Free Software Transforms Data

Before operating systems separated programmers from direct control of hardware, I would send arrays of data to a dual DAC card and view the information on an oscilloscope. If I wanted to use an FFT, I had to write my own code. Engineers today have many ways to process and view data within programs such as LabVIEW, DASYLab and Mathcad. But that type of software can dent your budget if you just need a simple way to examine data and look at it in the frequency domain. And you may need several dynamic link libraries or ActiveX controls to integrate data-acquisition equipment with third-party software.

Excel can acquire data from instruments and display data, too, but it provides only fundamental processing operations. As I explained in the last column, if you want to subject data to an FFT window function, you're pretty much on your own. Furthermore, I don't like Excel's graphing capabilities.

While doing some research, I uncovered the free WinDaq Waveform Browser (WWB) data-playback-and-analysis package from DATAQ Instruments. Although meant to work with the company's hardware and software, the program will accept data in several formats that include comma-separated values (CSV) you can obtain from an Excel spreadsheet or other application. Not only will WWB display data, it also lets you easily scale graphs and cursor movements let you pick out values at any point on a graph. The beauty of the WWB package is it gives you a quick way to look at information in the frequency domain without much effort. The package will run data through one of four window functions and produce a nice power-spectrum display of decibels versus frequency. The screen shot (below, left) shows a 1750-Hz sine wave (top) and the resulting power spectrum (bottom). You can format this type of display to show as many as 16 individual or 32 overlapped signals.

Among other things, the software lets you filter frequency domain information and perform a reverse FFT to show the filter's effects on the original signal. You'll find the WWB package a handy addition to your test-and-measurement toolkit. You can easily display test results and in combination with Excel, you can manipulate information. If you simply want to experiment with mathematically created signals, you can still combine Excel and WWB to provide a useful display, diagnosis and learning tool. Download the free software and associated Help file from the DATAQ website (see useful links, below).

DATAQ's software uses a complicated CODAS format, so before you can view data, it must go through a conversion process the WWB software easily handles to produce a WDQ file. I will post more instructions and sample files you can download and use with the WWB software (see useful links, below).