Physical Channels in Nchan 1samp

[labmaster]

I would like to read multichannel analog inputs (USB-6215) using Nchan 1samp function for monitoring.

The monitoring means I use software delay function for timing between routines.

In channel definition, I use "Dev1/ai0:1" for 2 channels input.

Does it mean DAQ read whether simultaneously from 0 and 1 channels or not?

[Gustep]

It depends on your card. As far as I know, M-Series cards have only a single ADC, and therefore can only measure one channel at a time. Multi-channel measurements are thus time-interleaved. However, the time delay is quite small, ca. 5-50 microseconds, depending on your sampling rate. Slower sampling rates mean longer interleaving delays, but also better accuracy and much better channel separation.

I believe if you want true simultaneous sampling, you need a card with multiple ADCs, such as the S-Series.

[NI-Bongo]

Hi labmaster,

Gustep is indeed correct.  M Series devices use a multiplexer and, by default, there is a 10 microsecond delay between the channels unless the sampling rate requires this delay to be shorter.  If phase relationships between signals are of critical importance in your application, an S Series Multifunction DAQ device or a DSA Device would be more appropriate because they have a separate ADC for each channel and truly sample simultaneously.

Here are some links to information you may find useful:

How is the Convert (Channel) Clock Rate Determined in NI-DAQmx and Traditional NI-DAQ?
http://digital.ni.com/public.nsf/websearch/42484E84DA98053686256D32006E0494?OpenDocument

How do I Increase Interchannel Delay Using NI-DAQmx or Traditional NI-DAQ (Legacy)?
http://digital.ni.com/public.nsf/allkb/65E7445DB1AA5DC586256A410058697B?OpenDocument

What Is the Difference Between Interval Scanning and Round Robin Scanning?
http://digital.ni.com/public.nsf/websearch/6e0238cc5d6441cd8025667c0065d939?OpenDocument