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some use a photocell looking for a light source thru the air
some use a nuclear source of ionizing radiation to ionize the air then measure its conductivity
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What size of wire used in smoke alarm system?
Different types of smoke alarms require different sizes of wire. Conductors connecting a mains-powered alarm to electricity might be sufficient for 20 amps (i.e., 12 AWG), while signaling wires could be 20 AWG, more or less, depending upon the current of the latching load and the round-trip distance from the panel to the alarm sensor.
What way can a sensor be used in a car?
A sensor can be used on a car for a number of things car alarm, video sensor, traffic sensor Type your answer here...
What is a function of a transistor in a fire alarm circuit?
A special sensor or transducer called a thermistor is used to detect an increase in the temperature of the surrounding air whenever smoke is produced by a fire. A different type of sensor is used to detect an increase in the size and density of particles in the surrounding air after it has been contaminated by smoke from a fire. Either sensor gives an output in the form of an increase in voltage whenever it detects an increased temperature and/or smoke particles. That increase in voltage is fed to the base of a transistor. When the voltage to its base increases, the current from the transistor's emitter to collector (or from its collector to emitter) increases and that increase in current operates the alarm. In other words, in a fire alarm circuit, the transistor acts as a switch which turns on the alarm whenever a sensor or transducer detects the presence of a fire, else it remains off.
What all is found in a fire alarm circuit?
There are many possible types of sensors and circuits for fire alarms. If you mean alarm SENSOR circuit, there are often two types to a smoke sensor: a power circuit and a sensor trip circuit. The power circuit supplies power to the sensor for its internal electronics and the sensor trip circuit is a separate pair of wires to the dry contacts that open or close to signal an unusual smoke or heat condition. Various supervisory means are used to determine whether the sensor is properly connected and operating (i.e., no open circuit or short circuit), such as an "end-of-line" (EOL) resistor, or a modulated, query-response or polling signal. At the alarm-panel end, each circuit would have its own connection for a zoned system: one pair for the power and the other pair for the trip circuit. Other types of circuits include heat detectors, manual pull stations, sprinkler flow switches, supervisory tamper switches, and other types of inputs. Output circuits could include lights, sirens, bells, door-closing signals, HVAC control signals (on or off), elevator return commands, remote signalling to monitoring centers, etc. Many residential fire alarm circuits now include one or more wires to connect the otherwise independent smoke alarms so that any one of them will trigger all the others, for better sound penetration of the alarm annunciation.
How is radioactivity used in smoke detectors?
There are two types of smoke detectors:Photoelectric Smoke detectorsIonizing Smoke DetectorsIonization smoke detectors are more commonly used. The smoke detector uses an ionization chamber and a source of ionizing radiation to detect smoke.Alpha particles are emitted from from the chamber, which ionize the air, so that the air conducts electricity and a small current flows.If smoke enters the alarm, it absorbs the alpha particles causing the current to reduce, and the alarm sounds.Generally, smoke detectors use a weak source made of Americium-241 (241Am95).Note: Alpha particles are the nuclei of a Helium Atom (4He2).
Your smoke alarm goes off without fire occuring?
If the smoke alarm goes off because of steam or smoke from cooking, the alarm should be moved to a better location or a different type of sensor used. It is very dangerous to have too many false alarms because people tend to ignore them, until the one time it really is a fire, and then it may be too late. If a smoke detector makes an intermittent "chirp", not a loud and continuous alarm, it may be signalling that it is time to replace the battery. Smoke detectors should be replaced every ten years, even if they still seem to be working, since they are only designed for a limited useful lifetime.
How are alpha particles used in smoke alarms?
Alpha radiation is emitted from the amercium button in a smoke detector. When smoke goes into the smoke detector it blocks the stream of alpha particles emitted from the americium. That triggers an alarm.
When is a smoke alarm used?
so that when there is a fire in their house or something and people are unaware of it....the smoke will start the alarm and then the person will do something about it...it basically lets them know that there is a fire.
What is a smoke alarm made out of?
Most smoke detectors work either by optical detection (photoelectric) or by physical process (ionization), while others use both detection methods to increase sensitivity to smoke. For the alarm part, in many single family detached and smaller multiple family housings, a smoke alarm is often powered only by a single disposable battery. An optical detector is a light sensor. When used as a smoke detector, it includes a light source (incandescent bulb or infrared LED), a lens to collimate the light into a beam, and a photodiode or other photoelectric sensor at an angle to the beam as a light detector. In the absence of smoke, the light passes in front of the detector in a straight line. When smoke enters the optical chamber across the path of the light beam, some light is scattered by the smoke particles, directing it at the sensor and thus triggering the alarm. An ionizing detector type of detector is cheaper than the optical detector; however, it is sometimes rejected because it is more prone to false alarms than photoelectric smoke detectors. It can detect particles of smoke that are too small to be visible. It includes about 37 kBq or 1 µCi of radioactive americium 241, corresponding to about 0.3 µg of the isotope. The radiation passes through an ionization chamber, an air-filled space between two electrodes, and permits a small, constant current between the electrodes. Any smoke that enters the chamber absorbs the alpha particles, which reduces the ionization and interrupts this current, setting off the alarm. From Wikipedia.
Names of different alarm systems?
Answers from Experts:There are four types of alarms used for the security of the house:1.Burglar alarms2.Smoke alarms3.Heat alarms4.Carbon monoxide alarms1.BURGLAR ALARMS:Burglar Alarms can be broadly categorized into 2 main groups:Know more about different alarm systems at link:http://www.gharexpert.com/articles/Security-Alarms-763/Which-various-types-alarms-used-se_0.aspx----
What three types of sensors are used in a greenhouse weather station?
Light sensor temperature sensor Humidity sensor these can all be used in a greenhouse
How many type of smoke alarms are there?
Smoke AlarmsTwo types of smoke alarms are available for home use. They are: The ionization type, which is the simplest, most commonly used and is usually the least expensive. This type reacts quicker to flaming fires.The second type is photo-electric, which reacts quicker to smoldering fires. Commercial photoelectric smoke alarms can also be used to cover large areas using point-to-point lasers.Other types of fire detectors, which are most often used in businesses and public buildings, are:Thermal - detect heat in a roomManual - has to be manually pulled to set off the alarm.Water-flow - Activated when a fire sprinkler has started flowing.Interconnected - This is a system that interconnects all the smoke alarms in a building so when one goes off, they all go off.Hard-wired Control Panel - Smoke and heat sensors (and other fire sensors) that are connected to a central panel where any sensor will set off a facility alarm and be communicated to fire dispatchers.The Lighter SideThere are two types: the one that works and the one that doesn't. There is the one you bought and installed, and the one you wish you had.
