Load Pin Optional Features
Strainsert offers a variety of load pin design options to fully optimize the force measurement solution.
Digital Strain Gage Modules (DCell) are compact, high-performance strain gage digital signal conditioner modules. They are aimed at applications which require high measurement accuracy, resolution, and stability.
The Strainsert 2-wire Loop Powered 4 to 20 mA Strain Gage Modules are specially designed, compact, high-performance strain gage analog signal conditioner modules. They are aimed at 350 Ohm sensor applications which require high measurement accuracy, resolution, and stability.
Bi-Axial Load Pins
Bi-Axial Load Pins are designed for applications that measure a radially applied force (Pr) where the load direction is unknown and/or changing in direction. This is facilitated by the installation of 2 perpendicular strain gage bridges (Px and Py), instrumentation, and geometric calculations.
One common use for a Bi-Axial Load Pin is at the hub of a sheave (or pulley) system, which is used to measure line tension. A Bi-Axial Load Pin installation has one end of the line at a fixed angle as a reference while the other end will vary in angle. See Strainsert Load Pin for Sheave Applications Note.
Download a PDF version of the Bi-Axial Load Pin Application Note
- Bridge Composition – Full
- Bridge Excitation – 10 (Typical), 12 Maximum – VDC Units
- Bridge Resistance – 350 Ohms (Nominal)
- Bridge Sensitivity – 0.5 or higher MV/V
- Temperature, Zero – ±0.01% (Nominal) – F.S/°F
- Temperature, F.S. – ±0.01% (Nominal) – Load/°F
- Zero Balance – ±3.0% (Nominal) – F.S.
- Non-Repeatability – ±0.25% (Nominal) – F.S.
- Non-Linearity – ±1% (Nominal) – F.S.
- Hysteresis – ±1% (Nominal) – F.S.
- Safe Overload – 150% (Typical) – F.S.
- Ultimate Strength – 300% (Typical) – F.S.
- Minimum Pin Diameter – 1 (Standard), 0.5 (with limitations) – Inch
- Pin Material – Stainless Steel 17-4; or higher strength stainless or alloy steels
- Crosstalk Error, After Correction – 5% (Maximum), <2% (Typical) – F.S.
- Sheave applications with variable angles
- Rotating joints
- Hinge pins
- Aircraft components (ex. landing gear)
- Loader Buckets
- Hydraulic Actuators
- Mooring Lines
Crosstalk error is observed when a radial force (Pr) is applied at varying angles and the sensor output magnitude does not fit the expected circular pattern. Instead, there are higher-than-expected readings at angles between the primary X and Y axes. This error is primarily caused by internal strain gage transverse sensitivity, which is due to physical design and construction constraints. Ideally, the ratio of transverse-to-axial sensitivity is negligible, however, this is not always the case in practice. Crosstalk error is unique and variable to each individual sensor Therefore, crosstalk errors may be marginal and crosstalk corrections may not always be required.
Crosstalk error mitigation efforts during sensor build may be difficult or impossible to achieve physically, regardless of technique or manufacturer quality. Therefore, to minimize the effects of crosstalk error, a mathematical correction is the most complete and preferred method. Strainsert has developed a mathematical crosstalk correction process, which provides realistic data that can be used in force analysis and stress calculations.
The inputs to the crosstalk correction function are the bi-axial strain readings and calibration constants. The calibration constants are determined during factory and/or in-place calibration.
The outputs of the crosstalk correction function are both Px and Py, which may be converted to Pr and angle (θ). This results in the most accurate measurement possible and is in the form of a corrected unit circle (range between 0 and 1 for loads between zero-scale and full-scale, respectively). This output may then be multiplied by the full-scale load value to determine the applied force in load units.
To determine the calibration constants, a factory crosstalk calibration is performed at Strainsert. For each crosstalk calibration, a Strainsert Crosstalk Correction Data report is provided. The crosstalk calibration consists of a series of angle measurements which can be either standard or customized to within a specified quadrant (0° – 90°, 90° – 180°, etc.). If the conditions of the target installation versus factory calibration are larger than expected, additional error may be introduced. Therefore, an in-place calibration is recommended after the clevis pin is installed. Using customer provided data, Strainsert will generate and provide an in-place Strainsert Crosstalk Correction Data report. The in-place calibration constants will then be used instead of the factory calibration constants.
Load Pins for Sheave Applications
Load Pins are designed into sheave applications for measuring line tension. Sheaves are designed with either a variable or constant wrap angle. For the variable wrap angle case, two strain gage bridges are installed perpendicularly (Px and Py). For the constant wrap angle case, one strain gage bridge is installed along the primary (sensing) axis of force (P).
Download a PDF version of Load Pin Note for Sheave Applications
Variable Wrap Angle
For a sheave with a variable wrap angle, the line enters and exits the sheave at 1 fixed angle point and 1 variable angle point.
During installation, ensure that the fixed angle point is oriented along either the X or Y axis. This is referred to as the “Level Line”, which is required for proper operation. If needed, ensure that Px and Py are crosstalk corrected prior to line tension and angle calculations using the Strainsert Crosstalk Correction Data report provided with the job and either the Crosstalk Correction User’s Guide or the Crosstalk Correction Quick Reference, provided separately.
Constant Wrap Angle
For a sheave with constant wrap angle, the line enters and exits the sheave at 2 fixed angle points.
To allow for proper orientation, ensure that the clevis pin and keeper flat are aligned with the axis of maximum sensitivity, which is at the center point of the wrap angle (θ).
Deep Sea Clevis Pin System
The Strainsert deep sea/high pressure Clevis Pin provides the ability to measure force at clevis joints under high pressure conditions. Complete systems are available, and include the instrumented Clevis Pin, cabling, and a digital display indicator.
- Output – 4-20 ma Loop Power or mv/V
- Input – 13 to 28V dc (4-20 ma Systems), 10V max excitation (mv/V Output)
- Non-Repeatability – ±0.15% F.S.O (Nom.)
- Non-Linearity – ±0.50% F.S.O (Nom.)
- Operating Temperature – 15 degrees F to 150 degrees F
- Storage Temperature – -40 degrees F to 160 degrees F
- Receptacle – Burton 55 Series (316 Stainless), Brantner or Customer Specified
- Cable Assembly – High Pressure, Marine (Lengths as Required)
- Pin Material – Monel, or 17-4 Stainless (Passivated, or other)
- Off-Shore Platform Crane, Winch Hook and Sheave Attachments
- Deep Sea Excavation and Trenching Systems
- Marine Research and Development
- Research and Development
- Towline Monitoring
- Mooring Lines
- Uni-Axial, Bi-Axial (Shown above) and Dual Bridge Force Sensing
- Integral Signal Conditioning
- System Calibration (5 Steps 2 Runs)
- 1500 psi Standard Rating
- Internal Strain Gaging
- Indicator Capabilities
- Custom Fit
- 2 Year Warranty
Dual Bridge Circuits
Dual bridge gaging provides two independent strain gage circuits. This option is advantageous for controlling multiple feedback systems as well as providing redundant force-measuring capability.
Strainsert - for superior internally gaged force transducers.
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- Product Quality
- Knowledgeable Technical Staff
- Standard and Custom Designs
- Customer Service
- Comprehensive Testing
For information on load pins, force sensing bolts, load cells, tension links or our high quality custom products, Contact Us for further assistance.