Posts

What is Moment Compensation?

/0 Comments/in /by

Moment compensation refers to a process of adjusting or counterbalancing the effects of an external force or torque, known as a moment, on a system or object. This is often done in engineering or physics contexts where precise control and stability are required, such as the design of force measurement applications.

Moment compensation is often used to prevent unwanted movements or deformations in systems, to ensure precision and accuracy in measurements, or to maintain stability and control during operation. Moment compensated load cells improve accuracy by compensating for the impact of external forces and moments on the measurement, allowing for more precise and reliable measurements.

Most load cells are sensitive to orientation and loading concentricity. When external forces or moments are introduced, measurement errors are more common and reduce the accuracy of the readings. These external forces or moments can come from various sources. Examples of external forces or moments that can affect the accuracy of load cells and require moment compensation:

  • Off-axis loading: When the load is applied off-center to the load cell, it creates a moment that can introduce errors in the measurement.
  • Temperature changes: Changes in temperature can cause thermal expansion or contraction of the load cell, which can introduce measurement errors.
  • Vibration: Vibrations from nearby equipment or processes can cause the load cell to vibrate, creating measurement errors.
  • Changes in orientation or position: Changes in the orientation or position of the load cell can cause gravitational forces or other external forces to act on the load cell, affecting the measurement.
  • Torque: When a load cell is subject to torque, such as twisting or bending forces, it can introduce measurement errors.
  • Wind or air currents: Air currents or wind can create external forces on the load cell that can affect the measurement

A load cell that is moment compensated can minimize or eliminate these errors, resulting in higher accuracy. Load cells with moment compensation can be more sensitive to slight changes in the load, as it can compensate for any external forces or moments that might affect the measurement.

Moment Compensation is an Interface Differentiator

Interface’s moment compensation process reduces force measurement errors due to eccentric loads by deliberately loading cell eccentrically, rotating load, monitoring and recording output signal, and then making internal adjustments to minimize errors. Every product we ship must pass moment compensation specifications and performance requirements. Every Interface LowProfile™ load cell is moment compensated to minimize sensitivity to extraneous loads, a differentiator from other load cell manufacturers.

When load cells are moment compensated, they can be used in a wider range of applications, including those with complex or dynamic loads, which might be difficult or impossible to measure accurately using a load cell without moment compensation. Interface’s LowProfile Load Cell models have the intrinsic capability of canceling moment loads because of its radial design. The radial flexure beams are precision machined to balance the on-axis loading.

Moment compensated load cells are designed to counteract the external forces or moments by using a configuration of strain gages and electronics that can detect and compensate for these forces. The strain gages are arranged in a way that allows the load cell to measure the force applied to it in multiple directions, and the electronics can then use this information to calculate the impact of external forces and moments on the measurement.

Interface uses eight gages, as opposed to the four used by many manufacturers, which helps to further minimize error from the loads not being perfectly aligned. Slight discrepancies between gage outputs are carefully measured and each load cell is adjusted to further reduce extraneous load sensitivity to meet exact specifications.

Moment compensation improves the stability of a load cell, particularly in situations where the load is off-center or subject to torque. This can prevent the load cell from shifting or becoming damaged, leading to more consistent and reliable measurements. It also improves the durability of a load cell, as it can help protect it from the impact of external forces or moments that might cause damage or wear over time.

ADDITIONAL RESOURCES

Addressing Off-Axis Loads and Temperature Sensitive Applications

Contributing Factors To Load Cell Accuracy

Off-Axis Loading 101

How Do Load Cells Work?

Load Cell 101 and What You Need to Know

Get an Inside Look at Interface’s Famously Blue Load Cells

Strain Gages 101

 

Load Cell Stiffness 101

/0 Comments/in , /by

Load cell stiffness refers to the ability of a load cell to resist deformation when a load is applied to it. It is a measure of how much a load cell will deflect or bend under a given load. Stiffness is an important specification of load cells, as it affects their accuracy and sensitivity.

Load cell stiffness is typically conveyed as the ratio of the load applied to the deflection of the load cell. For example, if a load cell deflects 1mm when a load of 100N is applied, its stiffness would be 100N/mm.

The selection of a load cell with an appropriate stiffness is critical to ensuring optimal performance in each application and should be carefully considered in the design and implementation of any measurement system. Load cell stiffness can significantly alter the performance.

High stiffness load cells are preferred in applications where high accuracy and precision are required, as they provide greater resistance to deformation and are less susceptible to measurement errors. High stiffness provides more precise and consistent measurements. They are the preferred choice for many applications, including in aerospace, robotics, material testing and of course calibration and metrology.

Low stiffness load cells may be used in applications where flexibility and compliance are necessary, such as in weighing systems that must accommodate vibration or movement. Load cells with low stiffness may be more suitable for applications where flexibility and compliance are important, such as in dynamic force measurement or shock testing.

The determination of load cell stiffness requires consideration of several key factors, including:

  • Load capacity of the load cell should be considered when determining its stiffness. Load cells with higher load capacities typically require greater stiffness to maintain their accuracy and precision under load.
  • Sensitivity of the load cell, or the amount of output change per unit of input change, should also be considered. Load cells with higher sensitivities may require greater stiffness to maintain their accuracy, as they are more sensitive to changes in the applied load. Read more in Load Cell Sensitivity 101
  • Environmental conditions in which the load cell will be used should also be considered, such as temperature, humidity, and vibration. In some cases, load cells with lower stiffness may be necessary to accommodate for environmental factors such as thermal expansion.
  • Application requirements specific to the use case, such as the required measurement range, accuracy, and resolution, will define the success of our project or program. Load cells with higher stiffness may be necessary for applications requiring high accuracy and precision, while load cells with lower stiffness may be more suitable for applications requiring greater flexibility and compliance.
  • Natural frequency, which is the frequency at which it oscillates when subjected to an external force is a consideration. Load cells with high stiffness have a higher natural frequency, which allows them to respond more quickly to changes in the applied force, resulting in faster and more accurate measurements.

Load cell design plays a critical role in controlling load cell stiffness. There are several key design factors that can affect the stiffness of a load cell, include material selection, geometry, strain gage placement and mechanical configuration. Read Get an Inside Look at Interface’s Famously Blue Load Cells to review our precision design features.

The choice of materials used in the load cell construction can have a significant impact on its stiffness. Load cells made from materials with higher Young’s modulus, such as stainless steel, are stiffer than load cells made from materials with lower Young’s modulus, such as aluminum.

Load cells with thicker walls, larger cross-sectional areas, and shorter lengths are stiffer than load cells with thinner walls, smaller cross-sectional areas, and longer lengths.

Strain gages placed closer to the neutral axis of the load cell will experience less strain and deformation, resulting in a stiffer load cell.

The mechanical configuration of the load cell, including the number and arrangement of its sensing elements, can also affect its stiffness. Load cells with more sensing elements arranged in a parallel or series configuration can be designed to be stiffer than load cells with fewer sensing elements.

Load cell design plays a critical role in controlling load cell stiffness to ensure that it meets the stiffness requirements of the application. If you have questions about the load cell that best fits your application, please contact us. Our experts are here to help.

ADDITIONAL RESOURCES

Interface Load Cell Field Guide

How Do Load Cells Work?

LowProfile Load Cells 101

Load Cell Basics Sensor Specifications

Load Cell Basics Webinar Recap

Off-Axis Loading 101

/0 Comments/in , /by

Off-axis loading refers to a situation where a load cell, which is a device designed to measure force or weight, is subject to forces that are not aligned with its primary sensing axis. Load cells are typically designed to measure forces that are applied along a specific direction or axis, which is known as the primary sensing axis. When forces are applied to the load cell in other directions, this is referred to as off-axis loading.

Off-axis loading can affect the accuracy of load cell measurements, as the load cell may not be able to accurately distinguish between forces that are applied along the primary sensing axis and forces that are applied in other directions. This can result in errors in the measured weight or force.

To minimize the effects of off-axis loading, load cells are often designed with measures to reduce sensitivity to forces applied in other directions. These may include mechanical features such as strain relief structures or specialized materials that are more resistant to off-axis loading. Additionally, load cells are often installed and used in ways that minimize the likelihood of off-axis loading, such as aligning the primary sensing axis with the direction of the applied force. Be sure to carefully follow all Force Measurement Installation Guides provided with sensor.

What can be done to protect from off-axis loading?

Off-axis loading can affect the accuracy of load cell measurements, so it is important to take steps to protect against it. Here are a few ways to do so:

  • Use proper mounting and alignment: Load cells should be mounted and aligned in a way that ensures that the primary sensing axis is aligned with the direction of the applied force. This helps to minimize off-axis loading and ensure accurate measurements.
  • Use appropriate accessories: Using accessories such as adapters or mounting bases can help to ensure that load cells are properly aligned and oriented, minimizing the potential for off-axis loading.
  • Use anti-rotation features: Many load cells are equipped with anti-rotation features, such as bolt-hole patterns or keyway slots, which help to prevent the load cell from rotating around its mounting point. This can help to maintain proper alignment and reduce the effects of off-axis loading.
  • Use overload protection: Overload protection features, such as limit switches or stoppers, can be used to prevent load cells from being subjected to excessive forces or moments. This can help to prevent damage to the load cell and ensure accurate measurements.
  • Use a protective enclosure: Load cells can be placed in protective enclosures that shield them from external forces and environmental factors. These enclosures can help to protect against off-axis loading, as well as other types of interference.

By taking these steps, load cell users can help to protect against the effects of off-axis loading and ensure accurate and reliable measurements.

Product designs that mitigate off-axis loading

Engineers are constantly working to design new load cells that are more resistant to off-axis loading.  In fact, Interface product engineers have several products that are designed to protect from off-axis loading, including:

  1. ConvexBT Load Button Load Cell
  2. SuperSC S-Type Miniature Load Cell
  3. MBP Overload Protected Miniature Beam Load Cell
  4. MRTP Miniature Overload Protected Flange Style Reaction Torque Transducer
  5. MBI Overload Protected Miniature Beam Load Cell
  6. LBMP Overload Protected Compression Load Button Load Cell
  7. SMT Overload Protected S-Type Load Cell
  8. WMCP Overload Protected Stainless Steel Miniature Load Cell with Male Threads

By optimizing the mechanical design of load cells to minimize their sensitivity to off-axis loading this can include use of materials, such as composites or alloys, which are more resistant to deformation and strain. It also includes the use of specialized geometries that can help to distribute forces more evenly and reduce the effects of off-axis loading.

As well, engineers utilize built-in electronic compensation to correct for the effects of off-axis loading. This may involve using additional sensors or feedback loops to monitor the load cell’s response to external forces and adjust the output accordingly.

Interface engineers use a multi-disciplinary approach to designing load cells that are more resistant to off-axis loading. By combining advances in mechanical design, electronics, manufacturing, and simulation, they are creating load cells that are the most accurate in by classification in the world.

ADDITIONAL RESOURCES

ConvexBT – The Most Innovative Load Button Load Cell

Eccentric Loading Analysis for SuperSC S-Type Miniature Load Cell White Paper

Addressing Off-Axis Loads and Temperature Sensitive Applications

Benefits of Proof Loading Verification

How Do Load Cells Work?

Load Cell Basics Webinar Recap

/0 Comments/in /by

Interface applications and load cell expert Keith Skidmore was the featured presenter at the latest ForceLeaders Forum hosted event, Load Cell Basics. In his comprehensive presentation, he highlights key subjects including fundamentals of load cell design, sensor specifications, use cases, troubleshooting and valuable performance related topics.

The entire event is now available on the Interface YouTube channel.

In this 60-minute virtual event, Keith highlights commonly asked questions from both new load cell users as well as for advanced engineers and force measurement pros.

What will you learn watching the online Load Cells Basics event?

  • Load cell designs and how they work
  • Capacities, models and how to choose the right load cell
  • Factors that can impact sensor accuracy
  • Performance, moment compensation, creep, and eccentric load sensitivity
  • Calibration and troubleshooting
  • Use Cases and FAQs

The team concluded the event by answering a series of questions from the participants. They addressed advanced technical and set-up questions, as well as frequently asked inquiries about common troubleshooting issues.

Here is a sample of questions that you can find answered in the Load Cell Basics recorded event:

  • Is the temperature compensation achieved using dummy gauges?
  • Does Interface offer or have their own software to read the TEDs?
  • Can we assume that all load cells are intrinsically safe for hazardous locations?
  • What is the IP protection rating for the electrical connection?
  • What is better way to tare load cells, by electronics or mechanical preload?
  • Which is the frequency measurement limit and how fast does the load cell respond?
  • What are recommended amplifier instrumentation brands?
  • What is the most frequent problem when installing a load cell?
  • Does the cables and amplifiers affect the results of the load cell calibration?
  • For an application to 10 kN (2250 lbf), is it too much to use a 2000 lb load cell or should we use the next higher capacity?
  • What is the maximum sampling frequency for strain gage load cells?

WATCH THE EVENT AND Q&A HERE: https://youtu.be/_oHvfAzHMig

If you have additional technical questions or would like to talk about your specific application requirements, contact our Interface Application Engineers here. 

Additional resources for troubleshooting can be found here.

Our Interface Load Cell Field Guide is also helpful for troubleshooting and advanced technical support references.  You can order here.