1 / 19

LVDT

LVDT. Linear Variable Differential Transformers. Jason Hart CEE 498. This presentation covers:. How LVDT’s work Types of LVDT’s AC vs. DC LVDT’s Applications to Structural Engineering Costs. How LVDT’s Work. Types of LVDT’s. Unguided Armature Captive Armature

tanith
Download Presentation

LVDT

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. LVDT Linear Variable Differential Transformers Jason Hart CEE 498

  2. This presentation covers: • How LVDT’s work • Types of LVDT’s • AC vs. DC LVDT’s • Applications to Structural Engineering • Costs

  3. How LVDT’s Work

  4. Types of LVDT’s • Unguided Armature • Captive Armature • Spring-extended Armature

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

  6. 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”). Measured Motion Elevation/Cross-Section View

  7. Unguided Armature • Well-suited for short-range, high-speed applications (vibration) Measured Motion time displ. Elevation/Cross-Section View

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

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

  10. Spring-Extended Armature 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 Elevation/Cross-Section View

  11. Spring-Extended Armature • The spring-extended armature is best suited for slow-moving applications. • Attachment between armature and specimen is not required.

  12. AC vs. DC

  13. AC LVDT’s • Smaller size • More accurate • Can operate within a wide temperature range • Lower unit cost. Advantages compared to DC LVDT’s:

  14. DC LVDT’s • Ease of installation and signal conditioning. Signal conditioning equipment is part of the LVDT. • Can operate from dry cell batteries • Usually lower system cost Advantages compared to AC LVDT’s:

  15. Applications to Structural Engineering • LVDT’s are reliable for measuring member deflection in many structural engineering experiments. • LVDT’s can measure displacement response directly in dynamic experiments. • Mounting the LVDT to a stationary location is critical.

  16. Costs – Unguided Armature LVDT An LVDT with a 3” range purchased from Macrosensors, Inc. in quantities of one or two: • Costs $330 for AC. • Costs $485 for DC.

  17. Costs – Spring Extended Armature LVDT An LVDT with a +/- 2” range purchased from Macrosensors, Inc. in quantities of one or two: • Costs $1156 for AC. • Costs $1359 for DC. In general, costs of LVDT’s range from $50 to $1600, without considering specialty LVDT’s such as hermetically sealed.

  18. 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.

  19. References Figure on slide 3 (How LVDT’s work): http://www.daytronic.com/products/trans/lvdt/default.htm Figure on slide 12 (AC vs. DC): http://www.macrosensors.com/ms-lvdt_faq-tutorial.html Cost information obtained from Microsensors, Inc. Links to LVDT manufacturers found in report by Tjen Nung Tjhin updated on April 24, 2001.

More Related