Design and construction of high sensitivity a.c. suceptibility bridge

Abstract

We h ave used an ex i s ting d esi gn of an inexpe nsive mutual i ndu ctance bridge cir cu it to construct a h i g h Sensitivity A.C. Su sceptibility bridge. which uses i n t eg r a t e d ope rati ona l amplifiers. This b r idge c ircuit in c onjunction with a lock in amplifier ca n be u sed for measur e me nt of magn e tic sus c ept i b i lity o f ferro , f e rri, a nd paramag net ic sampl es . The circu it employs operational amplifiers both fo r balancing the br i dge and fo r detecti n g t h e d iff e ren i a l s i gnal from the sample co il . The s i mp l e d esign of the e nt i re system and th e use of l ow cost compo ne nts ar e the spec ial features of thi s system . At present the se n s itivity of the b ri dge is approx imately , O.lmV , and f u rther improve ments ar e possi ble. The e ff ec t of t e mperat ur e o n the electronic nois e i n t he syst e m was a l so dete rmined . We a l so f ind good agr eement betwe en the known va lue of permeabi l ity of magnet ic steel and the va lue by u s , u s ing th is bridge circuit meas u r ed .