User manual

Chapter 3 Software Overview
NI-DAQ User Manual for PC Compatibles 3-32 ni.com
Figure 3-10. Double-Buffered Data Acquisition Application
Building Block 3, Checking
Multirate Scanning
Use multirate scanning to scan multiple channels at different scan rates
and acquire the minimum amount of data necessary for your application.
This is particularly useful if you are scanning very fast and want to write
your data to disk, or if you are acquiring large amounts of data and want to
keep your buffer size to a minimum.
Multirate scanning works by scanning each channel at a rate that is a
fraction of the specified scan rate. For example, if you want to scan four
channels at 6,000, 4,000, 3,000, and 1,000 scans per second, specify a scan
rate of 12,000 scans per second and a scan rate divisor vector of 2, 3, 4,
and 12.
No
Ye s
Ye s
No
Next half buffer
ready for transfer?
DAQ_DB_HalfReady
DAQ_DB_Transfer
Data acquisition
complete?
Retrieve half of the data in
the data acquisition buffer.
Check for next half
buffer availability.