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Load Cell Stiffness 101

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

Strain Gage Design Under Eccentric Load WRSGC Presentation

By Ashlesa Mohapatra, product design engineer, Interface

In the global marketplace, Interface is well known as providing the force measurement industry’s most reliable and accurate products. One of the key reasons that Interface consistently earns this recognition is because we manufacture our own strain gages. Products engineered and manufactured at Interface use our proprietary strain gages, and each designed for the specific transducer model based on the application type and environment for use.

As an example of our dedication to quality and excellence in performance as it pertains to strain gages, I recently shared a technical presentation on the negative effects of eccentric load and how strain gage design can reduce these challenges.

Below is a brief recap of this presentation made to the attendees of the Western Regional Strain Gage Committee meeting that took place in Tempe, Arizona in October 2022. The summary explains why strain gage design can make all the difference in quality versus poor performance with load cells.

Interface redesigned the strain gages on one of our mini load cells, the LBSU Miniature Load Cell Load Button, also known as our ConvexBT – The Most Innovative Load Button Load Cell. Our goal in the redesign was to create more controlled and repeatable loading, in turn creating a more predictable output. Our research focused on strain gage designs for load cells where mechanical moment compensation is not feasible.

The main challenge with this initiative was overcoming the errors associated with eccentric loading by making the installation process smoother through a redesign.  This is difficult because strain gages are very small in size and therefore more difficult to work with, in addition they are extremely sensitive to the environment with factors like temperature, humidity, cleanliness and electric interference all potentially effecting performance.

Before diving into the redesign, I would like to touch on eccentric loading and the errors it will cause, as well as the varied factors in strain gage manufacturing that can lead to errors causing eccentric load. There are two types of eccentricity: loading and mounting. Eccentric load results from improper loading or mounting of the strain gage, which leads to off-axis loads and bending. This causes several problems including distorted measurement results, decreased load cell accuracy, and diminishing life of the load cell.

When a strain gage is mounted on the load cell incorrectly or gages are badly bonded, it will almost always be an error source and contribute to mounting errors. Also, when strain gages are not bonded to the load cell at appropriate temperature and humidity, it leads to bubbles under the gage. Chemical composition of the strain gage is critical, such as the adhesive between the foil and backing, based on the application in which load cell will be used in a lab, machine, or testing program.

With these factors in mind, we set out on a redesign continuous improvement project. The previous design of this products strain gages was rectangular in shape. So, when the load cell was loaded, eccentrically or not, the strain field would not pass through because of shape. Therefore, we began to look at other shapes for our strain gage design, ultimately landing on a circular “diaphragm” style strain gage that allow strain fields to pass through.

One of the features of this newly designed strain gage is the proprietary adhesive foil we used to adhere the foil to the backing. This adhesive provided a great deal of benefit including a lower modulus of elasticity making it resilient to adhesive failure, and the elasticity also allows for better flow.

Another feature is the full bridge gage pattern we used that provides three key advantages. This includes fewer solder joints and reduced risk for electrical shorts due to simplified wiring, reduced symmetry error, and consistent thermal performance.

One process improvement we wanted to point out was that in our calibration process we only used 5V excitation voltage. Most manufacturers use 10V to calibrate their load cells. Due to lack of thermal mass in the thin diaphragm design of our strain gage, the zero will shift due to high voltage and low poor heat dissipation with 10V. We use a 5V excitation voltage to calibrate these miniature load cells instead of the alternative to prevent overheating of the cell.

To further improve the design, we enhanced the inspection process. Our diaphragm gages are quality inspected for accurate mounting with visual and electrical testing. Visual testing includes checking for air bubbles under the gage, badly bonded edges, unreliable solder connections and flux residues. Electrical tests include checking for electrical continuity and insulation resistance.

We then moved our attention to the circuit board. Some manufacturers use a circuit board in the cable due to the limited space within the cell to improve zero balance zero balance and to better compensate for temperature. However, bending or moving this cable would put pressure on the board and shift the zero. Therefore, we elected to install an abradable compensation resistors inside the flexure instead of the cable. This keeps the compensation resistor close to the gages and is intimately bonded to the body of the sensor to improve the reaction time of the cell to temperature.

To evaluate and confirm that our design was superior, we assessed three different strain gage styles: the rectangular gages (discreet gages), patch gages, and our diaphragm gage. Each of the gage styles were placed on three different load cells and loaded at one degree centricity. This test was run at 45 degree increments eight times. The results showed diaphragm style provided more reproducible result under eccentric load compared to other gages.

This was an interesting undertaking that taught the project team a lot about strain gage design and eccentric load. What I took away from this experience, other than a superior design for our ConvexBT Load Button Load Cells, is that any commercially successful product has a strong process behind it. You also need to have a clearly defined process that includes a continuous improvement plan. Interface Minis are a popular product line that has been around for many years. As soon as a product like this hits a point of stagnation, it will lose its hold on the market. I am proud of our team’s ability to avoid stagnation by taking critical steps to improving the Mini product line, maintaining our reputation for having the best quality, accurate and reliable products no matter the capacity available for precision force measurement.

Western Regional Strain Gage Committee (WRSGC), a technical division of the national Society for Experimental Mechanics (SEM), was established to promote a free interchange of information about strain measurement techniques using strain gages.

Interface is a proud member and sponsor of WRSGC. Our engineers participate in the technical conferences, in both presentation and attendance. Interface’s Product Design Engineer Ashlesa Mohapatra presented at the event held in Arizona, October 17-19, 2022.

2022 Test and Measurement Industry Trends

Interface continues to experience significant growth in demand and fulfillment of our precision measurement products and services. Despite the ongoing challenges in supply and overall health and economic concerns, our focus has remained steadfast to serve customers with innovative solutions, facilitated requests for specialized engineering and production requests and expeditiously working to meet the delivery schedules aligned to our customers’ requirements.

As the overall T&M industry grew, so did the demand for engineers and manufacturers across all industries to have proven solutions from their test and measurement equipment, expanded capabilities from sensor technologies, as well as explore new ways of optimizing products with real-time, accurate measurement.

As we look ahead to 2022, we are also investing in new and existing trends and exploring how they will shape the overall market next year and beyond. To help prepare our customers, here are our predictions for the new year, along with what is hot and trending in force measurement. The following provides some insights from our experts on how Interface is prepared to address these trends, while continuing to serve our customers at the highest level of satisfaction. Here is Interface’s viewpoint on market trends and predictions for 2022 and beyond.

Big Data Continues to Rule Product Design and Test

Over the last few years, we’ve shared our view on the Industry 4.0 revolution and how Interface customers are demanding more data from their T&M tools to give exactness in accuracy and all-encompassing performance data at the earliest phases of product design. Not only will this continue, but it will expand rapidly. In the force measurement world, Interface has responded by serving our customers with new innovations in multi-axis sensors that provide more force data on more axis. Interface offers a wide variety of multi-axis sensors including 2, 3 and 6-axis sensors. We certainly anticipate a continued growth in demand for multi-axis sensors as our product line expands to meet the requirements.

In addition, Interface is seeing more requests from manufacturers and product designers to embed sensors and measurement capabilities within their products. To enable continuous improvements and advancements in smart manufacturing and product designs, sensors are being used to provide real-time feedback on machines, components, equipment, and consumer products. These sensors are often designed in or embedded into the OEM product to predict the health in each type of use case, as well as notify users when a repair or adjustment is needed for safety, user satisfaction, and controlled maintenance. In the manufacturing applications, this capability significantly reduces facility downtime. To meet this demand, Interface is investing in more automation capabilities within our own manufacturing facilities to produce high volume sensor solutions for OEM customers. This market is growing rapidly, and Interface is working hard to meet the needs of our customers that need our products in volume.

New Advancements in Strain Gages

Another trend that Interface is actively investing in is new strain gage technologies and manufacturing techniques to better serve the high-production and OEM markets. Interface uses proprietary strain gages for all products we manufacture. When OEMs are making high-volume product orders and need sensors that fit their exact needs without breaking their budget, Interface is ready to meet the demand. One of the ways that force sensor manufacturers can meet OEM cost needs is through innovation in strain gages, the heart of any measurement device. Interface deploys a team of resources to design and build custom strain gages when a unique solution is part of the design requirements. Interface has expanded our specialization and expertise in mechanical engineering, chemical engineering, and metallurgy to meet this specific trend and need. We are currently undergoing critical R&D to find new ways to develop these components and working directly with customers to meet their data requirements. Check out this post on strain gages.

Growing Demand for Wireless Solutions

Another trend that is continuing to gain momentum is the growing need for wireless measurement solutions. Wireless systems are helping manufacturers simplify the integration process and create a cleaner safer test environment with far less wiring. Wireless communication is also playing a major role in advanced manufacturing and smart products. By connecting systems wirelessly, users can monitor testing and in OEM applications, review the health of a system, from a central point. This includes for components used in the field, underwater or via remote locations for assembly and test.

These wireless systems also help improve accuracy significantly. Wireless technology has gotten to the point where we can receive more accurate readings when converting from an analog to a digital signal. This is especially important in highly complex and regulated industries like aerospace, energy, or medical. Wireless solutions will continue to grow, and Interface continues to develop new wireless total system solutions for our various product lines.

Faster, More Efficient Calibration Services

One of the most critical facets of working in manufacturing and technology is meeting the demands of our clients in an extremely timely manner. Innovation, advancements and testing demands slows down for no one, and our customers are no exception. This also requires regular maintenance and servicing of our devices. Interface recommends annual calibration services to ensure your force and torque measurement products are performing as designed. We understand they need our products and services fast. As part of our commitment to customers, Interface provides high quality calibration services that are key to long lasting and accurate force sensors. This service has grown rapidly alongside the force measurement industry and we’re receiving more re-calibration orders than ever before. To meet this demand, Interface is investing heavily in both people and technology to further expedite this process and meet our promise of expeditious turnaround times for calibration services. Read more about calibration here.

Complete Systems

Sometimes out-of-the-box meets the exact requirements, sometimes it’s in the box.  Interface continues to expand our product mix to include advanced instrumentation, accessories, sensors and unique housing for full systems due to growing demands. Our team of solution engineers partner with our customers to identify the specifications and understand the application to build completely custom solutions, from single sensors to complete systems. These systems can be used within lab testing environments or as remote testing solutions.  Learn more about the capabilities of our custom solutions team here.

These are just a few of the many trends occurring in test and measurement into 2022 and beyond. Technology is progressing at a rapid pace. Our customers need more data, that’s abundant and accurate. Our sensors are seeing new application and use cases, ranging from testing unmanned space vehicles to smart agriculture components.

Rest assured, Interface is deeply invested in addressing these trends and serving our customers in the new year and beyond with critical innovation. It’s what we’ve been doing since 1968. We see an abundance of opportunities and possibilities in working with our customers to get the best products for their projects, programs, and OEM products. Whether they need our standard, engineered-to-order, and custom solutions, we are here to serve and ready for 2022. How can we help you?

Additional Resources

Interface Multi-Axis Sensor Market Research

Interface All-In-One Custom Test Systems

Additional Interface Calibration Grade Solutions

 

Load Cell Basics Technical Q&A Part One

Interface recently hosted a webinar, Load Cell Basics, where our experts answered a series of questions from event attendees.  In the interest of sharing what we know and addressing some frequently asked inquiries, we are offering a new series in our Interface IQ blog entitled Interface Technical Q&A.  At the conclusion of our presentation, we had several questions related to the basics of load cells.  We will be answering them in two posts.  Here is the first list.

Why Does Interface Use Proprietary Strain Gages?

Strain gages are a key component to any load cell. Making our own strain gages gives Interface full control over our design and production, ensuring we can meet our specifications with certainty in quality, accuracy, and dependability. Interface strain gages are precision matched to the load cell material to counteract the temperature effect on output. We have different load cell materials and that means we use different strain gages for each type.

Our strain gages are simple in design, and we don’t use compensation resistors making them a more reliable circuit.  They don’t have to go through resistors; thus, the accuracy and precision measurement is more reliable and capable of faster thermal and higher outputs.

What Type of Temperature Testing Do You Do on Interface Load Cells?

Interface performs both hot and cold thermal compensation from 15˚ – 115˚F, including adjust and verify cycle. Most other manufacturers of load cells provide only the hot side (60˚ – 160˚F) testing. The slope of the curve is much flatter near room temperature and identical at both ends of the slope.  The result is minimal variation across the entire thermal range.  We also offer custom calibrated ranges by request. Read more about temperature compensation here.

Is Temperature Compensation Achieved Using Dummy Gages?

The simple answer is no. Interface does temperature compensation of output by matching the strain gage to the material temperature compensation of zero. This is achieved by using a wire in the circuit that opposite resistance changes to the circuit.

Do You Have Software to Read TEDS Available to Use with Interface Load Cells?

Interface does offer instruments that can use the TEDS data and instruments that can write the TEDS data to the chip. Interface has software that hooks up or attaches to the TEDS chip reader writer so that when we program a chip during manufacturing of load cells in our factory, we have software we use to complete this function.  We also do offer this software for commercial use.

Is it Acceptable to Regularly Use a Load Cell Above Its Specified Capacity?

The short answer is no.  You want to reserve the “above capacity” for accidents. We are aware that people will do this in practice and the load cell will typically work reasonably well above capacity.  The problem is you want to handle that the answer is no you’re consuming your safety factor and you don’t have any extra head room for something that goes wrong.  Also, using the load cell above capacity doesn’t exactly follow the same calibration curve.  As an example, if you are using a 10k load cell with a 10k calibration and you are running tests at 12k, you may have higher errors.  You can ask us to calibrate the load cell to the 12,000 lbs.; however, you must note this can reduce the safety factor and that is why we do not recommend it.

Does Variable Altitudes Impact Performance?

Interface does have the ability to handle different pressure scenarios. Interface sends our products out ventured, if necessary, to be able to tolerate pressure change without causing any zero shift. If you do have applications where you will have either high pressure requirements or pressure change throughout the test, we certainly have solutions that can accommodate that requirement.  Work with your application engineer to ensure you have the exact testing requirements detailed when you are ready to buy your next load cell.

Can Cables Influence Temperature Errors?

If you’re adding cable to the load cell and for example, you have a 10-foot cable you want to add 100 feet more of cable, that adds resistance. The lower gauged cable, the better. A 22-gauged cable is better than a 28-gauged cable, so use a thicker cable and it will have less resistance impact on the measurement.

Is Creep Due to Material or Strain Gages?

Essentially all the elements in the sensor and everything mechanical will respond to creep.  The goal is to match the creep behavior of the bridge to the creep behavior of the load cell material or the flexure. Yes, creep affects both, but you want the result to trend in the same direction so that you get minimal error or change in the signal because of creep.

Are All Load Cells Intrinsically Safe?

They are intrinsically safe devices; however, anytime there is a hazardous environment or intrinsic safety requirements, please contact an application engineer to review the sensor use case and to factor in all aspects of your testing and use environment.  The load cells are typically working off 5-volt 10-volt and you need to look at all aspects of the location. For more information about our specialized line visit load cells for harsh environments.

This is the first in a new series of Interface Technical Q&A.  Do you have a question for our technical experts?  Send an email to digmktg@interfaceforce.com and we will add it to a future post.  If you have an immediate question, be sure to contact us today and let us know how we can support you.  You can also reference our technical support resources online for help.

Contributors:  Keith Skidmore and Brian Peters

Additional Resources

Load Cell Basics Webinar Recap

Interface Load Cell Field Guide

Faces of Interface Featuring Jeff Boyd


Interface Regional Sales Director Jeffrey Boyd has a long history in the force measurement industry and is an incredible addition to the Interface sales team. You see, force measurement runs in Jeff’s blood!

Jeff originally got into the industry because he watched and listened to his dad talk about his experience at another force measurement manufacturer, Sensor Development. In fact, his dad actually helped start the company when he joined the owner shortly after the company was founded. You could say that Jeff was somewhat groomed for success in this field.

To prepare for his destined career, Jeff spent a few years at Oakland University. After that, he quickly joined up with his dad at Sensor Development. Jeff started in the calibration department, learning the ins and outs of strain gages, load cells, torque sensors and everything in between. After a few years, he was leading both the calibration services and customer service department. Jeff was in charge of ensuring customer satisfaction when products came in for repair, service or calibration.

After several years getting hands on with the products and developing critical expertise in the various sensors the company sold, Jeff decided it was time to transition into a sales role. He originally began as a sales engineer helping to develop customer quotes and working directly with the engineering department on custom applications. His success in sales lead him to become a regional sales manager in 2014.

From 2014 to 2017, Jeff served as regional sales manager for Sensor Development until it was bought out by HITEC Sensors and was renamed to HITEC Sensors Development. Jeff remained with HITEC for another four years before it was time for exploring new opportunities.

Due to his experience in the industry, Jeff was familiar with the Interface brand and our product’s reputation for quality and accuracy. Right about the time Jeff’s time with HITEC was coming to end, Interface had an opening for a Regional Sales Position due to Keith Skidmore‘s promotion to our specialized Custom Solutions team.

Jeff joined Interface in the Spring of 2021 and is a perfect fit, technically and professionally. Not only because of Jeff’s years of experience, also because he continues to live in Michigan and will be covering Interface’s Central U.S. region working with our manufacturer’s representative firm, Stress Analysis Services. He’ll be working with our sales reps, including John Guy, and our customers to ensure they get exactly what they require from Interface. He knows the area and knows the needs of the industry well.

As for why Jeff chose Interface, he says it’s because of the people. Throughout the interview process and during these first few weeks, Jeff mentioned how supportive and friendly his teammates and the leaders of the company are working to ensure his success. He also sees the trajectory that Interface is currently on and knows that he will have an opportunity to grow and thrive alongside Interface.

When he’s not helping customers find the perfect product or customer solution for their test and measurement needs, Jeff is spending time with his wife and his five grown sons and granddaughter. Living through the cold Michigan winters make vacationing to the warmth a must. Jeff and his wife frequently travel to Las Vegas and Arizona or any other warm state to escape. Though, they also like to spend some of their time cheering on their favorite football teams. Notably, the household is a bit divided when it’s game time. Jeff is also an avid golfer and spends a lot of his down time on the course.

We’re so glad to have Jeff on our team as our new ForceLeaders member and we can’t wait to see what we’ll achieve together in interest of our valued Interface customers.

Interface Engineered to Order Solutions

Load cells and torque transducers come in many different capacities, sizes and capabilities. They are used in nearly every industry that manufactures any type of hardware device or component. From testing minute forces on miniaturized medical devices, all the way up to measuring force in the construction of enormous suspension bridges or even rocket engines. The point is, there is no one size fits all in the force measurement world when performance matters.

What makes Interface uniquely the leader and is a true differentiator in the force measurement industry is our ability to provide engineered to order solutions to meet our customer’s exact application requirements.

Innovation across multitudes of industries has provided the opportunity to be more creative in utilizing Interface proprietary technology and engineering talent in the development of new force measurement devices. More and more we find ourselves leaning on our experts using our proprietary strain gages and product designs to develop solutions that meet the needs of our customer’s unique projects and end-products.

Through our work on modifications and custom solutions, we have expanded our product offerings to more than 37,000 uniquely designed products spanning across 52 years of development. Once initiating as a custom solution, many of these products have made their way into our catalog as standard products based on growing trends and larger demands.

There is also another form of customization, or more accurately termed modification, that we are seeing more and more as Interface grows our engagement with OEM customers. We call this “engineered to order” solutions. These solutions are different from full customization and critical in serving our diverse customers.

Designers and builders of high-volume products may have opted in the past for simplistic testing technology that lacks consistency, quality, accuracy and reliability. As product failures or customer satisfaction wanes based on performance, OEMs are driven to find force measurement solutions they can depend on for precise measurement and performance. This is also indicative of the times we are in utilizing advancements in production, technology and even robotics to produce products.

It is essential for product makers and engineers to find reliable solutions for accurately monitoring and testing product performance in real-time. In short, they need sensor capabilities that meet their product manufacturing volume, safety requirements and overall robust product performance standards. This is very typical in industrial markets where OEM customers want to monitor machines in the moment and more accurately predict fatigue or when a machine will need to be repaired, reducing overall downtime and saving money.

To best serve OEM customers and testing engineers with premium and affordable force measurement solutions, Interface offers engineered to order capabilities for the masses. Engineered to order means Interface can deliver force measurement solutions from our massive catalog that are modified to meet the features and specifications that our customers require, while still retaining the premium accuracy, quality and reliability Interface is known for across every industry we serve.

Interface Application Engineers work closely with our customers to determine the exact specs their product requires and deliver a manufacturing plan that meets their volume, accuracy and reliability needs through an engaged process. We plan, coordinate and team together to build the right product, for the right time and right price. Most importantly, we can modify most of our products in our entire catalog, giving flexibility within a precision line of solutions.

OEMs, product designers, and testing experts do not need to compromise performance. Interface’s engineered to order process combined with our automated production lines allows us to provide the same great quality force sensor our customers expect from an industry leader.

Interface excels when we partner with our customers in the earliest phases of development to ensure we provide the best solution, based on size, capacities and performance capabilities. By sharing design plans, we can collaborate with our customers to provide the best outcome. Ready to engage our experts?  Contact us here.

The Five Critical Factors of Load Cell Quality

Accurate data and high-quality test and measurement programs have many contributing factors. None are more important than the devices and equipment used on the test line. At Interface, we understand this better than anyone else.

Quality is why our force measurement products are used and known across multiple, highly regulated, and complex industries for providing the most reliable and accurate data anywhere. It is also why Interface is recognized as the preeminent leader in load cell quality.

How do we reach this high standard that we continue to hit with every product that leaves our facility? It is our overriding commitment to quality and consistency. The most important aspect of this is the fact that Interface controls the entire manufacturing process of our load cells. Many providers outsource certain components like that strain gages. We build the strain gages, the load cells, integrate the strain gages into the load cells and we do our own test, calibration, and quality inspection on each device.

Through our development process, which has been created and perfected over 52 years, we have learned what makes a great load cell. To start, Interface Chief Engineer Ken Vining outlines the top factors in load cell quality.

Five Most Critical Factors of Load Cell Quality

#1 Repeatability

Repeatability is first on the list and it is what our customers consider the most important aspect of buying an Interface load cell. Anyone can develop a load cell that is accurate for the first 10 to 15 measurements, but as environmental factors and stress are inflicted upon the load cell it needs to last. Due to our experience in this industry, we understand how certain temperatures, loads and other factors can diminish the accuracy of a load cell. This is one of the reasons we work so closely with our customers. Every application is different, and if we understand the application, we can deliver a custom load cell that withstands the various stressors over time without providing diminishing returns. This ensures that our customers receive the same, high-quality data after 10 years of use that they received on day one.

#2 Longevity

Like repeatable data accuracy over time, the load cell also needs to feature a high-quality and ruggedized build to last physically. Constant application of weight, pressure or torque can diminish the build quality and strength of a load cell if it does not meet the material requirements of the application. This can also reduce accuracy and lead to higher costs if customers must replace their load cells regularly. Interface has worked across a wide variety of industries and we understand the materials necessary for nearly any environment. With proper use, build quality and routine maintenance, load cells should last a very long time. In fact, Interface still has load cells in use in the field from when we started building quality product more than five decades ago.

#3 Accuracy

Data accuracy is affected by a litany of factors in load cells. In fact, we wrote an entire white paper on this very topic called, “Contributing Factors to Load Cell Accuracy.” Once again, the application of the load cell is what determines the conditions that affect accuracy. These conditions include creep, side and eccentric load, temperature, humidity, the mounting process and more. Interface can customize each of our load cells to ensure these conditions are accounted for to maintain premium accuracy.

#4 Sensitivity to Off-Axis Loads

A typical load cell is designed to measure load in one direction. However, nearly any project using force measurement test processes is going to introduce an off-axis load. If the load cell is not designed to adjust for this and compensate for what is called moment, the data output will be skewed. This is another reason that customers need to be extremely specific when discussing the application of the load cell. There are several ways to compensate for moment; however, most of these adjustments are physical and occur in the design and manufacturing process. With a correctly calibrated and designed load cell, off-axis loads will be eliminated and will not affect the accuracy of the data.

Special Note: Our recent release of the new ConvexBT product, the first to market miniature load button load cell that is designed to solve for off-axis (eccentric) loading. Read more here.

#5 Access to Prominent Force Measurement Experts

Every factor of quality listed above is realized and accomplished through a close and transparent relationship between customer and force measurement provider. Every application dictates a different force measurement solution. When we understand the application, we can select the right type of load cell or customize an off the shelf load cell to meet the quality and accuracy needs necessary for any project. This is why a customer’s access to a force measurement expert is an integral part of load cell quality.

Every force test and measurement project can create a different challenge and developing an accurate and reliable load cell to meet those challenges can be tough. Therefore, Interface considers these five factors, and hundreds more, for every product we engineer and build. This is our unwavering commitment to quality and customer satisfaction.

Contributor:  Ken Vining, Chief Engineer and Head of Quality

Interface Mini Load Cells Growing in Product Use and Testing

One of the biggest manufacturing trends over the past decade is the miniaturization of hardware components. Reducing the size and weight of products and the components, while increasing the power of complex technology systems, is growing in use across all industry segments using force measurement in design and production.

The growing trend to utilize sensor technology in miniaturized products has been especially significant in the medical, consumer products, technology and robotics industries. These industries are looking to fit more force and measurement capabilities into a package that is the same size, or in many cases, considerably smaller than previous generations of like products.

To address this expanding trend, Interface Mini™ Load Cells were designed specifically for light touch, light weight, high accuracy, and robust performance to utilize for OEM products and smaller testing applications in confined spaces. Our miniature load cells provide exceedingly accurate measurements, similar to our full-size load cells and utilize our proprietary alloy strain gages. Capacities are available as low as 0.11 lbf / 0.5 N and as high as 100 kN.

These small-scale load cells are engineered and manufactured to provide extremely accurate output data with the same degree of precision performance as our standard load cells. OEM’s must have this sort of precision force technology because many of the devices being made today are minuscule and more complex in comparison to earlier products and testing application use cases.

In the medical device industry, innovative and often small new products are used in various life-saving applications. Any inaccuracy or miscalculation of force can have devastating effects. Take a look at how our Interface LBS Miniature Compression Load Button Load Cell and 9330 High Speed Data Logging Indicator were used to record the force measurements when designing and testing vascular clamp surgical devices. You can also read about the Vascular Clamp application note here.

In our earlier Mini Load Cells 101 blog, we discussed the features and benefits of Mini Load Cells in detail. Today, we are highlighting some of our best-selling and new Mini Load Cell solutions available from Interface.

QS48 TruckSpecial Note: A large variety of our standard miniature load cells are available today through our QS48 e-commerce site for easy online ordering. Click here to order now through our QuickShip program and get your mini’s in as little as 48 hours! If you need something specifically customized, reach out to our expert application engineers who can work with you to design custom miniature load cells that will fit your exact requirements.

INTERFACE MINI™ LOAD CELLS

MB Miniature Beam Load Cell

Model MB is a miniature beam load cell used in medical test machines and a variety of low capacity applications. Performance on this product is +/- 0.03% FS and available capacities are 5 to 250 lbf (22.2 N to 1.11 kN).

Product Features:

  • Proprietary Interface temperature compensated strain gages
  • Performance to 0.03%
  • Low height – 1-inch max
  • Eccentric load compensated
  • ±0.0008% /˚F – max temperature effect on output
  • Low deflection

MBP Overload Protected Miniature Beam Load Cell

Model MBP series load cells provide similar performance to Model MB series with the added safeguard of internal overload protection. This patented overload protection is accomplished via hard stops that are EDM machined into the load cell flexure. This provides greater overload protection (2.5-10lbf ±1000% of full-scale capacity, 100 N ±500% of full-scale capacity), giving the user added protection in more severe applications.

Product Features:

  • Proprietary Interface temperature compensated strain gages
  • 10x overload protection
  • Low height – 1in max
  • 0.0008%F temp. effect on output
  • 5′ Integral Cable (custom lengths available upon request)
  • NIST Traceable Calibration Certificate

WMC Sealed Stainless Steel Miniature Load Cell

Interface Model WMC Stainless Steel Miniature Load Cell is excellent for industrial applications because of its stainless steel, sealed, environmentally protected construction. This product is available in capacities ranging from 5 to 500 lbf (22 to 2200 N).  Submersible versions of this product are available as well.

Product features:

  • Environmentally sealed tension and compression load cell
  • Proprietary Interface temperature compensated strain gages
  • Tension and compression
  • Small Size
  • Stainless Steel Construction
  • Submersible

SSM and SSM2 Sealed S-Type Load Cells

Model SSM is a moderately priced highly-accurate sealed load cell for test machines and other general purpose applications. This product is available in capacities ranging from 50 to 10K lbf (200 N to 50 kN).

Product Features:

  • Proprietary Interface temperature compensated strain gages
  • Environmentally sealed
  • 0.02% non-repeatability
  • 0.0008%/°F (0.0015%/°C) temp. effect on output
  • 0.025% creep
  • Tension and compression

LBM Compression Load Button Load Cell

Model LBM Compression Load Button is very popular.  It is constructed from stainless steel and has a small size. This product is available capacities range from 25 lbf up to 50K lbf.

Product Features:

  • Temperature compensated
  • Integral load button
  • Small diameter
  • Environmentally sealed
  • Stainless steel

LBS Miniature Load Button Load Cell

Model LBS Miniature Compression Load Button is constructed from stainless steel and has a small size. This product is available capacities range from 5 lbf up to 1K lbf (22.2 N to 4.45 kN).

Product Features:

  • Temperature compensated
  • Integral load button
  • Small diameter
  • From 0.12″ height

LWPF1 Press Force Load Washer Load Cell

Model LWPF1 Press Force Load Cell is one of several load washer load cells available from Interface. It features a large thru-hole and short overall height. This product is available in capacities ranging from 2 kN to 100 kN (450 to 22.5K lbf).

Product Features:

  • Short height
  • Large thru hole
  • For press-force monitoring

BPL Pedal Load Cell

BPL Pedal Load CellThe Model BPL is a very LowProfile® load cell is used for measuring force on brake pedals. Interface Model BPL has the lowest sensitivity to off-center loading available and will outperform any competitive model.

Product Features:

  • Lowest nonlinearity and hysteresis of any brake pedal load cell – < 0.05%
  • Ultra-low height
  • Low sensitivity to off-axis loads
  • Mounts directly to pedal with included strap(s)
  • Interchangeable mounting plates
  • For use with gas, brake or clutch pedal
  • Storage case included

There are more than 30 different Interface Mini Load Cells and sensors available, in addition to our ability to provide modified and custom Mini Load Cells solutions. To find the Interface Mini that works for your needs, or to learn more about our expanding lineup of load cells and torque transducers, please visit /products/.

Envisioning the Future of Force Measurement

It is estimated that the force measurement sensor industry market, which includes strain gages and load cells, is valued at $2 billion annually. This is a result of the diverse amount of application uses for these types of sensors, whether embedded into an OEM product or for use in test and measurement. With innovations pushing product designers, this segment of the overall sensor market is growing rapidly from the advancements in robotics, semiconductors, automotive, aerospace and defense.

In these areas of growth, Interface continues to focus on the manufacturing and sales of precision force measurement products. For 52 years, Interface remains the leader in accuracy and quality. There are no plans to change that focus. What is changing is the market place and opportunities for using precision sensor technology of all sizes and capacities, whether that be for electronic vehicle testing or industrial automation, launching spacecraft or introducing new robots.

The way we develop force measurement products is continually evolving. It is our responsibility to understand trends in the engineering, testing and manufacturing, as well as identifying customer needs, in order to develop new force measurement innovations for today and into the future.

Technology is moving at a fast pace, and it’s imperative that companies like us rise to meet the demand for new innovations to solve modern and future design and testing challenges. In last week’s blog, we detailed our product development process and our evolution over the years to meet these demands. Product development has grown from a process to something that we engage in every day, especially in the customization of our standard products as well as introduction of new solutions.

The voice of our customer is instrumental in defining this development journey. We learn about new trends and opportunities for expanding our product line by listening to our customers and team members. At Interface, we know that in order to continue building upon our half-century legacy, it’s critical to keep an open mind to new solutions and continually learn how our customer’s industries are evolving too.

Interface recently had the opportunity to contribute article to two different publications that outlined our thoughts on the trends in force measurement. We were able to lean on our entire team to discover what they believe is the future of our industry. It was not only a fun exercise to take a step back and look into the future, but it was also encouraging because we realized that many of these trends are things that Interface has placed a heavy focus on in our strategic plans for the months and years to come.

Included below are links and a quick synopsis of recent articles by Interface ForceLeadersthat were published in Machine Design Magazine and Metrology News.

Machine Design Magazine: 2020 Trends in Force Measurement Sensors

Until about 10 years ago, the force test and measurement industry had been fairly unimaginative. It had developed a standard way of building analog load cells, torque transducers and other devices, and it worked for many years. However, as most of the rest of the technological world advanced and big data changed the way engineers and manufacturers work, this age-old force measurement analog technology stood out with no way to improve data collection or make it more efficient.

The digital revolution has pushed load cell manufacturers to look around and think about how customers develop products and how factories and production lines operate. Here are some of the trends force-measurement companies must get in line with or risk disappearing, as defined by Keith Skidmore, Regional Sales Director at Interface. Click here to read more

Metrology News: The Future of Force Measurement

The rise of the Internet-of-Things (IoT) and “Big Data” has had a tremendous impact on almost every industry, including force measurement. Up until about ten years ago, the industry had remained steady and predictable. There was a standard way of building load cells using analog technology that was widely accepted, and they served their purpose well. In this article Ted Larson, VP Product Management and Marketing at Interface explains the industries recent transition and what lays ahead. Read more here.

Interface will continue to remain future-focused in an effort to serve our clients force measurement needs for now and beyond. If you are interested in learning more about custom solutions or new applications, contact us here.