TRANSDUCERS It converts one form of energy into another form of energy, either for measurement or for control. If it is for measurement, then And if for it is called as Inputcontrol, then, Actuator. transducer or sensor.
Those which provide Active electrical signalsTransducers in the form of voltage & current.
It belongs to one HALL EFFECT of the TRANSDUCERSGalvanomagnetic phenomena. It was discovered in 1879.
CONTD. In which interaction between magnetic field & moving electrical charges results in the development of forces that alter the motion of the charge. The Hall effect is observed in all metals, but it is prominent in semiconductor materials.
CONTD. A thin strip of bismuth or n-type germanium is subjected to magnetic field B normal to its surface, while it carries a current along the length of the strip, but normal to B.
CONTD. The magnetic field exerts a The edge surfaces act like charged force(known as Lorentz force) on electrodes and the potentialthe electrons moving at a velocity difference measured b/w P & Q is v, with the result that some of known as Hall potential Eh, which them drift towards the edges of increases with increase of B & I. the strip.
CONTD. The build up of the charge on the edge surfaces will, in turn, develop an electric field(Hall field) of such a polarity that counteracts the collection of charges on the surfaces. The force on the electrons due to Hall field & Lorentz force balance each other finally.
CONTD. If e is the charge of The time required the electron, then to reach this the Lorentz forceequilibrium is about Bev & the force due10 to the power -14 to Hall field are s. equal to each other.
• Hence, Bev = e /b) • Or, = Bbv(volts) • If mobility of the charge carriers is represented by χ, then v is given by • V= χ /L • The Hall coefficient depends on the no. of free charge carriers per unit volume. • = ( )/(n ) n
APPLICATIONS It is preferred for mapping of The Hall effect magnetic field With & wihtout transducer is around conductors the presence ofprimarily suited for carrying large metallic objects inthe measurement currents under their vicinity.of magnetic fields. different flow conditions,
CONTD. This transducer has made it possible to measure dc & ac currents in conductors without interruption of the circuit and without making any electrical contact with the conductor. The range of current that can be measured in this manner can be as low as 0-1 mA or as high as 0-1 kA.
CONTD. It is used as a ProximityIn Instrumentation, the Hall detector, and also toelement is highly valued for measure the change in the its speed of response in The advantages are its strength or direction of thedetection of changes in the small size & high sensitivity. magnetic field due tomagnetic field to which it is displacement or nearness exposed. of the test object.