What error are you getting? If you are using USB-6259, it multiplexes the input so it is not exactly simultaneous.
If you are using a DAQmx API, you should just do what it says below.
Thank you. It is very useful. Let me explain to you more. MY device is NI USB-6259(BNC). I am trying to read two XY piezo stage AI(Analog Input) signal and one AI from detectors through lock-in amplifier. My goal is to read and synchronize these three signal. Now I did by DAQ assistance through Explorer It is working. But It cannot show simultaneously. and did not show any error.
You should use hardware that supports simultaneous analog input such as USB-6353 or NI 9215 when you want to acquire simultaneously, especially when you want to analyze data from a lock-in amplifier.
That being said, if you could attach a screen capture of VI, I could take a closer look.
I suspect you're trying to run 3 distinct AI tasks simultaneously. Instead you should include all 3 AI channels in 1 task. There's only 1 timing engine available for AI, so you can't run separate tasks at the same time.
As stated before, those channels will be multiplexed and have a small fixed timing offset for when their A/D conversions are captured. If you sample at 1 kHz, all 3 channels will be updated every 1 msec. But for each msec interval, the individual channels will be converted at a different offset within that msec. These offsets *will* be hardware-timed and consistent.
There are apps where it's ok to ignore this offset, apps where it's sufficient to know about it and compensate appropriately, and apps where you must use a device capable of true simultaneous sampling. Dunno which kind you have.