Hello all,
I have a question about time delays between channels of NI PCI-6259 daq card.
We are acquiring analog voltage data using DAQ assistant of LabView 8.5. We have two BNC terminal blocks,we use 8 differential
channels of the first(BNC-2090) and two channels from the second(bNC-2090A).
Recently we have noticed a time delay between outputs of two sensors and we decided to make a test if it has something to do
with the daq card(since it is a multiplexing card, not a simultaneous sampling one).
We used a signal generator to produce a square wave and use the card to read the same signal from different channels using different sampling rates.You can find the time delay graphs between channels with different sampling rates in the attachment. Some results coincide with what i expected to see. I expected a pattern with increasing sample rate: larger time delay at the furthest channel and the maximum time delay to be equal to the period of the signal.This happens for some cycles at 20k and 40k but does not happen at 30k and 60k. This makes me consider using 30k for daq but I want to understand the reason. Is it something about the properties/internal timing of the card? I need time delay caused by the card to be negligible. I want to figure out if we need a synchronous card.
Does anyone have any experience about this subject?
Thank you in advance.
PS: attached graphics. Channel 2 is reference. All timings are in milliseconds.
1 - time delay for all channels at 30k.
2 - time delay between ch2-ch3(nearest) at all sampling rates.
3 - time delay between ch2-ch10(furthest) at all sampling rates.
Gokcen
