Low Pass Filter Essay

1018 Words 4 Pages
1. Introduction
The purpose of this experiment was to gain an understanding of how to use a signal generator, acquire data, understand the concept of a Low Pass Filter, gain knowledge of time domain sampling and sample rate, learn how to analyze and present data in MATLAB, as well as learn how to calibrate a microphone and record sound pressure data. To accomplish this the role of an electronics technician whose responsibility was to validate the performance of data acquisition equipment that will be used to acquire data on an upcoming project was taken on.
2. Effect of a Low Pass Filter
In order to determine the effect of a low pass filter the NI9234 module was connected to the output of the function generator and set to channel 0. The Data
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Time Domain Sampling
Implementing the signal generator a sine wave was generated with an amplitude of approximately 3 volts and a frequency of 800Hz. One second of data was recorded at the following sample rates: 2048, 3200, 6400, and 25600 samples/sec. The LPF in the DAQ was then set to 1Hz below the Nyquist frequency for each different sample rate. The maximum amplitude seen for each acquisition were as follows:
• 2048Hz: 1.5229e-04 V
• 3200Hz: 1.1791e-04 V
• 6400Hz: 1.3520e-04 V
• 25600Hz: 9.6897e-05 V
As evidenced by the above data, the maximum amplitude changed based on the sampling rate that was used. With (______) data samples per period of the sine wave are expected for each of the following frequencies.
• 2048Hz: (__)
• 3200Hz: (__)
• 6400Hz: (__)
• 25600Hz: (__)
5. Microphone
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A sine wave was generated with the function generator at 200Hz. The amplifier was turned off and the volume, or gain, was adjusted so that the tone could be heard but a level that was not loud enough to disturb the other groups in the lab. The microphone was then placed close to the speaker 3-6 inches away using the stand that was supplied. The DAQ system chosen to record the tone was microphone in order to determine the sound pressure level of a tone. The LPF settings were then changed to ensure that the recording was

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