and Data Acquisition-DAQ
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Art of Signal Sampling and Aliasing:
"What We See is Not What It Is"!
LabVIEW(VIRTUAL INSTRUMENT ENGINEERING WORKBENCH), a graphical programming language by National Instruments®, is especially suitable for developing automated instrumentation systems using the PC plug-in Data Acquisition (DAQ) boards. It may be effectively used for engineering data acquisition, analysis, and presentation. The plug-in DAQ is a very flexible, computerized measurement of real world analog signals (like with an oscilloscope) and generation of analog signals (like with a function generator) and much, much more. A typical DAQ system may consist of transducers, signal conditioning hardware, plug-in DAQ boards, and LabVIEW® application software. Examples include monitoring and controlling complete measurement (or process) system, etc. The National Instruments® has a Web site: [http://www.natinst.com] with a lot of useful information for us. You may navigate through different options, like Data Acquisition, Tutorial, Signal Conditioning Tutorials, or Glossary, what I will highly recommend.
Demo-box and Lab-PC+ board:
[Lab-PC+ DAQ board] [full Specifications][Configuration Instructions] [I/O Connector]
In our Computer Lab 1st floor (AutoCAD back room) there is a set of computers equipped with Data Acquisition hardware: Lab-PC+ DAQ board [full Specifications][I/O Cnnector], cable, and Demo-box with terminals [Demo-box Diagram] (3 for analog input, 2 for analog output, 1 for counter, and Ground terminal-center pin in Function Generator area), for your own REAL measurements of your own signal sources (± 5V, or 0-10V range). The Demo-box also incorporates, for your convenience, a simple Function Generator, in addition to a trigger switch and digital port LEDs. Now, in addition to computation and simulation, you can do REAL measurements with our personal computers.
Go to Instructions for our First DAQ Lab. Submit a typed report on your measurements and calculated results with appropriate comments and conclusion.
NOTE 1: We have to configure any plug-in DAQ board in order to choose among its different features, and for the board to properly communicate between two "worlds": (1) external "measurement world," or sensor's signals via the external cabling (analog I/O settings configuration); and (2) the DAQ board has to communicate internally with "PC world," via its bus-interface (PC bus interface configuration). Older boards require appropriate DIP switch and jumper settings and the corresponding software settings, while the newer, so called "plug-and-play" or PnP boards, are completely software configurable. Go to Instructions for our First DAQ Lab and see Configuration Instructions for LabPC+ board. Consult the corresponding hardware and software manuals, online help, or National Instruments Web site: www.natinst.com .
NOTE 2: The hardware, operating system, application software, and the corresponding set-ups are being upgraded and modified all the time, so that actual setup may very in time or from computer to computer. However, the instructions given should help you in making necessary adjustments if any. For general questions regarding use of CEET hardware and software including the "Login" procedure, consult the Computing Lab Assistant on duty or any Computer Services staff.
Use LabVIEW Virtual Scope application file 490LVDAQ.LLB,
[Ver.5], especially developed for use with DEMO-BOX [Demo box Diagram].
It will transfer your computer into a color, multifunction, multi-channel oscilloscope.
Copy it for your use, or Open (load) it from the LabVIEW File menu and Run its 490LVDAQ.vi. Practice (play), learn and have fun!
and Signal Conditioning:
In our MEE Labs (2nd floor) we are using Plug-and-Play (PnP) multifunction AT-MIO-16DE-10 boards, which are configured more conveniently by software. We have couple of DAQ set-ups with SCXI signal conditioning to measure vibration of beam (pinned on a potentiometer as an inexpensive sensor), see LabVIEW program, Ver.5 and its Virtual instrument Front panel, and also two units on wheeled carts as "mobile" computerized DAQ systems.
Measure the above two vibration beams' "ringing" and natural frequencies, and the damping ratios (our Text, Eqs. 3.13, 3.15a and 3.17, p.99-100). Submit a typed report on your measurements and calculated results with appropriate comments and conclusion.
From your Text by L.K. Wells and J. Travis, LabVIEW FOR EVERYONE, Prentice Hall PTR, 1997, or
a newer textbook by R.H. Bishop, Learning with LabVIEW , Addison-Wesley, 1999.
Important NOTE:This covers basic LabVIEW and DAQ overview. It is up to you to use your Text and software and our Lab resources as references, and apply your knowledge to your individual lab project. Our TA is given extra assignment and time to "play and master" the LabVIEW and DAQ in order to help you. However the ultimate responsibility is yours. Wish you good luck and success.
A/O/I to control and measure a motor rotation:
[Virtual Instrument] [AT-MIO-16DE-10 board][I/O-Connector]
See also, "Instrumentation with Computerized Data Acquisition for an Innovative Thermal Conductivity Apparatus."
Study the above DAQ hardware setup (see schematics) and LabVIEW software application (see program) about the control and measure of a motor rotation (see description of the complete apparatus). Change the settings for different levels of steady rotations, observe and record the measured values. Switch to harmonic (A/O) voltage mode and observe the corresponding variable rotation of the motor. Record and comment your measurements and observationns.
PS 1: An application of data acquisition and LabVIEW for measurements and control of a research apparatus, with use of: (1) analog input and siganl conditionning for rotation, heating power, and temeperature measurements; (2) analog output for continuous, variable rotation control, and (3) digital and counter/timer inputs/outputs for swithcing and variable-duty-cycle heating power control, is described in: Kostic, M., "Data Acquisition And Control for An Innovative Thermal Conductivity Apparatus Using LabVIEW(c) Virtual Instrument." Laboratory Robotics and Automation Journal, Vol.10, No.2, pp.107-111, Wiley, 1998.
* You may run an experiment over the Internet: Art of Signal Sampling and Aliasing: "What We See is Not What It Is"! provided by Mechyanical Engineering Department at Northern Illinois University, or
* run another experiment over the Internet provided by The National Diagnostic Facility, Remote Laboratory Operation at Illinois Institute of Technology.
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