External Trigger: Reference or Start

[Shaft DAQ]

I'm trying to do DAQmx for a shaft encoder, and would like to see my data at specific points of the the shaft rotation (say at 3 quarters of each rotation) .

1) What trigger should I use (appears when clicking on trigger option in DAQ Express): Start or Reference?.

2) The shaft runs @ max frequency of 50 Hz. What will the suggested number of samples will be if I need the results for a few seconds?

I'm using:

LabVIEW 7.1

PCI 60 24 e

BNC 2090

Many Thanks..

Mohamad

[Joseph_Loo]

If you want to see the results at 3/4 I suggest the sample rate be more than 8 (nyquist limit, 2 x 4) * 50 (50 hz)  Then multiply the sample rate * number of seconds you want to view. Obviously the higher smaple rate, the more accurate you can get to the 3/4 rotation location.

I use reference for my trigger.

[Shaft DAQ]

Hi Joseph Loo ,

Many Thanks for your message... I'll try that