PRESENTATION ON

LVDT

FUNCATION An LVDT Displacement Transducer have 3 coils ; a primary

and two secondary's.

The transfer of current between the primary and the secondary's of the LVDT displacement transducer is controlled by the position of a magnetic core called an armature.

On our position measurement LVDTs, the two transducer secondary's are connected in opposition.

At the centre of the position measurement stroke, the two secondary voltages of the displacement transducer are equal but because they are connected in opposition the resulting output from the sensor is zero.

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As the LVDTs armature moves away from centre, the result is an increase in one of the position sensor secondary's and a decrease in the other. This results in an output from the measurement sensor.

With LVDTs, the phase of the output (compared with the excitation phase) enables the electronics to know which half of the coil the armature is in.

The strength of the LVDT sensor's principle is that there is no electrical contact across the transducer position sensing element which for the user of the sensor means clean data, infinite resolution and a very long life.

Our range of signal conditioning electronics for LVDTs handles all of the above so that you get an output of voltage, current or serial data proportional to the measurement position of the displacement transducer.

CIRCUIT

SECONDARY 1 SECONDARY 2

MATHEMATICAL EQUATION Transformer

The basic transformer formula, which states that the voltage is proportional to the number of coil windings, is the backbone of the LVDT. The formula is,

Vout/Vin=Nout/Nin

where N is the number of coil windings and V is the voltage read out.

This equation is,

D=MVout

where D is displacement of the iron core with respect to the transformer, and M is the sensitivity of the transformer (slope of the displacement-voltage curve).

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Ratiometric Wiring LVDTAnother commonly used LVDT wiring is known as ratiometric wiring, as shown schematically below.

Ratiometric Wiring The displacement for ratiometric LVDT's is given by the

relation,D=M * VA-VB/VA+VB

UsedMostly as a sensor in different field