How to synchronize two counter output

[0905jjo]

Hi, 

I have some issue related to synchronizing two counter output.

I use sample clock to match time interval between two counter output. 

But, when I check the two counter output by using a oscilloscope, time interval between two counter output is not constant (For example, the time interval in 1st measurement was 1ms, but the time interval in 2nd measurement was 5ms.)  

How should I do in order to synchronize two counter output ? 

Here is my VI and the diagram  

Thanks

[Kevin_Price · Accepted solution]

You need to have both CO tasks trigger off the same signal.  Here's a modified version of your vi to try out where I generate such a triggering pulse with a DO bit.  You'll need to check the terminal pin assignments on your device -- the key is that you choose a DO line that doubles as a PFI pin.  Configure DO by referring to it as port#/line# and configure the counter triggers by referring to it by its PFI#.

-Kevin P

[0905jjo]

I did not think trigger. Time interval between two counter output is constant in the modified version.

Really appreciate your help. Thank you

Jo