Fundamental Electrical and Electronic Principles, Third Edition

Magnetic Fields and Circuits 139Method:1 Ensure that the core is completely demagnetised before starting.2 Zero the Hall probe, monitoring its output with the DVM.3 Connect the circuit as in Fig. 4.24 .4 Increase the coil current in 0.1 A steps, up to 2 A. Record the DVM reading ateach step.Note: If you ‘ overshoot ’ a desired current setting. DO NOT then reduce thecurrent back to that setting. Record the value actually set, together with thecorresponding DVM reading.5 Reduce the current from 2 A to zero, in 0.1 A steps. Once more, if youovershoot a desired current setting, DO NOT attempt to correct it.6 Reverse the connections to the psu, and increase the reversed current insmall steps until the DVM indicates zero.Note: The Hall effect probe output (as measured by the DVM) represents theflux density in the core. The magnetic field strength, H , may be calculatedfrom NI / .AprobeHallProbeCircuitVd.c.p.s.u.magneticcircuitFig. 4.247 Plot a graph of DVM readings ( B ) versus H .8 Submit a full assignment report.