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-761701-5445301555752012956900096000730005673725center242009600015009968191859Wentworth Institute of Technology | 11/14/1400Wentworth Institute of Technology | 11/14/144761781centerELEC 320-03Andrews, David L.00ELEC 320-03Andrews, David L.-129540centerLow Pass Filter Lab Report00Low Pass Filter Lab Report47625007610475A test structure for the effect of changing resistance within a low pass filter circuit00A test structure for the effect of changing resistance within a low pass filter circuitAbstract:The objective of the Low pass filter lab is to test the effect of changing the resistance in a low pass filter circuit. A low pass filter circuit, consisting of one resistor and one capacitor is created and tested. The Frequency of the electronic signal is then swept while the Amplitude is measured to capture any affects. Introduction:A low pass filter is an electronic circuit which attenuates and input signals which are above a certain cutoff frequency. These filters are often used in audio applications, also known as a treble cut filter. Here we test how the resistor in a low pass filter affects. Experimental ProcedureSet Up:Using a split alligator wire, hook up a waveform generator to the positive and negative terminals of the shown circuit. Attach the multi-meter positive terminal in between the resistor and capacitor, as well as its negative terminal to the ground. Procedure:Using the given “Frequency Sweep” labview program, sweep the frequency of the input signal from 10 to 100000 HzAt a certain point on the generated graph will be a vertical red line. Record the x position of this line as the experimental cutoff frequencyIllustration of set up:43040301570383DMM00DMM42622892165792DMM00DMM12895111616614WaveformGenerator input00WaveformGenerator input24417192308165WaveformGenerator ground00WaveformGenerator ground3864634781134Capacitor00Capacitor26218201135284Resistor00Resistorcenterbottom00Shown below is the circuit used for this experiment. The generated wave from travels from the left hand red alligator clip, through the resistor, past the positive DMM connection, through the capacitor, and to ground. Resultscenter33381950center92253500center690245Trial SEQ Figure \* ARABIC 1: 470 Ohm Resistance0Trial SEQ Figure \* ARABIC 1: 470 Ohm Resistance For this experiment, four different resistors are used; red, green yellow and blue. Shown below are the voltage sweep graphs for each of the LEDs listed. The Y-axis is amplitude, X-axis is frequency (Hz, Log scale) center509270000center4894125Trial SEQ Figure \* ARABIC 3: 4700 Ohm Resistance0Trial SEQ Figure \* ARABIC 3: 4700 Ohm Resistancecenter2356485Trial SEQ Figure \* ARABIC 2: 1000 Ohm Resistance0Trial SEQ Figure \* ARABIC 2: 1000 Ohm Resistancecenter43830600center222885Trial 4: 10000 Ohm Resistance0Trial 4: 10000 Ohm ResistanceTrial #Resistance (ohms)Capacitence (farads)fc (Hz) Theoretical fc (Hz) ActualLog ScaleNormal Scale1470.000.000001338.633.402511.921000.000.000001159.153.001000.034700.000.00000133.862.26182.0410000.000.00000115.922.05112.2DiscussionLow-Pass Filters, also able to be thought of as high-cut filters, allow signals up to a certain frequency to pass through unaffected. This point is called the cutoff frequency; any signal above this frequency is attenuated in amplitude as it passes through.550388619734191μF001μF4305764122293410k Ω0010k Ω3703320638175000leftbottom00As displayed by the above four graphs and table, the cutoff frequency can be altered by changing the resistance in the circuit. The red line within each graph designates the cutoff frequency; notice how the line moves further left when a higher resistance is applied. The same affect is easy to see within the above table. The frequency sweep controller interface created in labview is shown below.ConclusionThe behavior of low pass filters is useful in applications requiring filtration of a signal, often in digital and audio uses. In digital applications the filter can be used to smooth sets of data, as well as in analog to digital conversion. For audio applications, the low pass filter is used to smooth out audio signals. The results of this trial confirm the effect of changing a low pass circuit’s resistance. Both the calculated and experimental cutoff frequencies show the same trend as the resistance changes. ................
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