how to use triggering for impact hammer

[rico1985]

Hi,

I used a impact hammer and one pcb accelerometer to do some beam tests. I want signal express to start log data once I use the hammer knock something. The following is my setup in signal express.

Triggering type: Analog Edge. Trigger source: the channel of the hammer
Slope: falling. Level: 0

However, once it started to run, it said "Logging was stopped because an error occurred with a Step in the Project. If this error is because of a device buffer overflow, you can improve performance by turning off display updates using the "View>>Update Signal Views While Running" menu item. You can also change the way signals are logged by changing the Logging Options in the Tools>>Options dialog. Turning off "Prepare log data for viewing" will greatly improve performance." I changed everything, but it didn't work.

Should I use other triggering types?

Thank you,
Ningyu

[Brooks_C]

Hello Ningyu,

In order to diagnose this issue it would be good to know the following:

1.  Is the acquisition ever starting or does this error occur as soon as the step runs?

2.  Does the acquisition ever receive your trigger?

3.  What sort or acquisition rate are you using and what is the clock configuration?  (Sample rate, samples to read, sample mode, etc.)

Let me know what you find and we can go from there.

Cheers,

[rico1985]

This error occurred after I ran the project. I am not sure whether the acquisition received my trigger.

Sample to read: 100000  sampling rate: 10k Hz

The attached is my project. I am doing an impact hammer test. I hope signal express starts to log data once I use the hammer to knock the structure. Is it possible for me to use trigger window to do this? If I don't use trigger, I need to delete data from ambient vibration everytime I do my tests.

Thanks,

[Brooks_C · Accepted solution]

Hello Ningyu,

In your current project it looks like you've configured an analog start trigger for a rising edge at the value of 20.  Since the input range for your task is +/- 10 volts I don't think it’s possible for you to ever receive this trigger.  I think that you should look at the parameters on the triggering tab of your DAQmx Acquire step.  You need to make this analog level and slope in the range of your signal in order to trigger off of it.  Also, if you're only interested in logging the data on peaks, you may want to consider using an analog reference trigger.  This will let you acquire data only around the peaks--all other data will be ignored.

Here is information about the analog level you set:  https://www.ni.com/docs/en-US/bundle/ni-daqmx/page/analeveltrig.html

And here is a description of start and reference triggers:  Tips and Techniques in Data Acquisition Triggering - NI-DAQmx

I hope this helps and have a great weekend!