LVDT


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What Is An LVDT ?

The letters LVDT are an acronym for Linear Variable Differential Transformer, a common type of electro mechanically transducer that can convert the rectilinear motion of an object to which it is coupled mechanically into a corresponding electrical signal. LVDT linear position sensors are readily available that can measure movements as small as a few millionths of an inch up to several inches, but are also capable of measuring positions up to + - 20 inches (+ -0.5m).

How Does An LVDT Work ?
Figure 2 illustrates what happen when the LVDT’s core is in different axial positions. The LVDT’s primary winding,P, is energized by a constant amplitude AC source. The magnetic flux thus developed is coupled by the core to the adjacent secondary windings, s1and s2. If the core is located midway between s1 and s2, equal flux is coupled to each secondary so the voltages, E1 and E2, induced in the windings s1 and s2 respectively, are equal. At this reference midway core position, known as the null point, the differential output, (E1-E2), is essentially zero.


LVDT Support Electronics
some applications Although an LVDT is an electrical transformer, it requires AC power of an amplitude and frequency quite different from ordinary power lines to operate properly (typically 3 Vrms at 3 kHz).