Force Sensors
Force sensors are devices that convert mechanical forces such as weight, tension, compression, torque, strain, stress, or pressure into an electrical signal. This output signal can then be used to...
The Uses & Advantages of Load Pins
A load pin is a sensor utilized to measure force or weight in various research, control, measurement and testing applications. The load pin force sensor converts a force into an electrical signal. The load pins provide durable and accurate measurement, even in extreme environments such as space, oceans, mines, and deserts, amongst others. An example of the value of load pins, due to their design, is identifying applied forces, and measuring and preventing overloads transferred through the pin joints.
A key benefit of force sensors, especially load pins, is the use of internal strain gauges. Developed by Strainsert and patented, this internal gauge technology significantly expands the applications of load pins. This proven technology has demonstrated its reliability and effectiveness for more than six decades.
This functionality is achieved through the pin's design, which includes a small internal cavity along its neutral axis to accommodate and safeguard the internal components, keeping the gauges isolated from external conditions. Additionally, load pins are crafted from high-strength stainless or alloy steel to enhance their linearity and ensure consistent performance.
While standard load pins are suitable for many uses, the growing diversity of applications has made custom load pins increasingly essential. The option to acquire load pins tailored to specific requirements offers a significant benefit. Strainsert has streamlined the custom design process, enabling efficient and cost-effective production to meet tight deadlines.
How Do Load Pins Work?
Load pin strain gauges are generally connected in a Wheatstone bridge configuration. When powered by a constant voltage, this bridge setup generates a variable output voltage that correlates to the force exerted on the elastic component. Thus, a load pin transforms the mechanical input into an electrical output through a series of physical quantity conversions.
- Force is converted to mechanical stress according to the fundamental equations of strength from materials science.
- Stress is converted to strain according to Hooke's law.
- Strain becomes a relative resistance variation.
- Variation in relative resistance is converted to a change in the output voltage by means of the Wheatstone bridge.
To summarize, when a load is applied to the Load Pin, it causes deformation. This deformation is detected by the strain gauges and subsequently transformed into an electrical signal that can be measured through the Wheatstone bridge.
Applications for Load Pins
Quantifying forces on a structure often requires costly and complex equipment. Load pins address this issue by being integrated directly into assemblies, replacing standard, non-instrumented pins or shafts within the load path. When force is applied to these instrumented load pins, the strain gauges generate a signal that enables precise load measurement, including under high stress and overload conditions.
Load pins find use in a variety of applications. Here are a few examples:
- Bearing Blocks
- Brake Anchors
- Structural Tests
- Flight Simulators
- Winch/Crane/Lifting Systems
- Landing Gear Clevis Joints
- Mooring Lines/Lanyards
- Sprocket/Pulley Axles
- Bombay/Cargo Doors
- Railroad/Towbar Connections
- Armament Suspension Systems
- Rocket Reaction Forces
- Aircraft Wing Joints
- Conveyors
- Test Machines
- Hydraulic Actuators
- Nuclear Fuel Rod Control
- Robotic Pin Joints
- Sheave Axles
- Ground Support Equipment
Typical Features of a Load Pin
Constructed from durable stainless steel or other high-strength alloy steels, load pins offer excellent corrosion resistance. This makes them suitable for deployment in extremely challenging environments.
Many load pin systems come with built-in thermal compensation. They are designed for straightforward installation and upkeep, offering a cost-effective solution for challenging load measurement scenarios. An optional wireless transmitter for these load pins features integrated electronics, allowing for cable-free monitoring. When correctly installed and calibrated, load pins can serve as direct replacements, reducing installation expenses and eliminating the need for extra hardware components in the load path.
Why is Calibration of Load Pins Essential?
Load pins play a vital role across various sectors such as aerospace, marine, oil and gas exploration, military, aviation, and automotive industries. Ensuring accurate force measurements is essential for addressing product liability and safety concerns. Adhering to traceability standards aligned with NIST is often necessary to meet ISO and AS certification requirements.
Load pins can experience degradation over time due to factors such as usage, mishandling, drift, or aging. To maintain accuracy, it is essential to calibrate them periodically. Wear and tear can affect the load pin’s reliability, potentially causing issues from electrical interference, mechanical effects, instrumentation faults, or loose connections. Additionally, neglecting to inspect or clean load pins can lead to operational problems, as even in clean settings, particulate matter can accumulate. Conducting regular annual calibrations ensures that the load pins continue to perform at their best.
Ştefănescu, D. M. (2020). *Handbook of Force Transducers: Features and Uses*. Springer Nature.
Ştefănescu, D. M. (2011). *Handbook of Force Transducers: Fundamentals and Parts*. Springer-Verlag.
