Types And History Of Heat Detectors Engineering Essay

Types And History Of Heat Detectors Engineering Essay Fire is one of the biggest threats people are facing in our society these days. Many methods are being used to prevent such danger on the citizens, such as making sure that every house has a fire extinguisher incase of fire starting in a persons house. These methods are improving by time and are getting more advanced and safer for the protection of people. Many changes were made to a fire alarm, yet the most recent and favorite ones are the fire detectors with all its types. However, to avoid danger most latest buildings provide each flat with a fire detector that can detect any hazard that will be caused by fire caused unintentionally. Fire alarms consist of many different types mainly smoke alarm detectors and heat detectors. We chose to build our own heat detector that detects any change in the temperature of the room. This experiment will include mainly a heat sensor and a temperature detector, and a buzzer that turns on when the temperature changes. The report includes a search on different types of fire alarms and their use. Types of fire alarms à ¢Ã¢â€š ¬Ã‚ ¦ It is definitely hard to get robbed and lose your belongings, yet a thief will leave your home where you live with your family and are considered your shelter. Fire will leave nothing except ashes of what was before a house. However, fire can be a very destructive force. Acting too late in the instance of a fire can not only entail the loss of your property, but of your life as well. This is the reason is why having a fire alarm in your home is necessary. Brief historyà ¢Ã¢â€š ¬Ã‚ ¦ The first automatic electric fire alarm was invented n 1890 by Francis Robbins Upton. In late 1930s the Swiss physicist Walter Jaeger tried to invent a sensor for poison gas. He expected that gas entering the sensor would bind to ionize air molecules and thereby alter an electric current in a circuit in the instrument. Francis Upton His device failed (small concentration of gas had no effect on the senors conductivity). When Jaeger lit a cigarette he was surprised to notice that a meter on eh instrument had registered a drop on current. Therefore, he discovered that smoke particles had done what poison gas could not do. Jaegers experiment was one of advances that paved the way for the modern day smoke detector. Smoke detectors started off with a generally high price that people couldnt afford, except for major businesses and theaters. The first affordable smoke detectors were invented by Duane D. Pearsall and Stanley Peterson in 1965, featuring individual battery powered units that could be easily installed and replaced. The first units for mass production came from the manufacturing mind of Stanley B. Peterson in 1975 at Duane Pearsalls company in Lakewood. These first units were made from strong fire resistant steel and shaped much like a bees hive. The battery was a rechargeable specialize unit created by gat es energy. We all know that fire alarms are designed to alert people to the possibility of a fire in their homes. Although any smoke alarm can be useful, it is often recommended that you choose a specific type of fire alarm for your home. This is because certain types of fire alarms can be more suited for certain places and for certain people. There are different types of fire alarms that people usually choose from to use in their houses for protection. Smoke detector 1) Smoke alarm detectors These are the most common types of fire alarms. Often, the term smoke alarm is used interchangeably with fire alarm. Smoke alarms actually detect smoke, not the actual fire. There are generally two types of smoke alarms: A) Photoelectric This type of fire alarm sees the smoke. This fire alarm is particularly responsive to smoldering fires or the type of fires that give out a lot of smoke. These are ideal for places where there are things like PVC (Polyvinyl chloride) or foam. This fire alarm, though, is slightly more expensive than ionization alarms. This fire alarm must also be kept clean since it can give off false alerts due to dust and insects. In one type of photoelectric device, smoke can block a light beam. In this case, the reduction in light reaching a photocell sets off the alarm. In the most common type of photoelectric unit, however, light is scattered by smoke particles onto a photocell, initiating an alarm. In this type of detector there is a T-shaped chamber with a light-emitting diode (LED) that shoots a beam of light across the horizontal bar of the T. A photocell, positioned at the bottom of the vertical base of the T, generates a current when it is exposed to light. Under smoke-free conditions, the light beam crosses the top of the T in an uninterrupted straight line, not striking the photocell positioned at a right angle below the beam. When smoke is present, the light is scattered by smoke particles, and some of the light is directed down the vertical part of the T to strike the photocell. When sufficient light hits the cell, the current triggers the alarm. Figure 1 -In this type of detector there is a figure 2- When sufficient light hits the cell, T-shaped chamber with a light-emitting the current triggers the alarm. Diode (LED) that shoots a beam of light across the horizontal bar of the T. B) Ionization This type of fire alarm detects the invisible particles caused by combustion. As opposed to the photoelectric fire alarm seeing the smoke, this type feels the smoke. This can best detect flaming fires with no visible smoke. However, you should not place this type of fire alarm in the kitchen as it is susceptible to false alarms. It is also cheaper than other types of fire alarms. Ionization detectors have an ionization chamber and a source of ionizing radiation. The ionization chamber consists of two plates separated by about a centimeter. The battery applies a voltage to the plates, charging one plate positive and the other plate negative. Alpha particles constantly released by the americium knock electrons off of the atoms in the air, ionizing the oxygen and nitrogen atoms in the chamber. The positively-charged oxygen and nitrogen atoms are attracted to the negative plate and the electrons are attracted to the positive plate, generating a small, continuous electric current. When smoke enters the ionization chamber, the smoke particles attach to the ions and neutralize them, so they do not reach the plate. The drop in current between the plates triggers the alarm. Which Method is better? Both ionization and photoelectric detectors are effective smoke sensors. Both types of smoke detectors must pass the same test to be certified as UL smoke detectors. Ionization detectors respond more quickly to flaming fires with smaller combustion particles; photoelectric detectors respond more quickly to flaming fires. In either type of detector, steam or high humidity can lead to condensation on the circuit board and sensor, causing the alarm to sound. Ionization detectors are less expensive than photoelectric detectors, but some users purposely disable them because they are more likely to sound an alarm from normal cooking due to their sensitivity to minute smoke particles. However, ionization detectors have a degree of built-in security not inherent to photoelectric detectors. When the battery starts to fail in an ionization detector, the ion current falls and the alarm sounds, warning that it is time to change the battery before the detector becomes ineffective. Back-up batteri es may be used for photoelectric detectors. Ionization chamber Heat detector Smoke alarms in homes can go off whenever theres smoke present. If a person smokes cigarettes, burns food or lights incense, a smoke alarm might go off. A heat detector, on the other hand, is indifferent to how much or what type of smoke is in the air. It will only react when it detects a change in heat, associating that heat change with the possibility of a fire in the area. 2) Heat alarm detectors- are devices that respond to changes in temperature of the surrounding area. If the ambient temperature rises above a predetermined threshold an alarm signal is triggered. In the case of sprinkle systems, water will be released to extinguish the fire. Heat detectors can also be further broken into two main classifications: Rate-of-rise heat detectors- ROR heat detectors react to the sudden change or rise in ambient temperature from a normal baseline condition. Any sudden temperature increase that matches the predetermined alarm criteria will cause an alarm. This type of heat detector can react to a lower threshold condition than would be possible if the threshold were fixed. A typical alarm may sound when the rate of the temperature rise exceeds the rate that was chosen as the normal safe rate of the temperature per minute. However, it detects fires that rapidly grow in intensity. This method responds to abnormally fast temperature increases. Fixed temperature heat detectors- this type of detector reacts when the ambient temperature reaches a fixed point. The most common fixed temperature point is 136.4 F (58C). Recent technological developments have enabled the perfection of detector that activate at a temperature of 117 F (47 C), providing increased time to escape. This method detects fires that build temperatures to a high level at a slow rate. This method responds to a specific temperature setting. A fixed head detector must be completely heated to alarm temperature and therefore a disastrous interval in time may occur with a fast rate fire. Which method is better? Heat detectors commonly have a label on them that says not a life safety device. That is because heat detectors are not meant to replace smoke detectors in the bedrooms or in the hallway outside of the bedrooms. A heat detector will nonetheless notify of a fire in a kitchen, where smoke detectors should not be installed. This will allow more time to evacuate the building or put out the fire if possible. Each type of heat detector has its advantages, and it cannot be said that one type is better than the other. If we placed a rate-of-rise heat detector above a large, closed oven, then every time the door is opened an alarm could be generated due to the sudden heat transient. In this situation the fixed threshold detector would probably be best. If a room filled with highly combustible materials is protected with a fixed heat detector then a fast-flaming fire could exceed the alarm threshold due to thermal interval. In that case the rate-of-rise heat detector may be preferred. The secret of the heat detection units sensitivity is in the design. The outer shell is made of a rapidly expanding alloy which closely follows changes in surrounding air temperature. The inner struts are made of a lower expanding alloy. Designed to resist thermal energy absorption and sealed inside the shell, the struts follow temperature changes more slowly. A slow rate fire will heat the shell and struts together. At the set point, the unit will trigger, actuating the alarm or releasing the extinguishment. A transient rush of warm air up to 40 °F /min. may expand the shell, but not enough to trigger the unit. By ignoring transient warm air excursions, the DETECT-A-FIRE unit virtually eliminates false alarms prevalent with rate-of-rise devices. If a fast rate fire starts, the shell will expand rapidly. The struts will close, actuating the alarm or releasing the agent. The faster the fire rate of growth, the sooner the DETECT-A-FIRE unit will react. Why Heat Detectors? No annoying beep when the battery is low Best loop capability Affordable compared to other detectors Immunity towards electromagnetic interference Resistive against contagion like UV and IR rays No necessity to change batteries Inherently secure and reliable

Satellite Radio :: Technology Essays

Satellite Radio When I drive my car around town running errands and going from place to place, it’s nice to listen to the radio. Now since this distance I am traveling seems to be within a 30-40 mile radius, flipping through the stations is not much of a problem for me. Now on the other hand, I do travel out of town frequently, and I hate it when I want to listen to the radio and there is no signal. The reason why none of us can is because radio signals don’t carry much farther than the town’s radius. Trying to find a station in the static is very annoying. Most of the time (especially in Iowa it seems) there are no stations for miles. Now who would honestly like to travel like that? Not me that is for sure. There is an alternative though. It’s not very expensive to get either. Satellite radio is the key to traveling without boredom. Satellite radio’s signals are cast from over 22,000 miles away from the earth’s surface. There is no static interferen ce either! From personal experience, I have sold these radios for a company. I don’t want to persuade anyone either way towards one brand or the other. AS I have researched though, there are subtle differences in each provider. For instance, if price is an issue, there are plenty of options that are affordable. The bills are monthly for the two that I have looked into, but depending on the different perks, the price can really make all the difference. â€Å"Radio to the Power of X†, is the slogan used for XM satellite radio. There is no contract requirement any longer to listen to premium quality music, with few to zero commercials. It’s only 9.99$ per month for any service plan. Here are a few perks for XM radio; †¢ 68 commercial free music channels. †¢ 33 channels of sports, news, talk & entertainment †¢ 21 channels with instant traffic and weather †¢ Delphi Unit-portable or fixed in a car. †¢ Receiver lists the artist and song. †¢ 2 satellites orbiting the earth †¢ Only 9.95$ per month These are just a few of the perks that XM has to offer. XM has teamed up with pioneer, Jensen, and audiovox to create the car decks that are â€Å"XM ready† so the price of the equipment can be very affordable. The Delphi unit is a little more expensive, but depending on when you want to listen to radio, whether it is at home or in the office, this unit is a prime choice.

African American and Conflicting Perspective Essay

Every individual has a perspective on things in life and their personal idea of the truth. These are universal concepts and are widely seen in ted Hughes poems â€Å"birthday Letters†. Birthday letters is a set of poems, said to have been written by Hughes for six years prior to his death, on his ex wife’s birthday each year this the selection of poems being called birthday letters. The selection on poems surrounds his problematic marital issues between himself and his wife Sylvia Plath. It is also to show the conflicting perspective on their relationship. This is mainly towards the criticism he received all those years after her suicide. He had been blamed for being the catalyst for her suicide/death and so began a collection of poems regarding their relationship but in some way, excusing himself and explaining that she was already on a destructive path. Through two of his poems, Fulbright scholars and the shot, an understanding of the poems have thrown lighten the concepts of conflicting perspectives. Two other complementary texts such as letters from two jima and to kill a mockingbird convey conflicting perspectives however on issues such as racial discrimination and the perspectives of an opposing country that has been marked as enemies. Fulbright scholars are the first poem in the birthday letters collection. Hughes here tries to remember how he met her and first know of her existence. He does this whilst looking at a picture that was taken at university, when he was a naive young man. He ponders about her throughout the poem trying hard to delve into his psyche hopelessly to recollect something about her when they met at a party. This can be noted by the quote â€Å"were you among them? † which refers to the picture of Fulbright scholar. In terms of conflicting perspectives, the e poem can also be seen as a text that he wrote implicating how difficult it is t recall that first meeting, however he begins to explain his perspective of Sylvia Plath. He says â€Å"your exaggerated American grin for the cameras† which referred to her as someone with false appearances. The various techniques Hughes used to convey his ideas were the use of rhetorical questions such as â€Å"were you among them? †, the repetitions of the word maybe and the use of the I persona, and metaphors such as the â€Å"first fresh peach†. Rhetorical questions he used as a means of asking himself how he met her and what she first looked like to him. The metaphor ‘delicious peach† can be said to be another way to say she was the first girl he â€Å"ever tasted†, in terms of the experience of truly liking someone who seemed special to him. Reputation is used throughout the poem of maybe can be analyzed as a way of trying to remember what he saw of her and his knowing of her existence. The ‘I’ persona is an important tool in terms of Hughes alluding to the very personal nature of his reflection. The poem ‘the shot’ is also one from the collection and conveys Plath as someone different to what her fans saw her to be. As he says that she was deceitful in terms of appearance of a good and decent person/poet. In the poem, the shot is a metaphor of Plath being bullet shout out a gun. It can also e sad that Hughes thinks that he was the one shot. Hughes perspective on paths â€Å"destructive path† is one that she has always been on, saying that she was already a bullet long before she has met him. Followers of Plath as a victim view him as a catalyst for her suicide but in the poem he tries to explain that she was already suicidal as she tried to commit suicide when she was younger. The use of word â€Å"daddy† is one of great importance as it refers to her childish attachment to her father. This is also the title of her famous poem daddy. Hughes also explains that from his perspective, that he himself has become the father figure that she had ways been looking for. Overall, the concept of the two poems depict conflicting perspectives through analysis of ted Hughes’ birthday letters. The text letters from Iwo jima is similarly to birthday letters, a conflicting perspective however of the Japanese however of the Japanese soldiers during the American invasion of to two jima in ww2. It depicts their perspective throughout the turbulent time, showing that even were still human beings with the same universal feelings. Clint eastwood directed the film letters from Iwo Jima in 2006, trying to show an American or non Japanese audience their side of the story or their perspective. Here, a conflicting perspective is shown. Throughout the film, eastwood wants us to empathise with the Japanese perspective f the same terror and emotions that the Americans felt at that time too. The main character is a young Japanese soldier called saigo who is little enthused on fighting and going to war. This is all seen through techniques eastwood input such as flashbacks- which were important in the film. The audience is then able to see how the soldiers were like before the war and what it was like for them when they got conscripted. Their reflections are a huge part in their conflicting perspective and also a great important technique is the Japanese language. Eastwood used the language to give a strong sense of ethnicity and strong sense of tradition. To kill a mocking bird written by Harper lee in 1960 conveys the conflicting perspectives of the treatment of African Americans in Alabama. This conflicting perspective is seen through the eyes of a young white girl, rather than n African American person. The text shows her view o the racial discrimination against the Negroes and the treatment, prejudice and violence they receive. The event takes place that’s how a conflicting perspective is the court case scene, where an African American man is accused of raping a young white girl. The perspective here is not only through the girl, Scout Finch, but also her father Atticus finch which is the lawyer defending the accused. However he took on a case he know that with all the racial discrimination and prejudice around, he would inevitable lose. The fact that he took on the case shows a conflicting perspective of a white American man who has no prejudice against African Americans. The daughter scout finch views the situation on a different level as well as she was basically raised by African American woman and didn’t judge her, as many people did in Maycomb County. She begins to see and understand the prejudice and discrimination when the man is accused of rape as the majority people did not like his race at that time. It was seen as stereotypical to blame him for the rape. The conflicting perspective here is that the perspective o a young white American and her family on the treatment the Negroes received. It can be said that harper lee wanted the audience to challenge their beliefs and see events from the perspective of a young child who is horrified by the treatment of the Negroes.

The Hierarchy Of Gender Is An Issue That The Entire World...

The hierarchy of gender is an issue that the entire world has faced for many years. In the United States, there is a large problem with women being represented in politics. This can be traced back to how children are placed into different hierarchies of males being masculine and females being feminine through their clothes, toys, and more. However, the issue is also caused by the media’s portray of female politicians in comparison to male politicians. The media’s reporting of the 2016 presidential candidates have impacted the way the candidates speak on each other, and the general publics opinion on different candidates. In the United States, people are faced with the hierarchy of gender from childhood. Infant males are designated with blue, seen as superior and masculine, while infant females are given the color pink in all aspects to be seen as feminine. This culture transpires into their young childhood in the forms of toys. Female toys are often domesticated items such as playhouses, kitchen sets, and baby dolls. On the other hand, male toys are more career oriented, construction sets, science experiment kits, policemen and firefighting figurines. As the children grow up, they are trained to think within this gender dichotomy of masculine versus feminine. It is well known that women are not see as prevalent in the United States government. Only twenty-five percent of legislative positions are held by women in the country, there has never been a female president, andShow MoreRelatedGender Roles And Inequality During The 21st Century Essay1425 Words   |  6 PagesIn context of today, gender roles and inequality is controversial and has sparked numerous social debates across the world. However, the role of gender has not just become an issues in the 21st century but in truth has been affecting the lives of men and woman for hundreds of years. 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