Diff Trafo

8/3/2019 Diff Trafo

http://slidepdf.com/reader/full/diff-trafo 1/21

DIFFERENTIALDIFFERENTIAL

TRANSFORMERTRANSFORMER Arizal Arizal DwiantaraDwiantara & Cancer& Cancer DevarthaDevartha

8/3/2019 Diff Trafo


DEFINITIONDEFINITION

DIFFERENTIAL TRANSFORMER is an ironDIFFERENTIAL TRANSFORMER is an iron--corecoretransformer with movable core. Atransformer with movable core. A

differential transformer produces andifferential transformer produces anelectrical output voltage proportional to theelectrical output voltage proportional to thedisplacement of the core. It is used todisplacement of the core. It is used tomeasure motion and to sensemeasure motion and to sense

displacements.displacements.

8/3/2019 Diff Trafo


LVDTLVDTLinear Variable DifferentialLinear Variable Differential

TransformersTransformers

8/3/2019 Diff Trafo


This presentation covers:This presentation covers:

How LVDTs workHow LVDTs work

Types of LVDTsTypes of LVDTs

AC vs. DC LVDTs AC vs. DC LVDTs

Applications to Structural Applications to Structural

EngineeringEngineering

8/3/2019 Diff Trafo


How LVDTs WorkHow LVDTs Work

8/3/2019 Diff Trafo


Types of LVDTsTypes of LVDTs

Unguided ArmatureUnguided Armature

Captive ArmatureCaptive Armature

SpringSpring--extended Armatureextended Armature

8/3/2019 Diff Trafo



Measured Object

Armature fits loosely

in the bore

Armature must beattached to the specimen

Body must be separatelysupported & properly aligned

Elevation/Cross-Section View

8/3/2019 Diff Trafo



There is no wear on the LVDT because noThere is no wear on the LVDT because nocontact is made between armature andcontact is made between armature and

bore.bore.LVDT does not restrict the resolution of LVDT does not restrict the resolution of

measured data (infinite resolution).measured data (infinite resolution).


Measured Motion

8/3/2019 Diff Trafo



WellWell--suited for short suited for short--range, highrange, high--speedspeedapplications (vibration)applications (vibration)

time

displ.


Measured Motion

8/3/2019 Diff Trafo



Body must be separately supported

Measured Object

Armature must be attached tothe specimen

Armature is both guided andrestrained by a low friction assembly

8/3/2019 Diff Trafo



Advantages compared to unguided armature: Advantages compared to unguided armature:

Better for longer working rangesBetter for longer working ranges

Preferred when misalignment may occurPreferred when misalignment may occur

8/3/2019 Diff Trafo


SpringSpring--Extended ArmatureExtended Armature


Measured Object

Like the captive armature, it hasa low-friction bearing assembly

Internal spring to continuouslypush the armature to its fullest possible extension

8/3/2019 Diff Trafo


SpringSpring--Extended ArmatureExtended Armature

The springThe spring--extended armature is best suitedextended armature is best suited

for slowfor slow--moving applications.moving applications.

Attachment between armature and Attachment between armature and

specimen is not required.specimen is not required.

8/3/2019 Diff Trafo


AC vs. DC AC vs. DC

8/3/2019 Diff Trafo


AC LVDTs AC LVDTs

Smaller sizeSmaller size

More accurateMore accurate

Can operate within a wide temperature rangeCan operate within a wide temperature range

Lower unit cost.Lower unit cost.

Advantages compared to DC LVDTs: Advantages compared to DC LVDTs:

8/3/2019 Diff Trafo


DC LVDTsDC LVDTs

Ease of installation and signal conditioning. SignalEase of installation and signal conditioning. Signalconditioning equipment is part of the LVDT.conditioning equipment is part of the LVDT.

Can operate from dry cell batteriesCan operate from dry cell batteries

Usually lower system cost Usually lower system cost

Advantages compared to AC LVDTs: Advantages compared to AC LVDTs:

8/3/2019 Diff Trafo


Applications to Structural Applications to StructuralEngineeringEngineering

LVDTs are reliable for measuring memberLVDTs are reliable for measuring memberdeflection in many structural engineeringdeflection in many structural engineeringexperiments.experiments.

LVDTs can measure displacement responseLVDTs can measure displacement responsedirectly in dynamic experiments.directly in dynamic experiments.

Mounting the LVDT to a stationary locationMounting the LVDT to a stationary locationis critical.is critical.

8/3/2019 Diff Trafo


RVDTRVDTRotaryRotary Variabel Variabel DifferentialDifferential

TransformerTransformer

8/3/2019 Diff Trafo


A variation of the LVDT A variation of the LVDT

Intended for angular displacement andIntended for angular displacement androtary position sensing.rotary position sensing.

In all respects it is identical in operation toIn all respects it is identical in operation tothe LVDT device but the rotary motionthe LVDT device but the rotary motionimposes certain restrictions on itsimposes certain restrictions on its

construction.construction.The span is given in angles and can be upThe span is given in angles and can be up

toto ±±3030rr toto ±±4040rr. Beyond that the output is. Beyond that the output isnonlinear.nonlinear.

8/3/2019 Diff Trafo


RVDTRVDT

8/3/2019 Diff Trafo


Response of RVDTResponse of RVDT

Diff Trafo

Documents

Transcript of Diff Trafo