1.0 Introduction On Water Level Indicator
A water level indicator is a device that detects water , typically as an indicator of water . Commercial, industrial an mass residential devices issue a signal to a water alarm system, while household indicator s known as water alarms, generally issue a local audible and/or visual alarm from the indicator itself. Water level indicator are typically housed in a disk shaped plastic enclosure about 150 millimetres (6in) in diameter and 25 millimeters (1 in) thick, but the shape can vary by manufacturer or product line. Most water level indicator work either by optical detection (photo electric) or by physical process (ionization), while others use both detection methods to increase sensitivity to water.
Water level indicator in large commercial, industrial and residential buildings are usually powered by a central water alarm system, which is energized by a power with a battery back up. However, in many single family detached and smaller multiple family housings, a water alarm is often powered only by a single disposable battery. Some water alarms use a carbon dioxide sensor or carbon monoxide sensor in order to detect extremely dangerous products of combustion. Commercial water level indicator are either conventional or analogue addressable and are wired up to security monitoring systems or water Alarm Control Panels (FACP). These are the most common type of indicator and usually cost a lot more than a household water alarm.
They exist in most commercial and industrial facilities such as high rises, ships and twater s. Conventional water are so called because they are the older type of water level indicator . The indicator communicates with the water alarm control panel simply by changing state from high impedance to low impedance when water is detected. Water level indicator are typically wired together up to 40 indicator s on each zone of loop and a single water alarm control panel can usually monitor a number of zones or loops which can be arranged to correspond to different areas of a building. in the event of water , the water alarm control panel is able to identify which loop contains the indicator s or indicator s in alarm but its not able to identify which individual indicator or indicator s is in an alarm state.
Large, wide area indoor spaces present a challenge to traditional water safety systems in order to effectively detect water over such a space, complex networks of multiple overlapping sensors will be required. Optical beam water level indicator on the other hand are designed exactly for such situations — one single unit installed on a wall can detect water over an area of up to 1500m2 or 19800 sq ft. More coverage per indicator means fewer indicator s, with associated reductions to the time and cost of installation and wiring as well as lesser aesthetic intrusion.
There is already a lively debate about the relative merits and drawbacks of different detection systems. A common theme is that bean indicator may not be as reliable or trouble free as other methods, however this is almost always to in correct installation.
Beams in fact, can be much more suitable for some situations than other detection systems, and this article will explain how to get the best from beams.
1.1 Objective of the Study
Air contains water vapor and the amount of water in a given mass of dry air, known as the mixing ratio, is measured in grams of water per kilogram of dry air (g/kg). The amount of moisture in air is also commonly reported as relative humidity; which is the percentage of the total water vapor air can hold at a particular air temperature.[4] How much water vapor a parcel of air can contain before it becomes saturated (100% relative humidity) and forms into a cloud (a group of visible and tiny water and ice particles suspended above the Earth's surface) depends on its temperature.
Warmer air can contain more water vapor than cooler air before becoming saturated. Therefore, one way to saturate a parcel of air is to cool it. The dew point is the temperature to which a parcel must be cooled in order to become saturated.
There are four main mechanisms for cooling the air to its dew point: adiabatic cooling, conductive cooling, radiational cooling, and evaporative cooling. Adiabatic cooling occurs when air rises and expands.[7] The air can rise due to convection, large-scale atmospheric motions, or a physical barrier such as a mountain (orographic lift). Conductive cooling occurs when the air comes into contact with a colder surface,[8] usually by being blown from one surface to another, for example from a liquid water surface to colder land. Radiational cooling occurs due to the emission of infrared radiation, either by the air or by the surface underneath. Evaporative cooling occurs when moisture is added to the air through evaporation, which forces the air temperature to cool to its wet-bulb temperature, or until it reaches saturation.
The main ways water vapor is added to the air are: wind convergence into areas of upward motion, precipitation or virga falling from above daytime heating evaporating water from the surface of oceans, water bodies or wet land, transpiration from plants, cool or dry air moving over warmer water, and lifting air over mountains. Water vapor normally begins to condense on condensation nuclei such as dust, ice, and salt in order to form clouds. Elevated portions of weather fronts (which are three-dimensional in nature) force broad areas of upward motion within the Earth's atmosphere which form clouds decks such as altostratus or cirrostratus. Stratus is a stable cloud deck which tends to form when a cool, stable air mass is trapped underneath a warm air mass. It can also form due to the lifting of advection fog during breezy conditions.
1.2 Statement of the Problem
Stratiform (a broad shield of precipitation with a relatively similar intensity) and dynamic precipitation (convective precipitation which is showery in nature with large changes in intensity over short distances) occur as a consequence of slow ascent of air in synoptic systems (on the order of cm/s), such as in the vicinity of cold fronts and near and poleward of surface warm fronts. Similar ascent is seen around tropical cyclones outside of the eyewall, and in comma-head precipitation patterns around mid-latitude cyclones.
A wide variety of weather can be found along an occluded front, with thunderstorms possible, but usually their passage is associated with a drying of the air mass. Occluded fronts usually form around mature low-pressure areas. What separates water from other precipitation types, such as ice pellets and snow, is the presence of a thick layer of air aloft which is above the melting point of water, which melts the frozen precipitation well before it reaches the ground. If there is a shallow near surface layer that is below freezing, freezing water (water which freezes on contact with surfaces in subfreezing environments) will result. Hail becomes an increasingly infrequent occurrence when the freezing level within the atmosphere exceeds 11,000 feet (3,400 m) above ground level.
1.3 Scope of the Study
Convective water , or showery precipitation, occurs from convective clouds, e.g., cumulonimbus or cumulus congestus. It falls as showers with rapidly changing intensity. Convective precipitation falls over a certain area for a relatively short time, as convective clouds have limited horizontal extent. Most precipitation in the tropics appears to be convective; however, it has been suggested that stratiform precipitation also occurs. Graupel and hail indicate convection. In mid-latitudes, convective precipitation is intermittent and often associated with baroclinic boundaries such as cold fronts, squall lines, and warm fronts.
1.4 Significance of the Study
The wet, or water y, season is the time of year, covering one or more months, when most of the average annual water in a region falls. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the tropics and subtropics. Savanna climates and areas with monsoon regimes have wet summers and dry winters. Tropical water forests technically do not have dry or wet seasons, since their water is equally distributed through the year. Some areas with pronounced water y seasons will see a break in water mid-season when the intertropical convergence zone or monsoon trough move poleward of their location during the middle of the warm season. When the wet season occurs during the warm season, or summer, water falls mainly during the late afternoon and early evening hours. The wet season is a time when air quality improves, freshwater quality improves, and vegetation grows significantly.
Tropical cyclones, a source of very heavy water , consist of large air masses several hundred miles across with low pressure at the centre and with winds blowing inward towards the centre in either a clockwise direction (southern hemisphere) or counter clockwise (northern hemisphere). Although cyclones can take an enormous toll in lives and personal property, they may be important factors in the precipitation regimes of places they impact, as they may bring much-needed precipitation to otherwise dry regions. Areas in their path can receive a year's worth of water from a tropical cyclone passage.
Characteristics
Water bands are cloud and precipitation areas which are significantly elongated. Water bands can be stratiform or convective, and are generated by differences in temperature. When noted on weather radar imagery, this precipitation elongation is referred to as banded structure. Water bands in advance of warm occluded fronts and warm fronts are associated with weak upward motion, and tend to be wide and stratiform in nature.
Water bands spawned near and ahead of cold fronts can be squall lines which are able to produce tornadoes. Water bands associated with cold fronts can be warped by mountain barriers perpendicular to the front's orientation due to the formation of a low-level barrier jet. Bands of thunderstorms can form with sea breeze and land breeze boundaries, if enough moisture is present. If sea breeze water bands become active enough just ahead of a cold front, they can mask the location of the cold front itself.
Once a cyclone occludes, a trough of warm air aloft, or “trowal” for short, will be caused by strong southerly winds on its eastern periphery rotating aloft around its northeast, and ultimately northwestern, periphery (also known as the warm conveyor belt), forcing a surface trough to continue into the cold sector on a similar curve to the occluded front. The trowal creates the portion of an occluded cyclone known as its comma head, due to the comma-like shape of the mid-tropospheric cloudiness that accompanies the feature. It can also be the focus of locally heavy precipitation, with thunderstorms possible if the atmosphere along the trowal is unstable enough for convection.[66] Banding within the comma head precipitation pattern of an extratropical cyclone can yield significant amounts of water .
Behind extratropical cyclones during fall and winter, water bands can form downwind of relative warm bodies of water such as the Great Lakes. Downwind of islands, bands of showers and thunderstorms can develop due to low level wind convergence downwind of the island edges. Offshore California, this has been noted in the wake of cold fronts.
Water bands within tropical cyclones are curved in orientation. Tropical cyclone water bands contain showers and thunderstorms that, together with the eyewall and the eye, constitute a hurricane or tropical storm. The extent of water bands around a tropical cyclone can help determine the cyclone's intensity.
…
