lab9 - MEEN 260 Texas A&M University Laboratory Manual...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
MEEN 260 Laboratory Manual Texas A&M University 1 A NALOG F ILTER D ESIGN AND I MPLEMENTATION Last Updated Nov. 5, 2010, D. Freeman Purposes of the Experiment 1. To gain experience in utilizing circuit theory to design a filter. 2. To get hands-on experience in building a real filter and testing it. 3. To demonstrate how analog and digital devices may work together. 4. To give students experience in filtering vibration signals from a real device. Theory Passive Filters A passive low pass filter is made up a simple resistor, capacitor circuit as shown below. vi vo R C Figure 1: Passive low pass filter The input voltage may be a time varying signal, say a combination of sinusoidals. (Recall that we can break down arbitrary signals into their sinusoidal components using Fourier Series.) For example the original signal, i v may be written (or approximated by) a three or four or five terms series as .... ) 3 sin( ) 2 sin( ) sin( 3 , 2 , 1 , + + + = t V t V t V v i i i i ω where ,... , , 3 , 2 , 1 , i i i V V V are the amplitudes of the relevant components. These may be 10 volt, 3volts, 1volt, etc, respectively.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
MEEN 260 Laboratory Manual Texas A&M University 2 The higher frequency components are likely noise or fluctuations that we would like to get rid of (filter out.) The above filter produces an output, o v which has the same components as the original signal i v but at reduced amplitude: .... ) 3 sin( ) 2 sin( ) sin( 3 , 2 , 1 , + + + = t V t V t V v o o o o ω where ,.... , , 3 , 2 , 1 , o o o V V V are the amplitudes of the sinusoidal components in o v . In general, ,.... , , 3 , 2 , 1 , o o o V V V are smaller than their counterparts in the input signal, ,... , , 3 , 2 , 1 , i i i V V V . For instance, depending on what values we choose for R and C in the filter, 1 , o V may be very close to 1 , i V , say 98% of this value, but 2 , o V may be about 70% of 2 , i V and so forth. The reason for this is that the filter attenuates each signal according to its frequency; the higher the frequency, the larger the attenuation (hence the smaller the amplitude of the given component in the output signal.) The passive filter shown above is simple and can be in principle used to filter out unwanted components of a given signal. However, since it is made up of entirely passive components (resistors and capacitors) it has to draw current from the input and will also “load” whatever circuit is connected to the output stage. Op Amps can eliminate this problem since in an op-amp; the current that that is drawn from the input stage is very small (since op-amps have large internal resistances.) Likewise op-amps supply current to drive their output and hence minimize the impact of the filter on the output circuits. In this lab we will use active filters using op-amps. Active Filters Using Op-Amps
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

Page1 / 16

lab9 - MEEN 260 Texas A&M University Laboratory Manual...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online