Streaming (digital) using Labjack U3HV and DaqFactory Express

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Personally, I'd consider using one of the Timing modes of the LabJack instead of trying to do it using streaming. This will likely be more precise and more accurate. It will, however, require a little more wiring.

As to your questions:

1) hard to say. It could be as simple as the presentation interval isn't as constant as you think. It also may be something to do with the parallel port. Its not going to be DAQFactory. It takes whatever it gets from the LabJack and doesn't process it at all. If all your measured times were shorter than the actual time, I'd say a data point or two was being missed, however DAQFactory isn't going to add data points on its own, so if some times are longer than actual, this is not the problem. As I said, its most likely real in the signal.

2) this is likely because the other, non-connected digital lines on the parallel port are being pulled high. Either that, or they are used for something else. Why are you using the parallel port?

Simplify the system as much as possible. Lose the parallel port if you can. Use a separate sensor (optical?) to determine when a record is presented.

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