LVDT or Linear variable differential transformer is a passive transducer and is commonly employed to measure force (or weight, pressure and acceleration etc. which depend on force) in terms of the amount and direction of displacement of an object.
Construction :
It consists of one primary and two secondary windings S1 and S2. These are place on either side of the primary mounted on the same magnetic core. The magnetic core is free to move axially inside the coil assembly and the motion being measured is mechanically coupled to it. The two secondary winding have equal number of turns but are connected in series opposition. Emf induced in them are 180° out of phase. The primary is fed form an a.c source.
Working Principle:
When the core is in the centre (reference position) and induced voltages E1 and E2are equal and opposite. Hence they cancel out and output voltage is zero. When the external applied force moves the core towards coil S2, E2 is increased but E1 is decreased in magnitude though they are still anti phase with each other. The net voltage available is (E2 - E1) is in phase with E2.
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