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Hall ef­fect sen­sors were first used as mi­crowave power sen­sors. th­ese now per­vade ev­ery­thing from au­to­mo­biles to com­put­ers to ma­chine tools. take a peek into the dif­fer­ent types of Hall ef­fect sen­sors

Electronics For You - - TUTORIAL - D B B

Since its in­tro­duc­tion sev­eral years ago, the Hall ef­fect sen­sor has cap­tured the imag­i­na­tion of de­sign engi­neers. Be­ing solid­state, it is a more re­li­able ap­proach than electro­mechan­i­cal coun­ter­parts. Since the Hall ef­fect sen­sor has no mov­ing parts, low- level loads last well beyond bil­lions of op­er­a­tions. There are many ap­pli­ca­tions of Hall ef­fect sen­sors. How­ever, se­lec­tion of the proper type is crit­i­cal for any ap­pli­ca­tion.

What’s a Hall ef­fect sen­sor

Sen­sors can be clas­si­fied based on the phys­i­cal ef­fects that they can re­spond to. Hall ef­fect sen­sors are unique in that their prin­ci­ple of op­er­a­tion is based on mixed ef­fects.

When a cur­rent-car­ry­ing con­duc­tor is placed into a mag­netic field, a volt­age is gen­er­ated per­pen­dic­u­lar to both the cur­rent and the field. This prin­ci­ple is known as the Hall ef­fect. So Hall ef­fect sen­sors de­pend on the elec­tric cur­rent as well as the mag­netic field.

Typ­i­cally, a Hall ef­fect sen­sor has three wires or ter­mi­nals: one for ground, one for sup­ply (or ref­er­ence) volt­age and one for the output sig­nal. The sup­ply volt­age is nec­es­sary to cre­ate the switch­ing ef­fect that takes place inside the sen­sor.

In prac­tice, the ba­sic mag­netic field sen­sor—Hall el­e­ment—is con­structed from a thin sheet of con­duc­tive ma­te­rial with output con­nec­tions per­pen­dic­u­lar to the direc­tion of cur­rent flow. When sub­jected to a mag­netic field, it re­sponds with an output volt­age pro­por­tional to the mag­netic field strength. The volt­age output is in mi­cro-volts (μV) range and re­quires sig­nal con­di­tion­ing elec­tron­ics to achieve use­ful volt­age lev­els.

The ad­di­tional elec­tron­ics needed is a dif­fer­en­tial am­pli­fier and a tem­per­a­ture com­pen­sa­tion cir­cuit. Volt­age reg­u­la­tion is also re­quired when operating from an un­reg­u­lated sup­ply. When the Hall el­e­ment is com­bined with this as­so­ci­ated elec­tron­ics, it forms a ready-to-use Hall ef­fect sen­sor, which is an in­te­grated cir­cuit chip that con­tains a Hall el­e­ment and the sig­nal con­di­tion­ing elec­tron­ics.

Ac­cord­ing to Honey­well’s eall Ef­fect pens­ing and Ap­pli­ca­tion, although Hall ef­fect sen­sor is a mag­netic field sen­sor, it can be used as the pri­mary com­po­nent in many other types of sens­ing de­vices. If the quan­tity to be sensed in­corpo-

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