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Quality Engineers Require Accurate Force Measurement Solutions

In engineering and manufacturing, when introducing a product onto the market the requirements and regulations can be immense. Each industry has strict guidelines to ensure safety, durability, quality, and overall customer satisfaction. To meet these requirements, most product and component maker will have experienced quality engineers to help meet the necessary requirements in production.

Quality Engineers work in a variety of industries including automotive, transportation, infrastructure, aerospace and defense, industrial automation, medical and healthcare devices, and consumer product manufacturing. Their role is to monitor, test, and report on the quality. They are also instrumental in strategy, process development, and increasing output. Depending on the position, they are responsible for inspecting and testing raw materials, components, mechanical systems, hardware and software, as well as final products.

The Quality Engineer works with manufacturers, developers, project managers. Commonly, they are aligned with quality assurance and quality control teams to develop processes, test procedures and implement systems that ensure manufactured products and fabrication processes meet quality standards, safety regulations, and satisfy all stakeholders. They are the safeguard for companies that are creating, building and distributing products and materials.

Accuracy of testing and measurement data is fundamental to quality engineers. Critical to quality assurance and control processes, quality engineers rely heavily on all types of Interface high-accuracy load cells, weighing systems, and instrumentation for force measurement quality systems. Manufacturing quality engineers rely on products from Interface to test both products and equipment on a manufacturing line to ensure they perform reliably and meet certain safety standards.

Force measurement systems also make role of a quality engineer easier through the use of accurate data. This is because force measurement often enables automated, real-time monitoring of many processes used in the making of things. Interface precision load cells are used to monitor assembly line machine processes, test and monitor automation equipment like robotics, and weighcheck systems, and ruggedized equipment for quality control onsite and in remote locations.

Included below are a few examples of how force measurement systems are used in quality engineering.

Medical Device Interventional Guidewire Quality Inspection

A medical device manufacturer needs to do quality checks on threaded ends of their interventional guidewire devices. The threaded end of the guidewire contains an extremely small 000-120 thread that needs to be tested with go and no-go gauges in order to see if it will mate with other critical subassemblies. They requested a custom made turnkey test stand that is both inexpensive and flexible for varying lengths and models of guidewires.  Interface suggests a system where the customer can axially load and insert the guidewire through the MRT Miniature Flange Style Reaction Torque Transducer, secure it, and use an automated stepper motor on a slide base to test the thread quality. When in use, the MRT measures the torque magnitudes of both no-go and go gauges which indicate quality of the threaded guidewire.

Snack Weighing and Packaging Machine Quality Monitoring

One aspect of quality in the consumer packaged goods space is ensuring equal distributions of individually wrapped snack bags such as chips or candy. When snack manufacturing brand wanted to weigh the amount of their snacks that is automatically dispersed into the bags during the packaging process, Interface offered a solution. We suggested multiple SPI Platform Scale Load Cells, and installed them to the potato multi-head weigher and packaging machine. The SPI Platform Scale Load cells were installed inside of the mount that attaches the head weigher to the packaging machine. Force results from the potato chips were read by the load cells and sent to the ISG Isolated DIN Rail Mount Signal Conditioner, where the customer is able to control the automated production from their command center. The customer was able to determine the weight of the potato chips being distributed into their bags with highly accurate results. They also were able to control the automated production process with the provided instrumentation. They will use this same weighing method for other snacks that need to be packaged utilizing this machine.

Vehicle Crash Test Load Cell Wall Quality Inspection

A facility wanted to do crash tests on their vehicles for quality inspection. There are multiple tests such as structural testing of the vehicle, developmental tests, and regulatory and compliance tests and they needed to measure the force of the vehicle crash tests, on all axes. Interface’ suggested using multiple 3A400 3-Axis Force Load Cells, and attach it to the back of a cement crash wall. When connected to the BX8-HD44 Interface BlueDAQ Series Data Acquisition System, force result measurements will be recorded and displayed with the customer’s PC or laptop. The customer was able to measure the force of impact for all of their different vehicle crash testing demonstrations.

The applications of force measurements for quality engineers are large, and the necessity of obtaining this data is critical to creating, safe, reliable and high-quality products.

ADDITIONAL RESOURCES

Interface Solutions for Material Testing Engineers

Why Civil Engineers Prefer Interface Products

Why Product Design Engineers Choose Interface

The Five Critical Factors of Load Cell Quality

Our Reputation is Defined by Our Industry-Leading Quality

Interface Solutions for Research and Development

Top Five Reasons Why Calibration Matters

Applied metrology is the measurement science developed in relation to manufacturing and other processes, ensuring the suitability of measurement instruments, their calibration, and quality control.

Calibration is the practice of evaluating and adjusting equipment to ensure precision and accuracy. Calibration for force measurement determines whether a sensor is working properly, as well if it needs repair or replacement.

Calibration is critical in the application of test and measurement because it provides controlled methods using equipment and systems that ensure reliability, accuracy, and quality.

We recently shared in our Accurate Report on Calibration seminar, the top five reasons why calibration matters. Below highlights each why.

#1 Reason Why Calibration Matters – Understanding Uncertainty

  • 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 Newton unit of force within this required uncertainty.

#2 Reason Why Calibration Matters – Quality and Specifications

  • Calibration ensures the transducer is performing to listed specification.
  • It avoids costly impacts or escapes to manufactured goods and products.
  • Maintaining quality of manufactured device to original specifications is an important reason why calibration matters.
  • It certainly minimizes the cost of poor quality.

#3 Reason Why Calibration Matters – Minimize Downtime

  • Proactive maintenance will always take less time than reactive problem solving and repairs.
  • Identify and repair or replace system components before they fail through regular calibration.
  • Plan calibration intervals to minimize downtime, as a schedule is preventative maintenance.

#4 Reason Why Calibration Matters – Data Accuracy

  • All load cells are subject to potential performance degradation due to mistreatment or drift, impacting data integrity.
  • Pre and post test verification provide assurances in data validity.
  • Confidence in critical measurements is imperative.

#5 Reason Why Calibration Matters – Accreditation and Certifications

  • Calibrations provide adherence to quality management systems and requirements, especially ISO certifications and compliance.
  • It assures that measurements gathered within the valid calibration period are reliable, trustworthy, and defensible.
  • Traceability of measurement is guaranteed with certifications.

To start, every sensor Interface manufactures is calibrated and certified in our fully accredited calibration labs before it leaves our facilities. We do so under ISO 17025 standards with full NIST traceability for quality assurance. Annually, we provide more than 100,000 calibrations on force and torque measurement devices.

We also provide complete calibration services and repair on any sensor we make, as well as other manufacturer’s equipment. Our experienced calibration lab technicians offer a complete range of calibration services for load cells, torque transducers and other force measurement devices, including:

  • Scheduled Repairs for Ongoing Inventory Management
  • RMA Tracking and Permanent Archive of Test Data
  • Custom Calibration Services
  • Certification

Calibration is a necessity as any product can degrade, resulting in a decline in accuracy. Interface recommends every device go through a calibration service annually to maintain the integrity of the sensor performance. If you need assistance in scheduling a calibration service or requesting help, contact us here.

We also offer a range of calibration grade equipment for labs and to use for self-service calibration.  This includes our verification load frames, calibration systems, calibration grade load cells and lab instrumentation. Read Calibration Grade Load Cells and Systems and Additional Interface Calibration Grade Solutions to learn about these and other products.

ADDITIONAL RESOURCES

Recap of Accurate Report on Calibration

Interface Calibration 101

GS-SYS04 Gold Standard® Portable E4 Machine Calibration System

Shunt Calibration 101

Extending the Calibration Range of a Transducer

Calibration-and-Repair-Brochure-1

 

 

Exploring Interface Capabilities and Differentiators

Interface is the largest producer of load cells defined by a particularly important core differentiator. The Interface difference is precision.

How do we maintain this standard of excellence? Interface is directed by our foundational 4-pillars for success: quality, service, accuracy, and innovation. This applies to anything and everything that we do, including manufacturing premium force measurement products, engineering and design, custom solutions, providing calibration and repair, and in our commitment to service.

Interface has long been known for providing accuracy-based sensor technologies, innovative solutions, engineering excellence and quality products that our customers trust. We have detailed our breadth and depth of capabilities and differentiators for our products that are designed to serve customers across a growing number of industries.

In our online capabilities statement, you can find:

  • Interface differentiators
  • Interface core products and expertise
  • Certifications
  • Industry NAICS and PSC Codes
  • Interface’s Company Snapshot

Our customers around the world are innovators, market leaders, boundary-breaking, finding ways to do things differently, make things safer, improve products and create new all through the measurement of force. We provide solutions for test and measurement, as well as OEM. This includes companies in aerospace and defense, automotive and vehicle, medical devices, energy, industrial automation, entertainment and amusement, agriculture, maritime, infrastructure, and equipment manufacturing.

As world’s trusted leader in force measurement technology, design, and manufacturing, it is important that we guarantee the highest quality performance of load cells, torque transducers, multi-axis sensors, wireless telemetry, instrumentation, calibration and more. To do this, it is the Interface people, technology, manufacturing, engineering, and force measurement solutions that make the difference.

Here are just a few of Interface’s key differentiators and capabilities:

  • PROPRIETARY STRAIN GAGES: We make our strain gages and assemble them in the same buildings as our final sensor testing is performed in-house to ensure the quality and accuracy.
  • THE STANDARD: Interface is the standard for all load cells. Since 1968, our LowProfile® load cells have been used throughout the world because of their accuracy and dependability.
  • CALIBRATION: Our trademarked Gold Standard Calibration System is the industry ‘gold standard’ for test and measurement.
  • SYSTEMS: Interface is the only major load cell company offering a comprehensive system for customers to calibrate their own load cells.
  • CERTIFICATIONS: Every load cell we make is individually calibrated and tested through a series of performance tests before it leaves our facility.
  • STANDARD, ENGINEERED-TO-ORDER AND CUSTOM: We design and build our force measurement solutions, delivering the broadest variety of available options in the industry.
  • TEAM: Our team is an extended network of professionals that design, build, administer, sale and support our customers with the best force measurement solutions that fit their exact requirements based on expertise and experience.

You can see all the Interface differentiators in our capabilities statement.

We’ are proud of the Interface brand, our five-decade legacy as a leader in the industry and fact that we are a women-owned manufacturing company. We guarantee our products quality because every employee and partner take pride in our work. It is our dedication to deliver on our promise.

Capabilities-Statement

Types of Force Measurement Tests 101

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

Specifying Accuracy Requirements When Selecting Load Cells

When selecting a load cell, it is important that your selection matches the type of application use case. If it is for general test and measurement requirements, a load cell model and capacity may differ from a load cell you design into a product or machine.

The first place to start in your transducer selection process of a load cell is to identify what you want to measure and your tolerance in accuracy.

Other questions will define the type of load cell, capacity, and measured specs. Do you want to measure tension, compression only, tension and compression, torque, or something else like pressure? What are your cycle counts for testing? What is the amount of measurement range you require? How controlled will the force be, both in orientation and magnitude consistency?

Once you identify early characteristic requirements for how you use the sensor, it is easier to begin evaluating options to optimize measurement accuracy.

Several aspects impact the accuracy of a load cell measurement, including:

  • Sensor Specifications
  • Mounting configuration
  • Calibration type
  • Instrumentation
  • Cables
  • Uncertainty of calibration

Every load cell should have a detailed specification datasheet that outlines key performance factors by model and size.

This post begins in defining specifications for accuracy as outlined for every Interface manufactured load cell. These accuracy-related specifications include:

  • Static Error Band %FS – The band of maximum deviations of the ascending and descending calibration points from a best fit line through zero output. It includes the effects of nonlinearity, hysteresis, and non-return to minimum load.
  • Nonlinearity %FS – The algebraic difference between output at a specific load and the corresponding point on the straight line drawn between minimum load and maximum load.
  • Hysteresis %FS – The algebraic difference between output at a given load descending from maximum load and output at the same load ascending from minimum load.
  • Nonrepeatability %RO – The band of maximum deviations of the ascending and descending calibration points from a best fit line through zero output. It includes the effects of nonlinearity, hysteresis, and non-return to minimum load.
  • Creep % – The change in load cell signal occurring with time while under load and with all environmental conditions and other variables remaining constant. Expressed as % applied load over specific time interval.
  • Eccentric Load Sensitivity: ECCENTRIC LOAD – Any load applied parallel to but not concentric with the primary axis. Results in moment load. SIDE LOAD – Any load at the point of axial load application at 90° to the primary axis.

Interface load cells are designed for precision, quality, and accuracy. Though the ranges may differ in specifications slightly, most of the performance data will far exceed industry standards. As we always say, Interface is the standard for load cell accuracy.

We will be outlining additional impacts on accuracy in upcoming posts. If you have questions on any product and specifications, as to whether it is the right load cell for your use case, contact us for help.

Additional Resources

Contributing Factors To Load Cell Accuracy

Application Notes

Accuracy Matters for Weighing and Scales

Interface Ensures Premium Accuracy and Reliability for Medical Applications

Interface Accelerates Accuracy in Test and Measurement

Interface Presents Load Cell Basics

I’ve Got a Load Cell Now What? Episodes 1 and 2

I’ve Got a Load Cell Now What? Episodes 3 and 4

Understanding Load Cell Temperature Compensation

The performance and accuracy of a load cell is affected by many different factors. When considering what load cell will work best for your force measurement requirements, it is important to understand how the impact of the environment, in particular the temperature impact on output.

An important consideration when selecting a load cell is to understand the potential temperature effect on output. This is defined as the change in output due to a change in ambient temperature. Output is defined as the algebraic difference between the load cell signal at applied load and the load cell signal at no load. You can find more detailed information in our Technical Library.

Temperature affects both zero balance and signal output. Errors can be either positive or negative. To compensate for this, we use certain materials that are better suited for hot or cold environments. For instance, aluminum is a very popular load cell material for higher temperatures because it has the highest thermal conductivity.

In addition to selecting the right material, Interface also develops its own proprietary strain gages, which allows us to cancel out signal output errors created by high or low temperatures.

In strain gage-based load cells, the effect is primarily due to the temperature coefficient of modules of elasticity of the force bearing metal. It is common in the industry to compensate for this effect by adding temperature sensitive resistors external to the strain gage bridge which drop the excitation voltage reaching the bridge. This has the disadvantages of adding thermal time constants to the transducer characteristic and of decreasing the output by 10%.

Our load cells are temperature compensated for zero balance. By compensating for zero balance, we can flatten the curve in the relationship between temperature and zero balance. An uncompensated load cell has a much more severe curve, which ultimately affects accuracy and performance.

Interface offers thousands of load cell designs, standard use and for hazardous environments. For instance, rocket engine tests subject our load cells to extremely high temperatures. For use in various maritime industry projects, they can be used in very cold coastlines and even submerged in cold water. No matter where you are, environment influences the load cells performance.

If you are concerned about temperature, Interface provides specifications for every load cell we manufacture. The Interface specification datasheet, as see referenced here, is available for download by product. It always includes all the necessary data required to understand the load cell’s ability to perform at the highest-level including compensation range, operating range, effect on zero balance and effect on span.

One thing that is also unique about our products is that while most competitors only compensate for hot temperatures (60 to 160 degrees Fahrenheit), Interface covers both hot and cold thermal compensation from 15 to 115 degrees Fahrenheit, including adjust and verify cycles.

Be sure to tune into Load Cell Basics, where Keith Skidmore discusses temperature compensation.  He notes during this informative presentation that if the temperature is changing during a test that can affect the zero and the output of the load cell. How much effect depends how much temperature is changing and how well the load cell is compensated against the errors, which can be either positive or negative. Good news is they are repeatable from test to test so if you have large temperature swings you can characterize the system and then subtract out the shift if you know the temperature effect on zero.

Interface Application Engineers are available to answer questions regarding the effect of temperature on force measurement data, or the different ways we can help design a solution to compensate for your environment.

Quality is Top Reason Customers Choose Interface

In our latest customer feedback survey, we asked those that rely on Interface why they buy from us. The overwhelming top response was product quality. One of the trademarks of Interface is ensuring that our products meet not only the demand of what is needed in the market for measurement sensors, but that the precision, accuracy, and quality of everything we build is market leading. Best in class.

Our customers drive Interface innovation. We are continuously looking at trends, special requirements and future outlooks to determine what solutions can meet today’s requirements and those in the future. It was noted in the survey that customers depend on Interface for this expertise and experience. That is why it is central in our business strategy and key for Interface’s success to ask, listen and learn from those that rely on our force measurement solutions in their businesses.

A hallmark to our semi-annual survey is the Net Promoter Score (NPS) question that is designed to measure loyalty. We asked again in this latest Spring 2021 survey, “How likely is it that you would recommend Interface to a friend or colleague?” Respondents are then asked to rate their response by selecting 0-10 with 10 being extremely likely and 0 not at all likely. The percentage of those that select 9 or 10 are considered promoters of the Interface brand. Anyone that scores 6 or below is considered by NPS standards to be a detractor. The percentage of promoters minus the percentage of detractors are gives you an NPS score.

We are very excited to announce that Interface’s current Net Promoter Score is +73.

The founders of NPS note that outstanding companies in their class average between a +30 to +50. We are honored by the recognition coming directly from our customers.

“This is a great result! We appreciate the recognition of our team member’s hard work to generate such customer satisfaction and loyalty. Global brands recognized around the world and who are famous NPS power users rarely report scores as high as Interface. We are honored to have such loyal customers, as seen in an outstanding +73 NPS. Remarkably, this came during a period where the customers’ most recent experience likely was influenced by the pandemic strain.” Greg Adams, CEO

We learned from our customers when we asked, “What are the most important reasons why you choose to buy from Interface?”, that product quality matters most, followed next by calibration and repair services, accuracy specifications, experience working with Interface and brand reputation. We also looked at trends in future product demands and the ability to buy online through our QS48 online shopping service.

Our customers were very forthcoming in their preferences for technical support, with phone and email taking top positions. This was followed by using our technical library, video demonstrations and numerous product and technical manuals.

We also gained great insights from our customers when we asked, “How can we improve your overall experience working with Interface?”  All feedback matters to us. It’s what we gain through this transparent and open process that we know where we can look to improve. In fact, we are determined to look at every opportunity presented in the survey to make operational improvements that benefit our customers in all areas from design to shipments.

“Our team performance demonstrates the winning position we are all committed to at Interface. Customer experience is central to what we do and it’s our focus to continuously exceed expectations. As great as this score is today, the better news is that we have the opportunity to improve further and define our future as the market leader by delivering the best for our customers.” Greg Adams, CEO

Our last question in the survey, we asked, “How satisfied are you with Interface and your customer experience?” and we learned that 98% of our customers are satisfied and 83% are very or exceedingly satisfied. We appreciate all those that provided their candid responses in our Spring Customer Satisfaction and NPS Survey. Our work continues to make sure what we do goes above and beyond and delivers on our promise to exceed expectations.

 

Load Cell Basics Sensor Specifications

When selecting a load cell, it’s critical to understand the major factors impacting sensor accuracy. These factors are determined by the materials and components used in the construction of the load cell, the calibration, instrumentation, the accessories such as cables, and mounting installation. Each must be considered in the specific use cases for the load cells.

During our virtual event, Load Cell Basics, applications expert Keith Skidmore detailed everything you need to know about load cells and how to choose the right load cell.  First, Keith highlighted four vital application considerations:

Mechanical – Dimensions and Mounting

Electrical – Output and Excitation

Environmental – Temperature and Moisture

Performance – Accuracy and Thermals

Taking a deeper dive into performance, an important consideration when selecting your load cell are the sensor specifications and how they impact accuracy. The sensor specifications relate to the max error of various parameters. The specifications are always included in product spec sheets and are expressed using the following values – %FS, %RO, %, %/°F, time-related. Specifications listed relate to the max error for accuracy and temperature.

Interface provides all sensor specification data for our load cells in the product datasheets found on each product page for easy download.

The information we provide for every load cell typically includes:

Accuracy:

  • Static Error Band
  • Non-linearity
  • Hysteresis
  • Non-repeatability
  • Creep
  • Side Load Sensitivity
  • Eccentric Load Sensitivity

Temperature:

  • Compensated Range
  • Operating Range
  • Effect on Zero
  • Effect on Span

Further definitions can be found in our online technical glossary.  Here are a few that we highlighted in the Load Cell Basics webinar.

Static Error Band: A band encompassing all points on the ascending and descending curves centered on the best fit straight line. It is expressed in units of %FS.

SEB Output: The output at capacity based on the best fit straight line.

Non-repeatability: The maximum difference between output readings for repeated loadings under IDENTICAL LOADING AND ENVIRONMENTAL CONDITIONS. In practice, there are many factors that affect repeatability that ARE NOT included in the non-repeatability specification. It is normally expressed in units of %RO.

Non-linearity: The difference in the output from a straight line. It is normally expressed in units of %FS.

Hysteresis: The difference in the ascending versus descending curves. This is normally expressed in units of %F.

Understanding these factors and the maximum error for your specific project is critical to selecting a load cell and getting the best possible data out of it.

To learn more about sensor specifications for load cells, review the product specs on each datasheet or in our product catalogs. For additional help, call to speak with our application engineers at 888-557-2533.

To view additional online events, please go to our events page.

 

How to Choose the Right Load Cell

Load cells are used to test and confirm the design of hardware, components, and fixtures used across industries and by consumers. From the structural integrity of an airplane to the sensitivity of a smartphone touchscreen, there’s a load cell available to measure force. In fact, here at Interface we have over tens of thousands of products used in force measurement, for all types of different applications.

How do engineers and product designers go about choosing the right load cell for a specific application or testing project?

Have no fear, Interface has put together a short guide on choosing the load cell that is right for you. This blog will cover the basic questions to answer when selecting a product, as well the most important factors affecting load cell choice.  Be sure to watch the online video, Load Cell Basics, that highlights key factors of consideration when choosing the right load cell for additional insights.

The basic questions you need to consider when selecting a load cell include:

  • What are the expected loads? What is the minimum and maximum load you’ll be measuring?
  • Is there any potential for higher peak loads than what you intend to measure? What are these expected peak forces?
  • Is it tension, compression, or both?
  • Will there be any off-axis loads? If so, what is their geometry? Do you want to measure them too?
  • Will it be a static, dynamic or fatigue measurement?
  • What is the environment in which you’ll be conducting your test? Will the load cell need to be sealed?
  • How accurate do your measurements need to be? Do they need to be at the highest accuracy of ±0.02-0.05% or within ±0.5-1%?
  • What additional features, accessories and instrumentation does your application require to complete a test?
  • Do you need standard electrical connectors or customized options? What about additional bridges or amplifiers?
  • How are you planning to collect and analyze the data output from the load cell?

Next, these are the most important factors affecting accuracy, which will have a heavy influence over the load cell you choose. It’s important to understand how your application and the load cell will be affected by each of the factors, which include:

  • Mechanical – Dimensions and Mounting
  • Electrical – Output and Excitation
  • Environmental – Temperature and Moisture

One of the most important factors in choosing the right load cell is understanding how it will be mounted for testing or as a component within a design. There are a wide variety of mounting types including threaded connections, inline, through hole or even adhesive. Understanding the mounting type that suits your application is critical to getting the correct data because a poorly mounted load cell will distort the results and can damage the load cell.

The mounting process also requires you to understand which direction the load is coming from, in addition to any extraneous loads that may be present. The load cell mating surface is also an important factor. For example, when using our LowProfile® load cells without a pre-installed base, the best practice is to ensure that the mating surface is clean and flat to within a 0.0002-inch total indicator reading and is of suitable material, thickness, and hardness (Rc 30 or higher). Also make sure that bolts are torqued to the recommended level.

If you’re conducting a fatigue measurement, it’s also important to address the frequency and magnitude of load cycles with your load cell provider. Factors to address include single mode versus reverse cycles, deflection versus output resolution, and material types. Interface offers a wide variety of fatigue-rated load cells that are perfect for these types of applications.

Another consideration in choosing the right load cell is the electrical signal. Load cells work by converting force into an electrical signal. Therefore, it’s important to understand the electrical output type necessary for your application, which could include millivolt, voltage, current or digital output. You can find the excitation voltage data on our website for each of our load cells. Additional considerations include noise immunity, cable length and proper grounding.

The environment is also a critical factor in ensuring accurate performance of your load cell. Interface provides load cells in a variety of material types including aluminum, steel, and stainless steel. Each material has a variety of properties that make them more suitable for different environments. For a more in-depth perspective on the different strengths and weaknesses of materials, please read our blog titled, Considerations for Steel, Stainless Steel and Aluminum Load Cells. For applications where load cells need to be submerged in liquid or enter an explosive environment, we also have a variety of harsh environment and IP rated load cells, in addition to load cells suitable for high humidity or splash resistance. Learn more about our intrinsically safe load cells here.

Learn more about choosing the right load cell in these online resources:

WATCH: Load Cell Basics with Keith Skidmore

WATCH: How to Choose a Load Cell with Design Engineer Carlos Salamanca

READ: Load Cell Field Guide

VISIT: Interface Technical Library

To learn more about choosing the right load cell for any application, connect with our applications engineers about the force measurement needs for your next project at 480-948-5555.