larger the dynamic range is. The dynamic range obtained with an average time of 3 min is 0.8 dB higher than that obtained with an average time of 1 min.Generally speaking, the longer the averaging time, the higher the test accuracy. In order to improve the test speed and shorten the overall test time, the test time can be selected within 0.5 3 min.In the connection test of optical fiber communication, satisfactory results can be obtained by selecting 1.5 min (90 s).3 three common methods of OTDR testingWhen OTDR tests optical cables and optical fibers, the test occasions include factory test of optical cables and optical fibers, construction test of optical cables and optical fibers, maintenance test and regular test of optical cables and optical fibers. The test connection of OTDR is shown in Figure 1.The test connection method is: OTDR - optical fiber connector - the first optical cable - the second optical cable - the nth optical cable, and the terminal is not connected to any equipment. According to the actual test work, there are three main methods:3.1 OTDR backward test methodThis method is mainly used to monitor the optical cable connection. The optical cable connection must be equipped with a special optical fiber fusion machine and optical time domain reflectometer (OTDR). After welding a fiber core, the welding machine will generally give the estimated attenuation value of this contact. This method of testing has three advantages:(1) OTDR is fixed, omitting the vehicles and a lot of manpower and material resources required for instrument transfer;(2) The test point is selected in the place where there is mains power without gasoline generator;(3) The test points are fixed to reduce the stripping of optical cables.At the same time, this method also has two disadvantages:(1) Due to distance and terrain constraints, it is sometimes impossible to ensure smooth communication;(2) With the continuous increase of connection distance, the test range and accuracy of OTDR are limited.At present, there are generally three methods to solve these problems:â‘ The use of mobile phones in the city and suburbs can keep the testers and successors in touch at any time, facilitate organization and coordination, and improve work efficiency.â‘¡ Contact by telephone. Make sure to connect one optical fiber (such as blue optical fiber unit and red optical fiber) to the optical telephone as the connecting line. Of course, the last optical fiber used for communication cannot be monitored because it cannot be contacted during fusion and fiber winding. Even so, the possibility of problems will be greatly reduced (if it is a 24 core optical cable, the probability of problems will be reduced to less than 1 / 24 of the original).â‘¢ When the optical cable connection reaches a relay distance, the OTDR moves forward.The test practice shows that these monitoring methods are effective to ensure quality and reduce rework.3.2 OTDR forward one-way test methodOTDR is tested at the first joint point in the optical fiber connection direction, and construction vehicles are used to transfer the test instruments and testers in advance. Using this method for monitoring, the test point and connection point always have only one disc of optical cable length, the attenuation accuracy of the test joint is high, and it is convenient for communication. At present, the length of one optical cable is about 2 3 km. In general terrain, communication can be ensured by using walkie talkie. If the optical cable has a corrugated steel strip protective layer, you can also use the magnet telephone to contact.The disadvantages of this test method are also obvious. Moving OTDR to each test point is labor-consuming and time-consuming, which is not conducive to the protection of instruments; The test points are also limited by the terrain, especially when the line is far away from the highway and the terrain is complex. Portable OTDR is selected for monitoring. The short-range test does not require high dynamic range of the instrument, and the small 0tdr has small volume, light weight and convenient movement, which can greatly reduce the workload of testers and improve the test speed and work efficiency.3.3 OTDR forward two-way test methodThe OTDR position is still the same as the "forward one-way" monitoring, but two optical fibers are respectively short circuited at the beginning of the connection direction to form a loop. This method can not only meet the optical fiber test of relay section, but also monitor the optical fiber connection. When testing the optical fiber in the relay section, the incident light pulse, reflected light pulse, joint point, fracture point, fault point and attenuation distribution curve can be clearly seen on the display screen of the optical time domain reflectometer. The OTDR test event type and display are shown in Figure 2, which can provide convenience for optical cable maintenance.When monitoring optical fiber connection, due to the increase of loopback point, the bidirectional value of connection loss can be measured on OTDR. The advantage of this method is that it can accurately evaluate the quality of the joint.Due to the test principle and optical fiber structure, there will be false gain and false large attenuation in one-way monitoring with OTDR. For an optical fiber connector, the mathematical average of attenuation values in two directions can accurately reflect its real attenuation value. For example, the attenuation of a connector measured from a to B is 0.16 dB, and that measured from B to a is -0.12 dB. In fact, the attenuation of this connector is [0.16 (- 0.12)] / 2 = 0.02 dB.4 ConclusionAs the main instrument of optical fiber communication,

In many years of specific work, people have found that there are many differences between the common faults of high-voltage cables and low-voltage cables. Most of the faults of high-voltage cables are dominated by common faults of operation, and most of them are common faults of high resistance, which can be divided into leakage and flashover; The common faults of cable can only be led, short circuit and open circuit (naturally, high-voltage cable also includes these three conditions). In addition, the cable also has the following characteristics in the whole process of specific application: 1. The laying is blind, and the relative path is not very clear. 2. When laying, it is not buried after filling sand and bricks like high-voltage cables. On the contrary, the buried depth is shallow, which is easy to be damaged by external forces and common faults occur. 3. Cables are generally short, ranging from tens of meters to 500 meters, unlike high-voltage cables, which are usually 500 meters to many kilometers. 4. The compressive strength of the insulating layer is low. When solving common faults and making connectors, the processing technology is relatively simple. 5. Most cables are often burnt and damaged at common fault points. The common fault point is that there is no mark on the surface of the cable, which is very rare. ⒍ the required load changes greatly, and the two colors are usually unbalanced, which is very easy to get hot, resulting in common faults. Considering the above characteristics of the cable and the proposals clearly put forward by many customers and the specific application status of people in each region, the scientific research staff has successfully developed and designed the DW cable fault test mobile phone positioning system: the system software includes two parts: rangefinder and detector. The range finder of hn-213x system software is a completely intelligent system and personalized design scheme. It automatically detects the cable fault point without manual service, analyzes the common fault wave type, and immediately gives the distance between common fault points and common fault characteristics. The rechargeable battery power supply system is selected, which is convenient for field work, small in size, light in weight, easy to use, and does not need all auxiliary machinery and equipment. The cable fault detector of hn-213x system software is an instrument and equipment for simultaneous and accurate positioning and detection of the laying relative path, buried depth and common fault points of directly buried cables. Because it is a mobile phone positioning system for common cable faults based on the magnetic effect of current and the basic principle of step voltage, it mostly considers all standards of cable fault test. This kind of detection system software has many advantages compared with the cable fault detector based on the impulse flash method: 1. A variety of test standards are integrated and the results are mutually certified to clarify the uniqueness of common fault points. 2. Small size, light weight, easy operation by one person, no auxiliary machinery and equipment. 3. The rechargeable battery power supply system is selected, which is suitable for field work without ignition, charge and discharge. 4. The relative path search of cable (which can be clearly in the middle of 30cm), buried depth detection and accurate positioning of common fault points are carried out in the same step with high efficiency. 5. Clarify the common fault points, and the instruments and equipment have visual display information without wave type analysis. ⒍ it will not be harmed by underground conditions (such as bifurcation of cable, bundling, distortion of connector, etc.). Like detecting bombs, it searches common fault points point by point, and the accurate positioning deviation is within more than ten centimeters, which is very accurate. ⒎ it will not be harmed by ground conditions, such as floor tiles, road greening, concrete ground, etc. 8. Check the safety on the spot, there is no risk to the inspector, and there is no secondary damage to the cable. ⒐ high quality and low price are acceptable to ordinary customers. We know that the insulation layer of cable is relatively low. In addition, the electric flow is very large in the whole process of operation, and there are significant characteristics after common faults. The actual classification is as follows: the first kind of common faults: a piece of cable is burned out or a phase is burned out. This kind of common faults lead to the posture of current relay on the distribution box, and the cable is seriously damaged at the common faults. The second type of common fault: short circuit fault of each phase of the cable. Similarly, this type of common fault causes the current relay and voltage relay on the distribution box to be in a bad position, and the cable is also seriously damaged at the common fault point (possibly caused by external force). The third type of common faults: the cable can only be short circuited in one phase, the current relay posture, and the common fault points are slightly damaged but significantly exposed. It may be due to the high voltage of this phase or the quality of the cable. The fourth type of common fault: internal short circuit fault of cable, no mark can be seen on the surface. This kind of common fault is generally caused by the quality of cable, which is relatively rare. Common faults of hn-213x cable can be easily detected by the fusion application of rangefinder and detector in mobile phone positioning system. In addition, the characteristics of different common faults and the length of cable can also be detected separately. The actual situation is as follows: the first type of common faults and the second type of common faults. If the cable is short (less than 500m), the common fault detector can be used to accurately locate the common faults immediately without the cooperation of the distance finder. The common fault points can be identified by stepping in the hand receiver along the relative path (the relative path can be measured while walking). The third type of common fault: because the cable is slightly damaged at the common fault point, the data signal sent by the transmitter leaks less here. When accurately locating the common fault with the detector, the marking scope is narrow. At this time, the distance between the common fault points can be measured with the distance meter, and then the accurate positioning with the detector is also very convenient. The fourth type of common fault: this type of common fault is the most difficult to predict among all cable faults at this stage. At this time, you can use a rangefinder to detect the cable on both sides of the cable, and then compare the detection results with the specific length, so that the common fault point can be defined in a small range (1-3m). At this time, dig the cable and find the problem, Or decisively cut off this section of cable (because the cable is very cheap, the insulation layer is low, and the connector is easy to do), or use a detector to select the audio frequency for accurate positioning in this section, which can also identify the common fault points. At this stage, the cable fault detector based on impulse flashover method, which is applied by many customers of cable fault detector in power engineering, generally can use a distance meter to roughly measure the distance between common fault points when dealing with common faults of low resistance of cable and common faults of dead grounding device (the distance detection of such common fault points does not need high-voltage charging and discharging machinery and equipment, and the bottom pressure single pulse method is used) However, ignition, charging and discharging and listening to sound are still used for accurate positioning of common fault points. In addition, the relative Pathfinder of such instruments and equipment is separated from the designated instrument, which makes it impossible to specify the relative path at the same time when selecting the correct relative path, and usually deviates from the relative path when specifying. Moreover, due to the limitation of the basic principle, the relative Pathfinder of such instruments and equipment finds the relative path of the cable It is impossible to find the exact relative path of the cable when the cable is in the middle of the total width of 1-2m. Considering the applicability, hn-213x cable fault detector just fills the shortcomings of the application. It can accurately locate the common fault points of the cable, detect the buried depth and the relative path smoothly. The instruments and equipment are very vivid in the marking of common faults, relative path and buried depth No need to do technical index analysis or rely on the working experience of the operator. It makes the original complex fault test work become a relaxed and interesting thing. Therefore, many customers of impulse lightning cable tester can form a set of extreme low-voltage cable fault tester if they have another DW cable fault detector and the original distance finder. In addition, the The common faults of low resistance and short circuit of external high-voltage cable can also be specified quickly to improve the efficiency many times.

Since the buried cable appeared in our life, cable fault detection has become a test of people's work. How to accurately find out the cable fault point through layers of soil requires not only the experience of maintenance personnel, but also corresponding equipment support. Cable fault tester is one of the commonly used detection equipment. Today, we mainly discuss the difference between the medium and low voltage cable fault tester and the traditional one. Difference analysis between medium and low voltage cable fault tester and traditional cable fault tester: first, introduction of fixed-point method of cable fault. There are two kinds of cable fault rough measurement methods: electric bridge method and pulse reflection method. There are the following methods for cable fault fixed point: 1. Acoustic measurement method: acoustic measurement method is used for fixed point, which is a common method for cable fault fixed point from the past to the present. And it is the most effective method. However, the instrument used has developed from a simple acoustic electric amplifier to an acoustic magnetic synchronous fixed-point instrument widely used now. The fixed point of acoustic measurement method is applicable to high-voltage cable, low-voltage cable, directly buried cable, cable trench cable, etc. 2. Step voltage method: step voltage method is adopted for fixed point, which is mainly aimed at the fixed point of outer sheath grounding fault with requirements for cable outer sheath insulation. Now, step voltage method can also be used for fixed point of grounding fault of some directly buried unarmored low-voltage cables and wires. 3. Electromagnetic method and audio method: it is feasible to fix the point with electromagnetic wave or audio method in principle. However, from the current situation, there is no fixed-point instrument with reliable performance and practical application. In other words, the fixed-point instrument using electromagnetic wave fixed-point is still being developed by various scientific research institutions, which needs to be further verified and improved in practice to reach the practical application level. 2、 Introduction to medium and low voltage cable detector (bridge tester): most of the medium and low voltage cable detectors in circulation in the market now complete the function of cable fault rough measurement. Its principle is generally using the electric bridge method, but now it has adopted computer technology and intelligent electric bridge. There are low-voltage bridge, high-voltage bridge and so on. Some instruments also use the principle of ultra-high voltage digital bridge. The voltage applied to the fault point is generally more than 200V, and the most Gao can be added to 20kV. For cable fault with low fault resistance (resistance less than 600m & omega;). The fault distance can be roughly measured with medium and low voltage cable detector. Scope of application: applicable to leakage fault test with low fault resistance value. It is generally used for cable fault test below 6000V & lt; Rough measurement of fault distance & gt Advantages: for cable faults suitable for testing, it is simple to use and has low technical requirements for users. Fool test. In addition, for some fault points, such as some cable joint faults, due to the long creepage distance of the fault point, the fault of flashover discharge cannot be formed. Because the pulse flash method cannot be used to roughly measure the fault distance, the electric bridge method has its advantages. In the actual test, when the insulation resistance of the fault point is lower than 100m, but the high-voltage flashover test (impulse voltage is greater than 20kV), the low-voltage measured discharge current displayed by the operation box does not exceed 5a, and the sound is clear when the ball gap is discharged, which indicates that the fault point has not formed flashover discharge, and the flash tester displays the full-length waveform of the cable. In this case, we can basically conclude that the cable intermediate joint is faulty. The middle head can be excavated directly, and the cable fault pointing instrument can be used for accurate pointing, so as to further diagnose the fault point.

Brief introduction of power cable fault tester power cable fault tester is a special cable detection equipment used to solve the test of open circuit, short circuit, grounding, low resistance, high resistance flashover and high resistance leakage faults of power cables, as well as the * * test of open circuit and short circuit faults of coaxial communication cables and local telephone cables. It can also test the cable path, buried depth, radio wave velocity, verify the cable length, and establish cable files for daily maintenance and management. Brief introduction power cable fault tester is applied to various industries such as power, communication, petrochemical industry, coal mine, metallurgy, aerospace and so on. Xi'an cable fault tester is a pioneer in the field of cable fault testing. Based on the industrial embedded computer platform system, the advanced network and digital communication technology are adopted, which greatly improves the use function and test accuracy of the instrument. As we all know, no matter the high resistance fault or the rear * * point of the cable, it is inseparable from the special booster device for cable fault detection. In the past, the test transformer, operation box and pulse capacitor were used to boost the voltage, which has the disadvantages of bulkiness and complex wiring. The cable fault high-voltage signal generator solved this problem and made the cable fault detection portable, This * * improvement has been highly praised by the industry. Dear customers: the company also has underground pipeline detector, high-voltage cable fault tester and cable fault locator products. You can call the company's service phone through the website to learn more product details. Perfect and beautiful service is our pursuit. New and old customers are welcome to buy their favorite products at ease. We will serve you wholeheartedly!

Cable has a very important application scenario in our daily life. It can be said that we can't live without cable. In order to ensure the normal use of the cable, it is necessary to regularly detect and maintain the cable. In case of cable failure, the fault point shall be found out in time for maintenance. There are many cable fault maintenance methods. Today, I mainly introduce one of the high-voltage cable fault detection methods, pulse flashover method. For high resistance fault, due to the large resistance at the fault point, the reflection coefficient at this point is very small or almost equal to zero. When measured by low-voltage pulse method, the reflected pulse amplitude at the fault point is very small or there is no reflection, so the instrument can not distinguish it. There are two common high voltage flashover measurement methods, namely DC high voltage flashover measurement method (direct flashover method for short) and impulse high voltage flashover method (impulse flashover method for short). 1、 DC high voltage flashover method (referred to as direct flashover method) when the fault resistance is very high and a stable resistance channel has not been formed, the gradually increased DC voltage can be applied to the tested cable. After reaching a certain voltage value, the fault point is preferably broken down to form flashover. The flashover arc is used to form a short-circuit reflection on the added voltage, and the reflected echo is formed by a high resistance source at the input end to form an open circuit reflection. In this way, the voltage will be reflected many times between the input and the fault point until the energy is exhausted. 2、 Impulse high voltage flashover method (impulse flashover method for short) when the fault resistance is reduced and a stable resistance channel is formed, the DC high voltage cannot be added due to the limitation of equipment capacity. At this time, it is necessary to use impulse voltage test. The DC high voltage charges the cable through the ball gap until breakdown, and still generates short-circuit reflection with the flashover arc formed by it. The measuring inductance L shall be added at the cable input end to read the echo. The radio wave is reflected by short circuit at the fault point and l at the input end, and multiple reflections will be formed during this period. Due to the self induction phenomenon of inductance L, it begins to show open circuit reflection due to the current blocking effect of L, and shows short-circuit reflection after a certain time with the increase of current. The whole circuit consists of capacitor C and inductance L, which constitutes a large process of L-C discharge. Therefore, the wave process at the line input is a nearly attenuated cosine curve superimposed with fast pulse multiple reflection wave. 3、 High voltage cable fault detector is generally used. High voltage cable fault is high resistance fault, and high voltage flashover method is used to measure the distance of fault point. This method uses st-330b cable fault locator as experimental equipment. 1. Wiring mode: firstly, complete the wiring of high-voltage flashover as required; Then, connect the sampler with the ranging host with a double clamp test line, and then place the sampler next to the grounding wire of the high-voltage capacitor. 2. Equipment operation (1) start up, select the sampling method as flashover, the pulse width is the default, the cable type is the physical type, and the reading accuracy is the default. (2) Use the high-voltage equipment to discharge the cable, and then click the orange sampling button on the right to start sampling until the waveform is collected. Press the sampling key again to stop sampling. (3) Study the waveform, move the vernier ruler to the starting point and ending point of a waveform, read the waveform, and the distance of the fault point will be automatically measured in the upper left corner.

Generally, the radiation path of high-voltage cable is easy to determine, but the high-voltage cable needs to be filled with sand bricks to be deeply buried. Its fault point is difficult to find. The radiation length of low-voltage cable is short, the radiation is random and the path is unclear. The following small series will introduce the fault finding and detection methods of low-voltage cables. You can simply understand. In order to solve the problem of low-voltage cable fault, researchers have developed and produced a cable fault tester based on the principle of impulse flash method. In order to find and detect the fault of low-voltage cable, first measure the distance with rangefinder. In fact, first judge whether the cable fault is high resistance, low resistance or grounding, and adopt different test methods according to this condition. If it is a ground fault, the low-voltage pulse method of the rangefinder is directly used to measure the distance; If it is a high resistance fault, the high-voltage impulse discharge method should be used to measure the distance. When using the high-voltage impulse discharge method to measure the distance, there are many auxiliary equipment: such as high-voltage pulse capacitor, discharge ball, current limiting resistance, inductive coil and signal sampler. The operation is troublesome, unsafe and dangerous. What is more cumbersome is to analyze the sampling waveform, The knowledge requirements of testers are relatively high. The second step is to find the path (this step can be omitted if the path is clear). When finding the path, add a signal (path signal generator) to the cable, and then the receiver receives the signal. Walk along the path with the signal once to determine the path of the cable. However, the range of this path is about 1-2 meters, which is not particularly accurate. The third step is to accurately locate according to the measured distance. It is based on the sound generated by ignition and discharge. When a loud sound is heard from the headset of the pointing instrument, that is, the location of the fault point is found. Due to listening to the sound, it takes a lot of time to find it due to the influence of environmental noise. Sometimes it can't be found until the evening. When it comes to cross-linked cables, it takes more time. Generally, the sound of internal discharge of cross-linked cables is very small. After almost no hearing, it is only measured. Therefore, this method can solve most of the power cable faults with oil impregnated paper as insulating material. For the cable faults with crosslinked material and polyethylene material as insulating material in recent years, the test effect is not ideal, because the sound generated by ignition and discharge is often very small (the cable skin is not damaged, but the internal discharge of the cable), In this case, only other methods can be used to solve it. We know that the insulation requirements of low-voltage cables are low, and the current is large during operation, which has obvious characteristics after failure. It is specifically classified as follows: class I fault: the whole cable is burned out or a phase is burned out. This fault causes the current relay on the distribution cabinet to act, and the cable is seriously damaged at the fault. Class II fault: each phase of the cable is short circuited. Similarly, this kind of fault causes the current relay and voltage relay on the distribution cabinet to act, and the cable is seriously damaged at the fault point (possibly caused by external force). Class III fault: the cable has only one phase open circuit, the current relay acts, and the damage at the fault point is light but obvious. It may be that the phase current is too large or caused by the cable quality. Four types of faults: internal short circuit of cable, no trace can be seen on the surface. Such faults are generally caused by cable quality, which is relatively rare.