3D NMR
Offsets and Spectral Widths
In triple resonance experiments (deuterium optional), usually the following settings are specified for each involved channel:

Channel
f1
f2
f3
f4
Nucleus
1H
13C
15N
2H
Offset
o1p
o2p
o3p
o4p
Carrier
4.75 ppm
37 ppm (aliphatic)
52 ppm (alpha-carbons)
172.5 ppm (carbonyl)
115.5 ppm
3 ppm

You can define offsets and spectral widths into Biotool: