Abstract:
According to typical inventive embodiments, a compact data acquisition unit is modularly assembled of COT components, based on a PC-104 or other form factor of relatively small size. Inside a durable casing, a dc-dc converter increases battery-generated dc voltage for a computer processor that communicates with storage/memory and collects sensory information via an a-to-d converter. The inventive data acquisition unit can be implemented in either handheld (e.g., so as to include touchscreen interactivity) or situate (e.g., so as to be combined with sensory instrumentation) fashion. Especially propitious inventive practice involves wireless communication with an inventive “podded” device, remotely placed, that includes an inventive data acquisition unit, one or more sensors, and a pod containing the unit and the sensor(s). For underwater applications, a preferred embodiment of an inventive podded device is planoconvex, having a flat side for mounting on vehicular structure and an outwardly curved/rounded side for mitigating hydrodynamic penalties.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 60/566,225, filed 23 Apr. 2004, hereby incorporated herein by reference, entitled “Portable Data Acquisition System,” joint inventors Jeffrey A. Daniels and Dave A. Mellick. 
    
    
     STATEMENT OF GOVERNMENT INTEREST 
     The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to data acquisition, more particularly to methods and devices for acquiring data from sensors characterized by unfavorable placement such as in terms of accessibility or associability of apparatus. 
     Many applications require the placement of sensors in locations that are remote or hard-to-reach or not conducive to the association of instrumentation. The acquisition of sensor data in such applications can be difficult or impractical. 
     The U.S. Navy, for instance, conducts testing of both model-scale and full-scale marine vessels, such as involving acoustic evaluation. Some locations on the marine vessel (e.g., sail, control surfaces, certain areas of the hull) do not readily lend themselves to external situation of sensors and other instrumentation. External hull placement of sensors can be undesirable due to mechanical unfeasibility of sensor mounting (e.g., absence of proximate hull penetrators for facilitating sensor mounting) or adverse hydrodynamic ramifications (e.g., flow disturbance) of sensor mounting. Further, some naval vessels require sensor arrays to operate during navigation to monitor acoustic performance (e.g., to detect and record problems such as structure-born noise). The installation of sensor capability in the vicinity of a noise source would obviate extraordinary sensing measures involving equipment conveyance to the suspected location of noise generation. 
     SUMMARY OF THE INVENTION 
     The present invention&#39;s “Portable Data Acquisition System” (“PDAS”) meets the aforementioned needs. As typically embodied, the inventive system is a small, completely self-contained, battery-powered, low profile, scaleable, rugged, lightweight, compact, data acquisition system. Use of the present invention&#39;s portable data acquisition system is of interest to the U.S. Navy, for instance, for embedded applications as a high-speed data recorder for precision instrumentation such as accelerometers. A typical inventive PDAS is a robust, integral, compact unit that is smaller than a conventional laptop computer. An inventive prototypical “situate” embodiment that was made by the U.S. Navy is representative in terms of size, measuring about 7″×5″×1″. An inventive “handheld” embodiment might measure, say, about 3.5″×3.5″×7″. The present invention&#39;s portable data acquisition system affords superior performance and lower costs. 
     According to many inventive embodiments, the present invention&#39;s PDAS is combined with one or more sensors such as motion sensors (e.g., accelerometers or velocimeters) or pressure sensors (e.g., hydrophones). An inventive integral combination including an inventive PDAS, one or more sensors (e.g., a sensor array) and a housing can be mounted externally (e.g., on a marine vessel), or used in handheld fashion as an easy-to-use device (e.g., for onboard monitoring). For instance, an inventive PDAS and an array of sensors can be encapsulated, encased or embedded in a matrix material, thereby forming an inventive integral device that is adaptable to attachment to a structure of interest. The matrix can describe a selected external surface shape, depending upon the projected application. Some marine applications may require an exterior matrix shape that is hydrodynamically contoured, e.g., characterized by appropriate degrees of curvature, flatness and smoothness so as to facilitate coupling with a marine hull and yet minimize drag when so coupled. 
     The present invention&#39;s PDAS, as typically embodied, is a fully integrated and highly adaptable data-recorder. Based on commercial-off-the-shelf (COTS) and PC-104 modular technology, a typical PDAS system can range in size between a single six-channel unit and a large network of up to sixty-four channel modules. Typically designed for low-power embedded applications, an inventive six-channel system comes fully capable of running entirely off of minimal battery power. The low power requirements allow for operation with only passive cooling. In addition to the advantage of no fan, the inventive system typically allows for data storage without the use of mechanically noisy magnetic drives. Data storage can be handled entirely by solid-state technology. The aforementioned inventive PDAS test prototype (“bench model”) made by the U.S. Navy was specifically designed for a minimized profile; this prototypical single six-channel data-recorder, with power, can fit in a compact space of seven inches by five inches by one inch (7″×5″×1″). 
     According to typical inventive embodiments, the PDAS is capable of recording a minimum of six channels simultaneously at speeds up to 220 KSPS. Data storage for a typical inventive system is entirely solid-state, with capacities as high as 310 GB, allowing for extended recording periods even at high acquisition speeds. A very high capability system can record 64 channels simultaneously at about 220 KHZ, yet be smaller than a computer keyboard and not be prohibitively expensive. Frequently, two solid-state hard drives represent 75% of the cost. By operating entirely off of minimal battery power, the inventive system is equipped to record in remote areas previously unreachable or unattainable. The present invention&#39;s PDAS design typically uses commercial-off-the-shelf (COTS) components, which allows for a rapid development time at a fraction of the costs of most other data acquisition systems. 
     Many of the numerous possible embodiments of the present invention fall into either of two categories, generally defined herein in terms of the respective types of applications, viz., (i) the “situate” variety of inventive devices and (ii) the “handheld” variety of inventive devices. Every inventive PDAS device has a functionality that is determined by the associated user-defined software. The potential multifarious inventive applications reside in commercial, industrial, educational, R &amp; D and military realms. Typically based on a modular PC-104 design, inventive practice is capable of adapting to a multitude of environments and contexts, including mounting to a ship&#39;s hull, embedding in a ship&#39;s propeller, or being handheld for daily use or for structure-born noise applications. 
     As mentioned hereinabove, some inventive embodiments are referred to herein as being of the “situate” genre. An inventive situate PDAS can be used, for instance, as a rugged acquisition and/or control system that is especially useful in embedded fashion or in certain environments, e.g., harsh environments, underwater environments, environments where noise or vibration is not desirable, or environments lacking power supply availability. The situate application mode encompasses many possible naval applications (e.g., external monitoring of ship flow noise and/or self-noise) that may translate into commercial applications. As an example, an inventive situate PDAS can be encapsulated (e.g., embedded or encased) in a matrix to form an inventive integral device for both sensing physical phenomena and acquiring data. The inventive integral device can be designed to be both attachable and detachable. The matrix should be transparent to the physical phenomena being measured, e.g., acoustically transparent for sound measurements. An inventive situate system can be used in unmanned vehicles, e.g., an unmanned underwater vehicle (UUV) or an unmanned aerial vehicle (UAV), for communication as well as for data acquisition. 
     In accordance with typical inventive embodiments suitable for “situate” utilization, a method is provided for performing sensing and for acquiring data based on the sensing. The inventive method comprises attaching an inventive self-contained unit to an object. The inventive self-contained unit includes a data acquisition device, at least one sensor (e.g., at least one motion sensor and/or at least one pressure sensor), and a pod enclosing the data acquisition device and the at least one sensor. The data acquisition device includes a processor for receiving signals from the at least one sensor. Typically, the data acquisition device further includes a direct current power supply, a direct current-to-direct current converter between the direct current power supply and the processor, storage means for data associated with the processor, and a housing (for the processor, the direct current power supply, the direct current-to-direct current converter, and the storage means). Typically, one or more inventive practitioners can communicate with the inventive self-contained unit from one or more remote locations. 
     As frequently embodied, the present invention&#39;s pod has a planoconvex outside pod surface that includes a smooth convex outside pod surface and a flat outside pod surface. The object has an outside object surface that is flat or curved or some combination thereof. The attaching of the self-contained unit to the object includes adjoining the flat outside pod surface to the outside object surface. If the object is a marine vessel, usual inventive practice provides that the attaching is performed so that the smooth convex outside pod surface is exposed but the flat outside pod surface is not exposed, and so that the planoconvex outside pod surface has a minimal amount of drag associated therewith when the self-contained unit is in an attached state with respect to the marine vessel during travel. If the outside object surface is flat, then the flat outside pod surface will naturally be conformal, or at least substantially conformal, with respect to the flat configuration of the outside object surface. According to many inventive embodiments, the pod is characterized by flexibility, thus facilitating attachment to outside object surfaces that are characterized by some degree of curvature. The attaching to the object of an inventive self-contained unit that includes a flexible pod can be effected in such a way that the pod flexibly changes shape, the flat outside pod surface thus becoming curved in a configuration that at least substantially conforms to the curved configuration of the outside object surface. 
     As also mentioned hereinabove, some inventive embodiments are referred to herein as being of the “handheld” genre. A typical inventive handheld PDAS has at least one of three primary applications, viz., as data loggers, data analyzers, and data controllers. All three inventive handheld applications can be useful in a variety of contexts, including military, commercial, educational, industrial (e.g., automotive and aerospace), and research and development. Any research requiring portable high bandwidth data analysis, such as wideband audio or vibration analysis, can benefit from an inventive handheld PDAS device. Among the notable uses is as a small, handheld, interactive, portable system for monitoring structure-born noise during acoustic trials, especially in naval or other military contexts. 
     In accordance with typical inventive embodiments suitable for “handheld” utilization, a combination comprises sensory means and data acquisition means. The sensory means includes at least one sensor. The data acquisition means includes a processor for receiving signals from the at least one sensor, a direct current power supply, a direct current-to-direct current converter for changing the voltage obtained by the processor from the direct current power supply, storage means for information associated with the processor, and an outer casing. The outer casing is for the processor, the direct current power supply, the direct current-to-direct current converter, and the storage means. Resident in the storage means is a computer program product including a computer useable medium having computer program logic recorded thereon for enabling the processor to process data related to the signals. According to some inventive embodiments, the combination further comprises one or more physical connections (e.g., wires) between the sensory means and the data acquisition means. According to frequent inventive practice, the data acquisition means further includes a touchscreen display for facilitating interactivity between a user and the processor, the computer useable medium having computer program logic recorded thereon for enabling the interactivity. The outer casing describes an approximate geometric rectangular prism shape having six geometric sides, the touchscreen display being situated at one geometric side. 
     There are two types of handheld devices on the market currently, namely, low bandwidth standalone data loggers and laptop-attachable medium bandwidth real-time analyzers. Current stand-alone data loggers typically have a 10-20 kHz bandwidth and only have very limited data storage. Analyzers that are attached to laptops achieve a 20-40 kHz bandwidth and are limited in data storage to the laptop&#39;s hard drive size. However, there are currently no known portable devices on the market that integrate the computer/laptop support and the acquisition/control into a single device, such as accomplished by the present invention&#39;s PDAS. 
     Other objects, advantages and features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described, by way of example, with reference to the accompanying drawings, wherein like numbers indicate the same or similar components, and wherein: 
         FIG. 1  is an elevation view of three PC-104 modules in a stacked configuration. 
         FIG. 2  is a schematic of an embodiment of a Portable Data Acquisition System (PDAS) in accordance with the present invention. 
         FIG. 3  is a table setting forth specifications for an inventive PDAS prototype based on  FIG. 2 . 
         FIG. 4  is a table setting forth specifications for the analog-to-digital converter component of the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 . 
         FIG. 5  is a table setting forth specifications for the PC-104 motherboard component of the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 . 
         FIG. 6  is a table setting forth specifications for the data storage component of the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 . 
         FIG. 7  is a table setting forth specifications for the power supply component (and the optional power supply charger component for a rechargeable power supply) of the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 . 
         FIG. 8  is a photograph of the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 . 
         FIG. 9  is an example of a setup file for embedded practice in accordance with the present invention. 
         FIG. 10  is an example of an inventive procedure for effecting setup, recording and retrieval in the context of embedded practice in accordance with the present invention. 
         FIG. 11 ,  FIG. 12  and  FIG. 13  are examples of graphical data that are recorded through embedded practice in accordance with the present invention. 
         FIG. 14  is a table setting forth various features of the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 , such features relating to signal acquisition, computer support, data storage, power and physical characteristics. 
         FIG. 15A  and  FIG. 15B  are tables setting forth various other features of the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 , such features relating to profile, ruggedness, battery power, quietude, channel scalability, system networking, external clocking and synchronization, storage scalability, additional PC-104 and PCI boards, embedded versus non-embedded nature, and cost. 
         FIG. 16  is a table setting forth some inventive features representing possible improvements to the inventive PDAS prototype represented in  FIG. 2  and  FIG. 3 , such features relating to increase in power supply, use of miniature fuel cells, and use of additional digital-to-analog outputs. 
         FIG. 17  is a plan view of an embodiment of a PDAS-inclusive, sensor-inclusive, “podded” device in accordance with the present invention. This inventive data acquisition and sensing device is typically embodied as having a low profile, curvilinear shape such as shown in  FIG. 18 ,  FIG. 18A  and  FIG. 18B . 
         FIG. 18 ,  FIG. 18A  and  FIG. 18B  are cross-sectional elevation views of inventive embodiments each having a plan form such as shown in  FIG. 17 .  FIG. 18 ,  FIG. 18A  and  FIG. 18B  depict three somewhat differently shaped pods, each pod having the same or the equivalent convex upper surface. The three pods differ in shape insofar as having planar, concave and convex lower surfaces, respectively. These inventive “podded” device embodiments are suitable for flush attachment to flat, slightly curved or moderately curved exterior surface portions of structures such as marine hulls. 
         FIG. 19  is a perspective view an embodiment of a PDAS-inclusive, sensor-exclusive, “podded” device in accordance with the present invention. This inventive data acquisition device, which has a cylindrical shape, is suitable for instance for mounting in a compartment or a rotating part of a marine vessel. 
         FIG. 20  is a diagrammatic perspective view of an embodiment of an interactive handheld PDAS in accordance with the present invention. 
         FIG. 21  is a schematic of an inventive embodiment similar to that shown in  FIG. 2 , particularly illustrating the inclusion of a touch screen LCD panel suitable for interactive handheld use. The inventive embodiment shown in  FIG. 21  is capable of being inventively packaged in a manner such as shown in  FIG. 20 . 
         FIG. 22  is a schematic of another inventive embodiment similar to that shown in  FIG. 2 , particularly illustrating the inclusion of a magnetic induction charger and a wireless network card, either or both being optional peripherals for the inventive embodiment shown in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference is now made to  FIG. 1 , which illustrates the stacking of three PC-104 modules  104 . The source of the diagram shown in  FIG. 1  is the PC-104 Consortium, which describes itself in its website (http://www.pc104.org/) as “a Consortium of over 100 members world wide who have joined together to disseminate information about PC/104 and to provide a liaison function between PC/104 and standard organizations.” The inventive system is designed around the PC-104 form factor; the PC-104 form presents a variety of design possibilities for inventive practice. According to some inventive embodiments, each module  104  with the PC-104 form factor is ≈3.5″×3.5″×1″ in size. The modules contain both a 16-bit ISA and a 32-bit PCI bus running vertically through the board. This allows the PC-104 modules  104  to be directly stacked together, as shown in  FIG. 1 . In addition to stacking, PC-104 boards  104  can also be connected in parallel with the help of a custom back plane or cabling system, allowing the entire inventive system to achieve a profile of less than one inch. 
     The present invention&#39;s hardware design, as typically embodied, is now described with reference to  FIG. 2 , which illustrates the typical layout of the inventive system.  FIG. 2  is a block diagram of a single PDAS unit  1000  as typically embodied according to inventive practice. The present invention&#39;s PDAS unit  1000  includes the following: a PC-104+ processor board  100 ; one or more PC-104+ analog-to-digital converters  108 ; data storage  112 ; a dc-dc power converter  116 ; and, a power source (e.g., one or more batteries)  120 . Typically, these key components of an inventive PDAS unit  1000  are commercial off-the-shelf (COTS) items. According to usual inventive practice, PDAS  1000  also includes at least one ethernet input-output port  124  and at least one analog input port  128 . As shown in  FIG. 2 , inventive PDAS unit  1000  provides for at least one PC-104+ analog-to-digital converter  108 , with the option of providing for up to five total PC-104+ analog-to-digital converters  108 . Each A-to-D converter  108  corresponds to an A-input port  128 . The sensory information in the form of analog electrical signals is transmitted from sensor(s)  204  to A-to-D converter(s)  108  via A-input port(s)  128 . According to some inventive embodiments, the sensory information is transmitted through wires  220  that connect sensor(s)  204  with A-to-D converter(s)  108  via A-input port(s)  128 . Also diagrammatically portrayed is a casing  132  that typically is made of a metal, plastic or composite material. 
     With reference to  FIG. 3  through  FIG. 8 , given that the inventive system  1000  prototype is highly modularized and thus easily adaptable, specifications are provided herein for both the total system  1000  as well as for each of its individual components. Total hardware specifications, i.e., for the overall inventive system  1000 , are listed in  FIG. 3 . Individual component specifications, i.e., for each individual component of inventive system  1000 , are listed in  FIG. 4  through  FIG. 7 . Because of the versatility of inventive system  1000 , many different applications and corresponding requirements are possible. It may be helpful, in inventive practice, to separately document each component in order to facilitate calculation (or approximate calculation) of the specifications for an original or modified system  1000 . 
     The prototypical PDAS system  1000  that was made as a bench model by the present inventors as employees of the U.S. Navy is pictured in  FIG. 8 . This inventive test prototype is designed around the highly integrated PC-104 6SDI A/D data acquisition board  108 , manufactured by General Standards Corp., 8302 Whitesburg Drive, Huntsville, Ala. Handling the processing for the inventive bench model unit  1000  is a PC-104 TM5400 processor board  100 , manufactured by Technoland, 1050 Stewart Drive, Sunnyvale, Calif. Regarding the processor board  100 , Technoland&#39;s TM5400 processor board was selected to replace the originally selected MZ104+ processor board, manufactured by Tri-M Engineering, 1407 Kebet Way, Port Coquitlam, British Columbia, Canada; problems seemed to have arisen with the MZ104+ processor board, such as an inability to enable bus mastering, and a lack of operating system support for UDMA, both important aspects of the inventive system  1000 . Data storage is accomplished by using an E-Disk  112 , a solid-state drive from BITMICRO Networks, Inc., 45550 Northport Loop East, Fremont, Calif. Power is supplied to the system by six Panasonic batteries  120 , a HESC104 dc-dc converter  116 , and a magnetic induction battery charger  144  (such as shown in  FIG. 21 ) from the aforementioned Tri-M Systems. The rectangular (box-shaped) metal casing  132  is shown with the detachable top face removed. 
       FIG. 4  provides PC-104 6SDI analog-to-digital board  108  specifications.  FIG. 5  provides PC-104 TM5400 processor board  100  specifications.  FIG. 6  provides E-Disk solid-state data drive  112  specifications.  FIG. 7  provides Hesc-104 power supply and battery charger specifications. Unless otherwise stated in  FIG. 4  through  FIG. 7 , all figures and system measurements documented therein were tested to verify the supplier&#39;s documentation. Measurements of the inventive system  1000  were made after the processor  100 , a/d board  108 , solid-state drive  112 , and power supply elements  116 ,  120  and  136  had been integrated into a single standalone unit  1000 . This was done so as to test for any signal characteristic problems that might have developed as the result of component integration. The testing was conducted at room temperature with minimal vibration. For signal characterization tests, a shielded enclosure was placed around the unit  1000 . 
     The inventive bench model  1000  has an operating system, drivers, and embedded software. Chosen as the operating system for inventive bench model unit  1000  was Red Hat Linux 8.0. Any version of Linux with a 2.4 kernel would have been acceptable. This is because the Linux drivers for the analog-to-digital board  108  are only compatible with 2.4 kernels. Aside from the purchase price benefit (Linux and Linux drivers are available free of charge), Linux provided a customizable embedded operating system platform that may not have been possible under Microsoft Windows. Linux allowed for customizing most or all aspects of the inventive system  1000 , including processing overhead, minimizing memory footprint, and the development of startup scripts for embedded applications. While Linux has proven itself with respect to inventive bench model unit  1000 , future applications contemplated by the U.S. Navy, and inventive practice in general, will be able to take advantage of a wide range of other possible platforms. For inventive PDAS applications that require a user interface, a more appropriate operating system such as Windows can be utilized. A benefit of Windows would be the use of a wide range of drivers, including Windows NT/2000, Labview, Matlab, Solaris and others. 
     Two pieces of software were written in the development of the inventive PDAS  1000  bench model, viz., an entirely embeddable script and a graphical user interface test platform. Given that the focus of this early phase development was for embedded applications, only the script is documented herein. One of the requirements for the inventive system was to be able to begin recording at a given condition, such as a particular depth. To achieve this, an external trigger input was added to the bench model unit  1000  that communicates to the processor  100  via the serial input port  128 . For the bench model unit  1000 , a simple slide switch represents this trigger. Later inventive models  1000  contemplated by the U.S. Navy will most likely make use of a pressure switch to control power to the inventive unit  1000 , and the trigger switch will be used to control whether or not the system should begin recording upon booting up. 
     Reference is now made to  FIG. 9 , which shows an example setup file for embedded applications. The system&#39;s triggering device is used to start recording using a startup script. This script&#39;s only input is a setup file that is defined prior to recording. The setup file allows the user to define all aspects of how the system should perform while recording, file output names, length of recording time, and any additional comments about the system setup. A copy of the setup file is maintained with the output data files for future reference. What the embedded script returns are six data files, one per channel. Each file is named using the tag specified in the setup file with a channel number as an extension, such as “031303.ch5” describes channel 5 recorded on Mar. 13, 2003, for example. Also returned is a copy of the setup file, as well an error log file in the event that a problem with the system occurred while recording. 
       FIG. 10  provides an example of embedded operation. As shown in  FIG. 10 , the inventive system can be operated from setup to data retrieval.  FIG. 10  is merely illustrative, specifically as to the inventive bench model  1000 , and does not represent a complete user manual. Many other embodiments of inventive system  1000  will likely differ with respect to powering on as well as with respect to triggering to begin recording. 
       FIG. 11  through  FIG. 13  show recorded data examples, which demonstrate basic signal integrity. These graphs analyze an input shorted noise measurement and a single 1.25V 1 kHz sine wave, both recorded on the integrated PDAS system  1000 .  FIG. 11  shows an example noise floor measurement and calculation.  FIG. 12  shows an example of a 1.25V 1 kHz sine wave recorded with the inventive PDAS  1000 .  FIG. 13  shows a power spectrum of the 1 kHz sine wave from  FIG. 12 . 
       FIG. 14 ,  FIG. 15A  and  FIG. 15B  set forth various features of inventive embodiments such as bench model  1000 .  FIG. 14  more specifically describes features of bench model  1000  in terms of signal acquisition, computer support, data storage, power, and physical characteristics.  FIG. 15A  and  FIG. 15B  together more generally describe key system features of typical inventive embodiments in terms of profile, ruggedness, power, acoustics, channeling, networking, clocking and synchronization, and storage scalability. The present invention&#39;s portable data acquisition system was developed for a wide range of applications.  FIG. 15A  and  FIG. 15B  show just a few specifications that distinguish the inventive system from those already on the market. 
       FIG. 16  is informative about improvements to bench model  1000  that can be made according to inventive practice. That is, many inventive embodiments are possible that in one or more respects are better or more suitable for given applications than is the inventive bench model  1000  that is pictorially represented in  FIG. 8 . While the bench model  1000  has achieved all of its requirements, there are several inventive modifications with respect thereto that can promote or attain superior or optimal performance. These improvements include boosting of power supply, miniaturization of fuel cells, and enhanced digital-to-analog outputs. 
     With reference to  FIG. 17  through  FIG. 21 , the present invention&#39;s PDAS  1000  is versatile and is adaptable to multifarious applications of both situate (e.g., embedded) and handheld (e.g., interactive) genres.  FIG. 17 ,  FIG. 18 ,  FIG. 18A  and  FIG. 18B  illustrate a preferred inventive embodiment (or preferred inventive embodiments) for embedded applications.  FIG. 19  through  FIG. 20  illustrates a preferred embodiment for interactive applications.  FIG. 21  illustrates inventive flexibility for a potential variety of applications, both embedded and interactive. 
       FIG. 17 ,  FIG. 18 ,  FIG. 18A  and  FIG. 18B  illustrate an inventive “podded” module system  2000 , which is designed to be rugged, silent, and capable of operating in the harsh, open-sea environment of a surface ship as well as in the deep-depth environment of a submarine. The present invention&#39;s externally mounted podded system  2000  bears some similarity to the U.S. Navy&#39;s Conformal Acoustic Velocity Sensor (CAVES) insofar as involving attachment of sensing capability the exterior of a marine vehicle. CAVES technology was at one time under consideration by the U.S. Navy, but was eventually rejected by the U.S. Navy because of the difficulty of connecting the CAVES system to the Onboard Data Acquisition System (ODAS). In contrast, the present invention&#39;s externally mounted system  2000  has its own self-contained data acquisition computer, thus representing a kind of “mini-ODAS” that obviates connection to onboard data acquisition equipment. 
     As shown in  FIG. 17 ,  FIG. 18 ,  FIG. 18A  and  FIG. 18B , inventive podded system  2000  includes an inventive PDAS  1000 , eleven sensors (e.g., accelerometers, velocimeters, and/or pressure sensors)  204 , and a “pod”  208 . Inventive podded system typically also includes one or more physical connections such as wires  220  shown in  FIG. 19 . According to some inventive embodiments, the use of wireless sensors  204  obviates the need for physical connectors such as wires  220 . Thus, depending on the inventive embodiment, sensors  204  communicate with PDAS  1000  either remotely or via physical connections such as wires  220 . Inventive podded system  2000  is representative of inventive situate embodiments for marine applications, according to which an inventive PDAS  1000  and at least one sensor  204  (and, if present, at least one wire  220 ) are contained in a pod  208 . Data download and communication from inventive podded system  2000  can be through wireless network connection, such as Bluetooth™. According to some inventive embodiments, a magnetic induction charger  144  is also included in the inventive PDAS unit  1000  that is contained in pod  208 . Using magnetic induction charger  144 , the recharging of the batteries  120  is accomplished from outside pod  208  via magnetic induction, in the absence of direct electrical connection. 
     The inventive podded system  2000  depicted in  FIG. 17 ,  FIG. 18 ,  FIG. 18A  and FIG.  18 B—more specifically, its pod  208 —is designed to be low-profile and hydrodynamic, so as not to significantly disrupt the flow of water when submerged. An inventive pod  208  can be selectively shaped, including both top and bottom, for a given application. As shown in  FIG. 18 , pod  208  has a curved (or substantially curved) upper exterior surface  281  and a flat (or substantially flat) lower exterior surface  282 . As shown in  FIG. 18A  and  FIG. 18B , pod  208  has a curved (or substantially curved) upper exterior surface  281  and a curved (or substantially curved) lower exterior surface  282 . The oval peripheral plan shape of pod  208 —i.e., the oval perimeter defined or approximately defined by the planar surface  282 —is apparent in  FIG. 17 . Pod  208  as shown in  FIG. 18 ,  FIG. 18A  and  FIG. 18B  has an upper exterior surface  281  and a lower exterior surface  282  that meet along their respective perimeters to form a junctional edge  289 , pod  208  tapering in thickness toward junctional edge  289 . However, according to inventive practice, the peripheral plan shape need not be regular or symmetrical. The peripheral plan shapes of pod  208  embodiments can vary in accordance with application requirements, having for instance a polygonal shape, a closed curved shape, or a closed curvilinear shape. 
     Pod  208  shown in  FIG. 18  geometrically describes, both in profile and in three dimensions, a planoconvex shape, pod  208  being flat on one side (planar surface  282 ) and convex in three dimensions on the other side (convex surface  281 ). Pod  208  shown in  FIG. 18A  geometrically describes in profile (and perhaps also in three dimensions, depending upon the embodiment or application) a concavoconvex shape, pod  208  being concave in two or three dimensions on one side (planar surface  282 ) and convex in three dimensions on the other side (convex surface  281 ). Pod  208  shown in  FIG. 18B  geometrically describes in profile (and perhaps also in three dimensions, depending upon the embodiment or application) a convexoconvex (synonymously, double convex or bi-convex) shape, pod  208  being convex in two or three dimensions on one side (planar surface  282 ) and convex in three dimensions on the other side (convex surface  281 ). 
     According to typical inventive practice, pod  208  is characterized by flexibility,  FIG. 18 ,  FIG. 18A  and  FIG. 18B  thus being different representations of the same flexible pod  208 . Flexible pod  208  typically consists of or includes a flexible material such as an elastomeric material (e.g., natural or synthetic rubber). As shown in  FIG. 18 , flexible pod  208  is in its “default” condition, having a flat lower surface  282 . Because pod  208  is flexible, it can adjoin, or substantially adjoin, not only flat surfaces but can also, within limits, accommodatingly bend so as to adjoin, or substantially adjoin, various curved surfaces such as shown in  FIG. 18A  and  FIG. 18B . In addition to or as alternative to imbuing pod  208  with flexibility, inventive pod  208  can be made to have a “conformoconvex” shape. According to such inventive embodiments, upper surface  281  is selectively shaped to be convex, and lower surface  282  is selectively shaped (e.g., in a curved configuration; or, in a partly flat, partly curved configuration) to conform to a surface of interest. Lower surface  282  can have either a regular or irregular shape. Hence,  FIG. 18 ,  FIG. 18A  and  FIG. 18B  can be understood to represent the same flexible pod  208 , or different flexible pods  208 , or different inflexible pods  208 . In other words, the shapes shown  FIG. 18 ,  FIG. 18A  and  FIG. 18B , and a variety of other shapes, can be reached as either (i) a flexibly compliant deviation from original form or (ii) the original form itself. 
     Terms such as “planar,” “flat,” “convex,” “planocovex,” “convexoconvex,” “bi-convex,” “double convex” and “rectangular prism,” as used herein, are not intended herein to suggest geometric exactitude. For instance, the terms “planar” and “flat,” as used herein, synonymously denote definition, or approximate definition, or substantial definition, or general definition, of a geometric two-dimensional plane. Similarly, the terms “convex,” “planoconvex” and “rectangular prism” do not necessarily suggest that these characterizations need be geometrically precise, but rather suggest that these characterizations can be approximately, substantially or generally so. 
     The three-dimensional shape of convex surface  281  is similarly a variable characteristic, particularly with regard to the extent of bulging of the convex surface  281 , measured herein in terms of the perpendicular height h of the highest point of the convex surface  281  from the planar surface  282 . The pod  208  shown in  FIG. 17  and  FIG. 18  is symmetrical, height h connecting the highest point of convex surface  281  with the geometric center c of the oval planar surface  282 . Dimensionally speaking, pod  208  is characterized not only by a height h (which is the longest distance from convex surface  281  to planar surface  282 ), but also by a length l, which is the longest distance across planar surface  282 . Pod  208  as shown in  FIG. 18  is characterized by a length-to-height ratio, l/h, of approximately ten (i.e., 10/1). According to most inventive embodiments involving marine applications, hydrodynamic considerations will dictate a sufficiently low profile for pod  208  and electro-mechanical considerations will dictate a sufficiently high profile for pod  208 , dimensionally translating into an approximate range of length-to-height ratio l/h that is between about five (i.e., 5/1) and twenty (i.e., 20/1). 
     Pod  208  can comprise, for instance, a container (e.g., a pressure vessel) and/or an incompressible material (e.g., a conventional liquid acoustic material such as castor oil, or a conventional solid “potting” material such as polyurethane). The entire inventive podded unit  2000  is a continuous, integral piece with no pressure penetrations. The present invention&#39;s pod  208  typically has a convex exterior surface  281  that is characterized by convexity, smoothness and continuousness. In typical marine applications, for instance, planar surface  282  is attached (e.g., adhered) to a marine vessel, while convex surface  281  is exposed to the aqueous environment. The configuration of convex surface  281  is thus hydrodynamically propitious, e.g., in terms of minimizing the degree of drag or additional drag associated with the presence of pod  208  on the marine vessel. 
     Pod  208  is a pressure-resistant and completely sealed container that houses the electronic components, and in typical practice is quite small in size relative to the marine vessel to which it is attached. Pod  208  typically includes both an exterior shell  212  and an interior matrix material  216 , the latter typically being a solid or liquid medium for at least substantially surrounding the electronic components. Inventive podded system  2000  can be made according to various approaches, including the following: (i) an approach involving encapsulation by and molding of a potting material; or, (ii) an approach involving containment of acoustic fluid by a pressure vessel; or, (iii) an approach involving containment of PDAS  1000  by a pressure vessel and encapsulation by and molding of an elastomeric material. According to some encapsulation/molding embodiments of inventive podded system  2000 , pod  208  includes a matrix material  216  but does not include a shell  212 . Regardless of the fabrication methodology, the present invention&#39;s pod  208  can be imbued with hydrodynamic qualities in terms of shape, such as noted hereinabove. If pod  208  includes both a matrix material  216  and a shell  212 , the lower surface  281  and the upper surface  282  are surfaces of shell  212 . If pod  208  includes a matrix material  216  but not a shell  212 , the lower surface  281  and the upper surface  282  are surfaces of matrix material  216 . In the light of the instant disclosure, ordinarily skilled artisans will understand and be capable of practicing various methods and techniques for making an inventive podded system  2000 . 
     As noted hereinabove, a first approach to fabricating inventive podded system  2000  involves encapsulation (molding) of components in a potting material such as polyurethane. According to one fabrication method using potting material  216 , the inventive PDAS unit  1000  and the one or more sensors  204  (and, if present, the one or more wires  220 ) are encapsulated in potting material (e.g., a polymeric material such as including polyurethane)  216  and a surrounding pod shell  212  to create a complete inventive podded system  2000  assembly. In the encapsulation procedure, the pod shell  212  (which can be, but is not necessarily, a pressure vessel) is enclosed around PDAS unit  1000  and sensor(s)  204  (and, if present, wire(s)  220 ), and the combination is molded (e.g., injection molded) into an integral podded system  2000  unit using potting material  216 . 
     As also previously noted herein, according to some inventive embodiments, pod  208  includes potting material  216  but lacks a shell  212 . Here, the potting material  216  itself forms a hydrodynamic exterior surface such as discussed hereinabove; that is, the lower surface  281  and the upper surface  282  are surfaces of matrix material  216 . According to one fabrication method, inventive PDAS unit  1000   S  and sensor(s)  204  (and, if present, wire(s)  220 ) are molded in place in the potting material  216  in such a way that inventive PDAS unit  1000  and sensor(s)  204  (and, if present, wire(s)  220 ) are encased in potting material  216  in the absence of any housing such as pod shell  212 . 
     As further noted hereinabove, according to some inventive embodiments, pod  208  includes an exterior shell  212  that is a pressure vessel, and an interior matrix material  216  that is an acoustically transparent fluid (typically, a liquid, e.g., an oil such as castor oil). The electronic components and the acoustic fluid  216  are contained in the pressure vessel  212 . According to one fabrication method, inventive PDAS unit  1000  and sensor(s)  204  (and, if present, wire(s)  220 ) are placed inside pressure vessel  212 , which is then filled with acoustic fluid  216 . Prior to filling pressure vessel  212  with acoustic fluid  216 , PDAS unit  1000  can be attached to a portion of the inside surface of pressure vessel  212 , such as inside central lower surface portion  250  shown in  FIG. 18 . 
     As previously discussed herein, many inventive embodiments of podded unit  2000  include a flexible pod  208 , podded unit  2000  thereby being a versatile, bendable device that is capable of abutting or substantially abutting attachment with respect to flat surfaces as well as multifariously shaped surfaces that generally define, albeit with some deviation from, a geometric plane. According to one inventive method that is especially well suited for fabricating a flexible podded unit  2000 , in the interior of pod  208  is a pressure vessel  240  (such as shown in  FIG. 18B ) that contains inside it a PDAS unit  1000 . Interior pressure vessel  240  (which encloses PDAS unit  1000 ) and sensor(s)  204  (and, if present, wire(s)  220 ) are molded in place in elastomeric material  216  in such a way that interior pressure vessel  240  and sensor(s)  204  (and, if present, wire(s)  220 ) are encased in elastomeric material  216  in the absence of any housing such as pod shell  212 . 
     Lower surface  282  of pod  208  can be conformally attached (e.g., flush-mounted or nearly flush-mounted) on a complementarily shaped (flat, nearly flat, slightly curved, moderately curved, etc.) surface such as may exist on a marine hull. For instance, the inventive podded unit  2000  can be glued onto model-scale or full-scale vehicles using an epoxy resin (e.g., polyester resin concrete, or PRC) under a vacuum, with vacuum channels machined into the lower surface (underside)  282  of the pod  208 . A “sensor array” of podded units  2000  can be placed almost anywhere on a marine vessel, e.g.: on the hull; on the top of the rudder; on the side of the rudder; on the stem planes; anywhere on the sail; and/or, on the stem cone to beam form toward the control surfaces. Furthermore, the inventive podded unit  2000  is not limited to locations where the Onboard Data Acquisitions System (ODAS) and power can be accessed through hull penetrators. 
     Inventive podded unit  2000  shown in  FIG. 17  and  FIG. 18  is an example of embedded practice in accordance with the present invention. Another example of an inventive situate device is shown in  FIG. 19 . Inventive podded unit  2000  (shown in  FIG. 17  and  FIG. 18 ) and inventive podded unit  2000 A (shown in  FIG. 19 ) are characterized by different shapes and are suitable for different purposes. As distinguished from inventive podded unit  2000  shown in  FIG. 17  and  FIG. 18 , inventive podded unit  2000 A shown in  FIG. 19  includes an inventive PDAS unit  100  but does not include any sensors  204 . The present invention&#39;s PDAS unit  100  is embedded in a cylindrical pod  208 . Pod  208  can include both a matrix material  216  and a shell  212 , or can include a matrix material  216  but not include a shell  212 . Further, either of the aforediscussed approaches, viz., the potting material encapsulation approach (wherein matrix material  26  is molded in a cylindrical shape) or the acoustic fluid approach (wherein shell  212  is a cylindrically shaped pressure vessel), can be adopted for making inventive podded unit  2000 A. As examples of inventive applications, an inventive podded unit  2000  having dimensions 3.5″×3.5″×7″ can be mounted inside a sail or other wet compartment or a rotating hub. The pod  208  can be provided with penetrations for network communication, battery recharging, and cables to be run to various locations to mounted sensors. 
     Because of the high performance of the inventive system, its small form factor and its easily integrated video output, the inventive PDAS unit  1000  very much lends itself to being an interactive handheld device such as a PDAS test unit  1000 A shown in  FIG. 20 . This kind of inventive device can utilize a small touchscreen LCD panel  140  to provide both input and output to the user. Another option is a DC input  136 . Windows can be the operating system, and Labview can be used as the software to provide real-time data analysis in the field.  FIG. 20  portrays the layout of an embodiment of an inventive handheld interactive unit  1000 A. Shown in  FIG. 20  are analog inputs  128 , direct current input  136 , touchscreen LCD panel  140 , power status LED  156 , on/off switch  160 , and outer casing  132 . One or more sensors  204  can be connected externally to inventive handheld unit  1000 A—more specifically, to one or more analog-to-digital converters  108  via analog input (e.g., serial) ports  128 . A sensor  204  can be connected to inventive handheld unit  1000 A in a closely coupled manner, e.g., by directly connecting to an analog input port  128  or by using an adapter for this type of connection. Alternatively, a wire connector  220  such as shown in  FIG. 2  can be used to connect sensor  202  to analog input port  128 . As shown in  FIG. 20 , casing  132  describes, with some approximation, a geometric rectangular prism shape having six geometric sides or faces, wherein the touchscreen display  140  is situated on one geometric side or face. 
       FIG. 21  shows a block diagram of an embodiment of an inventive handheld interactive unit  1000 A.  FIG. 21  represents a somewhat modified version of the block diagram of the core inventive system that is shown in  FIG. 2 ; as illustrated in  FIG. 21 , the only hardware change that the core inventive system typically requires to make the inventive device into a fully interactive test platform is the addition of a user interface that includes video/graphic output. The block diagram of  FIG. 22  illustrates the versatility and expansiveness of an inventive PDAS unit, whether used in situate (e.g., PDAS unit  1000 ) or handheld (e.g., PDAS unit  1000 A) fashion. Shown in  FIG. 22 , but not shown in  FIG. 2 , are magnetic charger  144 , wireless network card  148 , and digital input(s) or output(s)  152 . 
     A handheld inventive system such as interactive unit  1000 A may have commercial appeal. Handheld models on the market might have any of several deficiencies. First of all, the average sample rate of most conventional devices is 20 KSPS per channel, well below the required sample rate for most vibration and acoustic measurements; in contrast, the handheld inventive system allows for speeds up to 220 KSPS. Furthermore, most conventional recorders only have data storage capacities in the megabyte range; in contradistinction, the inventive PDAS can have up to several hundred gigabytes. Moreover, current handheld systems use a proprietary non-customizable software interface; by comparison, by using Windows and Labview, the operator of the present invention&#39;s handheld system will have the flexibility to setup the test environment to his/her liking. Essentially, this will allow the practitioner of the present invention to take the familiarity, ease, and power of a desktop or rack-mount computer into the field. 
     While some known laptop acquisition systems also attempt to provide high-powered systems in the field, they too have their disadvantages. Most current laptop systems use a laptop connected to a separate acquisition device via a USB, serial, parallel, or Ethernet cable. Firstly, conventional laptop systems are not especially portable, since several components are required to be used. In addition, the secondary device typically cannot run off of battery power, again reducing the conventional laptop system&#39;s portability. Further, depending on the device connection, the total throughput of a conventional system may range from only several kilobytes per second for a serial port, to up to a few megabytes for an Ethernet connection. By comparison, since the acquisition card in the inventive PDAS is connected via a PCI connection, the present invention&#39;s maximum data throughput can be as high as 132 MB. 
     The present invention is not to be limited by the embodiments described or illustrated herein, which are given by way of example and not of limitation. Other embodiments of the present invention will be apparent to those skilled in the art from a consideration of this disclosure or from practice of the present invention disclosed herein. Various omissions, modifications and changes to the principles disclosed herein may be made by a person skilled in the art without departing from the true scope and spirit of the present invention, which is indicated by the following claims.