Precision current regulator for NMR electromagnets

[Display omitted] •Improves current regulation for superior field stability.•X50 improvement in field stability.•Uses dc-dc current transformer (fluxgate) device.•Inexpensive.•Can be applied to essentially any current source. When using electromagnets or non-persistent superconducting magnets, the field stability can be directly proportional to the current stability. We present here a simple design for a current regulator based upon a high-precision, dc-dc fluxgate transformer. The output current and NMR frequency are stabilized by about a factor of 50, over times of order one hour. The method can be applied to essentially any current supply.