1 / 12

Load Cells

Load Cells. Erwin Kohler. Definition. A load cell is a force transducer that converts force or weight into an electrical signal The strain gage is the heart of a load cell. Factors Affecting Load Cells. Manufacturer: The precise positioning of the gage Mounting procedure Materials used

hei
Download Presentation

Load Cells

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. Load Cells Erwin Kohler

  2. Definition • A load cell is a force transducer that converts force or weight into an electrical signal • The strain gage is the heart of a load cell

  3. Factors Affecting Load Cells • Manufacturer: • The precise positioning of the gage • Mounting procedure • Materials used • User: • Impact and hysteresis • Test modes: tension/compression • Off-axis loads

  4. S-type (tension-compression) • Compression Hanging scales 50 – 5000 Kg Silos, tanks and weighbridges5,000-60,000 Kg Classification and Application Bending beam Single point Platform scales1-1000 Kg Low profile: load and pallet scales5-500 Kg Shear beam Low profile: load and pallet scales500-5000 Kg

  5. Compression Load Cells Preferred by testing engineers • Higher output • Better fatigue life • Better resistance to extraneous loads • Greater stiffness • Overload protection

  6. Falling Weight Deflectometer (pavement testing) Load Cells in Engineering Testing Force versus deflection. Fatigue tests Adhesive and paints peel force

  7. Load Cells Errors • Impacts and hysteresis • Metal retains a history of its previous loadings • When the loading is properly done, then the curve will return to zero • If, by mistake, 80% of load is applied by impact and then returned to 60%, then the load cell would be operating on a minor hysteresis loop • DON’T IMPACT LOAD CELLS

  8. Load Cells Errors • Test modes and calibration • Load cells are routinely conditioned in one mode (either tension or compression) and then calibrated • Determine test mode needed • Some cells can be operated in both modes without reconditioning, but result in non-return to zero after looping through both modes • Special fatigue load cells: • Sharp corners and edges are polished to avoid crack propagation • Longer service life including fully reversed, full capacity loading cycles

  9. Load Cells Errors • On-axis loading • All on-axis loading generate some level of off-axis extraneous components because of load carrying members causes friction that transmits side load • Avoid flat-to-flat load, because it is impossible to maintain two surfaces parallel enough to guarantee that the force will end up being centered • Compression cells have load buttons Load button: - 4” for 10,000 lbf - 6” for 50,000 lbf -12” for 200,000 lbf 3/8” off center with 5 degrees misalignment causes large moment

  10. Load Cells Errors • Nonrepeatibility • Function of the resolution and stability of the signal conditioning electronics • Load cells typically have nonrepeatibility which is better than the load frames, fixtures and electronics used to measure it.

  11. Reference Prices LOAD SENSORS . Low Cost Compact Compression Load Cells $399 . Subminiature Compression Load Cells - High Stability $395 . Miniature Load Beams $599 . Miniature & Compact Tension/Compression Load Cells - High Output $565 . Industrial Flat Disc Tension/Compression Load Cells - Stiff Shear Design $899 ACCESSORIES . Compression Load Button Adapters for Load Cells $60 . Tension Pull Plates for Load Cells $150

  12. Manufacturers • Measurement specialists www.measurespec.com • Entran sensors and electronics www.entran.com • Tedea Huntleighwww.aboutloadcells.com • Interface www.interfaceforce.com

More Related