The origin of the time stamp depends on the type of network module you are using. The following discussion covers how time stamps are generated with the FP-1600 and FP-1000:
http://exchange.ni.com/servlet/ProcessRequest?RHIVEID=101&RNAME=ViewQuestion&HOID=50650000000800000020230000&ECategory=Distributed+I%2FO.FieldPoint
My best recommendation is to purchase another CTR module. Using software timing will usually give you erratic results. That being said, make sure to use the "tick count (ms)" function if you must use software timing. That is the most accurate method for software timing. Also, you should set the counters to reset on read as recommended in Method 2 of this KnowledgeBase:
http://ae.natinst.com/operations/ae/public.nsf/fca7838c4500dc108
62567a100753500/d8db42f9fdc3607e862568640047f144?OpenDocument
Regards,
Michael Shasteen
Applications Engineering
National Instruments
www.ni.com/ask
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