Measurement Computing DASYLab - Manual (Page 54)

A-18 Configuring DASYLab for WaveBooks 989693 DASYLab - Standard Driver
Card Setup and Clock Settings Windows
For example: at 10 uSecs apart: if the Sampling Rate is set to 100Hz and there are
10 channels being read, then the 10 channels will be read in 100 uSec. 10 mSec later, they will be read
again. The time between each channel read is fixed. The time between each scan read is adjustable using
the Sampling Rate.
WaveBook
For WaveBook, each channel in a scan is read 1 uSec apart.
For example: at 1 uSec apart if the Sampling Rate is set to 100Hz and there are
5 channels being read, the 5 channels will be read in 5 uSec. 10 mSec later, they will be read again. The
time between each channel being read is fixed. The time between each scan read is adjustable using the
Sampling rate.
Block Size
The Block Size determines how DASYLab will process the incoming data. DASYLab processes
data n samples at a time (n samples = 1 block). With a block size of 512, five hundred and twelve
samples will be collected before DASYLab processes any data. For slow acquisitions, this may be
considered too long.
As a rough rule of thumb, large block sizes are suitable for high speed measurements small block sizes lead
to short response times and are better suited for asynchronous output and online visualization.
Use small block sizes for slow acquisitions; and large block sizes for faster
acquisitions (1Hz, block size of 1; 20kHz, block size of 2048).
Sampled data can be transferred between the device and the PC in blocks of 2048 values each, or each
sample can be transferred individually. In order to provide maximum performance and online visualization
facilities, the appropriate transfer block size is selected automatically by the software.
Because DASYLab has to split computation time for the different actions performed, the block size
specified in DASYLab defines how many samples are processed by DASYLab in a time-step.