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Celulas de carga (Load Cells)

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Celulas de carga (Load Cells)

Notapor pichu » Vie, 04 May 2012, 10:50

GUIDE FOR LOAD CELLS


Part A : General acceptance of load cells and load receptors 4
in type approvals of weighing instruments
A.1 General acceptance of load cells (LCs) 4
A.2 Standard load transmission devices 6
A.3 Common load receptors 7
A.3.1 Acceptable solutions 7
A.3.2 Examples 11
A.4 Documentation 13
A.5 Wording in type approval certificates (TAC) 13
Part B : Testing and certification of load cells and load cell families 14
B.1 Metrological and practical aspects 14
B.1.1 Test procedures 14
B.1.2 LC series and families, selection of samples 16
B.2 Documentation 16
B.3 Test report 16
B.4 Test certificate (TC) 17
B.4.1 Layout of the test certificate 17
B.4.2 Contents of the annex of the TC 18
B.4.3 Revision of existing TCs
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Registrado: Vie, 08 Jul 2011, 22:01


Re: Celulas de carga (Load Cells)

Notapor pichu » Vie, 04 May 2012, 10:52

Load Cells A Primer on the Design and Use of Strain Gage Force Sensors



THE LOAD CELL PRIMER ................................................................................................... 7
The “Elastic Force Transducer” ............................................................................................ 7
Adding Sophistication............................................................................................................. 8
A Rudimentary Load Cell: The Proving Ring ................................................................ 10
Creep .................................................................................................................................. 10
Deflection Measurement ................................................................................................ 10
Temperature Effects ........................................................................................................ 11
Response to Extraneous Forces ...................................................................................... 11
Conclusion ......................................................................................................................... 11
Improvements on the Proving Ring Idea ......................................................................... 11
Introducing the Strain Gage ........................................................................................... 11
Thermal Tracking ............................................................................................................ 12
Temperature Compensation.......................................................................................... 12
Creep Compensation ...................................................................................................... 12
Frequency Response ......................................................................................................... 13
Non-Repeatability ............................................................................................................ 13
Resolution .......................................................................................................................... 13
Flexure Configurations: Bending Beams .......................................................................... 13
Bending Beam Cell ........................................................................................................... 13
Double-Ended Bending Beam Cell............................................................................... 14
S-Beam Cells ...................................................................................................................... 14
SMT Overload Protected S-Cell ........................................................................................ 15
LBM and LBT Load Button Cells ..................................................................................... 15
SPI Single Point Impact Cell ......................................................................................... 15
1500 Low Profile Rotated Bending Beam ................................................................... 16
Flexure Configurations: Shear Beams ............................................................................... 17
SSB Shear Beam Cell ....................................................................................................... 17
Low Profile Shear Beam Cell ......................................................................................... 17
Extraneous Load Sensitivity ........................................................................................... 19
The Low Profile Precision Series ................................................................................... 20
The Low Profile Ultra Precision Series ........................................................................ 20
©1998–2009 Interface Inc. All rights reserved. http://www.interfaceforce.com Page 4
The Low Profile Fatigue Rated Series ........................................................................... 20
Fatigue Rated Load Cell .................................................................................................. 21
Compression Loading ...................................................................................................... 21
WeighCheck Weighing System ..................................................................................... 22
LoadTrol Oil Well Pump-Off Control Cell ............................................................... 23
Competitive Load Cell Product Configurations ............................................................ 24
The Simple Column Cell ................................................................................................ 24
Advantages of the LowProfile Cell................................................................................ 25
Input/Output Characteristics and Errors ........................................................................ 26
Gage Interconnection Configurations ......................................................................... 26
Temperature Effect on Zero and Output .................................................................... 27
Load Cell Electrical Output Errors ............................................................................... 28
Resistance to Extraneous Loads ..................................................................................... 29
System Errors ..................................................................................................................... 29
GENERAL PROCEDURES FOR THE USE OF LOAD CELLS ............................... 31
Excitation Voltage ................................................................................................................. 31
Remote Sensing of Excitation Voltage .............................................................................. 32
Physical Mounting: “Dead” and “Live” End .................................................................... 33
Mounting Procedures for Beam Cells ............................................................................... 34
Mounting Procedures for Other Mini Cells .................................................................... 34
Mounting Procedures for Low Profile Cells With Bases .............................................. 35
Mounting Procedures for Low Profile Cells Without Bases ........................................ 36
Mounting Torques for Fixtures in Low Profile Cells .................................................... 37
LOAD CELL CHARACTERISTICS AND APPLICATIONS .................................. 38
Load Cell Stiffness ................................................................................................................. 38
Load Cell Natural Frequency: Lightly Loaded Case ...................................................... 40
Load Cell Natural Frequency: Heavily Loaded Case ..................................................... 42
Contact Resonance ............................................................................................................... 43
Application of Calibration Loads: Conditioning the Cell ........................................... 44
Application of Calibration Loads: Impacts and Hysteresis .......................................... 44
Test Protocols and Calibrations ......................................................................................... 44
Application of In-Use Loads: On-Axis Loading ............................................................. 45
Control of Off-Axis Loads .................................................................................................. 46
Reducing Extraneous Loading Effects by Optimizing Design ..................................... 46
©1998–2009 Interface Inc. All rights reserved. http://www.interfaceforce.com Page 5
Overload Capacity with Extraneous Loading ................................................................. 46
Impact Loads .......................................................................................................................... 46
MULTI-CELL STATIC OR WEIGHING APPLICATIONS .................................... 47
Equalizing the Loads in Multiple-Cell Systems .............................................................. 48
Corner Adjustment of Multiple-Cell Systems ................................................................ 50
Moment Compensated Platform ....................................................................................... 50
One-Cell Systems .................................................................................................................. 51
Two-Cell Systems ................................................................................................................. 52
Parallel Paths: Pipes, Conduit, and Check Rods ............................................................ 53
Paralleling Two or More Cells ............................................................................................ 53
Universal Cells .................................................................................................................. 53
Compression Cells ........................................................................................................... 56
MATERIALS AND PROCESS CONTROL TESTING ............................................... 56
Force Versus Deflection ....................................................................................................... 57
Shear Force Versus Compaction ........................................................................................ 57
Peel Force ............................................................................................................................... 58
Adhesive or Bonding Shear Force ...................................................................................... 58
Safety: Proof Testing and the Compression Cage .......................................................... 58
Finding Center of Gravity ................................................................................................... 59
FATIGUE TESTING .............................................................................................................. 60
Fatigue Capacity .................................................................................................................... 60
Use of Non-Fatigued-Rated Cells in Fatigue Applications .......................................... 61
Fatigue Capacity With an Added Fixed Load ................................................................. 62
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Registrado: Vie, 08 Jul 2011, 22:01


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