Track changes of signal parameters through time
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We will show you here how to track changes of some signal parameters during data acquisition or monitoring.

1. Let us take sound card device as an example. You can connect some signal source to it before you start (microphone). Open "Data acquisition" dialog ("Data Acquisition/Open data acquisition" menu item), choose DirectSound as device type and your sound card name as "Device". Leave all other default settings. Press OK and data acquisition signal window will open.

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2. While on data acquisition signal window, press FFT button in toolbar to calculate spectrum of a signal. Spectrum window appears and Control Window should look like this:

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3. As an example, we will track changes in signal RMS energy and the position of the peak spectrum frequency. Click on signal acquisition window and select "Instruments and markers/RMS" main menu option. Then click on FFT window and select "Instruments and markers/Maximum position (with marker)" main menu option. Two instrument windows appear showing current values from the signal and spectrum (all zeros because data acquisition is not running yet) The resulting Control Window should look like this:

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4. Now we would like to track (log) instrument values as they change through time. To do this click on each of two instrument windows and select "Log instrument values" from their right-click menu. In the small dialog asking you about buffer length for a log, leave default value of 100. Control window should look like this:

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5. Now go to data acquisition signal window and choose "Data acquisition/Start" menu option (or REC) button in toolbar. Recording from the sound card will start and instruments will change their values. On each instrument value change, the last value will be stored in a corresponding log window - log window signal will grow as new values come.

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6. Note that X-axis units on log window is "change" - it is simply an index of a value change starting from 0.

7. After 100 changes (remember your setting for buffer length), log windows will be full and display will start scrolling. You can use context menu to reset data (i.e. start from the beginning) or to stop/start logging. Value log signal will try to determine values for its X-axis automatically by backtracking through the analysis chain. If those X values are equidistant (i.e. difference between two consecutive values is always the same), those will be display on X-axis. If not, X-axis will switch to unit called "change" where each new value will simply be labeled with its index, i.e. 0,1,2,3,4,...

8. Instrument log windows can be used as any other signal window, i.e. you can calculate its spectrum, show them in overlay with other signals, store values in ASCII/CSV file etc.
Track changes of signal parameters through time