Circuit module for selective magnetic field scanning in magnetic resonance spectrometers

An inexpensive electronic circuit module has been designed and constructed to replace the “field scan potentiometers” of magnet power supplies used in old EPR spectrometers. Linearly varying AC and DC error voltages are generated by this circuit module. Apart from the obvious advantages gained by changing the mechanically controlled scanning to digitally controlled electronic scanning, this circuit also has the ability to scan selected field regions, with facility to go from one selected field region to another field region rapidly and automatically, (similar to the “tab” facility in a typewriter) thereby saving the time spent in the collection of useful data. In our design the bouncing problem associated with “key” operations has been elimitated by the use of appropriate software control. We have evaluated the performance of this circuit module by using it with a Varian Fieldial power supply.