Using Data Acquisition Triggering Options
SIGVIEW includes a comprehensive set of triggering options available for data acquisition from all supported devices. In this example, you will learn how to use these options to record multiple repeating events and use these recordings for further analysis. The events you are trying to record can be a hammer impact during vibration analysis, a sound from a musical instrument, or anything else.
1. We will start by opening a data acquisition dialog and applying some settings:
The device type, sampling rate, and block length are not important - you can set those as needed for your application.
The "Start recording after trigger" option is turned on. This means that SIGVIEW will start recording only after certain signal amplitude has been detected in the signal. The type of trigger is defined by the "Trigger on channel", "Threshold" and "Trigger type" options. In this example, SIGVIEW will start recording if absolute signal level on Channel 1 increases over 50% of the maximal signal amplitude (full scale).
You can also define offset for the recording start, relative to the trigger position. In this example, we instruct SIGVIEW to start recording 1000 samples before the position where the trigger was detected. You can define positive or negative offsets, i.e. start recording before or after the trigger. The maximal offset length is limited to the "Block length" number of samples.
After a trigger is detected in the incoming signal, SIGVIEW will start recording for "Recording length" duration, in this example, 2 seconds. You should set this parameter to be bigger than the maximal duration of the event you would like to record.
The "Re-Arm..." trigger option instructs SIGVIEW to start waiting for a new trigger as soon as one recording has been made. After SIGVIEW detects a trigger for the first time and records 2 seconds of a signal, it will automatically open a new data acquisition window with the same settings and will wait for another trigger in it. That way, each 2 second recording will remain in a separate window. You can define the maximal number of such windows with the "Max Re-Arm count".
2. Press OK in the data acquisition dialog and a signal window will open. Press the "Rec" button in the toolbar to start data acquisition, i.e. waiting for a trigger. Since there is still no signal, nothing will happen immediately. In the background, SIGVIEW is acquiring your signal and testing if the trigger has occurred. You will see a message "Waiting for trigger..." in the upper left part of the window.
3. Now, trigger the signal event by playing some sound, impacting with a hammer or doing anything else causing the energy to be detected in the acquired signal. SIGVIEW will start recording 1000 samples before the event and the recording will last 2 seconds.
4. As soon as the recording has finished, a new window will open, waiting for a next trigger. Please repeat this 5 times to get 6 windows with recordings. Your SIGVIEW window should look like this after you do it:
5. Now, use the “Window/Tile” option to arrange all windows. Select all signal windows in the Control Window (Context menu/Select all window) and select the “Zoom-Out” function in the toolbar to view the complete content of all signal windows. The SIGVIEW window will look like this:
6. While still in the Control Window, you can apply some analysis to all 5 recordings at the same time, for example FFT. In addition, you can show all recordings in an overlay window by using corresponding options from the Control Window's context menu.