What is LVDT ? AND How LVDT works? | Electrical Measurement Theory
The theory of LVDT is provided in this article in detailed knowledge. Working principle of LVDT and How LVDT works are explained in detail in this article. This theory is more important for get knowledge about electrical measurement.
LVDT stands for Linear Variable Differential Transformer.
LVDT is a passive inductive transducer and
commonly employed to measure force or weight.
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
Construction of LVDT is shown in below figure which is more helpful for understanding.
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| What is LVDT ? AND How LVDT works? | Electrical Measurement Theory |
It consists of one primary winding P and two secondary windings S1 and S2
which are placed on either side of the
primary mounted on the same magnetic core.
which are placed 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.
inside the coil assembly and the motion being measured is mechanically coupled to it.
The two secondary's S1 and S2 have equal number of turns but are connected in series
opposition so that e.m.fs.(E1 and E2) induced in them are 180 out of phase with each
other and, hence, cancel each other out.
opposition so that e.m.fs.(E1 and E2) induced in them are 180 out of phase with each
other and, hence, cancel each other out.
The primary is energized from a suitable A.C. source.
Working
When the core is in the center called reference position the induced voltages E1 and E2 are equal and opposite. Hence they cancel out and the output voltage Vo 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 antiphase with each other.
decreased in magnitude though they are still antiphase with each other.
The net voltage available is(E2-E1) and is in phase with D2.
Similarly, when the magnetic core moves towards coil S1,E1>E2 and Vo = E1- E2 and is in
phase with E1.
phase with E1.
Thus, we find that the magnitude of Vo is a function of the distance improved by the core and its polarity or phase indicates as to in which direction it has moved.
If core is attached to a moving object, the magnitude of Vo gives the position of that object.
