Hi Rajan,
I suspect that this is nc_proc related. When you process your spectra in Topspin it scales it with a parameter called nc_proc. With any data where you are wanting to compare intensities outside of Topspin, it is important that all the spectra were processed with the same nc_proc parameter. You can manually set the nc_proc factor when processing.
In fact, from Version 3.1.0 onwards Analysis will finally read in the nc_proc factor and automatically do the scaling for you. But in all previous versions you have to make sure the nc_proc values are the same.
Here are some useful instructions from the old V2 Mailing list made by Pat Edwards:
Process all your spectra as normal using xfb (or multixfb)
For each spectrum use the command “dpp” and note the value of
NC_proc (or alternatively use grep to search the procs files: i.e.
%grepNC_proc /*/pdata/1/procs)Note the largest value and then reprocess the data using the
command"xfb nc_proc " i.e. if you had
three spectra
for which the values of NC_proc were -3, -1 and 2 your would use “xfb
nc_proc 2”Use dpp (or grep) to verify that all spectra now have the same
valueof NC_proc.The data can now be used with Analysis.
Here is the info about nc_proc from the Topsin manual which will give you some background information:
NC_proc - intensity scaling factor
• used in 1D, 2D and 3D datasets in the first direction
• takes an integer value
• set by all processing commands
• only exists as processing status parameter
• Processing in Topspin performs calculations in double precision floating point but stores
the result in 32-bit integer values. During double to integer conversion, the data are scaled
up or down such that the highest intensity of the spectrum lies between 228 and 229. This
means the 32 bit resolution is not entirely used. This allows for the highest intensity to be
increased, for example during phase correction, without causing data overflow. NC_proc
shows the amount of scaling that was done, for example:
– NC_proc = -3 : data were scaled up (multiplied by 2) three times
– NC_proc = 4 : the data were scaled down (divided by 2) four times
• Although NC_proc is normally calculated by processing commands, 2D processing also
allows you to predefine the scaling factor with the argument nc_proc, for example, xfb
nc_proc 2, scales down the data twice. However, you can only scale the data more down
(or less up) than the command would have done without the argument nc_proc. The latter
is shown by the processing status parameter NC_proc (type dpp). Smaller (more
negative) values of nc_proc are ignored to avoid data overflow. The command xfb
nc_proc last takes the current value of the processing status parameter NC_proc (type
dpp) as input value.
Best wishes,
Vicky