I want to measure 3 signal at the same time
If this is the case, why not put all the 3 channels in the same DAQ assistant and acquire??
Well, If you try to run more than one DAQ assistant at the same time, you will get error: 50103, the specified resource is reserved
this
link will give you a clear picture of "end of the scan" and "end of measurement"
"If you had a task with two voltage channels and two thermocouple channels and you went back to add a new voltage channel, choosing "End of the scan" will add the new voltage channel to the end of list and it will be scanned fifth in the sequence. If you choose "End of the same measurement" the new voltage channel will be placed after the original two voltage channels and it will be scanned third in the sequence"