What is the best way to assign time stamps to counter input data?

Compact DAQ
NI 9411
Hi Everyone,
I am creating a chart recorder for collecting various engine data. I need to plot engine speed, crank angle, and various analog data on an XY graph. I am using a counter and a mag pickup to continuously measure the frequency of the flywheel teeth. From this data I create an array of timestamps based on accumulated periods for each frequency measurement. My problem is, how do I determine the absolute timestamp for the first frequency of the buffered data? I need to sync the frequency data with the analog data so I can plot it all vs time on an XY graph. The flywheel has 201 teeth and the engine runs at 600 RPM.
I am using a second mag pickup and counter to measure a single index pulse on the flywheel. This will be used to determine the crank angle. I also need to create a timestamp for each index pulse. What is the best way to do this?
Is it possible to treat the two mag pickups as an encoder and not use the B phase (direction) pulse?
I am fairly new to LabView and any help would be greatly appreciated.
Thanks in advance,
Kris

Hi Kris,
With analog and digital input tasks in DAQmx, it is possible to acquire data of the type 'waveform'.This includes timestamp information for the acquired data. This example is a good one to reference to understand how this is done: http://decibel.ni.com/content/docs/DOC-3749 .
With counter tasks in DAQmx, however, your best bet would be to use the 'Get Date/Time in Seconds' VI to obtain the absolute time. You can set this up so that the absolute time value is obtained right before the DAQmx read function is called, as shown below:
Are you trying to use the 9411 to read from the mag pickup? What type of data does it output?
For information on programming with NI-DAQmx, please refer to the following webpage: http://zone.ni.com/devzone/cda/tut/p/id/5438 . It is a very useful resource to get started on DAQmx applications! I hope this helps.
Vivek Nath
National Instruments
Applications Engineer
Machine Vision

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