1. L V D Ts What is an LVDT? An LVDT is a Linear Position Sensor An LVDT is a Linear Position Sensor With a Proportional Analog Output With a Proportional Analog Output An LVDT has 2 Elements, a Moving An LVDT has 2 Elements, a Moving Core and a Stationary Coil Assembly Core and a Stationary Coil Assembly

2. L V D Ts L inear V ariable D ifferential T ransformer L inear V ariable D ifferential T ransformer ► Transformer: AC Input / AC Output ► Differential: Natural Null Point in Middle ► Variable: Movable Core, Fixed Coil ► Linear: Measures Linear Position

3. How LVDT’s Work

4. Working principle of LVDT

5. Types of LVDT’s ► Unguided Armature ► Captive Armature ► Spring-extended Armature

6. Unguided Armature Measured Object Armature fits loosely Armature must be attached to the specimen Body must be separately supported & properly aligned Elevation/Cross-Section View

7. Unguided Armature ► There is no wear on the LVDT because no contact is made between armature and bore. ► LVDT does not restrict the resolution of measured data (“infinite resolution”). Elevation/Cross-Section View Measured Motion

8. Captive Armature Body must be separately supported Measured Object Armature must be attached to the specimen Armature is both guided and restrained by a low friction assembly

9. Captive Armature Advantages compared to unguided armature: ► Better for longer working ranges ► Preferred when misalignment may occur

10. Spring-Extended Armature Elevation/Cross-Section View Measured Object Like the captive armature, it has a low-friction bearing assembly Internal spring to continuously push the armature to its fullest possible extension

11. LVDT Characteristics

12. DC LVDT

13. Photograph of LVDT

14. Summary ► LVDT’s are robust equipment for measuring deflection. ► AC LVDT’s require separate signal conditioning equipment, while DC LVDT’s include signal conditioning equipment on the device. ► There are three types of LVDT: unguided armature, captive armature, and spring-extended armature. ► AC LVDT’s cost less than DC, but the entire measurement system must be considered.