Lab_01_LabView_F11

Lab_01_LabView_F11 - Laboratory#1 LABVIEW 7 EXPRESS AND...

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Laboratory # 1 : LABVIEW 7 EXPRESS AND DATA ACQUISITION MAE 650:431 Mechanical Engineering Laboratory Department of Mechanical and Aerospace Engineering Rutgers: The State University of New Jersey Safety 1. Do not begin lab until the teaching assistant has gone over equipment with the students. 2. Before starting check that wires are properly connected and not worn. 3. Only use the floppy disk provided or if using your own disk make sure that it has been scanned for viruses. 4. Do not store data on computer hard drive or make any changes to program. 1. PURPOSE 1. Introduction of the basics of data acquisition and computer controlled instrumentation. 2. Writing a simple LabVIEW programs 3. Program and use a data acquisition boards to measure: a) a time varying signal b) a thermocouple signal. 2. INTRODUCTION Since their inception computers have been common place in the experimental laboratories aiding in the analysis of data, speeding up the time required to conduct calculations, giving a convenient method to store and search through large quantities of data, control instrumentation, data acquisition, etc. The current laboratory will be concerned with the use of computers for instrumentation control and data acquisition. The first question, which may be asked, is how computers communicate with other instruments. Two common methods are serial communication (i.e. RS-232, USB, Firewire) and parallel communication. A third method of transferring data from an experiment to the computer is through a data acquisition (DAQ) board. Assume that you have an instrument, sensor, or device, which outputs a continuous voltage signal (termed an analog signal), which may vary in amplitude with time as shown in figure 1a. In general the voltage may be proportional to some physical property (temperature, pressure, distance) depending on the instrument. In order to convert the analog signal into a digital one, which can be recognized and stored by a computer, an analog-to-digital (A/D) converter must be used. This device converts analog signals to digital (figure 1b) where the signal amplitude is converted to an integer value determined by the resolution of the A/D converter. Obviously as the resolution of the device increases the voltage difference between successive voltage increments decreases leading 1
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Amplitude Time Data Point Number of Bits Figure 1. Schematic of analog (a) and digital (b) signals. to more accurate measurements. In practice sources of random noise limit the ability to increase the resolution simply by using an A/D converter with a larger number of bit resolution. In general the output of the A/D converter is calibrated so that the output recorded by the computer is in the appropriate property measured. The time difference between acquired data points is specified by the sampling rate given as (samples per second), or may be expressed as the A/D converter bandwidth (i.e. 100 kHz) which is the frequency at which measurements can be taken. The time between
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Lab_01_LabView_F11 - Laboratory#1 LABVIEW 7 EXPRESS AND...

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