lab2 - MEEN 260 Texas A&M University Laboratory Manual...

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MEEN 260 Laboratory Manual 1 L AB VIEW P ROGRAMMING P ART I Last updated Sept 5, 2010, R. Langari Introduction This course is designed to equip you to effectively plan and conduct experiments using modern sensing, signal conditioning, and data acquisition techniques. The ability to plan and conduct experiments is a valuable asset to the engineer because testing and experimentation plays an important role in validation of designs, verification of analytical results, and system modeling. The lab exercises in this course primarily involve the use of computer-based data acquisition to monitor the behavior of mechanical, thermal, and fluidic systems. This first lab exercise is designed to introduce you to the concept of computer-based data acquisition and to LabVIEW, a software package developed by National Instruments that will be used extensively in this course. Computer-Based Data Acquisition Often when studying mechanical systems, it is useful to use electronic sensors to monitor certain important system variables. Although the output from these sensors can be viewed using analog instruments such as oscilloscopes (see Figure 1) or voltmeters, it is sometimes preferable to use a computer to view and record data through the use of an Analog-to-Digital conversion card. One particular advantage of using computers in this way is that data can easily be stored and converted to a format that can be used by spreadsheets (such as Microsoft Excel) or other software packages for analysis. Figure 1: An Oscilloscope
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MEEN 260 Laboratory Manual 2 One important step in the data acquisition process is the conversion of analog signals received from sensing instruments to digital representations that can be processed by the computer. Since data must be stored in the computer’s memory in the form of individual data points represented by binary numbers, incoming analog data must be sampled at discrete time intervals and quantized (rounded off) to one of a set of pre- defined values. In most cases, this is accomplished using a Digital-Analog (D/A) conversion card. National Instruments LabVIEW LabVIEW is a software package that provides control and a user interface for the data acquisition process. Figure 2 below is a schematic showing the data flow in the data acquisition process. Lab VIEW PC System I/O Card User Interface Mechanical System Sensor Figure 2: Schematic of Data Acquisition Process LabVIEW plays a pivotal role in the data acquisition process. Through the use of Virtual Instruments (VIs), LabVIEW directs the real-time sampling of sensor data through the I/O card and is capable of storing, processing and displaying the data collected. In most cases, one or more sensors transmit analog readings to the I/O card in the computer. This analog data is then converted to individual digital values by the I/O
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MEEN 260 Laboratory Manual 3 card and is made available to LabVIEW, at which point it can be displayed to the user. Although LabVIEW is capable of some data analysis functions, is often preferable to
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lab2 - MEEN 260 Texas A&M University Laboratory Manual...

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