Application of operational amplifiers to magnetic measurements

The method of voltage integration using expensive stabilized high-gain and low-drift amplifiers has been previously described. Many low-price general-purpose amplifiers are now available, and their performance as voltage integrators (fluxmeters) is reported. The fluxmeter is intended for general use in factory test rooms where measurements consist of a single flux change over a few seconds unlike recording hysteresigraphs, where integration may be over several minutes, and where output voltage drift problems may arise. These electronic fluxmeters offer advantages over the conventional moving coil fluxmeter in that zero return is very fast and that they are particularly suited to pass-fail testing when used in conjunction with a reference voltage source and a voltage comparator. Both a reference source and a comparator can be constructed using similar types of operational amplifiers.