Weak electron

Monday, February 7, 2011

Weak current College】【power technology glossary (2)】.

CREST FACTOR crest factor in AC circuits, waveform peak and RMS (rms). In the transmit power under certain conditions, along with large peak, RMS Zeng (rms) zeng also. Therefore, the power consumption also zeng. Crest factor .sometimes used to illustrate the AC power cord of the stress in the current. Crest factor is basically the same information as the power factor describes, and, in the power terms, may be replaced by the power factor. Crossover adjustment CROSS REGULATION all output load .change on another way to output load adjustment function. Typically, no second adjustment (prospective adjustment) of the output circuit produces cross adjustment. Dramatic short circuit CROWBAR an overvoltage protection method. Overvoltage fault is detected, in order to protect the load, this circuit .allows the power output end rapid short circuit to ground. Current limiting CURRENT LIMITING an overcurrent protection circuit. In order to protect the load and power, current limiting protection circuit can limit the power of the maximum output current. Current-CURRENT MODE switching converter for .a control method, using the current-control method, the converter control circuit through a double loop, according to the detection of output current and output voltage pulse width, so that the stable output voltage. Current monitor CURRENT MONITOR output and output current proportional to .an analog signal. D the DC-DC CONVERTER DC-DC converter DC voltage transition from one to another voltage circuits. Also: dc dc converters, dc / dc converters, DC-DC converter DC DC-DC POWER SUPPLY for one .or more of the DC output voltage of power supply system. Also: dc dc power supply, dc / dc power supply, DC DC power good signal DC-OK SIGNAL monitoring DC output status signals. Derating DERATING in order to improve reliability .and reduce the operating specifications. In the power system, when the ambient temperature is high, in order to secure work, often need to lower the power output. Design life of power supply DESIGN LIFE expected service life. At this time, the power supply .operation should be consistent with the labeling requirements. Differential mode noise DIFFERENTIAL MODE EMI NOISE elimination, in two power cords to the power line between measured on a datum point of noise. Test results for two power line noise component. In the power system usually in .DC output and DC back-end test noise. Distributed power architecture DISTRIBUTED POWER ARCHITECTURE center power to each adjacent load power structure. Often using DC power supply. Drift DRIFT when power supply voltage, load and temperature, and other parameters remain unchanged, after the .warm-up process, the output voltage changes over time are called drift. Drive module DRIVER MODULE in separate or drive / times zeng module composite structure of the master control module. Drive module contains all the control circuits. Drop voltage DROPOUT AC input voltage lower .input voltage falls below this value, the output voltage is not stable. Online sexual power, a major drop voltage is determined by the power supply input voltage; most of the switching power supply, a major drop power decided to load current, input voltage low .-impact. Dynamic load regulation DYNAMIC LOAD REGULATION output current rapidly changing, the output voltage changes. E efficiency EFFICIENCY with percentage represents the total output power and input power ratio. Typically, the rated input voltage and 75% load, measuring or marking. Electronic .load ELECTRONIC LOAD received power output for a load of an electronic device. The load is typically can change dynamically, frequent changes or controlled by the computer. Electromagnetic compatibility and ELECTROMAGNETIC emission of electromagnetic waves COMPATIBILITYEMC on and feel standards. EMI ELECTROMAGNETIC INTERFERENCEEMI this is power .supply, or other electronic and electric equipment working in harmful noise. Equivalent series resistance EQUIVALENT SERIES RESISTANCEESR and ideal capacitors in series of resistance values. It can reflect the true nature of capacitors. F Mille Busbar FACTORIZED BUSVf by PRM or DC-DC converter produced .output voltage, and can be adjusted to control one or more product stability or VTMs. Mille-type power structure FACTORIZED POWER ARCHITECTUREFPAFPA (mille-type power architecture) is an innovative power distribution schema that the often used in distributed power architectures in DC-DC .converter's traditional function into voltage and voltage isolation / transformation component. Although the "pure" Mille-type power architecture (FPA) should be composed of various V • I chip (VIC), but the traditional power products, such as DC-DC converter ., non-isolated pol converters and switches are also constitute part of the FPA system. Fault TOLERANT CONFIGURATION FAULT-tolerant architecture uses they with the working circuit, access output isolation diode, single power supply (modules) of failure does not enable the output voltage .of power supply system. In this structure, single power supply fails, the relative with the system's total output current cannot be less than the load requirements of the current, that is, a single power supply fails, the relative with system cannot be overloaded. .Field-effect transistor FIELD EFFECT TRANSISTORFET majority carrier - voltage control-type transistors. FINMOD Huai lattices VI series converter module and related modules with no flange with fins package. FLATPAC Huai cell with 1, 2 or 3 channel outputVoltage AC-DC switching power supply .. Rated output power to 50-600W. Suspended output FLOATING OUTPUT power output terminal voltage, not to the other any one output, usually indicates that the output all isolation. Suspended output power can be output as voltage, output negative voltage. Non-suspended .output power supply has a public return line, therefore, an output of the DC voltage to another output..

Weak current College】【anti-static knowledge (7)】.

71. q: Wireless electrostatic discharge protection mean? A: the only applicable forced air corona discharge and ionization of measures can be widely used as "air ion generator." Electrostatic discharge system there .are several models to choose from, only cancel the discharge time, it depends on the charge-discharge rate, air flow speed and proximity up close to 2 seconds, the production period in urgent need of protection measures, but use a grounded wrist and ESD .floor mat, a second protection measures are also possible. 72. q: How can I tell if failure of the antistatic shielding bags, for example, the bag has a crease or small holes. A: MIL-B-81705C standard file you can find all your answers, in particular, if an anti-static shielding bags (model III) meet any of the following conditions, it can be considered as invalid: * Standard .electrostatic bags occurred MIL-B-81705C 4.8.4.1 section in the details of the stratification. * Electrostatic discharge electrostatic decay rate is more than 2 seconds. * The attenuation of electromagnetic interference not to 10dB. .* Small hole of diameter greater than 2mm. * You cannot shield 30kV following electrostatic discharge event. * Miles per square area on the surface resistance is greater than 1012, internal resistance per flat area is less than 105. < .br> In short, as the Faraday effect, if the shielding bags with creases or holes, so it still has a shielding effect. But will these electrostatic bag thrown away are more secure, this may take more test fee, proof of eligibility after just .replace it. 73, asked: 1, used in the production of hard disk clean room class 100, its nominal humidity level? 2, Pomalux is I know in electrostatic discharge security best only .a plastic material, but rather expensive, there are other similar materials? 3, there is no common ion generator? if so, what vendors? how can we test its results are correct? 4, electrostatic sensor reading why .would substantially change? (ie no repetitive or large jumps.) A: 1: good's nominal humidity at 40% -55%. You need to minimize corrosion, while at the same time as much as .possible to strengthen the electrostatic discharge protection. There you can test the humidity of paper available for your convenience. 2: static security good materials are vinyl, rubber, cardboard and polyethylene, etc., depending on your application. Electrostatic discharge safety .also means the loss characteristics of antistatic characteristics, and shielding characteristics, this also depends on your application. 3 and 4: charge plate will analyze instrument is monitoring the corona discharge of air carrier ion generator preferred instrument. Moreover, electrostatic sensor each .measurement a smaller area, electrostatic charge in conductive or insulated surfaces do not have to be balanced. If a substance subjected to electric or friction electric stimulation, free electrons occurs imbalances. Balance is not always consistent, electrometer sensor and the measured surface distance also further .so that this balance changes. The measuring surface geometry structure can also lead to changes in the field, for example, a surface (like a pyramid-shaped) comparison of flat surfaces have a stronger field, because the charge always accumulate in body-art .Department 74, asked: 1, conductive finger can reduce the load? loss of glove use conductive finger what benefits? 2, we have many 3M961 ion generator, the zero-level stations in .good enough? A: 1: the advantages of electrically conductive finger set depends on the following issues: the specifications of the conductive finger? do you want to handle any questions? operators feel most comfortable? do you want to .work in clean room inside job or not?, loss of gloves and will have less conductive finger ("104 = electrostatic discharge may occur, but when you use a loss of gloves when there is no difference. Glove hands than a set of covered area .larger, if you are 12 or more occasions to wear gloves, wear gloves will be more effective. 2: for zero-level stations, in any event, any particle tolerance cannot exceed 2.5 micron. The only way is to get an .ion generator for zero-level clean room to ensure clean indoor only part is a corona discharge emission source. You may know some with corona discharge emission source system, I'm not familiar with 961 units. If it is overhead or other "blower" .types of devices, so that it does not meet your standards. For 100-level, our overhead line is good, once you start to get ready. 75. q: Suppose our electrostatic discharge measures do very well, .but the following one thing not satisfactory: the staff of our company like the pink anti-static foam on computer motherboards, they felt that this would prevent the motherboard in ESD workstation produces sliding. Because they believe this will extend the life of the surface of .the workstation. However, I believe that this is not likely, because of the foam insulation. On the other hand, because the measurement, I bring an electrometer, placed in the things on this piece of foam (on the work surface) will consume .electric charge. So, this is acceptable? A: If pink foam not expendable and electrical connections to the land, then you're ready (General use). In fact this depends on your efforts to protect the product .from electrostatic discharge-sensitive. In order to measure up to the surface impedance of foam, you will need a megohm meter. At 10V and 100V two voltage measured at the surface resistance to 10 ^ 5-10 ^ 9, it is safe. < .br> You say you use the static electric field strength meter to measure, this is good, but this does not fully guarantee the foam is secure. You test this is only one characteristic of electrostatic Tester is discharge time. The most important thing is to .workSurface charge should be less than 100ms time eliminate clean. If you take a few seconds to clear out all charge, which will extend the charge relief time may give rise to an electrostatic discharge-sensitive parts subjected to electrostatic discharge. There are .other materials to choose from, you can place your work in electrostatic discharge protection for workstations, and no sliding characteristics. Type T2 floor cushion material is in this case the best choice. The following questions: A, I will .protect sensitive components? B, foam in the security level can be conductive losses? C, foam in charge may release the pained in about 100ms? D, foam necessary grounding it (if a conductive)? . E, operators need to wear a set of static discharge wrist? If you have agreed to the above questions, then you are using a number of security measures to prevent electrostatic discharge. 76. .q: my company in the bench trial, ESD footwear floor mat set and wrist. If the operator is being welded components and other can cause confusion or fever part, what other materials can be placed on the mat on the floor, without prejudice to the .electrostatic discharge performance? when space is limited, the operator does not have to move the floor mat? A: Yes, your best choice is the glass fiber reinforced plastic (FRP) solder fillers, is a high-heat resistant solder electrostatic .discharge floor mat. This allows you to check your standard rubber or vinyl floor mats electrostatic discharge table, or you can order a larger glass solder packing, that is, with grounding cord of Workbench floor mat. Rubber cushions also has good heat-resistance characteristics .(although not as FRP good). Recommended type T2 or model L Workbench floor mat. 77. q: If we are using the wrist and floor mats, you also need to put on a heel grounding device? if .you use the heel grounding device, you need to use floor coating? A: If the operations staff walking up and down, and close to sensitive components, you must use the heel grounding device. It will keep you in handling electrostatic discharge .-sensitive parts with security. If you transferred between workstation electrostatic discharge-sensitive products or components, the cart and the body should be grounded by the heel or shoes (human), drag the grounding wire (trolley). And with the proper ground floor .. In electrostatic discharge-sensitive area nearby introduced ground floor mats or antistatic floor coating is a very good idea, because these materials have excellent limits of antistatic characteristics of friction charging. If the staff must constantly move about, so in order to take full advantage .of safe ESD programme requires plankingwith layer of antistatic discharge of floor coatings and ESD shoes. 78. q: I work in a computer network, we know that mutual contacts of metal in the joints caused by oxidation, thus making .system cause problems. We are trying to take the best methods to troubleshoot it, some technical staff recommendations with rubber will clean the joints and other technical personnel claimed it would cause electrostatic discharge event, I ask that this be? A: Yes ., the eraser can be on the metal surface, so the friction charging may generate electrostatic discharge phenomenon, although this is work Workshop cleaning joints of a universal approach. But when the scrub lap surface, as long as it is grounded in respect to the risk .of electrostatic discharge to minimize, or in your bare hands, using a conductive rubber and wear a wrist grounding it set. The first thing to do is to pass on the most sensitive elements on each Board to estimate in order to determine its .sensitivity level (ESD sensitivity). This will tell you whether the Board is very sensitive to electrostatic discharge. If you do not need the sensitive, you may take a few simple prevention measures to avoid the potential danger of electrostatic discharge. Testing .electrostatic discharge sensitivity is the best way is to find a piece of old circuit boards, use the eraser to clean solder joint, and then use the electrometer to measure the scrubbing process of electric field (measuring voltage). The first step you need to put .the electrometer zero, after two readings taken before and after. If you read into the numbers more than 50V, it is recommended that you use this method to clean lap. Note that not all of the circuit board. Some boards may inline .some very sensitive to electrostatic discharge (0) components, or that is made up of different materials (such materials will have different frictional electrification priority) element, and so on. Eraser also have different friction up power sequencing / antistatic characteristics, so that each .circuit board should be regarded as an independent module. 79, asked: our production personnel protection measures including through electrostatic discharge clothes, if not in the front line of clothes clip to its level of shielding effectiveness, we have differences .. Overalls have no need to hold, in other words, if the work is not labelled, it will be screened? A: on the overalls are good, the benefit is that protection of external non-conductive and non-grounding clothing .. Even overalls are not wearing a seat, it still has some protection, because the back and sleeves, working on both sides were in peacetime covering the clothes, not only is the front cover. While the earlier part of the body is the most sensitive .products easy to close / contact parts. .

【 Weak current College 】 buy digital oscilloscope should pay attention to what issues 】

Digital oscilloscope triggers for a waveform, storage, display, measurements, waveform data analysis processing, and other unique advantages, its use is becoming increasingly popular. Because digital oscilloscope with analog Oscilloscopes have a large performance difference ., if used improperly, can produce larger measurement error, thus affecting the test tasks. Distinguish between analog bandwidth and digital real-time bandwidth Bandwidth is the most important indicator of the oscilloscope. Analog oscilloscope bandwidth is .a fixed value, and digital oscilloscope bandwidth analog bandwidth and two digital real-time bandwidth. Digital oscilloscope on repeating signal using sequential sampling or random sampling technology can achieve the highest bandwidth for digital real-time oscilloscope bandwidth digital real-time bandwidth and highest digital .frequency and waveform reconstruction techniques factor K related (digital real-time bandwidth = maximum digital rate / K), generally does not directly as an indicator. From the definition of two kinds of bandwidth can be seen, analog bandwidth only suitable for measurement of repeating .cycle signal, and digital real-time bandwidth at the same time suitable for repetitive signals and measurement of single signal. The manufacturers claim that the oscilloscope bandwidth can achieve much Siu, actually refers to the analog bandwidth, the bandwidth digital real-time is below .this value. For example say TEK Company TES3054B bandwidth for 500MHz, actually refers to its analog bandwidth, and the highest 500MHz digital real-time bandwidth can only achieve 400MHz far below analog bandwidth. Thus in the measurement of single signals, be sure to reference .the digital oscilloscope digital real-time bandwidth, otherwise the measurement will be to bring unexpected error. The sample rate Sample rate also known as digital rate refers to the unit of time, the analog .input signal sampling times, often expressed in MS / s. Sample rate is a digital oscilloscope, an important indicator. 1. If the sampling rate is prone to the phenomenon of mixtures If you .lose one signal oscilloscope as a sinusoidal signal, 100KHz oscilloscope displays the signal frequency is 50KHz, what's going on? this is because the oscilloscope sample rate is too slow, produces overlap. Overlap is the screen waveform frequency is lower than the actual frequency of the .signal, or even when the oscilloscope triggers the led on the light, and have displayed waveform is still unstable. Overlap of generated as shown in Figure 1. So, for an unknown frequency waveform, how to determine whether the displayed waveform has been producing mixtures .? you can slowly change the sweep speed t / div to a faster time base file, look for waveform frequency parameters are rapidly changing, if yes, describe waveform mixtures have occurred; or shaking of the waveform in a faster time base stalls stabilized, also .note the waveform mixtures has occurred. According to the Nyquist theorem, the sample rate is higher than the signal frequency components at least 2 times don't overlap occurs, such as a 500MHz signal, you need at least 1GS / s sample rate. There .are several ways you can easily prevent overlap occurs: Adjust the scanning speed; The use of automatic settings (Autoset); Try collection over to the envelope or peak .detect mode, because the envelope mode is multiple collection records for extreme peak detect mode, which is in a single collection records looking for maximum minimum value, both methods are detected faster signal changes. If the oscilloscope is InstaVu acquisition .mode, you can use, because this way acquisition waveform speed, use this method to display the waveform similar to use analog Oscilloscopes display waveform. 2. the sampling rate and the relationship between t / div < .br> Each digital oscilloscope maximum sample rate is a fixed value. However, in either the scan time t / div, sample rate fs from next-gives: Fs = N / (t / div) of N sampling .points for each cell When sampling point n is a value, the fs and inversely t / div, so the larger the sample rate as soon as possible. The following is a set of scan TDS3054B speed and sample rate of .the data: Table 1-scan rate and sample rate t / div (ns) 1252550100200fs (GS / s) 502510210.50.25 In summary, when using a .digital oscilloscope, in order to avoid overlap, the sweep speed stalls preferably placed sweep speed faster. If you want to capture the moment dying Burr, sweep speed stalls is best placed in the main scan speed is slower. Digital .oscilloscope rise time In analog oscilloscope, oscilloscope rise time is a very important indicator. In DSO, rise time even as indicators clearly show. Because digital oscilloscope measurements of the reasons that the automatic measurement of rise time not only with .the location of sampling points, such as indicated in Figure 2, a rising edge just landed in the middle of two sampling point, then rise time interval for the digitalization of 0.8 times. Figure 2 b of the rising edge of the central one sampling point ., the same waveform, rise time interval for the digitalization of 1.6 times. In addition, the rise time is also relevant with sweep speed, here is when the same waveform TDS3054B measurement of a group of sweep speed and rise time data: . Table 2 sweep speed and rise time t / div (ms) 502010521tr (μs) 800320160803216 By the above set of data can be seen, although waveform rise time is a fixed .value, and digital oscilloscope measurement results are different because the scanning speed is far. Analog oscilloscope rise time has nothing to do with the sweep speed, and digital oscilloscope rise time not only with the sweep speed, also the location of sampling points, use digital .oscilloscope, we cannot use analog oscilloscope, according to the measured time to reverse launch signal rise time. .

Weak current College】【lithium battery charging circuit theory and application of】.

Lithium-ion battery with its excellent characteristics, are widely applied in: cell phone, VCR, portable, cordless phones, power tools, electric toys, remote control or on the camera, and other portable electronic device.

I. lithium batteries and nickel-cadmium, nickel-metal hydride rechargeable batteries:

Lithium-ion battery anode to cathode typically graphite Crystal, as lithium oxide. Cathode ion rechargeable shili from embedded to negative campaign and graphite layers. Discharge, lithium-ion from graphite Crystal surface from within the anode to the cathode. Therefore, the battery charge and discharge lithium is always in the process of lithium-ion speciation occurs, rather than the form of lithium metal. Thus this type of battery is called lithium-ion batteries, or Li-ion battery.

Lithium batteries have: small size, large capacity, the weight is light, pollution-free, single voltage high and low self discharge rate, battery cycle number, etc., but expensive. Nickel-cadmium batteries due to low self-discharge capacity, and on the environment pollution, is gradually being phased out. Ni-MH batteries with high cost performance, and do not pollute the environment, but only a single voltage, thus using 1.2V scope be limited.

II. characteristics of lithium battery:

1, with higher weight energy ratio, volume energy ratios;

2, high-voltage, single-cell Li + battery voltage to 3.6V, equal to 3 only NI-CD or Ni-MH rechargeable battery-voltage;

3. low self discharge can be stored for a long time, this is the most significant advantages of the battery;

4, no memory effect. There is no lithium batteries NI-CD batteries of so-called memory effect, lithium battery charge before without discharge;

5, have long performance life. Under normal operating conditions, lithium battery charge/discharge cycle times larger than 500;

6, you can quickly recharge. Lithium battery usually uses 0.5 ~ 1 times the capacity of the charging current, so that the charging time shortened to 1 to 2 hours;

7, can be used in parallel;

8, since the battery does not contain cadmium, lead, mercury and other heavy elements, environmental pollution, the most advanced green battery;

9, the cost is high. And other rechargeable batteries, lithium battery compared to expensive.

3. the internal structure of lithium battery:

Lithium battery there are typically two shape: cylindrical and rectangular type.

Battery internal use spiral-wound structure, with a very fine and permeability of strong polyethylene film quarantine material in the interval between positive and negative. Positive electrode including lithium cobalt oxide and composed of lithium-ion collector and aluminum film composition of current collectors. Anode carbon by Flake material for lithium-ion collector and copper film composition of current collectors. The battery is filled with organic electrolyte solutions. Also equipped with a safety valve and PTC component, so that the battery in an unhealthy state and output short-circuit protection battery is not damaged.

Li + battery voltage to 3.6V, capacity is not likely to infinity, therefore, often a single lithium battery for series and parallel processing to meet the requirements of different occasions.

IV. lithium battery charge and discharge requirements;

1. rechargeable lithium battery: according to structure characteristics of lithium batteries, maximum charge termination voltage should be can't overcharge 4.2V, or they will take away the cathode of lithium-ion, and make too many battery scrap. Its charge and discharge requirements are higher, you can use the constant current, constant voltage dedicated charger for charging. Usually constant current charging to 4.2V/post-holiday to constant pressure and constant voltage charging, when the charging current drops to 100mA or less, you should stop charging.

Charging current (mA) = 0.1 ~ 1.5 times the battery capacity (such as 1350mAh battery, charging current can be controlled at 135 ~ 2025mA). Normal charging current can choose 0.5 times the battery capacity, charging time is about 2 to 3 hours.

2 lithium batteries discharge: due to the internal structure of lithium batteries, discharge shili ion cannot be all moved to the cathode, must remain part of the lithium-ion in negative for the next charge shili ion can easily embed channel. Otherwise, the battery life is reduced accordingly. In order to guarantee the graphite layer after leaving some discharge lithium ion, strictly limiting the minimum voltage discharge termination, i.e. lithium battery cannot discharge. Discharge voltage is usually 3 .0V/section, the minimum can not be lower than 2.5V/section. Battery discharge duration and battery capacity, discharge current size. Battery discharge time (hour) = battery capacity/discharge current. Lithium battery discharge current (mA) should not exceed three times the battery capacity. (Such as 1000mAH battery discharge current should strictly control within the 3A) or cause the batteries to be damaged.

Currently on the market within the lithium batteries are sealed with matching charge and discharge protection board. As long as you control the external charging and discharging current.

5. lithium battery protection circuit:

Two lithium battery charge and discharge protection circuit shown in Figure 1. Consists of two FET and private protection manifold S-8232, overcharge control tube FET2 and discharge control tube FET1 series to protect the circuit from IC monitors battery voltage and control, when the battery voltage is increased to 4.2V, overcharge protection tube FET1 due to stop charging. To prevent incorrect operation, generally with a delay detection tester for electronic circuit. When the battery is discharging State, the battery voltage drops to 2.55V, over discharge control tube FET1 due to load, the power supply. Overcurrent protection is in when the load on a large current flows, the control of the globe, FET1 stop to load discharge in order to protect the battery and FET. Overcurrent detection is to use the MOSFET on-resistance as the detection of resistance, voltage drop monitoring it, when the voltage drop over the set value when you stop discharge. In General, also in circuit with delay circuitTo differentiate the surge current and short circuit currents. The circuit of functional, reliable, professional and dedicated to buying, manifold amateurs are not easy to clone.

Saturday, January 29, 2011

【School】 combination of weak cold storage in the course of security issues】.

cold meat is meat production, processing, storage, transportation and sale of an important link in the cold chain, cold storage of meat in recent years, however, frequently dangerous situations. .Reporter learned from the China Meat Association latest cold storage, only the last 6 years, cold meat made a dozen main serious injury accidents, 20 from the cold fire. . According to the China Meat Association statistics, nearly twenty thousand of existing cold storage, refrigerated cold storage volume of about 8.8 million tons, of which the cooling material about 140 million tons refrigerated cold storage, refrigerated cold storage, freezing things about 7.4 million .tons. .China Meat Association executive vice president Deng Fujiang analysis, the former state-owned enterprises accounted for the capacity of cold storage refrigeration capacity of 2 / 3; the former state-owned and non-state cold delicate  throat several Kum? 0%, agricultural products, aquatic products processing more .developed provinces of the township, 100 tons of up and down the small refrigerator is widely distributed. .Age of these cold storage library more in 10 - 30 years or so, there are safety problems. .Reporter learned that the current cold storage fire safety accidents and cooling systems for the accident. .China's meat industry, cold storage refrigeration system using ammonia as a refrigerant most. .Ammonia is in our national standard level 4 mild toxic hazard, when the volume fraction of ammonia in the air 16% - 25%, the case of fire can cause an explosion. .According to Deng Fujiang introduced in the 20th century, 90 years, commonly used in polyurethane cold insulation works, which lead to security issues affecting both the quality of the project, but also shorten the life of cold storage, could easily lead to broken, damaged, collapsed, one of the most .is a fatal fire. .Refrigeration system in recent years, accidents have occurred: compressor damage, refrigeration equipment, accidents, escape of refrigerant, cooling system pipe cracking, valve damage, failure of such safety devices are on the rise. .Why risk frequent cold conditions? .Deng Fujiang analysis that originated from six major hazards: First cold storage management disorder. .China is not yet clear which government department is responsible for cold storage security management. . Second induction operating without a license. .Cold storage is not currently in many parts of the implementation of the provisions of refrigeration system certificates. .Particular county, township, town and rural areas were not nearly cold storage holder production operators, either did not receive pre-job related training, but the lack of emergency treatment and safe operation of the daily education. .Cold storage ammonia refrigeration system in case of leakage accident, front-line operatives basic perplexed. .The third is sick refrigeration system operation. .According to statistics, built in the 20th century, 80 years before cold storage cold storage capacity is currently about half of the country, most of the library more than 30 years old. .And many enterprises have failed to provide full and on time to stay cold repair funds, causing many dilapidated refrigerator, the cold storage refrigeration system ammonia refrigerant run, run, leakage is serious. . Fourth, the lack of protective equipment of ammonia refrigerant. .Such as personal protective clothing, oxygen breathing apparatus, protective gloves and protective footwear, eye and body spray washing, etc., can not do the time for rescue, in place. .Fifth, many companies cut back on cold storage ammonia refrigeration compressor operating operating personnel, the upper management of scarce professional and technical personnel in the refrigeration, cold storage refrigeration system in automatic control technology is generally not the case, once the exception, the entire refrigeration system will .unsupervised in the state. . Sixth, cold storage design, construction and installation market confusion, undocumented design, installation of undocumented, unlicensed construction is widespread. .Because of the cold storage of insulation materials, cooling systems and pipe the reliability of the selected container, structural configuration, scientific processes such as the formation of large hidden faults, some cold storage refrigeration system with a congenital defect, security can not be guaranteed. .The current lack of cold storage safety management how to reverse the situation? .Deng Fujiang make the following observations: First Amendment promulgated by the former Bureau of Internal Trade, "cold storage building construction and acceptance norms" and the former Department of Commerce issued the "cold storage management practices" and other relevant administrative regulations. . Second is recommended that the Government authorities to allocate more public safety fund, financed and commissioned by industry associations or the cold storage business to undertake the use of the relevant countries or involving public safety industry standard preparation. .Third, require enterprises to put on cold storage security agenda, to carry out self-test self-examination, to take remedial measures against potential accidents. .Establish a standard of management and emergency management and reporting system. .Companies develop safety standards, accountability to the people. .Within the enterprise to conduct regular safety checks, there must be plans for handling accidents and the corresponding equipment. .Fourth, to strengthen the retirement of the related refrigeration pressure vessels, pressure piping pipe recovery supervision. .Must not be allowed to re-pipe waste refrigeration equipment and cold storage and cold storage to flow back to the construction site to ensure the safetyof cold storage refrigeration system of qualified materials. .Five is to ask around to do with the ammonia pressure in the pipeline register, find out the real situation, know what to do supervision on the ammonia refrigeration equipment and piping for regular inspection, and make its security evaluation. .Six is to require all companies and departments in the engineering project, bidding, design, and construction process, the strict eligibility of the involved units, to eliminate "Executive Project," "human engineering" to eliminate "edge design, the construction side, while .production "and" self-design, self-installation, self-construction ", with particular attention to the construction unit of the qualification examination of polyurethane to enhance the project site management. . Seven is to ask the associations around the meat cold storage technology and safety management training, cold storage safe each examination. . .

【School】 VOD system weak Introduction】..

VOD system introduced VOD VOD: VOD (Video on Demand) video on demand, also known as interactive television on-demand system.. The traditional one-way television system information is sent, the user can only .passively receive.. The VOD is a "choice of control in the user" in the new concept of two-way video and audio based information system to achieve video and audio playback according to user needs the ideal program.. VOD is the future .information superhighway, an important part of architecture is the future of information services in the broadband services of the soul.. This technology is computer technology, network communication technology, multimedia technology, television and digital compression technology and other subjects in various fields, the product .of fusion cross * combination.. Through the VOD system can be video programs on demand, live real-time broadcasting (live online on the network), distance learning systems, remote video conferencing, remote monitoring and many other work.. Currently VOD VOD .system has been in the military, government, schools, intelligent community, hotels and other fields has been widely used.. System features: the system of the current popular use of Web browser technology, reduce, simplify the application client to .enhance the stability of the system operation, reducing the workload of system maintenance; system, the use of international and domestic standard protocol. technology, such as: network use IP, streaming video playback using advanced media player application framework using Web technology; same side .of the system used in the program memory database technology to simplify, facilitate program management.. Therefore, "ETRADE Ka Wah VOD video on demand system" is a mature real video server to the client-based, streaming video transmission using the VOD video .on demand system.. The VOD video on demand system is divided into: server management system and user-demand system.. The system is fully Web-based development, can be Internet / Intranet for seamless integration .with the following characteristics: Road, minimum performance requirements of servers: The system adopts the package of the most popular streaming media production, publishing and playback. technology to maximize the intrinsic performance of the hardware system, therefore, .production, publishing and playback software does not require additional purchase, the maximum reduction of server requirements and costs.. Road Optimal utilization of network bandwidth resources: video streaming solution of the system in the Microsoft Windows platform is .optimal, production-side with the player's video and audio quality are excellent and easy to use.. The use of the stream, each client receives the content through the network at the same time you can enjoy the show without having to first download the content .greatly reduces the wait time on the client and storage needs, but it also allows an unlimited length of the Demo, and live. broadcast.. Road Open video streaming network protocols: without special equipment or special set .of router, you can remote VOD VOD.. Road Fast video-on-demand Response: read the playback screen smooth and clear.. Support the industry's most advanced MPEG4 standard, while fully compatible with MPEG1, .MPEG2 video files and other standards may be minimal in the case of system resources to achieve DVD-level playback, true high-definition playback.. Road Video content editing simple and easy: simple, easy to use ., provides features such as pre-production, a powerful tool for video and audio editing system.. Road Any video content stored in the backup: the content of any video format, in accordance with AS easily backup ., so that use of renewable resources.. Road Zero maintenance clients: VOD system is completely Web-based development, the client can be realized using the IE browser on demand, without having to install any other software ., so that the client's zero maintenance.. Road Client terminal operation simple and easy: simply login through a browser in the terminal web server, the server will automatically log the video to achieve on-demand; in .the on-demand process, the easy free-motion video stream interception of the network,. Drag around the play, stop, fast forward, rewind, left and right channels.. Road Demand occurs during the terminal interrupted in demand .at the point of interruption when rapid recovery: remain as long as the video server to provide video services, two seconds, the terminal troubleshooting, on-demand can be interrupted at the rapid recovery.. Road And .convenient system maintenance and back office management settings: administrator can be any system maintenance and back office management settings.. Road Compatible with many media formats: encoded files can be adapted to a variety of .broadband streaming media formats, create wmv or asf files to implement on-demand.. Network environment: * HTTP-based network transport protocols and MMS video service system.. * Use of switched Ethernet (Switched Ethernet), asynchronous transfer .mode network (ATM) or Fiber Distributed Data Interface (FDDI) and other network technologies.. * Video Server via twisted pair, coaxial cable or fiber access networks, user terminals to access the LAN via twisted pair.. Broadband access and transmission networks: .10M, 100M switched Ethernet or 1000M.. * User terminal access speed: 10M or higher video server access speed: 100M, 155M or 1000M LAN ..

【 Weak current College 】 DVI signal transmission in multimedia solution application 】

one. using DVI signal strengths: 1. provides the best image quality.. Signal in VGA display, the notebook is the highest image quality.. CPU data to be .displayed to the graphics card to be processed to form a graphics display signal (digital signal), this digital signal directly drive LCD screen, the formation of the notebook display signal, which is the most "original" signal, not. by any treatment ., and losses.. The graphics signal (digital) through the D / A conversion, the formation of RGBHV signals, transmitted to the display device subject to approval by A / D process, to re-generate the digital signal to drive LCD and other .equipment, then the signal through the D / A,. D / A conversion, resulting in bandwidth, signal to noise ratio and other losses, such as: according to Nyquist sampling theory, the maximum analog bandwidth is only half the sample clock, and .56dB signal to noise ratio is only about (quantified by 8bit) ... However, if the graphics signal (digital) through and / serial conversion, the formation of DVI output, and then transmitted through the DVI to the display device and then only .after a serial / parallel conversion, you can directly drive LCD and other equipment, this process has not been A. / D, D / A conversion, will not cause signal loss.. 2. To reduce the signal loss during .transmission.. Analog signal transmission, because of the amplitude-frequency transmission system support and support group delay, high frequency interference, power ground interference and reflection effects of severe signal loss, works to solve the above problems and the difficulty of .dealing with. large, some even can not be solved.. But not when the digital signal transmission of these problems, the biggest advantage of digital transmission and anti-interference ability can be re-regeneration, Simply put, that is, as long as .the transfer process to ensure that "0", "1" Discrimination is not an error. receiving end of the signal is correct and non-destructive, and analog transmission in the difficult problem in the digital transfer process does not exist, this .is a fundamental solution to the problem, ensure that to the display device of the signal and laptop displays the signal as. give full play to the advantages of the display device, significantly improving the overall system display.. II. DVI .signal characteristics DVI signal theory, is the graphics to be displayed in the processed digital signal and HV RGB signal combination, according to the smallest non-zero coding, each pixel by 10hit the. → serial digital signals and convert the digital .stream encoded RG.B 4 groups with the pixel clock signal in accordance with the TMDS transmission mode, the flow rate of each channel of the original code 10 times the pixel clock to 1024 × 768 × .70 resolution, for example, pixel clock is .75MHz, the clock stream is 75MHz × 10, as 0.75GHz.. DVI-general in the 0.24GHz to 1.65GHz stream between.. DVI interface definition as shown below: DVI has .DVI1.0 and DVI2.0 two standards, which DVI1.0 of which only a group of signal transmission channel (data0-data2), transmission. The maximum pixel clock image 165M, the maximum signal transmission channel stream to 1.65GHz, the highest .resolution up to 1600 × 1200 × 60.. The DVI2.0 the two groups with all the signal transmission channel (data0-data5), transfer images to a maximum pixel clock 330M, can support 1920 × 1280 resolution, support for HDMI formats, .each channel's maximum signal transmission code. flow for 1.65GHz.. There is no DVI2.0 application, so all means are talking DVI1.0 DVI standards.. DVI defined DVI-I (Integrated) and DVI-D ( .Digital) two interfaces, can be seen from the interface definition, DVI-I DVI-D is in fact an increase on the basis of analog interface.. One view is that DVI-I is only a transitional interface will eventually develop into a DVI .-D and VGA were present situation, where we do not make improper evaluation.. We introduce DVI-D interface.. Three. DVI signal transmission problems DVI signal transmission has its particularity, that is too fast .because the data stream, making the transmission distance is limited to 1600 × 1200 × 60, for example, stipulated that can be transmitted .5 meters, in the current practice, to be completed by about 7 meters to 1280 × 1024 × 70, for .example, transfer of 10 meters is feasible.. Of course, use good cables, 1024 × 768 × 75 can be spread to 13-14 meters.. In the case of single-stage transmission, the primary problem is the problem drive capability, .that solve the "walk out" of the problem, but at the same time, even the digital signal, there are also long-distance transmission signal waveform distortion deformation, namely. After transmission by increasing the drive capability, the signal waveform to a .larger distortion of the signal received by the receiving end in "0" and "1" discrimination on the error, from the display point of view, there has been "wrong point", "wrong. point" when the .show will fail too, that no longer appear.. In fact, DVI signals over long distances, as the distance increases, the display can be observed are: good wrong point → point → → more wrong to fail.. Failure may be the signal ."walk," and can not get to the monitor, it may be "can walk", but "wrong point of" too much and failed.. Therefore DVI signal cable transmission is concerned, there are .different applications.. 1, Adepter, only the drive capability to solve the problem.. Signal input through the high-frequency amplifier, the drive to ensure that their may be some distance ahead, but is not responsible for signal shaping, can be cascaded ., it is suggested no more than three MS; 2, Repeater, when the signal input. be carried out and and and → string → string conversion, the signal will be re-shaping, and then drive through the drive circuit, which is a .forward concept.. As long as the signal does not come before the distortion level to determine the error, which produces the "wrong spot" level, then the signal sent back to class and just come out the same graphics card is the right signal .to send is at 7 meters distance. (1600 × 1200), can be cascaded, and the limited number of cascade.. 3, Line Driver, the DVI signal through a balanced approach, and after Repeater plastic handle which allows it to substantially increase .the transmission distance, an optional Line Driver 35 meters transmission distance of about (1600 × 1200), if it is 1024 × 768,. up to 45 meters, and can be infinite cascade, especially the Line Driver signals back-end applications, there .is no relay power supply problems.. DVI signals can also have other means of transmission, such as cable and optical fiber, cable ways have been discussed in the article, here only cable transmission.. The current data and practice, .through the network cable, the DVI signal means in accordance with Gigabit Net newsletter to sort and transport, 1280 × 1024 × 60 50 m can be transmitted in theory, if we can use the existing transmission cable. prospects very attractive, but inside there are .several problems, one can use Gigabit Ethernet to 1280 × 1024 × 60, resolution is not high, the actual use of this can be tolerated.. However, only one channel communication signal transmission, and DVI is also passed four signals, and signals on .the bit demanding, so cable must be specific (experiment if an ordinary network cable, can only transfer 1 - .2 m), which a lot of inconvenience for practical use, can not use existing network wire DVI signals, and then taking into account .the special converter cable prices and the price, it seems not a good choice but so suitable for general. cable look after the equipment out.. Four. DVI signal transmission performance / cost evaluation DVI signal transmission distance .according to different devices should be used in different, first cable, the cable has been able to find the current point of view, generally about 7 m to transfer (1600. × 1200), then I am afraid, something never done a long, .1280 × 1024 × 60 to to 10 meters, 1024 × 768 to go to 12-13 meters, the price of 20-40 yuan / m, other, DVI connector in the system. When demanding to do the same when the cable connector in .the technology and materials to do different, and the effect of transmission distance is different, so the price of finished product lines will be quite different.. Generally not recommended in the project Adepter, because there may be "wrong point" .;, but also in the design will not advance to consider what went wrong, especially in multi-path of the occasion, as with the Repeater, simple one, and. cost is not very different.. When the distance is more than " .a standard length "when the (1600 × 1200,7 meters), can be decided according to the distance Repeater or Line Driver, the difference is that the transmission distance of a Line Driver Repeater much larger than one, but the cost difference between a .. times.. Quo's Repeater in 1800RMB, while the Line Driver in 3400RMB or so.. $ 199 international Adepter around, Repeater $ 399 or so in the current Line Driver not found a similar product.. When the distance of 100 meters, because .the cable and the Line Driver taking into account the cost of equipment is recommended to use optical transmission, especially in certain special circumstances and occasions, on the optical transmission done before the introduction of a separate later.. But with the cable and lower the cost .of forwarding devices, optical transmission will be mainly used in ultra-long haul of the occasion.. Low cost DVI DVI transmission and the emergence of switch matrix, for paving the way for the application of DVI.. .;..