[Paraview] Problem with python_calculator - global_max()

[Manu GV]

Dear Paraview users,

I am visualizing 3-d scalar data(like pressure field). I visualizing 
iso-surface of this data with contour filter and want the maximum value 
of the scalar field to be displayed on screen. This is further animated.

Steps I follow:

pressure_data -> celldata_to_pointdata -> python_calculator 
max_pres=global_max(pressure_data), copy arrays selected.

"max_pres" shows the right data. But when I use contour filter on 
"python_calculator", values of "max_pres" become corrupted(i.e, show 
different value in information window of contour filter). Can anyone 
tell me why this happens?

And I am not understanding how to display "max_pres" value on my screen. 
Maybe its easy to do it but I am just stuck :(

Can anyone help me with this?

Thanks a lot in advance!!


Regards
Manu