Continuing with the previous post....
Another way to subtract spectra in order to see the differences between instruments in Win ISI, is to have two NIR files of the same samples scanned in both instruments:
after we see the plot of just one of them from which we want subtract the spectra of the other:
and now we go to: Options - Specify secondary file
and we select Subtract. After pressing OK we get the subtraction of the first sample of each spectra file. Pressing Plot All we can see the subtraction of all of them.
Now we can save the file with Options-Save selected curves