Computer Science Project
The system was installed to capture a few hours of data. To capture data I have used a program from the builder of the ADC, this program can record time, voltage and frequency of the input signal. I have record only time and voltage, a voltage of 0,01mV is a low noise and 0,4mV is a high noise. In the next weeks of the project I think to make more detailed tests of recording. The data recorded by the program can be copied to the clipboard and then pasted to Excel. In these tests I have used Excel to analyse captured data. We can see in the Fig.1 the system, with the power supply, preamplifier and laptop.
The converter ADC is connected to the port LPT1 like we can see in the Fig.2
The regulated power supply is used to power the preamplifier and the electret microphone.(Fig.3)
Fig. 4 show the small (8mm) electret microphone.
The software supplied with the ADC from PICO have many possibilities, visual observation of the signal, like a oscilloscope.(Fig.5)
We can observe the voltage, that is very important to make the necessary gain adjust of the preamplifier.(Fig.6)
The frequency analisys of the signal is another important characteristic of the software, but at these moment the noise is our target. (Fig.7)
The software record to a table the time and the voltage, this information can be copied to clipboard and than used by programs like Pascal, Java, Oracle, Excel, etc Fig.8
At these moment I have used the Excel to analyse the first hours of recording data. In Fig. 9 we can see 3,5 hours of recorded data between the 20H and 23.30H in a street near my house. We can see peaks of voltage that correspond to pass noisy motorcycles or cars.
In this capture I have record the voltages with steps of 5 seconds and than I have made a average in groups of 3600 seconds that correspond a 1 hour. Fig. 10 show this information, the voltages go down with increased hours. Between the position 3 and 4 of the chart (xx-axis) the voltage is lower that correspond a lower traffic.
JM Freixo Nunes © 2009