RF field strength control and an envelope detector.

A brief description of a radio-frequency (RF) field strength controller is presented along with an experiment to test the long-term RF field strength stability of a nuclear magnetic resonance (NMR) spectrometer. Active control of RF field strengths may be necessary for quantitative measurements of NMR parameters, especially when experiments require days to run. An envelope detector, easily incorporated in any spectrometer, is also presented. The envelope detector provides an easy way to observe the pulse sequence on an inexpensive oscilloscope and can be useful in troubleshooting.