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PC-Based vs. Stand-Alone Instrumentation
Compare for yourself....
Autonomy |
Universality |
Functionality |
Expandability |
Connections
Troubleshooting |
A/D, Signal Processing & Control |
Speed |
Accuracy
Autonomy
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PC-Based Systems
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Daytronic "Front-End" Systems
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Completely STAND-ALONE to ensure maximum system uptime; when multiple units are networked,
each node operates as an independent stand-alone system
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All data acquisition and control functions TRANSPARENT TO THE COMPUTER and continue without loss of configuration or data when the computer is down
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Universality
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PC-Based Systems
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Daytronic "Front-End" Systems
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Specific cards limited to particular transducer types and ranges
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FIXED ARCHITECTURE: The system is tied to a specific computer platform, and requires upgrading with each new computer generation
(high potential for rapid obsolescence)
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Accepts mixed inputs from VIRTUALLY ALL TRANSDUCERS for an exceptionally wide range of measurements
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Interfaces with VIRTUALLY ANY COMPUTER
under any operating system and programming language; positioned for compatibility with new computers as they become available
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OPEN-ARCHITECTURE LINKAGE makes real-time and historical data accessible via computer-independent third-party
software (Autonet, Labview, Lab Windows, Paragon, etc.)
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Functionality
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PC-Based Systems
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Daytronic "Front-End" Systems
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Depends on available computer hardware and software resources; often requires
multiple vendors and extensive programming
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Data displays are dependent on software; simultaneous display of multiple screens normally requires multiple computers, while display modifications usually require halting the process and reprogramming
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Standard operating firmware means NO PROGRAMMING: Simple English mnemonics initiate user-selected setup and run-time functions; the system can be up and running in a very short time
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SINGLE VENDOR, single responsibility
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Larger systems support MULTIPLE INDIVIDUALLY CONFIGURABLE DATA DISPLAYS with adjustable update rates; display formats may be created or modified by the operator
even while the measured process is running
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Expandability
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PC-Based Systems
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Daytronic "Front-End" Systems
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Depends on available computer expansion slots (even with an expansion chassis, you can quickly run out of slots!)
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Addition or replacement of cards entails
opening the computer--and all the risks associated with this action!
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INDEFINITELY EXPANDABLE through addition of mainframe racks and/or networking of individual "on-site" units
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Quickly and easily RECONFIGURAIBLE IN THE FIELD, with no computer programming; cards can be added or replaced WITHOUT TAKING THE MAINFRAME APART
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Connections
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PC-Based Systems
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Daytronic "Front-End" Systems
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Special transducer connection panels often required, with difficult access and cable hookups
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Proximity to process sensors limited by computer location and power source; usually requires a maze of cables back to the central computer
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DIRECT TRANSDUCER CONNECTIONS from rear of instrument, allowing quick disconnect while on-line
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Remote data collection and control units can be located CLOSE TO PROCESS SENSORS, greatly reducing costly and troublesome cable connections
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DC-powered units for vehicle operation
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Troubleshooting
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PC-Based Systems
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Daytronic "Front-End" Systems
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A/D, Signal Processing & Control
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PC-Based Systems
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Daytronic "Front-End" Systems
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ALL DATA PROCESSING PERFORMED BY THE COMPUTER;
this restricts the computer's time and ability to perform other critical tasks, while
adding significantly to the total software overhead and programming demands
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Critical control response time is difficult to determine because of variable processing speed and other factors
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SUPPLIES THE HOST COMPUTER WITH FINISHED ENGINEERING-UNIT DATA WHEN (AND ONLY WHEN) REOUESTED SO ALL THE COMPUTER NEEDS TO DO IS ASK FOR IT
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PROCESSING FUNCTIONS include automatic conversion to floating-point format; maintaining individual multichannel data displays; archiving and playback of historical data; limit checking and alarming; linearization and calibration; cross-channel calculations; analog and digital control outputs (including high-frequency analog output and PID loop control) with
precisely determined response times; counter/timer functions; on-line SPC; repon generation; and much
more--all completely independent of the computer
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Speed
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PC-Based Systems
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Daytronic "Front-End" Systems
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WITH CONVENTIONAL PC'S, YOU TRADE
OFF SOFTWARE OVERHEAD FOR FINISHED-ANSWER THROUGHPUT
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Unless you're exclusively interested in high-speed dynamic analysis, a fast sampling rate yields "raw data" only; to produce an acceptable "finished answer
rate--especially when a large number of channels must be processed--typically consumes 25% to 100% of the PC's time and resources, and also has an adverse effect on the screen update rate
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FINISHED-ANSWER PROCESSING (INCLUDING DATA DISPLAY AND REAL-TIME PROCESS CONTROL)
MAKES NO DEMANDS AT ALL ON THE HOST COMPUTER
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For systems with over 60 measurement inputs or with complex calculations, throughput of finished-answer data is
typically FASTER than the comparable PC-based system--and this includes computation of true average of highly dynamic variable--with no display update delay
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Accuracy
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PC-Based Systems
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Daytronic "Front-End" Systems
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Electrically noisy environment limits accuracy of sensitive input signals and the reliability of associated control functions
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Sampling of dynamic signals with unrestricted input bandwidth can produce
significant aliasing errors
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Lack of specific calibration functions requires user to improvise his own techniques, thereby introducing overall measurement inaccuracies
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Features the proven reliability of TRUE ANALOG SIGNAL CONDITIONING, with accurate, remotely sensed excitation and with separate amplifier, 3-pole filter, and selectable digital filter for each input
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LOW-NOISE FRONT-END ENVIRONMENT ensures drift-free measurement and dependable control action
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Optional synchronous data collection yields VIRTUALLY ZERO TIME SKEW
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Accurate BUILT-IN CALIBRATION for a wide variety of sensors
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