tag:blogger.com,1999:blog-33207527175511800262012-01-25T18:49:49.853-08:00Rohanhttp://www.blogger.com/profile/06564081797471038175noreply@blogger.comBlogger11100tag:blogger.com,1999:blog-3320752717551180026.post-89981853777961524602009-08-13T07:12:00.000-07:002009-08-13T07:23:17.702-07:00<div align="justify">The magnetoresistive sensors are based on the magnetoresistive effect. The magnetoresistive effect is the change of the resistivity of a current carrying ferromagnetic material due to a magnetic field. MGR sensor can be called as magnetically controllable resistors<br /><br />The below figure shows the Magnetoresistive effect.<br /><br /></div><div align="justify"></div><div align="justify"><img style="TEXT-ALIGN: center; MARGIN: 0px auto 10px; WIDTH: 400px; DISPLAY: block; HEIGHT: 138px; CURSOR: hand" id="BLOGGER_PHOTO_ID_5369452022966116658" border="0" alt="" src="http://2.bp.blogspot.com/_L4sYW0Y1_ho/SoQgKpNl4TI/AAAAAAAAACc/u4h8dxVe1qI/s400/MGR.jpg" /></div><p align="justify">When the current is passed through the ferromagnetic material the internal magnetisation vector(M) of the ferromagnetic material is parallel to the current flow. When an external magnetic field is applied in applied opposite to the direction of the current flow as shown in the figure the internal magnetisation vector changes its position(M1) by an angle depending on the strength of the magnetic field. The resistance depends on the angle formed by the internal magnetisation vector(M) of the ferromagnetic material and the direction of the current(I) flow. Resistance is largest if the current flow and the internal magnetisation vector are parallel. The resistance in ferromagnetic material is smallest if the angle is 90° between the current flow and the internal magnetisation vector.<br /><br />Normally 4 sensors are connected in a Wheatstone bridge configuration to form a complete MGR sensor with each resistor arranged to maximize sensitivity and minimize temperature influences. In the presence of a magnetic field, the values of the resistors change, causing a bridge imbalance and generating an output voltage proportional to the magnetic field strength. The Wheatstone bridge configuration provides reduction of temperature drift and doubles the signal output<br /><br />The advantages of MGR sensor are </p><ul><li><div align="justify">Non contact operation so there is no wear and friction. Hence unlimited number of operating cycles </div></li><li><div align="justify">high reliability due to their rugged construction</div></li><li><div align="justify">Low and stable offset </div></li><li><div align="justify">Due to its high sensitivity it can be used to measure weak magnetic fields</div></li><li><div align="justify">Low sensitivity to mechanical stress </div></li><li><div align="justify">Much more Insensitive to vibrations than inductive sensors</div></li><li><div align="justify">high operating temperature</div></li><li><div align="justify">wide operating frequency range (0 Hz to 1 MHz) </div></li><li><div align="justify">can be used in harsh environments</div></li><li><div align="justify">Reasonable cost</div></li><li><div align="justify">can measure zero speed </div></li><li><div align="justify">small size</div></li><li><div align="justify">fast response </div></li></ul><p align="justify">The disadvantages of MGR sensor are</p><ul><li><div align="justify">Sensitive to interfering magnetic fields. Very strong magnetic field can damage the sensor</div></li><li><div align="justify">Temperature drift </div></li><li><div align="justify">Limited linear range</div></li><li><div align="justify">Poor temperature characteristics </div></li></ul><p align="justify">Some of the applications of MGR sensor are</p><ul><li><div align="justify">wheel speed sensors </div></li><li><div align="justify">angle measurement </div></li><li><div align="justify">linear displacement measurement </div></li><li><div align="justify">current measurement </div></li><li><div align="justify">Earth magnetic field detection for compass and navigation applications</div></li><li><div align="justify">Metal detection</div></li><li><div align="justify">Magnetic field measurement </div></li></ul><div class="blogger-post-footer"><img width='1' height='1' src='https://blogger.googleusercontent.com/tracker/3320752717551180026-8998185377796152460?l=sensorsinfo.blogspot.com' alt='' /></div>Rohanhttp://www.blogger.com/profile/06564081797471038175noreply@blogger.com0