SRS Labs SR850 - Manual (Page 52)

2-40
Trace Math
Press <Left Limit>
Use the knob to position the cursor 3 divisions
to the right of the left limit.
Press <Right Limit>
Move the cursor farther to the right.
Press <Do Fit>
17. Press any key to continue.
Press any key to continue.
18. Press <Fit Type> twice to select Line.
Press <Do Fit>
Press any key to continue.
Press any key to continue.
19. Press [DISPLAY/SCALE]
Press <S/Div>
Use the knob to change the horizontal time
scale to 1 S/Div.
Press [CURSOR]
Set the left limit of the region at the start of the
signal decay.
Select the smallest region which covers the signal
decay.
Set the right limit.
The fit region is between the two limit marks (verti-
cal heavy dashed lines). Only the data between
the limits is used to calculate the fit.
Curve fit calculations can take a long time if the fit
region encompasses a lot of data points. Try to
use the smallest region possible when performing
fits.
The curve fit uses a multi-iteration chi-squared
minimization technique. After each iteration, the
value of chi
2 is displayed at the bottom of the
screen. Pressing the last softkey during the fit will
terminate the calculation after the current iteration.
The fit parameters are displayed in a window in
the center of the screen. The decay parameter b
should be 3 seconds (6 db time constant).
The first time a key is pressed, the parameter
window is removed. The curve fit is plotted over
the data on the graph.
The next key removes the curve fit from the graph.
Try fitting a line to this region.
Fit a line to this region.
Remove the parameter window. The calculated fit
is terrible of course.
Remove the curve fit.
Show the Display and Scale menu.
Highlight the horizontal scale.
Zoom in on the graph.
Activate the cursor.