1. Call up the pulse sequence "t1ir1d" (Bruker) or "s2pul" (Varian).
2. Set p1 and p2 (Bruker) or PW and P1 (Varian) to the 90 degree and 180 degree pulses , respectively.
Set the recycle delay, d1 (Bruker and Varian) to something you believe is much longer than the T1.
3. Set tau to a very small value (3 microseconds for example). Tau is d7 on a Bruker spectrometer or d2 on a Varian spectrometer.
4. Collect a spectrum and phase it such that all peaks are negative (one scan is often enough for protons). Store the phase correction.
5. Repeat step 3. increasing d7 (Bruker) or d2 (Varian) until the peak of interest is nulled. If the peak is negative, tau is too short. If it is positive, tau is too long.
6. The T1 of the peak of interest is the tau value for the null divided by the natural log of 2.