[time-nuts] labview, gpib, gps , logging data and lost data points!!

[Norman J McSweyn]

Hi!
I'm logging data from an HP 5335a (using it as a time interval counter). 
and from a Motorola gps board ( text data).
The test setup is comparing the 1pps output from the gps board to a 
divided (Thank you Dave Partridge!!!!!!) down 10 MHz from a Trimble 
Thunderbolt. The text data is used to post process the measurement from 
the 5335a reflecting the 1pps error (+/- 15E-9). The ver is LV 8

Code description:
Each instrument has it's own VI and I run them simultaneously, 
collecting data and storing it in text files. The individual vi's are 
for loops with the iterations being the number of seconds that I want to 
log. Inside the loop is obviously a delay. The data is time stamped with 
seconds enabled.

The problem is that somewhere in the 40k data points some (not all at 
the same time or sometimes one here and there or sometimes a bunch at 
once) aren't' collected.

Solutions that I've tried:
Using the 1pps to drive the parallel port so that I've got a hardware 
time hack. When I had both vi's in the same for loop things didn't go 
well. Not really sure what happened. Separated them. Works well now 
(except for the four or five lost data points in 40k)

Varying the time constant. It's helped lots, but I really don't' want to 
lose any data.

Have tried timed loops. Works fine with one process. Try to do two (gpib 
and serial for the gps) and it hangs the PC.

Solution that I think would work:
A way of firmly triggering a start event with labview. I've got a time 
server so windoze time (or lack of it!) is not an issue. (This may be an 
issue. Played around with it. Turning off polling made a difference.)

I'm not really a programmer. Actually play with trains for a living. 
Will be on vacation for the next week. Not much to do so I'll be able to 
play lots.
Thoughts, questions, comments and humor greatly appreciated.
Thanks for your time,
Norm n3ykf