Q: I have a signal I would like to analyze. How do I start?
A: Load it in SIGVIEW by using "File/Load signal" menu option. To take a first look at spectral characteristics of the signal, try "Signal tools/Time-FFT" menu option with default settings. You will get a 3D graphics showing the changes of all signal's frequency components through time.
Q: I would like to analyze recordings from my sound card/DAQ-device in real-time. How do I do it?
A: Try opening one of SIGVIEW examples first (Help/Examples option). You can start with: "Live stereo spectrum with 3D.sws" or "GetFrequency.sws". After loading, simply choose Data acquisition/Start menu option to start monitoring live signal.
Q: How can I exchange data with Microsoft Excel or other applications?
A: To import Excel data in SIGVIEW, save it as "Tab delimited (*.txt)" file from Excel. You should remove all unnecessary headers or additional text from the sheet before you do that. You can import such files in SIGVIEW by using File/ASCII/Import... menu option. To import SIGVIEW data in Excel, save it as tab delimited file by using File/ASCII/Export... menu option, and load those in Excel as Text-file.
Q: I would like to explore very low frequencies, under 1Hz. How do I get those in FFT graphics?
A: The lowest frequency of FFT result depends on the sample rate of the signal and the length of a signal segment used for FFT calculation. It will always be equal to SampleRate/SegmentSize. This is not a SIGVIEW limitation, but a mathematical rule for DFT and FFT. For example, if your signal is sampled at 22050Hz, and you perform FFT on its first 512 samples, the lowest frequency will be 22050/512=43.066Hz. If you perform FFT on a 1 second segment from the same signal, the lowest frequency will be 22050/22050=1Hz.
Q: How can I improve the spectral resolution of FFT result? The difference between two adjacent FFT points is 40Hz, and I would like to make it 1-2Hz.
A: The spectral resolution of FFT result depends on the sample rate of the signal and the length of a signal segment used for FFT calculation. It will always be equal to SampleRate/SegmentSize. This is not a SIGVIEW limitation, but a mathematical rule for DFT and FFT. For example, if your signal is sampled at 22050Hz, and you perform FFT on its first 512 samples, the difference between two adjacent FFT points will be 22050/512=43.066Hz. If you perform FFT on 1 sec segment from the same signal, the resolution will be 22050/22050=1Hz.
Q: There is only one FFT button - how can I get power spectrum, PSD, etc.?
A: All spectral analysis tools in SIGVIEW are integrated under FFT option. By default, this option will calculate and display standard Magnitude (Amplitude) FFT plot. If you open Properties dialog for the FFT window, you will be able to change all calculation parameters and to define what will exactly be the result of the calculation: Magnitude, Power spectrum, PSD,... You can change default settings by using Signal tools/Spectral analysis defaults menu option.
Q: I would just like to determine peak frequency of the signal - what are all these FFT parameters?
A: By default, SIGVIEW will calculate spectrum values with optimal parameters - you don't have to bother with complicated things. Just load your signal, press FFT button and then choose Signal tools/Instruments and markers/Maximum position menu option, and an instrument with wanted result will appear along with the marker in the FFT graphics.
Q: Can SIGVIEW display signals or FFT results as overlay graphics?
A: Yes, you can create overlay graphics by using context menus of each signal window, or by using Control window's context menu (select target signals first).
Q: Can I display spectrum on logarithmic X-Axis or Y-Axis?
A: Yes, you can open Axes settings for a FFT window (Edit/Axes settings menu option) and select "Logarithmic X-Axis" and/or "Logarithmic Y-Axis" option. There are also corresponding context-menu options available after mouse right-click on the window.
Q: Can I display spectrum graphics with Y-axis values in dB?
A: Yes, you can set spectrum values to be in dB (logarithmic axis) in Spectral analysis defaults or in properties for each FFT window.
Q: I would like to compare two signals - how can I do it with SIGVIEW?
A: You can compare signals in time domain by showing them as overlays in one coordinate system (context menus or from Control window) or by subtracting them to determine the difference (Signal tools/Signal calculator). To compare signals in frequency domain, you can calculate their FFTs and compare them, or you can use some of cross spectral functions available through Signal calculator. For example, coherence function will show you similarities between signals for each frequency component on 0...1 scale.
Q: Can SIGVIEW trigger some external event in case of a specific analysis result?
A: Yes, you can use "Trigger external application" option of SIGVIEW Instrument windows. These windows can measure different values from the signal and call external applications in case the measured value is in some defined range. As an example, SIGVIEW distribution includes application "Logger.exe" which can be used to simply log instrument values in a log file. Help file describes the requirements for such applications.
Q: How do I set default parameters for spectral analysis calculations?
A: Use Signal tools/Spectral analysis defaults menu option. After you set your preferences there, all new FFT calculations will use these settings.
Q: How can I set marker in a signal?
A: Markers in SIGVIEW are closely related with Instruments. Most Instrument can place corresponding marker in a signal. For example, if you use Maximum instrument to show you the maximal signal value, marker will be displayed on the signal graph maximal value location. You can turn marker on/off or set its parameters by editing instrument properties. If you want simply to set marker on some specific location in the signal, please use "Marker at..." instrument or "Place marker here" option from the signal's context menu.
Q: I performed FFT, but the Y-axis is not labeled. Which units are on Y-axis?
Since spectral analysis is used in many different fields, acoustics, vibration analysis, electronics, etc. , there are also many interpretations and units used for Y-axis values. SIGVIEW should be useful for spectral analysis in all of these application fields and therefore are the units simply omitted. Each user can define own units by using Axes settings for the FFT window.
Q: Can I show X axis in RPM instead of Hz?
A: Yes, you can select corresponding option on spectral analysis defaults or on Properties dialog for each FFT window.
Q: How can I print SIGVIEW graphics?
A: SIGVIEW does not directly offers printing services, because there are simply much better applications for this purpose. You can simply use "Edit/Copy picture to clipboard" menu option to transfer the bitmap of the active window to the clipboard. After you do that, you can open any other graphics-capable application (MS Word, Excel, Visio, Corel Draw, MS Paint) and paste the picture there. That way you can integrate SIGVIEW graphics with the rest of your text or you can edit graphics and print everything when you are finished.
Q: How can I save my work?
A: By using options in File menu: "Save workspace..." and "Load Workspace...", you can save all currently opened SIGVIEW windows (workspace) in a file and load it later. SIGVIEW does not save the actual content of every signal - it saves only a structure of your analysis system and file names of loaded files. For example, if you load a signal, perform an FFT on it and save that workspace, SIGVIEW will not save the actual values from the signal or values from the FFT. Only the name of the signal file will be saved along with information that you performed an FFT on it with certain parameters. Therefore, if you change the data in original signal file and reload SIGVIEW workspace, you will get changed signal data and the FFT from it. Generally, workspace file contains the information you see in Control Window plus properties for each window including axes properties and zoom info.