Depth Transducer Protective Assembly - Term Paper Example

Ocean depth probe Electromagnetic compatibility Transducers including sensitivity and other characteristics Depth of the Ocean was unfathomable through decades but due to recent investigations of various scientific instruments, the impossible mission is taking some accelerated pace with the advance of technical era and an assortment of researches and efforts have been specified to fathom the depth of the ocean. In the progress of this mission the need to study the feasibility of the measurement of the depth of the ocean cannot be denied and various compatibilities have to be sorted out for further advancement of the mission. The need for electromagnetic compatibilities can be established with the fact when we know about this. Electromagnetic Compatibility is the capability of electrical and electronic systems, equipments, and devices to operate in their intended electromagnetic environment within a defined margin of safety, and at design levels or performance, without suffering or causing unacceptable degradation as a result of electromagnetic interference (Electronic Project Design 2009). So, various aspects of the Ocean including the natural earth magnetic field at certain depth and the unnatural magnetic fields caused due to human being for their different installment of instruments have to be sorted out so that no interferences occur at the time of ocean depth probe. All types of equipments and systems must be designed to meet electromagnetic compatibility (EMC) specifications. To achieve this aim, special design techniques are necessary. Their effective use in practical applications depends on the understanding of the underlying physical principles. EMC problems involve complex electromagnetic interactions and hence can only be tackled effectively by a combination of experimental and numerical tools (Christopoulos 1992, pp. 239-247) At the time of investigation of the depth of ocean, using the different techniques to explore the ocean for various purposes the movement of the sound wave in the different level of water is different, depending upon the nature of the water quality and various objects and animal present at particular level. Thigpen et. al (1985) have find out that “in marine seismic exploration, an acoustic source disposed beneath the water surface generates a signal which is reflected from layers beneath the ocean floor and received by hydrophones connected to a remote recording unit.” The further investigation explains that “the received reflected signal provides information about the subsurface characteristics of the earth” (Thigpen, B B et al. 1985). This production of sound may interfere if not used properly for the investigation. In an experimental report find out by Thigpen et. al. (1985) shows that “conventional acoustic sources used in marine exploration consist of an array of many air guns or water guns fired simultaneously at pre-selected time intervals.” Explaining the effects by this experiment they say “the shape of the acoustic wave or "signature" of the array is dependent upon the depth at which the array is fired and on the synchronization of the firing instant among all the guns in the array.” They find out some contrast results with word of caution that “if one of the two parameters or both are not substantially the same for all guns the seismic signature will be less than optimum and if the depths of the guns are different, the firing instant of each gun can be changed by fractions of a millisecond so that the resulting acoustic wave front is at maximum amplitude and strength.” JAMSTEC (2007) has provided various techniques to measure the depth of ocean and to find out different aspects of benefit of ocean probe as follows: Sensors to Investigate the Ocean at Different Depths: With the use of CTD (Conductivity (salinity), temperature, depth), an observational instrument to measure the conductivity (salinity), temperature and underwater pressure (depth) of the ocean, electrically, with its deployment in the ocean connected by cable to observe a vertical profile of the temperature and salinity, a useful data is produced to be utilized to analyze the characteristics of seawater and current. Sampling and analyzing Seawater: With the help of water sampler, a pipe with lids at both ends, the samples of seawater at various levels in the ocean, is collected, by lowering it into the water until the desired depth is accomplished, and closing the open lids and raising back the lids. Then the collected water is analyzed using various equipments on board to precisely determine salinity, carbon dioxide for total carbonate, nutrients and dissolved oxygen. This data is useful in the analysis of the characteristics of seawater and current in combination with CTD data. Measuring Ocean Currents with Acoustic Waves: Acoustic Doppler Current Profiler (ADCP) emits acoustic waves, which is highly effected by plankton, drifting particles, and other objects present in seawater. Acoustic waves are used to determine the direction and speed of ocean currents at a particular depth by the Doppler shift with the combination of acoustic waves. The types of ADCPs are “devices that can be moored in the ocean, those that can be lowered from a ship via a cable in a fashion similar to water samplers, and those that are attached to the bottom of a ship's hull in order to perform surveys over wide areas while the vessel is moving.” Sensors to provide Instant Seawater Observations: Although there are times when ocean surveys are performed at a set location, it is more efficient to perform them while cruising. XBTs (eXpendable Bathythermographs) and XCTDs (eXpendable Conductivity, Temperature and Depth) include probes composed of a canister and sensors. The devices are dropped from a ship, and determine temperature for XBT (temperature and salinity for XCTD) using the attached sensors in the same way as CTD. Once deployed in the ocean, depth of probe is determined based on an empirical formula which assumes a probe free-fall during measurement. As their names suggest, the probes are expendable and do not have to be recovered. They therefore have the advantage of facilitating surveys while cruising along or in rough weather. Atmospheric and Oceanic Observation in the Pacific and Indian Oceans (JAMSTEC 2007). The TRITON array (Triangle Trans-Ocean Buoy Network) is a network of observational buoys and is deployed in the western tropical Pacific and eastern Indian Oceans for the purpose of understanding the phenomena of climate variability, such as El Nino in the Pacific Ocean, Indian Ocean Dipole Mode, and the Asian Monsoon. TRITON buoys observe wind, air temperature, humidity, air pressure, precipitation, solar radiation, and ocean currents, as well as water temperature and salinity to a depth of 750 m. The data is transmitted via satellite in real-time, and provided to researchers around the world, and is also utilized by operational meteorological agencies in a world for daily weather forecasts. Meteological/oceanographic data were collected at a total of 18 spots in tropical Pacific Ocean and Eastern Indian Ocean (JAMSTEC 2007). Other methods suggested by JAMSTEC (2007) are “Observation by drifting floats” and “Investigating changes of the Arctic Ocean”. Among them former is about Argo, an international project, with an endeavor “to build a real-time, high resolution monitoring system for upper and middle layers of the world ocean by deploying approximately 3,000 automatic drifting profiling floats, called Argo floats, into the world ocean with average spacing of about 300km.” JAMSTEC (2007) further tells “An Argo float basically drifts at a depth of 1,000 m. It goes down another 1,000 m every 10 days, and then ascend to the surface measuring temperature and salinity profiles. At the surface, it transmits the observed data to land-based facilities via the ARGOS satellite system, and then submerges again to 1,000 m. An Argo float repeats this observation cycle for about 4 years.” With the help of this observation the real time monitoring about the conditions of the ocean is possible. Giving the example of “Investigating changes of the Arctic Ocean” JAMSTEC (2007) confirms that “The Polar Ocean Profiling System (POPS) is an observation system using Argo floats and it was developed for the observations in the Arctic Ocean. A platform for POPS is installed on sea ice and a cable equipped with Argo floats is dropped into the ocean. The float measures water temperature, salinity, and pressure in the range of 10 m and 1,000 m depth.” A report shows that the ice of Arctic is decreasing “at a rate of more than 8% every 10 years, and detailed observation data is required in order to investigate the causes of this rapid change and the climatological role of the Arctic Ocean.” Classical example of multipoint measurement of Ultra Low Frequency (ULF) pressure field was described in early work published in the end of 50's where special reliable string vibration frequency dependence on tension based transducers ("Vibratron") were used for field measurement. Experimental data obtained in several Pacific Ocean regions were obtained and widely used for estimation of pressure fields in practice. To measure natural Ultra Low Frequency (ULF) pressure variations in the ocean two possible types of transducers were tested - specially constructed, with extremely high capacitance to be used with conventional preamplifiers and conventionally used resembling Bruel Kjaer 8100 or 8104 type hydrophones to be used with charge preamplifiers resembling 2651 type B & K. Construction of newly proposed transducers was presented before. The construction of conventional transducers, as it was mentioned, resembles B & K 8100 or 8104 hydrophones, but their capacitance was made a little higher. Special mechanical grids protecting the probe from environmental currents, for both types of transducers used in experiment were developed (Semenov 1994). References: Christopoulos, C 1992, Electromagnetic compatibility. II. Design principles, Nottingham Univ. IEEE Explore 2.6 ISSN: 0950-3366, Current Version Published: 2002-08-06, viewed 8th May 2009, http://ieeexplore.ieee.org/xpl/freeabs_all.jsp?tp=&arnumber=175387&isnumber=4461 Electronic Project Design 2009, EMC standards for appliances, Electronic Project Design, viewed May 10, 2009, http://www.electronics-project-design.com/EMC.html JAMSTEC (Japan Agency for Marine-Earth Science and Technology) 2007, Investigating the ocean, viewed May 10, 2009, http://www.jamstec.go.jp/e/about/equipment/observe/seawater.html Semenov, AG 1994, Ultra low frequency pressure transducer calibration, JOURNAL DE PHYSIQUE IV Colloque C5, supplkment au Journal de Physique 111, Volume 4, mai 1994, viewed May 8, 2009, http://jp4.journaldephysique.org/index.php?option=article&access=doi&doi=10.1051/jp4:1994550 Thigpen, B B, & Crump, Eugene E, Johnston, OA & Mcpeek, NK, & Mcneel, WO 1985, Depth transducer protective assembly, viewed May 8, 2009, http://www.freepatentsonline.com/4637000.html Further matter in the project The images from JAMSTEC CTD Sensor installed under water sampler CTD observation data CTD water sampling system born in MIRAI ADCP installed on the bottom of MIRAI TRITON TRITON buoy Meteological/oceanographic data were collected at a total of 18 spots in tropical Pacific Ocean and Eastern Indian Ocean Meteological/oceanographic data were collected at a total of 18 spots in tropical Pacific Ocean and Eastern Indian Ocean Argo floats meature temperature and salinity profile from 2,000m up to the surface evely 10 days, and then transmit the observed data to land-based facilities via satellites POPS platform installed on the Arctic ice. The platform moves around with the ice. POPS configuration Copyright 2007 Japan Agency for Marine-Earth Science and Technology Source: JAMSTEC (Japan Agency for Marine-Earth Science and Technology) 2007, Investigating the ocean, viewed May 10, 2009, http://www.jamstec.go.jp/e/about/equipment/observe/seawater.html Read More