docCHOOSING THE RIGHT LOAD CELL
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CHOOSING THE RIGHT LOAD CELL
CHOOSING THE RIGHT LOAD CELL 1 Types of Load Cells Bending Beam Single point weighbeam Bending Beam Miniature Diaphragm Column Shear pancake Diaphragm Diaphragm pancake Single Column Clevis Pin Bending Beam Shear Beam Multiple Column Donut Column Cannister S Type 2 Donut Application Segments Some Customers OEM Industrial weighing Retail weighing Oil & Gas Specialist Force Measurements Main Focus Process Weighing Main Focus Scientific weighing Test & Measurement Research/Calibration Force measurement 3 Application Segments FORCE MEASUREMENT INDUST RIAL W EIGHING OF F ICE W EIGHING RET AIL W EIGHING 4 Principle of the Load Cell Tension Compression 5 Principle of the Load Cell 10V 6 Principle of the Load Cell LOAD 10V 7 How a Load Cell is Constructed 8 How a Load Cell is Constructed 9 How a Load Cell is Constructed 10 How a Load Cell is Constructed 11 How a Load Cell is Constructed 12 How a Load Cell is Constructed 13 How a Load Cell is Constructed 14 How a Load Cell is Constructed 15 How a Load Cell is Constructed 16 How a Load Cell is Constructed 17 How a Load Cell is Constructed 18 How a Load Cell is Constructed 19 How a Load Cell is Constructed 20 How a Load Cell is Constructed 21 How a Load Cell is Constructed 22 How a Load Cell is Constructed 23 How a Load Cell is Constructed 24 How a Load Cell is Constructed Compression Tension 25 Elements of a Load Cell 26 Elements of a Load Cell 27 Elements of a Load Cell 28 Unique Load Cell Characteristic Load Cells form part of the structure that they are measuring 29 Load Cell Specifications Connection to measurement system Connection to structure Electrical Connection Signal O/P Mounting considerations Size Weight Excitation Sensitivity Additional O/Ps Sensor Properties External Internal Measurement Type Range Accuracy Environmental Extraneous Loads Temperature Range Overload protection 30 Specifying a Load Cell • So many combinations of specs are mutually exclusive: Specifying a load cell is trading one performance criteria against another. – Example • • • • Pick 3 and you compromise the fourth High load capacity Small size High accuracy Immunity to extraneous loads 31 Mounting 32 Mounting 33 Mounting 34 Mounting 35 Mounting 36 Mounting 37 Mounting 38 Mounting 39 Mounting 40 Mounting 41 Mounting 42 Mounting 43 Mounting 44 Mounting 45 Mounting 46 Mounting 47 Mounting 48 Mounting 49 Mounting 50 Load Range Mechanical failure Load Range Overload Range Usually same as load range 51 Progressive Damage Load Range 5 50 250 15000 50000 500000 Specials Model TG Model TH Model MPB Model WG Model LFH-71 Model 73 Load Range Model 43 Model 53 Model D Model 13 Model RM, RH, RF Model 82 Model 81 Model RGM, RGH, RGF Model 45 Model 46 Model 75 Model UG Model 41 Model 11 Model 34 Model 31 0 10 Tension 100 1,000 10,000 Load Range Compression Tension & Compression Fatigue rated version Fatigue rated version 52 100,000 Bending 1,000,000 Lbs Accuracy Model UG Model 47 Model 82 Model WG Model GR Model SP Model 49 Model 81 Model 41 Model 75 Model 31 Model RGM,RGH,RGF Model MBL Model 73 Model 34 Model 43 Model Model TG Model TH Model MPB Model 53 RM,RH,RF Model D Model 13 Model 11 Model LFH-71 53 COMPRESSION TENSION Physical Size TENSION/COMPRESSION 100,000 lbs 10,000 lbs Model UG 1,000 lbs 100 lbs 10lbs Model UG Model UG Model UG 0.02% 0.02% Model RGM,RGH,RGF 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.03% 0.03% 0.03% 0.03% Model 47 0.03% 0.03% Model RGM,RGH,RGF 0.03% 0.03% Model 47 Model 47 0.02% 0.02% Model 47 0.03% 0.02% 0.02% 0.03% 0.03% Model 49 0.03% 0.02% 0.02% 0.02% 0.02% Model 49 0.03% 0.03% Model 34 0.03% Model 34 Model 31 Model 49 0.03% Model 49 Model 34 Model 31 TENSION/COMPRESSION 100,000 lbs 10,000 lbs Model UG 1,000 lbs 100 lbs Model 31 10lbs Model UG Model UG Model UG 0.02% 0.02% Model RGM,RGH,RGF 0.02% 0.02% 0.02% 0.02% 0.02% 0.02% 0.03% 0.03% 0.03% 0.03% Model 47 0.03% 0.03% Model RGM,RGH,RGF 0.03% 0.03% Model 47 Model 47 0.02% 0.02% Model 47 0.03% 0.02% 0.02% 0.03% 0.03% Model 49 0.03% 0.02% 0.02% 0.02% 0.02% Model 49 0.03% 0.03% Model 34 0.03% Model 34 Model 31 Model 49 0.03% Model 49 Model 34 Model 31 Model 31 Model 31 Model 41 Model 41 Model 11 Model 11 Model 75 Model 11 Model 41 Model 41 Model 75 COMPRESSION Model 75 Model 75 Model 41 Model LFH-71 Model D Model MPB Model 53 Model D Model 53 Model D Model D Model 53 Mod el M PB Model TH Model WG Model TG Model WG Model MPB Model 53 Model TH Model 13 Model LFH-71 Model 13 Model LFH-71 Model 13 10,000 lbs Model 73 Model 13 Model 73 Model 73 Model 73 Model 43 Model 73 TENSION Model 43 Model 82 Model RM,RH,RF Model 43 Model 82 Model RM,RH,RF Model 73 Model 43 Model 82 Model 43 Model 31 Model 81 Model 41 Model 41 Model 11 Model 11 Model 75 Model 11 Model 41 Model 41 Model 75 COMPRESSION Model 75 Model 41 Model LFH-71 Model D Model MPB Model 75 Model 53 Model D Model 53 Model D Model D Model 53 Mod el M PB Model TH Model WG Model TG Model WG Model MPB Model 53 Model TH Model 13 Model LFH-71 Model 13 Model LFH-71 Model 13 10,000 lbs Model 73 Model 13 Model 73 Model 73 Model 73 Model 43 Model 73 TENSION Model 43 Model 82 Model RM,RH,RF 54 Model 43 Model 82 Model RM,RH,RF Model 73 Model 43 Model 82 Model 43 Model 81 Fatigue Rating High stress points reduced by strain gage placement to highest stress area. Structure cross sections increased Stress Levels Reduced below non-fatigue Rated load cells -Lower sensitivity Fatigue rated to 1000 million cycles compared to 1 million cycles 55 Extraneous Loading OFF AXIS LOADING TORQUE SIDE LOADING 56 Extraneous Loading Pancake Style load cells have excellent off axis immunity Typically 20% side load gives less than x% error Pancake design 57 Extraneous Loading Poor off axis performance due to dimensional geometry Distance from centerline to gauges Distance from centerline to gauges Miniature design 58 Extraneous Loading The larger the width to height ratio the higher the immunity to side load Poor Better Best Good Column design 59 Extraneous Loading Multiple column cells can reduce effects of off axis loading Column design 60 Extraneous Loading Multiple column cells can reduce effects of off axis loading Column design 61 Extraneous Loading S Beam designs are poor in side loading immunity and therefore poor in compression S Beam design 62 Extraneous Loading The use of load cells in tension and with rod end bearings eliminates side loading S Beam design 63 Product Range Load Cells Pancake 64 Product Range Load Cells Pancake Miniature 65 Product Range Load Cells Pancake Miniature Cannister 66 Product Range Load Cells Pancake Miniature Cannister Donut Style 67 Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style 68 Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style 69 Z Beam Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style 70 Z Beam Dynamic Load Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style 71 Z Beam Dynamic Load Special Applications Product Range Load Cells Pancake Donut Style Miniature Cannister Rod End Style Z Beam Dynamic Load Special Applications Non-Fatigue Rated Fatigue Rated Tension Compression Compression only Model 75 Tension Compression Model 73 Compression only Model 45 Ultra High Precision 10,000 lbs Model 73 Model 41 Model 73 Model 43 0.02% 0.02% 0.02% 0.02% Ultra High Precision 0.03% 0.03% 0.03% 0.03% Model 46 0.02% 0.02% 0.02% 0.02% 0.03% 0.03% 0.03% 0.03% Model 47 72 Model 49 Product Range Load Cells Pancake Miniature Cannister Sub miniature Tension Compression Compression only Donut Style Rod End Style Z Beam Dynamic Load Special Applications Miniature Tension/Compression Male thread Model 11 Tension/Compression Female Thread Model 13 Model 31 Model 34 Low Cost Compression Only High Capacity Compression Model 53 Model LFH-71 73 Product Range Load Cells Pancake Miniature Cannister Tension & Compression Donut Style Rod End Style Z Beam Dynamic Load Special Applications Compression Only 10,000 to 500,000 lbs 0.03% 100 to 200,000 lbs 0.03% Model WG 50,000 to 500,000 lbs 0.1% Model UG Model TG 15,000 to 3,000,000 lbs 0.25% 74 Model TG Model MPB Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style Compression only 15,000 to 200,000 lbs 150 grms to 30,000 lbs Model D Model TH 75 Z Beam Dynamic Load Special Applications Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style Tension Compression Z Beam Dynamic Load Special Applications Tension Model RGM Male-Male Thread Male-Male Thread Male-Female Thread Male-Female Thread Female-Female Thread Female-Female Thread Model RGH Model RM Model RH Model RF Model RGF 76 Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style Z Beam Dynamic Load Tension Only 100-20,000 lbs Model 82 77 5-250 Lbs Model 81 Special Applications Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style 78 Z Beam Dynamic Load 1000 lbs 10,000 lbs Model DLN Model DLS Special Applications Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style Z Beam Dynamic Load Clevis Pins Single Point Compression Build from scratch special 79 Special Applications Product Range Load Cells Pancake Miniature Cannister Donut Style Rod End Style Z Beam Dynamic Load Clevis Pins Single Point Compression Build from scratch special Specials Standard Product 80 Special Applications Market Segments: Weighing FORCE MEASUREMENT INDUSTRIAL WEIGHING OFFICE WEIGHING RETAIL WEIGHING 81 Market Segments: Weighing vs Force Measurement Force Weighing – – – – – – – – Fast Response Long fatigue life Large temp range Majority: Industrial Minority:Hostile Low compliance Low to medium volume Medium to high accuracy – NIST traceable – – – – – – – – – – 82 DC response Low cycle life Limited temperature range Majority: room environments Minority: salt and water Large deflections High volume High accuracy Low cost ‘Legal for trade’ Environmental Difficult to seal 83 Environmental Barometric pressure Single sided diaphragm Hermetically sealed 50 lb canister example 84 Environmental Barometric pressure Diaphragm each side equalizes pressure effects Barometric pressure 85 Environmental Aluminum only good to 120 F Stainless good to 500 F High temp strain gages High temp connector High temp solder 86 Electrical 350 ohm bridge with mV/V output Amplified output 0-5V 0-10V 4-20mA Note: Miniature and high temperature load cells do not have amplified outputs 87 Noise Immunity Supply + Ground 2 mV/V Signal +ve Signal to noise ratio = 20 (Digitizer error as much as 10%) Signal = 20 mV maximum Noise = 1 mV 88 Noise Immunity Internal amplifier fitted 15-32 V DC Supply Supply + Ground Signal +ve 0-10V output 89 Noise Immunity Supply + Ground 0-10V Signal +ve Signal to noise ratio = 10,000 (Digitizer error only 0.01%) Signal = 10 V maximum Noise = 1 mV 90