A 5.5-kOe 60-Hz magnetic hysteresis loop tracer with precise digital readout

A new hysteresis loop tracer (B-Hmeter), operating at 60 Hz, has been developed for use in the quality control of magnetic materials for magnetic recording. The instrument is suitable for making hysteresis measurements of hard magnetic materials with coercivities ranging from about 2.5 Oe (200 A/m) to 2.5 kOe (200 kA/m), which can be saturated (or nearly so) in fields up to -5.5 kOe (450 kA/m). Materials may be tapes, rods, or packed tubes. Precise measurements may be made by relatively untrained personnel. The pertinent specifications are as follows : 1) maximum applied field (Hm) to 5.5 kOe (450 kA/m) ; 2) sample flux range from 50 mMx (0.5 nWb) to 1 kMx (10 μWb) ; 3) direct digital readout of Hm, coercive force (Hci), maximum flux (\varphi_{mi}), remanent flux (\varphi_{r}), and loop squareness (box$^b$); 4) X-Y plotting of the hysteresis loop, the differentiated loop, orH_{ci}, \varphi_{mi}, \varphi_{r}, box$^b$, etc., versus Hm; 5) precision of flux and field measurements to the order of 1 percent. Contributing to the performance is a novel main coil design which generates a field constant to within 0.5 percent in a volume containing the sample and the pickup coils. The electronics package makes extensive use of analog function modules to process the signal information.