An electronic hysteresigraph, which integrates without recourse to electromechanical means and is free of drift, has been developed. In operation, a search coil surrounds the magnetic specimen to be tested, and the specimen is then subjected to a change in externally applied magnetic field strength. The time integral of the potential induced in the search coil is a measure of the magnetic flux change in the specimen. The induced potential is applied to a solid-state voltage-to-frequency converter which produces a series of output pulses, the number of which is proportional to ∫e dt. These pulses are summed on a digital counter to give a measure of the flux change. A digital-to-analog converter then provides a d-c output which drives the Y-axis of an X-Y recorder.

A signal proportional to the applied magnetic field strength is simultaneously fed to the X-axis of the recorder, and a continuous B versus H plot is obtained. This is a real-time mode as the response of the various measuring elements is practically instantaneous.

In considering the integrator, it is interesting to note that absolute accuracy traceability in calibrating the voltage-to-frequency converter is referred directly to the volt, as represented by the standard cell, and to the second, as represented by a crystal-controlled time base. This is in contrast to the generally used secondary standards of mutual inductance and current shunt millivolt drop.