Lab%203%20ME104%202008

Lab%203%20ME104%202008 - ME 104 Sensors and Actuators...

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ME 104 Sensors and Actuators Laboratory 3 Strain Gage Sensors Department of Mechanical Engineering University of California, Santa (Rev. 2007)
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Introduction In this laboratory, you will build an analog circuit that will enable you to use a strain gage 1 to measure the deflection of a metal ruler. You will then add a noninverting op-amp to amplify the voltage output from your circuit and an analog low-pass filter to remove voltage fluctuations caused by high- frequency noise. You will then use a LabVIEW program to compute the Power Spectrum of the output from your strain gage circuit before and after the low-pass filter. Background Reading 1. Histand and Alciatore, Introduction to Mechatronics , sections 9.3.1-2. Data Sheet , LMC6484 CMOS Quad Rail-to-Rail Input and Output Operational Amplifier , National Semiconductor Corporation. Available online at http://www.national.com/ds/LM/LMC6484.pdf . Experiment #1: Build an Analog Circuit for Obtaining Deflection Measurements Using a Strain Gage In this experiment, you will build an analog circuit for using a 350- Ω strain gage to measure the deflection of a metal ruler. You will then observe the voltage output from your deflection sensor circuit using an oscilloscope. The strain gage, which includes two wire leads, has already been attached (glued) to a bendable ruler. First, listen to your TA discuss these following topic, and take notes: - Importance of Strain Gauge - How does Wheatstone Bridge work? - Op Amp Review 1 Also spelled strain gauge . (Rev. 2007)
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1. Build the analog circuit shown in Figure 3 on an electronic breadboard. Remember to use red wire for positive power connections and black wire for ground connections. Since the strain gage has a resistance of (approximately) R SG = 350 Ω , the resistors 2 on the remaining three arms of the Wheatstone bridge should be matched such that R B1 = R B2 = R B3 = 350 Ω . For this lab, you will actually use R B1 = R B2 = R B3 = 348 Ω or R B1 = R B2 = R B3 = 357 Ω . The voltage output from the Wheatstone bridge is amplified by the LMC6484 operational amplifier, shown on the right side of the dotted line in Figure 3. Although the LMC6484 chip contains four op-amps with identical capabilities (see Figure 4), you will use only op-amp number one at this time (LMC6484 pins 1, 2, and 3). Choose the op-amp resistors such that R 1 = R 3 = 1 M Ω and R 2 = R 4 = 100 k Ω . Then, the voltage gain A V of your op-amp circuit will be: A V = 2 1 R R = 10 Provide power (V CC = +5 volts) and ground (GND) to your circuit board using the “5 V FIXED 3 A” output from your Tektronix PS280 DC Power Supply. 2 The R B resistors are known as “bridge completion resistors”. B (Rev. 2007)
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2. Place the ruler flat on your table so that it is not deflected. Turn on your oscilloscope and set its vertical scale to 50 millivolts/division and its horizontal scale to 400 milliseconds/division. Connect the voltage output V
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Lab%203%20ME104%202008 - ME 104 Sensors and Actuators...

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