Random and systematic uncertainties in pulsed NMR measurements of nuclear susceptibility are discussed. Methods for minimizing these uncertainties were developed with special reference to ultralow‐temperature applications. Compensation of spectrometer drift and the temperature dependence of the sample circuit using a precision calibrator technique is described. The calibrator was able to compensate for simulated two‐fold reductions in sample coil Q and in receiver gain to within accuracy of 1/2%, and to within 1% for 3‐dB changes in the transmitter output at low levels. Some data‐processing methods are discussed which allow the use of very small rf field pulses to reduce heating.