Acquisition Mode

Next select Acquisition Mode under the Param. Acquisition Mode controls how the data is acquired and under what conditions. It includes setting the trigger mode, trigger source, level, conditions and overlap.

Select Trigger Mode using the Mode Button. Transient capture projects such as impact hammer tests typically use Manual-Arm Trigger or Auto-Arm Trigger. Auto-Arm automatically accepts the data frame into the average and prepares the trigger for the next signal. Manual-Arm provides a graphical display of the data and allows you to accept or reject the frame into the average.

n Figure 114. Trigger Modes for Transient Capture.

Trigger Source defines which signal to use as the trigger source. Only signals specified in the CSA script are available as trigger sources. If a signal is not available then it can be added as a trigger source by editing the CSA file and downloading it to the CoCo hardware.

The Trigger Condition and Level Setup define the conditions that will trigger the acquisition. You can also edit the high and low level and the trigger delay. Alternatively you can change the level settings with the up and down arrow buttons.

n Figure 115. Trigger conditions and level setup for transient capture.

Overlap defines the amount of overlap between frames for averaging to reduce the time required to acquire a large number of averages.

n Figure 116. Overlap rate for transient capture.

After the Parameter Settings are specified the CoCo begins to wait for a trigger event. A window displays the time elapsed before a trigger event is detected.

n Figure 117. Waiting for trigger message.

When a trigger event is detected and Manual-Arm Trigger is selected, then a small window will show the data frame and give you the option to accept or reject the data. Accept will include the frame into the average and then ask you to proceed to the next trigger by pressing the Next button. Reject will discard the frame, not include it in the average and return to the waiting for trigger mode. If Auto-Arm Trigger mode is selected then the system will automatically return to the wait mode after each trigger event with no user intervention.

n Figure 118. Accept/Reject display for transient capture.

The frame average number is displayed in the status bar to help you monitor how many averages have been recorded. When the averaging mode is set to linear and you reached the averaging number you are prompted to restart a new test by pressing the Run Button.

When the averaging mode is set to exponential then new frames will be acquired and included in the average until you press the Hold Button. The system does not stop when the average number reaches the averaging number. The averaging number only defines the behavior of the averaging function. Exponential averaging is intended for continuous averaging to help observe how a signal changes over time or converges to a mean.