Tech Note 1015 Detail

Use of filter function to prevent log, ln, and sqrt of negative numbers.

Affected Products:

CI-6870 DataStudio Software (Single User)
PS-2002 Xplorer GLX

Problem/Symptom:
DataStudio and the Xplorer GLX calculator functions will return real values for the log, ln, and square root of negative numbers.

PASCO Solution:

Certain functions (log, ln, or square root) will not tolerate negative values in the input measurement that may arise due to small amounts of signal noise.

To prevent DataStudio or the GLX from trying to evaluate negative values in these expressions, the following filter function can be used:

y = filter(maximum, minimum, x),

where maximum is the maximum value of the input value to be fed into the function, minimum is the minimum value allowed as the input into the function (just above zero for ln, and log; zero for sqrt), and x is the input measurement.

Creation Date: 06/4/2009
Last Modified: 06/4/2009
Mod Summary: