SPAS 2009 can import signals that are stored in an ASCII text file. The file extension can be .txt or .dat. The format of the ASCII file that SPAS 2009 recognizes is shown below:
Depth = 2.50 m
0.40 1.92989e-03
0.80 1.71464e-03
1.19 1.53623e-03
1.59 1.30573e-03
1.99 1.01601e-03
2.39 5.20690e-04
2.78 6.08235e-05
3.18 2.25983e-03
3.58 5.18088e-03
3.98 7.79213e-03
4.37 1.66042e-02
The key rules for this format are:
| • | One single file can contain one signal only. |
| • | Each signal file must begin with a single line header. The first valid number in this line will be recognized as the depth where the signal was obtained. All subsequent data in this line will be ignored. |
| • | Subsequent lines will be treated as data lines. |
| • | Data lines are composed by two values: the time (in milliseconds) and the signal value (any unity), in this order. Data values may be separated by a single space character or tab character. |
Data files don’t have to be in order. SPAS 2009 automatically will insert them at the right place. You can import signals at any time in the analysis. To begin importing signals click on the Import signal button on the Signals toolbar as shown in the following Figure.
Import signal button on toolbar
The software will prompt you with a dialog waiting for a response regarding the type of signal you are about to import. Available types are Left and Right. Make a choice and click on the OK button.
Signal type selection dialog
The standard Windows open file dialog will appear. Navigate to the directory where you stored the signal files. Select the signals you wish to import and click on the Open button. To select multiple files you may use the mouse and the SHIFT button on your keyboard.
Open signal data file dialog
Note If an S wave is propagating at 200 m/s and two signals are recorded in two depths separated by a distance of 1.0 m, the time gap between the two respective peaks will be 1/200 s or 5 ms. If the sampling frequency is chosen to be 1000 S/s (Samples per second), the sampling period will be 1 ms. This will result in an uncertainty of 1 ms divided by 5 ms, which gives a 20% error. A sampling rate greater than 10,000 S/s is recommended, giving a typical error of 2%. SPAS 2009 uses by default a sampling rate of 20,000 S/s when importing signal data from an ASCII text file. You may alter this value by calling the Reload signals command. |