Mucha
Make sure you are using the Lab_ISCAN NI-DAQ functions for your acquisition. Also, make sure you are using correct values for sampInterval and scanInterval when calling Lab_ISCAN_Start.
sampInterval is the interval of the timebase between sampling each channel. To determine the time between the samples of each channel, mulitply the sampTimebase by the sampInterval.
scanInterval is the length of time that elapses between scans. Make sure that the scanInterval is greater than or equal to sampInterval*numChans + 5us.
Also, make sure to call DAQ_Clear before your program terminates or unpredictable behavior might occur.
Brian