Somat eDAQlite - Page 189

I2773-4.4 en
189
Somat eDAQ lite
Avoid redundant calculations in calculator computed channels
This is illustrated by the following example of an inefficient usage of eDAQ lite Desk
Calculator computational resources.
Comp_1 = (In_1 + In_2) / sqrt(In_1^2 + In_2^2)
Comp_2 = (In_1 - In_2) / sqrt(In_1^2 + In_2^2)
Here is a much more efficient usage.
Temp_1 = sqrt(In_1^2 + In_2^2)
Comp_1 = (In_1 + In_2) / Temp_1
Comp_2 = (In_1 - In_2) / Temp_1
Also, although probably much less obvious, the Temp_1 expression is more efficient
when written as follows.
Temp_1 = sqrt(In_1 * In_1 + In_2 * In_2)
For more information on the Desk Calculator computed channel, see “Desk
Calculator” on page 130.
Minimize the number of defined DataModes
For a test with 20 transducer channels defined at the same sample rate, it is much
more efficient to store all 20 channels in a single Time History DataMode, rather than
storing each channel in a separate DataMode. The reason for this is that there is only
one PC Card file opened and manipulated for each Time History DataMode and
having just one file to manipulate is much more efficient than having to manipulate 20
PC Card files at the same time.
Up sample digital input channels used for triggers
Often, a digital input channel is used to manually trigger DataMode storage. If the input
channels are defined for a 2500 Hz sample rate and storage rate, it is more efficient to
define the digital input channel at 100 Hz and then up sample by a factor of 25 to get
to the 2500 Hz sample rate required for the DataMode trigger. For more information
on the Up Sampler computed channel, see “Up Sampler” on page 152.
Do not use min-max tracking
The enable min-max tracking preference for Time History DataModes is in the TCE
Preferences menu. Min-max tracking can consume significant CPU cycles with a lot
of Time History DataMode storage.
Use a second eDAQ or eDAQ lite in networked mode
If another eDAQ or eDAQ lite is available, use it in networked mode with the first
eDAQ
lite and split the processing load as evenly as possible between the two
eDAQ
lite /eDAQ systems. For more information on networking, see “Networking
eDAQlite /eDAQ Systems” on page 39 and “Networking eDAQlite /eDAQ Systems”
on page 86.
Reduce the scope of the test
As a last resort, reduce the scope of the test by reducing sample rates, reducing
channel counts or eliminating computed channels and DataModes.
HBM: public