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Interface Solutions for Research and Development

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Among the many roles of force measurement in engineering and manufacturing, the role of force sensing in research and development may be the most exciting and important. Load cells and other types of force sensors qualify and collect data on exploratory projects across a wide variety of industries. These tests determine the viability of a potential project and eventually new innovations.

Research and development are core to most businesses to stay competitive. R&D is essential in creating new products and anticipating customer demands. Whether it is assessing the viability of a new IoT home technology for consumers or designing a component used in a new surgical medical device, research is core to the technical and technological development of most any product.

In an R&D environment, force testing helps to compare product materials, determine the strength materials and components, and evaluate environmental, ergonomic, and other features. Additionally, force testing is common across industries as a quality control measure to accurately check that a given group of products meet targeted design specifications, per performance, safety, and regulatory requirements.

Interface often works with engineers whose role it is perform research and development within their organization. R&D engineers use research theories, principles, and models to perform a variety of experiments and activities. Not only do R&D engineers create new products, but they often are responsible for the redesign of existing products.

Our goal at Interface is to help R&D engineers identify the best sensor-related products they can use to work through the problems they are seeking to solve. The products we provide validate findings through highly accurate sensor test and measurement data. There are some R&D applications that need just one or two load cells and basic instrumentation to conduct the project testing. Other times Interface is asked to create an application-specific engineered to order part or design a custom measurement solution to achieve the desired test and measurement outcomes. The later is often the case if a sensor is an actual part of the product design. Interface has helped R&D engineers assess all kinds of prototypes and early designs using our precision force measurement devices.

Force measurement is used throughout the product research and development lifecycle, from ideation and prototyping, to robust testing and eventual commercialization phases.

  • IDEATION: In the ideation phase, we provide force measurement solutions for testing materials for compatibility with the idealized product’s use cases.
  • PROTOTYPING: In prototyping, force sensors help engineers select a minimum viable product (MVP) design. Sensors are used in the lab environment to validate a product or component, or as an actual embedded sensors utilized for real-time feedback and performance monitoring.
  • TESTING: When a product moves into the testing phase, it ready for a more thorough batch of tests including cycle and fatigue testing. Our load cells, torque transducers and instrumentation are commonly used in these environments. Every product will require a sensor model that fits by specifications and capacity.
  • COMMERCIALIZATION: Finally, when a product is ready for commercialization, we provide products used to run a variety of tests to ensure the product is constructed in a way that is safe for the user and meets certain force related specifications for intended use.

To give you an example of how an R&D engineer utilizes force sensors, we have included a few application examples below.

R&D Testing for Bicycle Manufacturer

A bike manufacturing company R&D engineer created a new handlebar design. They need to test the handlebar concept for their bikes during the R&D phase to ensure they will perform for a rugged trail ride experience, while ensuring safety of the recreational equipment. The R&D team took the concept and conducted fatigue tests on their handlebars to observe its structure and performance durability before mass production.  Interface suggested using Interface Mini™ product SSMF Fatigue Rated S-Type Load Cells. Two of these s-type load cells are attached on either end of the bike’s handlebar stem, where it will measure the forces applied as the handlebar undergoes its fatigue test. Results can be measured, logged, and graphed with the SI-USB Universal Serial Bus Dual Channel PC Interface Module.

Research Rig Used for Testing Prosthetic Designs

Prosthetic limbs must undergo rigorous R&D testing prior to manufacturing. These critical apparatuses are tested for extreme loading that can occur during falls, accidents, and sports movements. Fatigue testing of prosthetic components determines the expected lifespan of the components under normal usage. R&D engineers use testing data to determine whether prosthetic materials and designs will withstand the rigors of daily use and occasional high load situations. For the R&D project, various configurations of compression and tension test machines can be used depending on the type of prosthetic device being tested. Often the same machine can be used for static and fatigue testing. For this application, an SSMF Fatigue Rated S-Type Load Cell is mounted between a hydraulic actuator and the device being evaluated. During static testing, loads are applied to the specimen using the load cell signal as force feedback control of the test machine. During a fatigue test, the actuator repeatedly applies and removes the force to simulate activity such as walking. Tilt tables may be used to apply forces at various angles to simulate the heel-to-toe movement of walking or running. The 9890 Strain Gage, Load Cell, mV/V Indicator with Logging Software was used to store the research data.

 

Electric Vehicle Structural Battery Testing for Prototype

Battery technology is critical to the evolution of electric vehicles, so there are a variety of tests performed on new innovations in EV battery technology. As electric vehicles push advancements in efficiency gains, structural battery packaging is at the forefront for optimization. This drives the need to validate structural battery pack design, both in terms of life expectancy against design targets as well as crash test compliance and survivability.  Interface’s solution for this challenge included 1100 Ultra-Precision LowProfile Load Cells in-line with hydraulic or electromechanical actuators in the customer’s test stand. Also utilized were 6-Axis Load Cells to capture reactive forces transmitting through pack structure. Multi-axis measurement brings greater system level insight and improved product success. The tests performed using Interface’s force measurement products were able to validate the battery packs strong structural design.

Proving Theoretical Cutting Forces Of Rotary Ultrasonic Machining

Rotary ultrasonic machining is a hybrid process that combines diamond grinding with ultrasonic machining to provide fast, high-quality drilling of many ceramic and glass applications. This new method has been theoretically proven using computer models. Rotary ultrasonic machining generates forces of an exceedingly small magnitude. To prove this theory, any load cell used for measurement must be sensitive, while at the same time retaining high structural stiffness within a compact, low-profile envelope. Interface’s 3A120 3-Axis Load Cell was installed in the rotary ultrasonic machine to measure the forces being applied to a sample part. With clear signals and minimal crosstalk, the applied forces are recorded and stored using an the BSC4D Multi-Channel PC Interface Module. The 3-Axis load cell provided excellent data helping uncover the relationship between machine cutting parameters and the forces applied on the component. Using this knowledge, the machining process was reliably optimized for new materials and operations.

The role of Interface as it pertains to R&D is constantly growing as engineers create new innovations to solve a myriad of challenges throughout the world. We provide the most accurate and reliable force measurement systems to help advance technology across industries.

ADDITIONAL RESOURCE

Interface OEM Solutions Process

Interface Solutions for Machine Builders

Interface Solutions for Consumer Product Goods

CPG Bike Frame Fatigue Testing

CPG Treadmill Force Measurement

CPG Golf Club Swing Accuracy

Interface Sensors Used for Development and Testing of Surgical Robotics

Fitness Equipment Makers Require Extreme Accuracy

Types of Force Measurement Tests 101

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There are distinct types of force tests that engineers, product designers, manufacturers, and test labs perform to accurately measure factors that control quality, safety, and reliability.

Testing force helps to qualify how something will react when applying load, either by a normal application or by pulling and pushing it fails. The type of force measurement classifications are compression, fracture, tension, flexure, and shear.

Interface provides a broad range of solutions for static and dynamic force measurement tests including standard and custom transducers, instrumentation, accessories, frames, calibration equipment and other components used for in force testing.

The most common categories of force testing include:

  • Tensile testing
  • Shear testing
  • Compression testing
  • Fatigue testing
  • Torque testing
  • Hardness testing
  • Static testing
  • Mechanical strength testing
  • Material testing
  • Proof load testing
  • End of line testing

There are variations to each of these test classifications, such as cycle testing is often a subset of fatigue and mechanical strength tests. Hardness testing is frequently referred to as nondestructive testing. Initial R&D tests typically center around choosing materials, strength and durability tests, compression ergonomic and abrasion tests.

Here are the general characterizations of the most popular types of force tests.

Tensile Test

Tensile strength is the ability of a metal to withstand a pulling apart tension stress. Performing a tensile test, sometimes referred to as tension testing, applies uniaxial load to a test bar and gradually increasing the load until it breaks. The measurement of the load is against the elongation using an extensometer. The tensile data is analyzed by using a stress-strain curve. Interface load cells are commonly used for various tensile tests when accuracy of measurement matters.

Compression Test

Compression is the result of forces pushing towards each other. The compression test is like the tensile test. Place the object in a testing machine, apply a load and record the deformation. A compressive stress-strain curve is drawn from the data. Interface provides load cells that measure compression-only or tension and compression measurements from the same device.

Torque Test

Torque measurement determines how an object will react when it is turned or twisted. There are two common use cases, fastening tests of objects or by testing rotating parts in an assembly. The two types of torque measurement are reaction and in-line, which are important when selecting the type of torque transducer to use in your test. The wrong torque can result in the assembly failing due to several problems, whether that is by torque testing bolts or engine parts. Parts may not be assembled securely enough for the unit to function properly, or threads may be stripped because the torque was too high, causing the unit to fail. Torque is a force producing rotation about an axis. This type of testing is also extremely popular in automotive to measure a variety of components.

Shear Test

Shear strength is the ability to resist a “sliding past” type of action when parallel, but slightly off-axis, forces, applied in the test. Shear force is directional force that is over the top of a surface or part. Shear is measured by tension or compression using a shear or bending beam load cell.

Hardness Test

Hardness testing, which measures the resistance of any material against penetration, is performed by creating an indentation on the surface of a material with a hard ball, a diamond pyramid or cone and then measuring the depth of penetration. Hardness testing is categorized as a non-destructive test since the indentation is small and may not affect the future usefulness of the material. There are a wide variety of hardness testing types as well.

Examples of Testing Types

Compression Test Example

Interface’s customer wanted to measure the amount of compression force a piece of candy could withstand to ensure its label is marked correctly. The purpose of the test was to correctly calibrate the equipment to provide the same stamping force each time without breaking the candy apart. An Interface Model WMC Mini Load Cell and 9330 Battery Powered High Speed Data Logging Indicator are used to measure the results. Read more about this compression test here.

Torque Measurement Example

In this example torque testing accurately measures the forced needed to securely fasten a bolt. This type of test is critical in highly regulated industries like aerospace and automotive to ensure every screw and bolt are not over or under-tightened. Interface’s LWCF Clamping Force Load Cell along with Interface’s INF-USB3 Universal Serial Bus Single Channel PC Interface Module provide a solution that monitors the force being applied during bolt tightening.

Shear Test Example

This example shows how aerospace manufactures use shear testing to measure the affects of wind as it moves past the wings, hull, and other components of a plane. Interface measured this force using a Model 6A154 6-Axis Load Cell mounted in the floor of the wind tunnel, and connected  to the scaled model by a “stalk”. A BX8-AS Interface BlueDAQ Series Data Acquisition System was connected to the sensor to collect data.

As products become more complex and technologically advanced, the test and measurement industry must provide solutions to monitor a wide variety of factors. This is no different in force measurement.

Interface has been involved in every type of force measurement type across a variety of applications both large and small. To learn more about our more than 36,000 product SKUs designed to conduct all these tests, from single load cells and torque transducers to complete testing rigs and systems. We also provide calibration services for all types of force measurement transducers. Contact us if you are unsure which force measurement solution best fits your testing plan.

Additional Resources

Tensile Testing for 3D Materials

Material Tensile Testing

Interface Solutions for Material Testing Engineers

Bike Handlebar Fatigue Testing

Interface Specializes in Fatigue-Rated Load Cells

Specifying Accuracy Requirements When Selecting Load Cells

Spring Compression Testing App Note

Insights in Torque Testing Featured in Quality Magazine

Industry Leader in Test and Measurement

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Interface was founded as a supplier of cutting-edge test and measurement industry solutions in 1968. It’s in our DNA and fundamental to what we’ve been engineering, manufacturing and selling for more than five decades. What started out as first to market with a pancake-style LowProfile load cell, has expanded into a broad mix of world-class test and measurement products and calibration services that enable T&M professionals full access to complete systems, from sensors to instrumentation.

Our mix of load cells, torque transducers, multi-axis sensors, calibration systems and other force measurement solutions allow engineers, product designers and manufacturers access to industry-leading testing devices that provide the most accurate and reliable data possible.

Whether that is testing the torque when applying a screw via robotics or verifying touch screen force for the latest 5G consumer hand-held device, we provide the sensors that test the machines, tools, and actual products before and in-market.

Interface is steadfast in ensuring the test and measurement professionals have more than quality sensors. We also provide T&M solutions to maintain and service testing equipment and devices used in labs and facilities throughout the world. The range of products we offer are from standard precision use to calibration-grade. Whether we are supplying our 1800 Platinum Standard Load Cell or a Verification Load Frame, Interface supports all types of T&M pros. Or as we like to call them, ForceLeaders.

Test and measurement use cases are growing due to the demands for miniature load cells, more data for intelligence gathering and automation functionality.  It is estimated that more than $27B is spent in the production of test and measurement equipment globally. And the market is growing due to professionals seeking advancements in equipment and sensor technologies for use in new products, maintaining equipment and sustaining usability with data and proven testing rigor.

Interface sensors are involved in a wide range of T&M applications across a multitude of industries, with increased visibility into new markets like IoT and smart data-drive technologies.

Trends in test and measurement that are fueling the greatest growth:

  1. Medical and healthcare devices using miniature and wireless sensor technologies
  2. Activation of sensors into real-time data monitors and feedback tools
  3. Networking and communications use with 5G and wireless sensor capabilities
  4. Robotics and industrial automation machines and equipment
  5. Safety and regulation equipment with performance sensors
  6. Consumer electronics durability and usability
  7. Environmental exposure and changing conditions, from submersible to extreme temperatures

Read more about the trends in test and measurement in 2022 Test and Measurement Industry Trends.

The reason Interface is the industry-leading provider is because T&M requires precision and reliability. Interface sensors are known for being the most accurate in the industry. From structural and material testing to static and fatigue testing, our products provide key data for manufacturers, engineers and testing professionals to ensure their products and services will hold up under designed loads and performance standards.

From our Ultra Low Capacity series measuring forces in mere grams to our LowProfile™ load cells with capacities up to 2 million lbf, our solutions can meet the needs for any test profile required when it comes to force.  In regard to torque testing, Interface can supply torque transducers with ranges as low as 0.005 Nm and up to 340K Nm to meet the needs of your test. Our overload protected low capacity load cells and torque sensor provide the most accurate results in the industry. In fact, T&M experts measuring torsion effects, tension tests, mass and kinetic energy are utilizing our products. Watch the video below to see some popular Interface Test and Measurement Product Solutions.

Interface provides an overview of solutions for the T&M industry, detailing our capabilities and providing an overview of some of recent applications. Of course, there are hundreds of use cases every year that depend on Interface, so these are just a couple highlights we thought you would find interesting below. Download the T&M Industry brochure at https://bit.ly/37q3Bnx. E-Bike Torque Measurement

An E-Bike manufacturer needed to test the torque on their electronic bicycles. They needed a torque sensing system that measures how much force the bike rider is pedaling onto the pedals, because this determines how much electric power the bike’s motor generates. Interface suggested installing the Model T12 Square Drive Torque Transducer where the pedal assist sensor would normally be. The T12 Square Drive Torque Transducer’s results can be recorded, graphed, and logged using the SI-USB4 4 Channel USB Interface Module when connected to the customer’s PC. Using this solution, the E-Bike manufacturing company successfully tested the torque on their electronic bicycles with Interface’s products and instrumentation. Read the full E-Bike app note here.

Proving Theoretical Cutting Forces of Rotary Ultrasonic Machining

Rotary ultrasonic machining is a hybrid process that combines diamond grinding with ultrasonic machining to provide fast, high-quality drilling of many ceramic and glass applications. This new method has been theoretically proven using computer models. Rotary ultrasonic machining generates forces of a very small magnitude. To prove this theory, any load cell used for measurement must be sensitive, while at the same time retaining high structural stiffness within a compact, low-profile envelope. Interface’s 3A120 3-Axis load cell is installed in the rotary ultrasonic machine to measure the forces being applied to a sample part. With clear signals and minimal crosstalk, the applied forces are recorded and stored using an the BSC4D Multi-Channel PC Interface Module. The 3-Axis load cell provides excellent data helping uncover the relationship between machine cutting parameters and the forces applied on the component. Using this knowledge, the machining process can be reliably optimized for new materials and operations. Learn more about this machining T&M app note here.

You can learn more about all types of T&M applications in our Applications Catalog, demonstrating the diversity and range of T&M solutions and ingenuity of our customers.

Additional Resources:

Interface Solutions for Testing Tools

Insights in Torque Testing Featured in Quality Magazine

 

AxialTQ Technical White Paper Details Comparative Testing

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Recently, Interface put together a full comparison of our AxialTQ™ Torque Transducer measurement systems versus a competitor’s system that offers a DIN120, 1kNm capacity transducer. To view the complete details, read the new Interface technical white paper A Comparison of Torque Measurement Systems, authored by Jay Bradley, Interface Electrical Engineering Manager.

Here is a brief overview covering the crucial results of the comparison testing.

About AxialTQ Torque Transducer

Since 2018, the AxialTQ has redefined the category of torque measurement systems in terms of function, accuracy, and customizable compatibility. It’s a must have torque transducer for anyone working to minimize uncertainty when measuring anything that turns. It is specifically designed for the expanding torque measurement needs in fields that include the automotive industry, as well as the aerospace and industrial automation sectors.

At the heart of AxialTQ’s innovation is the rotor and high-precision sensing element technology, which when combined with the electronics component, produces industry-leading accuracy. This product is also fully customizable due to its ability to use simultaneous analog and digital outputs. This is key, as it enables real-time control and data collection. The flexible capability of the stator and output module mounting offers an infinite number of configurations to meet any application needs.

AxialTQ was designed and engineered by Interface in direct collaboration with end-users who shared their wish-lists for operational priorities, user profiles, design specifications, feature preferences, and real-world field challenges they wanted a solution to resolve.

The unique decision to implement an axial gap, as opposed to the industry standard radial gap, means there is minimized concern that the shaft, rotor and stator will make contact, significantly reducing the possibility of damaging the system.

Installation Overview

AxialTQ features a 120° stator coil giving it the ability to be mounted in several different orientations. While the full stator loop of the competing system must be carefully aligned with the rotor. AxialTQ’s large axial gap of up to 6mm and radial gap of up to 12mm also allows for small misalignments or rotor movement. The competing system has a small radial gap of 1mm and ±2mm when installed, providing less flexibility and durability. The stators of both the AxialTQ and the competing system have multicolor status LEDs that indicate proper alignment and data transmission.

Performance Testing and Validation

The tests found that both systems performed well and met their respective operating specifications. Some of the dynamic testing was performed only once due to time constraints. This testing also has a greater uncertainty of measurement because of the test setup.

In this comparison we tested the installation process, as well as performance for the following specifications:

  • Zero balance stability
  • Shunt calibration stability and repeatability
  • Measurement repeatability
  • Measurement non-linearity
  • Measurement hysteresis
  • Axial force crosstalk
  • Zero balance over operating temperature
  • Axial gradient temperature performance

Overall, both systems performed in line with specifications. Areas in which the AxialTQ stood out included change in zero-balance readings, performance in operating temperature ranges, and in the in-house spin testing cycles.

Configuration Advantages

Unlike the competing system, the AxialTQ has one analog voltage or current output, two analog frequency outputs, and a digital serial output which are all active and independently scalable and filtered. This means that by applying different scaling to two different outputs, the AxialTQ can operate like a dual range sensor.

Durability

AxialTQ also has a significant advantage in durability. The large axial (up to 6mm) and radial (typically 12 mm) gaps between the rotor and stator make it highly unlikely that the rotor will contact the stator because of harmonic vibration, torque pulse or some other event. Both the rotor and stator coils of the AxialTQ are fabricated from 0.125in (3.18mm) thick FR4, with any conductors located at least 0.05in (1.27mm) from the edge. If damaged, these coils are easily replaced in the factory.

AxialTQ is innovative alternative to current systems and includes creative solutions to overcome some of the challenges that diminish performance in these systems as well. To learn more about go to our AxialTQ product page.

Additional Resources

Recap of Latest Spin on AxialTQ Webinar

AxialTQ Engine Dynamometer Application Note

The AxialTQ Dynamometer

AxialTQ for Anything That Turns and Needs Testing

Force Sensors Advance Industrial Automation

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Industrial automation heavily relies upon the use of sensor technologies to advance production and manufacturing. In the next phase of the industrial revolution, also referred to as Industry 4.0, gains in operational efficiencies are often rooted in innovative tools, robotics, and equipment renovations. These types of enhancements require use of interconnectivity, automation, machine learning, and real-time data. Interface is playing a significant role in enabling these advancements with smart force and torque measurement solutions.

Randy Franks at Sensor Tips poses the following question in a recent article: How can force sensing be integrated for Industry 4.0 upgrades?

“Upgrading facilities to industry 4.0 standards is one of the most significant trends in the manufacturing industry today. To do this, original equipment manufacturers (OEMs) are pushing hard to renovate their facilities with connected, automated devices and machines to create greater efficiency and cost savings. Smarter devices can ease the transition.”

He continues in his post to note, “For Industry 4.0, force measurement solutions providers are integrating actuators that move and control a mechanism or system with load cells to create fully automated force test systems.”

Illustrating how this work, Randy writes about manufacturers of mobile devices using force measurement testing automation to pressure test touch screens with the new Interface ConvexBT miniature-sized load button load cells. 

Click here to read the rest of the article.

Interface Force Measurement Solutions Featured in Quality Magazine

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Choosing a force measurement device and getting the most out of it is a tricky process, even for the most seasoned engineers. So, when Quality Magazine asked our Chief Engineer and VP of Quality, Ken Vining, to share his knowledge of force measurement, he decided to put together a guide on what to look for in force measurement equipment and how to use and maintain your equipment properly.

In his Quality Magazine article titled, “Selecting and Using a Force Measurement Device: Everything you need to know,” Vining explains the contributing factors to force measurement device quality and accuracy, as well as a few tips and tricks to make sure you’re getting the best possible accuracy and longevity out of your device.

Included below is a brief introduction from article:

Force measurement devices like load cells, torque transducers and data acquisition devices are used across industries to design and test hardware. They’re a key factor in the product development process because the force, torque and weight data they collect helps to ensure products are accurately constructed, work as intended, are safe for use, and can withstand the test of time. In highly regulated and complex industries like medical and defense, this data becomes even more important because any miscalculation in the design of a product can put lives at risk.

The first thing to understand is every project requiring a load cell or torque transducer has different variables affecting accuracy and quality. And for every situation in product development and testing, there is a load cell to fit your precise need. Therefore, the most important step in ensuring accurate and high-quality data is speaking to a force measurement expert about the details of a project.

There are five key factors you need to know related to data accuracy, and three factors related to force measurement device quality. I’ll explain why each factor can contribute to inaccuracies and what to look for when selecting a device based on material selection, build quality, and environmental factors… READ MORE

Additional Ken Vining feature

For additional information on selecting and using your force measurement device, please contact our solutions experts.

Robotics in Play with New Animated Application Using ConvexBT

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Numerous factors are driving the industry 4.0 revolution. From big data to IoT technology, industrial facilities and manufacturing plants are looking at new ways to automate their process and create a more efficient and cost-effective environment. One of the most important technology advancements in this mix is robotics.

Robotic equipment is a common industry 4.0 innovation used to create an autonomous or semi-autonomous machine capable of carrying out a variety of repetitive tasks that used to take up the time of skilled labor. Some of the tasks or processes that robotics enhance include stock management and logistics, manufacturing automation, janitorial duties and, there are even robotic applications called co-bots that assist human workers when ultra-high precision is needed.

To facilitate the demand for robotics, a variety of sensor and measurement components are necessary to ensure the highest quality and reliability of these application. Many tasks carried out by robotic applications are ultra-precise and require more accuracy than what a human hand or eye can handle.

Sensor technologies embedded in the actual robotics instrument must also be used to constantly calibrate or monitor the robotics. If robotics is used on an automated manufacturing line, any issues with the robotics can disrupt and compromise the entire process. Therefore, robotics manufacturers utilize Interface solutions when they need quality sensors that can monitor the precision of the robotics and ensure that their accuracy and reliability is maintained.

Interface develops high-quality test and measurement solutions designed for hardware testing of all kind. For robotics, our products are frequently used as a component within an OEM device. We understand the premium accuracy and reliability necessary to help develop robotics solutions and have provided both off-the-shelf and custom force measurement solutions designed to meet a variety of applications. We recently created an animated application note on an industrial automation robotic arm using our new light weight, light touch load button load cell, the ConvexBT.

The ConvexBT is designed for testing and also for full integration into the robotic element to measure the force pressure during use.  ConvexBT is available in multiple capacities, including our latest release of the 500lb and 1Klb models.

NEW! Interface Robotic Arm Application Note

A customer came to Interface with a robotic arm product that would be used to lift and move delicate objects, such as a glass bottle, in an automated environment. The goal in using Interface was to find a force measurement product that could ensure the robotic arm did not damage the products it was moving by applying too much force. The main component that Interface products would be applied to is the robotic arms’ clamp. The objective was monitoring the grabbing pressure of the clamp and ensure that the device would stop applying pressure when the necessary force was used to pick up the object without doing damage.

Using its new line of Load Button Load Cells, ConvexBT, and a DMA2 DIN Rail Mount Signal Conditioner, Interface provided a solution that would produce an electric signal on the clamping process that tells a controller to have the device stop applying pressure. Two ConvexBT products were connected underneath the rubber pads on both sides of the robotic arm clamping device. When the clamps made contact and applied pressure, the DMA2 Signal Conditioner converted the signal from the ConvexBT from MV/V to volts to a PLC controller. This signal tells the controller when to have the robotic arm stop applying clamping force.

Ultimately, the two ConvexBT Load Button Load Cells were able to accurately measure the amount of pressure applied to the object the robotic arm was lifting and moving without causing any harm or damage to the object.

This is just one of many examples of force measurement products being used in the robotics and automation industry. As the demand for robotics grows and a wider variety of applications are introduced, Interface will continue to engineer the best solutions to help customers reach the age of Industry 4.0.

To learn more about Interface solutions for the robotics and automation industry, please visit /solutions/. You can also check out our case study on the for industrial automation and robotics use here.

Load Cell Test Protocols and Calibrations

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In the Interface Load Cell Field Guide, our engineers and product design experts detail important troubleshooting tips and best practices to help test and measurement professionals understand the intricacies of load cells and applications for force measurement devices. In this post, our team has outlined some helpful advice for testing protocols, error sourcing and calibrations.

The first step in creating test protocols and calibration use cases is to define the mode you are testing. Load cells are routinely conditioned in either tension or compression mode and then calibrated. If a calibration in the opposite mode is also required, the cell is first conditioned in that mode prior to the second calibration. The calibration data reflects the operation of the cell only when it is conditioned in the mode in question.

For this reason, it is important that the test protocol, which is the sequence of the load applications, must be planned before any determination of possible error sources can begin. In most instances, a specification of acceptance must be devised to ensure that the requirements of the load cell user are met.

Typical error sources in force test and measurement are usually identified as being related to:

  • Lack of protocol
  • Replication of actual use case
  • Conditioning
  • Alignment
  • Adapters
  • Cables
  • Instrumentation
  • Threads and loading
  • Temperature
  • Excitation voltage
  • Bolting
  • Materials

In very stringent applications, users generally can correct test data for nonlinearity of the load cell, removing a substantial amount of the total error.  If this can’t be done, nonlinearity will be part of the error budget.

An error budget is the maximum amount of time that a technical system can fail without service level consequences. In force test and measurement, it is sometimes referred to as uncertainty budget.

Nonlinearity is the algebraic difference between output at a specific load and the corresponding point on the straight line drawn between minimum load and maximum load.

Nonrepeatability is essentially a function of the resolution and stability of the signal conditioning electronics.  Load cells typically have nonrepeatability that is better than the load frames, fixtures and electronics used to measure it.

Nonrepeatabillty is the maximum difference between output readings for repeating loading under identical loading and environmental conditions.

The remaining source of error, hysteresis, is highly dependent on the load sequence test protocol.  It is possible to optimize the test protocol in most cases, to minimize the introduction of unwanted hysteresis into the measurements.

Hysteresis is the algebraic differences between output at a given load descending from maximum load and output at the same load ascending from minimum load.

There are cases when users are constrained, either by requirement or product specification, to operate a load cell in an undefined way that will result in unknown hysteresis effects. In such instances, the user will have to accept the worst-case hysteresis as an operating specification.

Some load cells must be operated in both tension and compression mode during their normal use cycle, without the ability to recondition the cell before changing modes. This results in a condition called toggle, a non-return to zero after looping through both modes. The magnitude of toggle is a broad range. There are several solutions to the toggle problem, including using a higher capacity load cell so that it can operate over a smaller range of its capacity, use a cell made from a lower toggle material or require a tighter specification.

ONLINE RESOURCE: INTERFACE TECHNICAL INFORMATION

For questions about testing protocols, conditioning, or calibration, contact our technical experts. If you need calibration services, we are here and ready to help.  Click here to request a calibration or repair service today.

Understanding Uncertainty in Load Cell Calibration

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In force measurement testing, accuracy is the most critical factor in ensuring the data you collect can help to identify challenges, failures and opportunities in the product design and development cycle. Here at Interface, we have mastered the art of load cell accuracy by employing a vertically integrated manufacturing process that allows us to control the development of our products most critical components.

Even the most high-end manufactured load cells and finely tuned components endure accuracy degradation over continued use. Therefore, we have also invested in equipment and talent with deep expertise in load cell recalibration, as well as offering gold and platinum standard calibration systems to customers. Recalibration is recommended on an annual basis, or of course, whenever our customers feel they need to confirm they are getting the right data out of their load cells.

One of the key factors of calibration and recalibration is understanding how to estimate practical uncertainty in load cell calibration. Measurement uncertainty is defined as an estimate of the range of measured values within which the true value lies or, alternatively, the degree of doubt about a measured value. In every application, there will be an uncertainty requirement on the force measurement. The equipment used to make the measurement must be traceable to a realization of the SI unit of force (the newton) within this required uncertainty.

Each application is different in terms of its uncertainty requirement. For instance, an application testing force in the aerospace and defense or medical sector will include a much more stringent uncertainty requirement than something like a commercial scale used to measure someone’s weight or food. It is critical to understand the uncertainty requirement on the application to ensure the force measurement device used is calibrated to handle the project.

How does one go about estimating uncertainty in load cell calibration? The first thing to understand is the GUM, a guide to the expression of uncertainty in measurement. This guide establishes general rules for evaluating and expressing uncertainty in measurement that are intended to be applicable to a broad spectrum of measurements.

Next, we have included a list of different considerations, as we measure uncertainty here at Interface. These factors will help guide you as you determine uncertainty for yourself. This list includes:

  1. Determine what parameter is to be measured and the units of measure.
  2. Identify the components of the calibration process and the accompanying sources of error.
  3. Write an expression for the uncertainty of each source of error.
  4. Determine the probability distribution for each source of error.
  5. Calculate a standard uncertainty for each source of error for the range or value of interest.
  6. Construct an uncertainty budget that lists all the components and their standard uncertainty calculations
  7. Combine the standard uncertainty calculations and apply a coverage factor to obtain the final expanded uncertainty.

It is also important to consider the different methods of load cell calibration. There are three different methods, and each has an approximate feasible expanded uncertainty. The different calibration methods include:

  • Direct dead weight – this method is the best for accuracy at 0.005% uncertainty, but it is slow, and the equipment is space inefficient.
  • Leveraged dead weight – middle of the road for accuracy at 0.01% uncertainty, and slow and space inefficient.
  • Hydraulic force generation comparison – this method has reasonable accuracy at 0.04% uncertainty and is also the fastest and most space-efficient option.

The final point is the sources of error in calibration. Error is defined as the difference between the measured value and the true value. There is a long list of different factors that can cause error and increase uncertainty. These factors may include drift, creep, misalignment, or environmental factors such as temperature. To compensate for this, it is important to understand the various formulas that can be used to find the true value based on the given measurement and the various factors for error.

To learn more about uncertainty and the different ways users can address uncertainty and overcome it, please give us a call at 480-948-5555, or visit our website to contact our Application Engineers.

Contributor:  LaVar Clegg, Interface

Source: NCLSI Measurement Training Summit 2014