Hardware Triggering Issue

[Kevin_guy]

Hello.  I am having a bit of an issue using an impact hammer to trigger data acquisition. 

I am connecting a PCB 480E09 hammer into the Analog Channel 0 (ACH0) of an NI SCB-68 DAQ board.  Currently I'm just trying to get an example program to work (Acquire N Scans Analog Hardware Trig.vi). 

I know from using a simple waveform acquisition vi that for a moderate "hit," the hammer outputs around 0.1 V using a gain of 1.  So, I used the following parameters:

Triggering type: Analog. Trigger source: the channel of the hammer
Slope: falling. Level: 0  Trigger Level:  0.05

I figured with a trigger level of 0.05 the vi should be able to pick up a moderate hit.  However, the program only seems to work about 1/5 of the time.  When it works it collects data as I want it to, but the other times the trigger doesn't seem to work, and the program times out. 

Is it possible that the scans rate is not high enough for detecting the trigger?  If so, how do I increase it?  Is it okay the the trigger channel and the data acquisition channels are the same for the hammer?  Are there any other glaring problems with my setup? 

Any information/help would be much appreciated.  Thank you for your time

Kevin

[Jason_D]

Kevin_guy,

What version of LabVIEW do you have?  Do you have DAQmx or Traditional DAQ?  What is your current sample rate?  What is the rise time and peak duration of your signal? 

Yes you are probably not sampling fast enough to get the entire peak and thus not recording the signal accurately.  You can change the acquisition rate by the timing node in DAQmx or the AI Clock Config.VI in Traditional DAQ.  You might want to monitor the signal on a graph in your current program so that you get a rough idea what your program is dealing with.

The SCB-68 is a terminal block which is probably connected to your DAQ board if you could get the model number of that board it would be more help.