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Calibration Curve 101

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Calibration curves are essential for ensuring the accuracy of force measurements. They are used in a wide variety of test and measurement applications, including quality control, research, and engineering.

A calibration curve is a graph that shows the relationship between the output of a measuring instrument and the true value of the quantity being measured. In force measurement, a calibration curve is used to ensure that the force measuring device is performing accurately. In the context of load cell calibration, a calibration curve is a graphical representation of the relationship between the output signal of a load cell and the applied known loads or forces.

The load cell user will use a known force standard to create the calibration curve. The known force standard is applied to the force measuring device and the output of the instrument is logged via the supporting instrumentation. This process is repeated for a range of known forces.

The calibration curve for a load cell is created by plotting the output signals (typically in voltage or digital units) on the y-axis against the corresponding applied loads or forces on the x-axis. The resulting graph is the calibration curve.

Test and measurement professionals use the calibration curve to convert the load cell output to the true value of the force being measured. The curve helps to establish the relationship between the load and the output signal, and it provides a means to convert the load cell’s output into accurate force or weight measurements. For example, if the output is 100 units when a known force of 100 N is applied, then the calibration curve will show that the measurement using the load cell is accurate to within a certain tolerance.

Benefits of using a calibration curve in force measurement:

  • It ensures that the force measuring instrument is accurate and dependable.
  • It provides a way to convert the load cell output to the true value of the force being measured.
  • It can be used to identify and correct errors, including drift, sensitivity, overload and hysteresis.
  • It should be used for traceability and to track the performance of the measurement device over time.

Why does a calibration curve matter when calibrating load cells?

Load cells can be affected by a range of factors, including temperature variations, drift, and environmental conditions. The calibration curve helps identify and compensate for these factors. By periodically calibrating the load cell, any deviations from the original calibration curve can be detected, and appropriate corrections can be made to ensure accurate and reliable measurements.

The calibration curve for a load cell should be linear, indicating a consistent and predictable relationship between the applied load and the output signal. However, load cells may exhibit non-linear behavior, such as sensitivity variations or hysteresis, which can be accounted for and corrected through calibration.

The calibration curve allows for the determination of the load cell’s sensitivity, linearity, and any potential adjustments or corrections needed to improve its accuracy. It serves as a reference to convert the load cell’s output signal into meaningful and calibrated measurements when the load cell is used in practical applications for force or weight measurement.

Calibration curves are an essential tool for ensuring the accuracy of force measurements. They are used in a wide variety of applications, and they offer several benefits. If you engage in using load cells, it is important to understand the importance of calibration curves and how they can help you ensure accurate measurements.

Find all of Interface 101 posts here.

Interface recommends annual calibration on all measurement devices. If you need to request a service, please go to our Calibration and Repair Request Form.

ADDITIONAL RESOURCES

Interface Calibration 101

Interface Guides

Load Cell Sensitivity 101

Interface Force Measurement 101 Series Introduction

Extending Transducer Calibration Range by Extrapolation

Top Five Reasons Why Calibration Matters

Accurate Report on Calibration

Understanding GUM and Measurement Uncertainty

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Understanding GUM and adherence to good test and measurement practices are essential to minimize uncertainties and ensure reliable measurement results for every application.

In the context of test and measurement, GUM stands for Guide to the Expression of Uncertainty in Measurement. The GUM is a widely recognized and internationally accepted document published by the Joint Committee for Guides in Metrology (JCGM), which provides guidelines for evaluating and expressing uncertainties in measurement results.

GUM establishes general rules for evaluating and expressing uncertainty in measurement that are intended to be applicable to a broad spectrum of measurements. A critical portion of any measurement process, the GUM outlines a thorough framework for uncertainty estimation. GUM defines terms and concepts related to uncertainty, describes methods for uncertainty calculation, and offers guidance for reporting and the documentation of uncertainties in measurement results.

The GUM provides a systematic approach to assess and quantify uncertainties by source, including equipment constraints, environmental conditions, calibration procedures, and human factors. The standards set by GUM emphasizes the need for considering and quantifying all substantial uncertainty components to ensure reliable and traceable measurement results.

By following the principles and guidelines outlined in the GUM, test and measurement professionals, metrologists, and scientists ensure standardized approach to uncertainty evaluation and reporting, facilitating comparability and consistency of measurement results across different laboratories and industries.

The uncertainty requirement varies for different use cases and industry applications. For example, for aerospace, defense, and medical devices there are strict uncertainty requirements compared to commercial scales or measurement tests that do not need precision accuracy.

When estimating uncertainty in load cell calibration, it is important to refer to the Guide to the Expression of Uncertainty in Measurement (GUM). The GUM provides a comprehensive framework with general rules for evaluating and expressing uncertainty in measurement. It serves as a guide applicable to a wide range of measurements, providing valuable guidance on uncertainty assessment in load cell calibration and other measurement processes.

In test labs that utilize load cells and torque transducers, the principles and guidelines GUM should be consistently applied to accurately evaluate and express uncertainties associated with the measurements obtained from these devices.

The application of GUM in test labs using load cells and torque transducers requires a thorough understanding of the measurement process, relevant standards, and calibration procedures. Read Understanding Uncertainty in Load Cell Calibration for more information.

Different considerations to measure uncertainty

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

GUM is used to identify and characterize uncertainty sources that can affect the measurements obtained from load cells and torque transducers. These sources may include calibration uncertainties, environmental conditions, electrical noise, stability of the test setup, and other relevant factors. Each of these sources should be quantified and considered in the uncertainty analysis.

Quantitative estimates of uncertainty component contributions to the overall uncertainty need to be determined. This can involve conducting experiments, performing calibration procedures, analyzing historical data, or utilizing manufacturer specifications to obtain uncertainty values for each component.

Once sources and estimates are complete, next step is to combine the individual uncertainty components using appropriate mathematical methods prescribed by the GUM. These methods include root-sum-of-squares (RSS), statistical analysis, and other relevant techniques. The aim is to obtain an overall estimate of uncertainty that accounts for the combined effects of all relevant sources.

The GUM provides guidelines on expressing uncertainties in measurement results. It emphasizes the use of confidence intervals, expanded uncertainty, and coverage factors. The uncertainty should be reported alongside the measurement values, indicating the level of confidence associated with the measurement. This allows the users of the measurement data to understand the reliability and accuracy of the obtained results.

For additional information about GUM, errors and setting an uncertainty budget, watch our webinar Accurate Report on Calibration. The video is set to start on the topic of Measurement Uncertainty.

It is essential to consider the specific uncertainty requirement of the application to ensure that the chosen force measurement device is appropriately calibrated for the project. This resource is a helpful recap: Specifying Accuracy Requirements When Selecting Load Cells.

In addition, understanding GUM, reducing uncertainty with regular calibration of testing devices and proper maintenance of the equipment go together with GUM.

ADDITIONAL RESOURCES

Gold Standard® Calibration System

Accurate Report on Calibration

Technical Information

Load Cell Test Protocols and Calibrations

Regular Calibration Service Maintains Load Cell Accuracy

 

Signal Conditioners 101

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Signal conditioners are used in instrumentation, control systems, and measurement systems where accurate and reliable signal processing is a requirement. The purpose of a signal conditioner is to ensure that the electrical signal from a sensor is compatible with the input requirements of the subsequent signal processing equipment.

Primary features of signal conditioners include amplification, filtering, isolation, and linearization. It can perform various functions depending on the specific application and the type of signals.

Interface Signal Conditioners are used with a wide range of load cell and force measurement devices. Transducers convert force or weight into an electrical signal. The output signal of a load cell is typically in the form of a small electrical voltage that is proportional to the applied force.

Be sure to reference the Instrumentation Selection Guide to find instrumentation with signal conditioners that will best fit your force measurement application.

Understanding Signal Conditioners Use with Load Cells

Amplification: Load cells produce small electrical signals, which may require amplification to bring them to a usable level. Signal conditioners can include built-in amplifiers that increase the magnitude of the load cell signal. This amplification helps to improve the signal-to-noise ratio and enhances the sensitivity of the system.

Filtering: Load cell signals can be affected by electrical noise or interference, which can degrade the accuracy of measurements. Signal conditioners often incorporate filtering capabilities to remove unwanted noise and interference from the load cell signal. This ensures that the signal is clean and reliable.

Excitation: Load cells require an excitation voltage or current to function properly. Signal conditioners provide a stable and regulated excitation source to power the load cell. This excitation voltage is typically supplied to the load cell through the signal conditioner, ensuring consistent and accurate measurements.

Calibration and Linearization: Load cells may exhibit nonlinear characteristics, meaning that the relationship between the applied force and the output voltage is not perfectly linear. Signal conditioners can include calibration and linearization algorithms to compensate for these nonlinearities. By applying appropriate mathematical adjustments, the signal conditioner can provide a linear output that accurately represents the applied force.

Signal Conversion: Load cell signals are typically analog voltages, but they may need to be converted to digital format for further processing or transmission. Some signal conditioners include analog-to-digital converters (ADCs) that convert the analog load cell signal into digital data, enabling it to be processed by digital systems.

Signal Conditioner Considerations

  • Form factor design: box mount, DIN rail, in-line cable, integral to load cell
  • Output options: ±5/±10VDC, 0.1-5VDC, Current, Frequency, Digital
  • Polarity: Bi-polar or unipolar
  • Bandwidth
  • Onboard filtering
  • Power supply type: cable, built-in, wireless
  • Noise immunity

Interface Top Signal Conditioners

PRODUCT: DMA2 DIN RAIL MOUNT SIGNAL CONDITIONER

  • User selectable analog output +/-10V, +/-5V, 4-20mA
  • 10-28 VDC power
  • Selectable full scale input ranges 5-50mV
  • DIN rail mountable
  • Push button shunt calibration
  • 1000Hz bandwidth

PRODUCT: SGA AC/DC POWERED SIGNAL CONDITIONER

  • User selectable analog output +/-10V, +/-5V, 0-5V, 0-20mA, 4-20mA
  • 110VAC, 220VAC, OR 18-24VDC power
  • Switch selectable filtering 1Hz to 5kHz
  • Single channel powers up to four transducers
  • Selectable full scale input range .06 to 30mV/V
  • Sealed ABS enclosure
  • Optional bridge completion and remote shunt activation module

PRODUCT: ISG ISOLATED DIN RAIL MOUNT SIGNAL CONDITIONER

  • Galvanically isolated power supply
  • High accuracy
  • +/-5VDC or +/-10VDC Analog output (4-20mA optional)
  • 10-30VDC Power
  • Switch selectable filtering 1Hz to 1kHz (up to 10kHz optional)
  • Accepts inputs up to 4.5mV/V
  • DIN rail mountable

CSC and LCSC-OEM Inline Signal ConditionersPRODUCT: CSC and LCSC-OEM INLINE SIGNAL CONDITIONERS

  • IP67 stainless steel enclosure (CSC Only)
  • CE approved (CSC Only)
  • Zero and span adjustments
  • 1 kHz bandwidth

PRODUCT: VSC2 Rugged Compact Vehicle Powered Signal Conditioner

  • High accuracy precision bi-polar differential amplifier
  • ± 5 VDC Output
  • Accepts inputs from ±1.4 to ±-4.2
  • 1000 Hz low pass filter
  • Rugged design and compact size
  • Course, fine zero, and span adjustments
  • Activate R-CAL (Shunt Cal) with internal switch

Signal conditioners ensure that the load cell’s output is optimized for accuracy, stability, and compatibility with the measurement or control system. They help mitigate noise, amplify weak signals, provide excitation, and perform calibration and linearization to ensure precise and reliable measurements of force or weight.

Visit the Interface Instrumentation Selection Guide to see all the products available with signal conditioning functionality.

Watch this Testing Lab Essentials Webinar Part 3 to learn more about the benefits and use cases of Interface Signal Conditioners.

Testing Labs Choose Interface High Accuracy Products

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Specialists focused on testing applications work in a variety of testing lab environments. In each lab, technicians rely on the tools to collect and report on data that is used to make products safer, guarantee performance, ensure quality, and to meet the strict industry standards and requirements. Accuracy in testing data is dependent on the precision measurement devices and instrumentation used to capture the results.

We supply lab engineers with high-accuracy sensor technologies used to complete rigid test requirements. Interface is the top provider of test and measurement products used for structural and material testing, static and fatigue testing, torsion effects, tension tests, calibration testing, and environmental testing. Read more in Types of Force Measurement Tests 101.

Our standard high precision load cells, torque transducers, multi-axis sensors, and instrumentation are used on every continent for T&M. Based on our quality and performance, we are the chosen supplier to calibration and testing labs. We see our products used today for continuous improvement programs, advancements in smart manufacturing and new product designs.

If it must be measured, Interface has a solution. Our products are designed for small and large testing facilities, including calibration-grade load cells, load frames and test stands, along with data acquisition systems. The wide variety of our force measurement solutions designed for testing labs means we play a role in every industry that is making a physical product and the test labs that validates the products performance.

Testing Labs and Types of Testing Using Interface Solutions

General Automotive Test Labs:

  • Component and Sub-Component Level Testing
  • Suspension Testing
  • EV Battery Testing

Automotive Driveline Testing:

  • Engine Performance and Durability Tests
  • Motor Efficiency Testing
  • Power Analyzation (Electric)

Aerospace Testing:

  • Full Scale Structural Static Testing
  • Component Fatigue Test
  • High Precision Thrust Testing
  • Simulators
  • Wind Tunnel Testing

Geotechnical and Civil Testing

  • Concrete or Asphalt Core Testing
  • Soils Testing

General Structural and Component Testing

  • General Push and Pull
  • Design Proofing
  • Life Cycle Fatigue Validation

Medical Device Testing:

  • Prototyping
  • PPAP Validation and FDA Certification
  • Device Lifecycle Testing

Consumer Product Testing Labs:

  • Design Validation
  • Material Testing
  • Fatigue and Failure Tests

Interface recently highlighted testing lab applications in our Test Lab Essentials Webinar. Here you can see the lab use cases and products as they are reviewed by our applications experts.

Each of these testing types requires different force testing equipment, and our experts work directly with testing lab professionals to determine the products or systems they need for single and ongoing test requirements.

As testing technologies becomes increasingly complex, off-the-shelf products may not meet the needs of every Interface customer. We lend engineers expertise in test and measurement to support unique and custom requirements to get the right sensor, instrument, and system in place.

Since our first load cells were designed five decades ago, we have built millions upon millions of load cells and torque transducers used in testing labs around the world. Our products are built to withstand the rigor and requirements needed for high quality and reliable data collection in test and measurement. Our test customers depend on us for proving accuracy, consistency, and reliability in performance.

ADDITIONAL RESOURCES

Interface and Testing Lab Applications

Testing Lab Essentials Webinar

Engine Dynamometer App Note

Consumer Product Testing Case Study

Interface Solutions for Safety and Regulation Testing and Monitoring

Metrologists and Calibration Technicians 101

Motor Test Stand

GS-SYS04 Gold Standard® Portable E4 Machine Calibration System

Electric Vehicle Structural Battery Testing

Furniture Fatigue Cycle Testing App Note

Regular Calibration Service Maintains Load Cell Accuracy

 

Shunt Calibration Resistors 101

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Shunt calibration is a process of calibrating a measurement instrument using a shunt calibration resistor. The shunt calibration resistor is connected in parallel with the measurement instrument to provide a known resistance value, which is used to calculate the instrument’s accuracy.

In shunt calibration, a known current is passed through the shunt calibration (cal) resistor, which generates a known voltage drop across the resistor. This voltage drop is measured using the measurement instrument being calibrated, and the instrument’s accuracy is calculated based on the known resistance value of the shunt calibration resistor and the measured voltage drop. They create a simulation of load and verify the health of the sensor. Commonly, they are used to scale instruments.

The accuracy of the measurement instrument can be calculated by knowing the shunt resistor’s precision level and applying Ohm’s Law, which states that the current passing through a resistor is proportional to the voltage drop across it and inversely proportional to its resistance value.

Shunt calibration can be used to calibrate force measurement devices, including load cells. Interface provides shunt calibration resistors in our accessories line as “loose” resistors. They are also available with engineered to order requests for designs into cables, connectors and even within the load cell.

Shunt calibration is an important process for ensuring accurate and reliable measurements in various industrial, commercial, and scientific applications. It allows measurement instruments to be calibrated quickly and cost-effectively, and it improves the accuracy and reliability of the measurement data.

What is a shunt calibration resistor?

A shunt calibration resistor is a resistor that is connected in parallel with a measurement instrument to provide a known resistance value. The purpose of the shunt calibration resistor is to calibrate the instrument to accurately measure the current passing through it. Shunt calibration resistors are often used with load cells to improve the accuracy and reliability of their measurements.

How are shunt calibration resistors used with load cells?

Load cells typically generate a small electrical signal in response to applied force or weight. This signal is amplified and processed by a signal conditioning circuit before a data acquisition system or controller uses it. The signal conditioning circuit can utilize an internal shunt calibration resistor on the instrumentation side, or activate a resistor located upstream in the system.

Shunt calibration resistors located either in the sensor, cable, or instrument will be switched into the circuit during the shunt calibration process, shunting and diverting current in the process. This shunting effect unbalances the Wheatstone bridge, simulating loaded output from the sensor. Because the resistance value is known, sensor span output and thus instrument scaling can be accurately verified. This electrical simulated signal negates the need for physical force or torque calibration of the system.

The shunt calibration resistor provides a known resistance value, which is used to verify the health and output of the load cell, ensuring accurate system measurement of the applied force or weight. The resistor diverts a small portion of the load cell’s excitation current. The value of the shunt calibration resistor is carefully selected based on the load cell’s characteristics and the desired measurement accuracy.

Shunt calibration uses the shunt resistor to force a load cell bridge to provide a fake signal output. It allows one to check for sensor health and whether the signal behavior has deviated from an original calibration certification with initial shunt output data.

This forced signal output allows for the attached instrument to be scaled. This could be setting signal conditioner scaling:  When the load cell reaches max calibrated force, is the mV/V input properly scaled for the exact 5V, 10V or 20mA conditioner output? The other setting option is displayed units of measurement on a display: Is the load cell’s calibrated 3.999mV/V output at 100 lbs displaying 100 lbs on the display?

Shunt resistors are sized by resistance value to provide approximately two-thirds or three-quarters full scale output signal. Having this recorded value on the calibration certification the instruments can be scaled as necessary for full scale, and future shunt checks can ensure nothing is changing with the health of the circuit.

Interface Shunt Calibration Resistors – RCAL Resistors

Interface shunt calibration resistors, known as RCAL Resistors, are an accessory product. They are made from the highest components and processes to ensure the specifications for your Interface products perform to meet their published specifications. Available RCAL Models include RS-100-30K, RS-100-40K, RS-100-60K, and RS-100-120K are available.

Interface RCAL Resistors are high precision components and provide an effective, method for checking the calibration of a load cell system in the field or when a means of applying actual forces is unavailable.

  • Designed to work with Interface products.
  • Made with the highest quality components.
  • Created to maintain the specification of the product.
  • Precision wire-wound
  • 5 ppm/°C, 0.01%

U.S. dimensions and capacities are provided for conversion only. Standard product has metric capacities and dimensions. U.S. capacities available upon special request and at an additional cost.

What are the benefits of using shunt calibration resistors?

There are several benefits of using shunt calibration resistors in measurement applications:

  • Calibration: Shunt calibration resistors can be used to scale measurement instruments, ensuring that they provide accurate calibrated unit readings. Shunt calibration can often substitute the need for physical force or torque system calibration
  • Convenience: Shunt calibration can provide a quick and easy system health check either before or immediately after a test. Confirming stable and consistent shunt readings can ensure data integrity in between regular scheduled physical calibration intervals.
  • Cost-effective: Using a shunt calibration resistor is an inexpensive one time investment vs time and cost associated with pre or posttest physical calibrations. This brings the freedom for frequent and quick system calibration checks with minimal equipment down time.
  • Flexibility: Shunt calibration resistors can be used with a wide range of measurement instruments, allowing for greater flexibility in measurement applications. Additionally, many instruments allow shunt resistors to be interchangeable for support of varying sensor outputs.

Overall, shunt calibration resistors are a practical and convenient alternative to physical system calibrations. Shunt calibration resistors can be packaged into all Interface load cells with support across most of the available instrumentation as well. Frequent system health and signal stability checks are vital to ensuring consistent integrity with test data and shunt calibration resistors bring such empowerment for extraordinarily little initial investment.

Contributor: Brian Peters

Additional Resources

Metrologists and Calibration Technicians 101

System Level Calibration Validates Accuracy and Performance

Shunt Calibration for Dummies – Reference Guide

Shunt Calibration 101

Regular Calibration Service Maintains Load Cell Accuracy

Top Five Reasons Why Calibration Matters

 

 

Interface and Testing Lab Applications

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Test and measurement impacts nearly every industry.  At Interface, we classify Test and Measurement (T&M) as it’s own solutions market. Though testing is generally a service, the accuracy and quality equipment and tools that are required for performing these T&M services has created an industry in itself.

Throughout the Test and Measurement industry, there are several different classifications and testing lab types. Each of these different testing labs provide unique equipment for different forms of testing depending on the application, system or component. These different types test labs include:

  • Structural testing labs perform tensile, compression, bending, fatigue and hardness testing on materials, components, or assemblies.
  • Environmental testing labs evaluate the impact of environmental factors on products, components, or materials performing temperature, humidity, salt spray, and vibration testing.
  • Electrical testing labs determine the electrical properties of components or products using insulation resistance, electrical continuity, and dielectric strength testing.
  • Chemical testing labs determine the composition and purity of materials using chromatography, spectroscopy, and elemental analysis.
  • Product safety testing labs ensure that products meet safety and regulatory standards with flammability, toxicity, and durability testing.
  • Calibration testing labs ensure that measuring instruments and equipment are accurate and reliable. Common disciplines include force, torque, pressure, temperature and physical calibration. Read more: Interface Calibration 101
  • Non-destructive testing labs evaluate the integrity of materials with ultrasonic testing, magnetic particle inspection, and radiography.

Here at Interface, we are deeply ingrained in supplying nearly every type of testing lab out there with precision T&M devices, from the world’s best force measurement sensors to advanced instrumentation. Interface offers one of the most diverse force, torque, and weight related force sensor product lines in the market. It is why labs prefer Interface. In addition to our expanding line of  data acquisition systems, software and accessories, T&M engineers and lab pros find Interface as a one-stop-shop for simple and complex testing projects.

Testing Lab Applications Using Interface Products

Material Testing Lab – Press Form Monitoring

Customer Challenge: Press forming is a method to deform different materials. A force measurement solution is required to monitor the forces being applied by the press forming machine to ensure quality control and traceability during the production process.

Interface Solution: For large press forming machines, Interface recommended installing the 1000 High Capacity Fatigue-Rated LowProfile™ Load Cell. When the material was placed under the punch plate to form a shape, the force applied was measured and results were sent to the INF-USB3 Universal Serial Bus Single Channel PC Interface Module, where results can be graphed and logged.  Read: Press Forming and Load Monitoring

Medical Testing Lab – Specimen Research Linear Test Stand

Customer Challenge: Medical experts need the best equipment during research of multiple specimens. In this case, a medical researcher needed to monitor the load force of their linear actuator that uses a needle to collect material from the desired specimen.

Interface Solution; Interface’s SuperSC S-Type Miniature Load Cell was easily installed into the linear test stand. A needle with a gripper on the end was installed on the lower end of the SuperSC. As the needle is pushed to collect material of the specimen, the load feedback is captured using the 9330 Battery Powered High Speed Data Logging Indicator.  Read: Specimen Research App Note

Safety Test Facility – Bike Helmet Impact Test

Customer Challenge: A company wanted to test the impact of a bike helmet when dropped from different heights, onto a flat surface such as an anvil. This test is necessary to ensure consumer safety, and that their products are made of the highest quality until sold to the public.

Interface Solution: Interface suggested installing our 1101 Compression Only Ultra Precision LowProfile™ Load Cell at the bottom of an anvil. The bike helmet was then dropped from multiple heights, at multiple angles, onto the anvil. The measurements from impact were then recorded and logged using our INF-USB3 Interface Module.  Read: CPG Bike Helmet Impact Test

Product Test Lab – Touch Screen Force Testing

Customer Challenge: Touchscreen kiosks used in restaurants, retail and entertainment venues all need various tests to be performed to ensure functionality and sensitivity. One of those tests are force tests that touch screens to withstand high use by all types of consumers.

Interface Solution: Interface’s SMTM Micro S-Type Load Cell was installed on the customer’s force testing machine. The touchscreen was laid flat under the machine, and force tests were conducted in different locations of the touchscreen. With supplied BlueDAQ software, results are captured and reviewed using the 9330 Battery Powered High Speed Data Logging Indicator through an SD card.

These are just a few examples of where Interface products are involved in a wide variety of different testing labs and how T&M engineers are utilizing them. To learn more, check out our new Testing Lab Essentials webinar, which can be found here.


ADDITIONAL RESOURCES

Testing Lab Essentials Webinar Recap

Introducing the Interface Consumer Product Testing Case Study

Interface Solutions for Safety and Regulation Testing and Monitoring

Electric Vehicle Structural Battery Testing

 

Tension Load Cells 101

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A tension load cell is a type of force sensor used to measure tensile forces in materials, structures, or machines. It is used to measure the maximum load that a material can support without fracture when being pulled or stretched under the applied load. A strain gage manufactured inside the load cell sensor measures the deformation and converts it into an electrical signal.

The main difference between a tension load cell and a compression load cell is the direction in which they measure the force being pushed or pulled. Though most Interface high performance load cells are designed for both tension and compression, specific load cells are calibrated in tension only to measure forces that pull or stretch a structure. As the load cell stretches, it measures the resulting force.

It is customary practice for most labs to use tension and compression load cells, then determine its specific tension use case based on the requirements of a test project or product design. Tension and compression load cells are easily used for tension only but will measure both. Load cells can be calibrated in either tension or compression, and both tension and compression. The combined is more economical for test labs and most use cases.

Benefits of Tension Load Cells

Load cells that measure tension are preferred over other types of load cells when the force being measured is tensile in nature. They are accurate, reliable, and can be calibrated to suit different applications and environments. Additionally, they are easy to use and require minimal maintenance.

Accurate measurement of tensile forces: Tension-only load cells are specifically designed to measure tensile forces accurately, without being influenced by compressive or bending forces. This makes them ideal for applications where the force being measured is purely tensile, such as in the testing of cables, wires, ropes, or chains used in lifting applications and equipment. Interface Tension Links are preferred for these types of lifting and weighing use cases.

High sensitivity and resolution: Tension-only load cells typically have high sensitivity and resolution, meaning they can detect slight changes in the applied force. This makes them useful in applications where precise measurements are required, such as in the testing of materials with low tensile strength.

Easy installation: Tension-only load cells are typically easy to install and use, requiring minimal setup time and equipment. They are often designed with attachment points or hooks for attaching to the load being measured, which makes them convenient for use in the field or in a testing lab.

Durability and reliability: Tension-only load cells are often constructed from durable materials, such as stainless steel, which makes them resistant to corrosion and wear over time. They are also designed to provide reliable and consistent measurements, ensuring accuracy and consistency in test results.

Tension Load Cell Applications

Tension load cells are standard and their versatility in application use makes them popular in test and measurement. Tension load cells are used for test and measurement industry applications including in manufacturing, automotive, energy, aerospace, and infrastructure. For example, the transportation sector uses load cells to measure the tension in cables, wires, ropes, and chains. They are used in a diverse range of testing equipment to measure the strength and durability of materials. They are designed to provide accurate and reliable measurements of tensile loads and can be calibrated to suit different applications and environments.

Tension load cells are commonly used in applications for material testing to evaluate the tensile strength and elasticity of varied materials, such as metals, plastics, and composites. Tension testing is a valuable tool in materials science and engineering, as it provides valuable information about the tensile properties of a material. Some examples of tension testing include:

  • Determining the strength of a material: Tension testing provides a way to measure the maximum load a material can withstand before it breaks or fails. This information is crucial in determining the strength of a material and its suitability for different applications.
  • Understanding the ductility of a material: Tension testing can also be used to measure the amount of deformation a material can undergo before it breaks. This information is important in determining the ductility of a material and its ability to withstand bending and stretching without breaking.
  • Identifying defects or weaknesses in a material: Tension testing can help identify defects or weaknesses in a material that may cause it to fail under stress. By subjecting a material to increasing levels of tension, engineers can pinpoint the point at which the material fails and investigate the cause of the failure.
  • Comparing the properties of varied materials: Tension testing can also be used to compare the tensile properties of different materials. This information is useful in selecting the best material for a specific application and designing structures that can withstand the required loads.

Tensile Testing For 3D Materials

A customer wants to conduct a tensile force test on different 3D printing materials until failure. These different 3D printing materials being tested included PLA, PETG and ASA to see how they performed. The customer wanted to test the materials quality, strength, ductility, and stiffness. Interface recommended using our 1200 Standard Precision LowProfile™ Load Cell be installed into the customer’s test frame. The tensile test is conducted, and force results captured by the load cell are synced through the INF-USB3 Universal Serial Bus Single Channel PC Interface Module. These results can be displayed on the customer’s computer with supplied software.

Tension load cells are used in structural testing to measure the tension in structures used in construction, aerospace, maritime, and infrastructure. For example, tension load cells are commonly used for bridges, buildings, and towers, to ensure they can withstand the forces in their design and application.

Tension load cells are often used within manufacturing machines and equipment for monitoring and real-time force measurement. For example, in a facility they are used to measure the tension in cables or wires during production, to ensure they meet the required specifications and are safe for use.

Research and development for all types of applications need to assess the tensile properties of new materials or structures, to assess their suitability for different applications, from medical devices to product simulations.

If your next project needs an accurate tension load cell, contact our application experts to see which model best fits your exact requirements.

ADDITIONAL RESOURCES

Interface Solutions for Material Testing Engineers

Tensile Testing for 3D Materials App Note

Testing Lab Essentials Webinar

Bolt Tension Monitoring

Mooring Line Tension Testing App Note

Tension Links 101

Testing Lab Essentials Webinar Recap

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Interface recently hosted an in-depth discussion about one of our favorite topics, testing labs. Our focus in this technical webinar centered on test lab devices, instrumentation, industry testing lab challenges and considerations, along with best practices. We also took a deep dive into different testing lab applications and how to modernize your test lab.

Force measurement experts Elliot Speidell and Jeff Boyd delivered an engaging and knowledgeable seminar, Testing Lab Essentials: Today + Tomorrow.  Bringing decades of first-hand experience, they were able to provide product examples, tips, recommendations and lessons learned in working with testing lab professionals across industries, from automotive to medical devices.

Initial discussions in the event covered test lab basics, including types of products should be in every lab that performs testing of force, torque, and weight. The quick summary, force, torque and weight measurement devices including load cells and torque transducers of various models, calibration grade equipment and published standards, test stands, data acquisition systems and safety equipment.

One of the first steps in assessing any lab is the type of measurement equipment on hand to perform various testing requirements. Transducer selection criteria includes mechanical connection and load application, force magnitude and loading condition, cycle count, form factor restrictions, environmental conditions, additional measurements needs, such as multiple axis.

Testing labs often require different types of load cells depending on the type of products being tested and the applications in which the load cells will be used. Here are some common types of load cells used in testing labs:

  • Compression load cells: Used to measure the compressive force applied to an object. They are commonly used in materials testing to measure the strength of materials such as concrete, metals, and plastics.
  • Tension load cells: Used to measure the tensile force applied to an object. They are commonly used in materials testing, such as in tensile strength testing of metals and other materials.
  • Shear load cells: Used to measure the shear force applied to an object. They are commonly used in materials testing, such as in shear strength testing of materials.
  • Multi-axis load cells: These load cells are capable of measuring forces in multiple directions and are commonly used in structural testing applications.
  • Torque transducers: Used to measure torque or twisting forces. They are commonly used in automotive testing, industrial machinery, and other applications where rotational forces are important.
  • Fatigue-rated load cells: These load cells are designed to withstand high-cycle fatigue testing and are commonly used in materials testing and durability testing of products.
  • Low profile load cells: These load cells are designed to fit into tight spaces and have a low profile, making them ideal for use in small-scale applications.
  • High-capacity load cells: These load cells are designed to measure large forces and are commonly used in heavy machinery and structural testing.

Instrumentation is central to any testing lab environment. The three most common types of instrumentation found in test lab includes:

  • Indicators: Indicators are used to convert the input signal to a local displayed value.  Often they will have features like, peak capture, alarms, and analog outputs.
  • Signal Conditioners: Signal conditioners are used to convert (amplify) one type of electrical signal into another. 
  • DAQ: Data acquisition systems are used to collect and analyze data from measurement devices. These systems may include software, hardware, and data processing equipment.

In a series of follow-up InterfaceIQ Blog posts we will detail other topics covered in this information packed discussion, including modernization, load frames and test stands, do and don’t tips, plus frequently asked questions.

Watch the complete webinar here:

How Load Cells Can Go Bad

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Load cells are electronic devices that measure the force applied to them. Interface products are made to last, in fact we have many load cells that are in-market and being used for high-accuracy testing that were manufactured decades ago. Why do they last? Quality of design, material construction, build process, calibration, and regular maintenance prolong the life of a load cell.

Like any electronic device, load cells can go bad for a few reasons. It is also important to know that load cells can be repaired. Outside of complete destructive testing, the following issues are most common for how load cell can go bad.

Overloading: Load cells have a maximum capacity, and if they are subjected to a force beyond that limit, they can get damaged. Overloading can cause the load cell to deform or break, resulting in inaccurate readings or complete failure. Preventative options are to use overload protected load cells.

Mechanical and physical damage: Load cells are sensitive devices and can be damaged by impact, vibration, or shock. Mechanical damage can cause the load cell to deform or lose its calibration, resulting in inaccurate readings. Physical damage to devices is often because the load cells are dropped or mishandled during use.

Moisture: Load cells are often used in damp or wet environments, and prolonged exposure to moisture can cause corrosion or damage to the internal circuitry. Environmental exposure to moisture can also cause electrical shorts or create a conductive path between the components, resulting in inaccurate readings or complete failure. Review submersible options if testing in these environments is common.

Temperature: Load cells can be sensitive to temperature changes, and extreme temperatures can cause damage to the internal components. Thermal expansion or contraction can cause mechanical stress, resulting in deformation or damage to the load cell. Interface offers high-temperature and low-temperature load cells options.

Electrical noise: Load cells are susceptible to electrical noise, which can cause interference in the signals and result in inaccurate readings. Electrical noise can be caused by electromagnetic interference (EMI), radio-frequency interference (RFI), or other sources of electrical interference.

Aging: Not all load cells are made the same way. Interface load cells are designed to outlast any testing use for long-periods, we are talking millions of cycles. However, some load cells can wear out over time due to repeated use, exposure to the environment, or other factors. Aging can cause a decrease in sensitivity, accuracy, or stability, resulting in inaccurate readings or complete failure. All load cells need good health checks to stay working at optimal performance.

To avoid load cell failures, it is important to use them within their rated capacity, protect them from mechanical damage, and provide adequate protection from moisture, temperature, and electrical noise. Regular maintenance and calibration services, preferably every year, can also help ensure accurate and reliable performance over time.

What is the best way to determine if a load cell is bad or not working?

There are several ways to determine if a load cell is bad or not working. Here is a reminder of five quick checks:

#1 Visual Inspection: Start by visually inspecting the load cell for any signs of physical damage, such as cracks, deformations, or loose connections. Check for any corrosion or signs of moisture, as well as any visible wear and tear.

#2 Zero Balance Testing: A zero balance test is a quick and straightforward way to check if a load cell is functioning properly. With no weight applied, the load cell should read zero. If it does not, there may be an issue with the load cell or its connections.

#3 Load Testing: Load testing involves applying a known weight to the load cell and checking the reading. If the load cell is accurate, the reading should match the known weight. If there is a significant discrepancy, the load cell may be faulty.

#4 Bridge Resistance Tests: Load cells are typically constructed with a Wheatstone bridge circuit, which can be assessed for proper resistance values. If there is a significant deviation from the expected resistance values, there may be an issue with the load cell or its connections.

#5 Temperature Tests: Load cells can be sensitive to temperature changes, and extreme temperatures can cause damage to the internal components. Evaluating the load cell at different temperatures can help to identify any issues with temperature sensitivity.

Interface provides complete evaluations of any product we manufacture, to determine if the load cell is working properly. To request services, go here.

How does calibration help load cells from going bad?

Calibration is the process of adjusting a load cell to ensure its accuracy and reliability in measuring weight or force. Regular calibration is essential for maintaining the accuracy and reliability of load cells. Interface recommends annual calibration services as a preventative measure and for good maintenance of your force measurement devices.

Calibration helps to ensure that a load cell provides accurate and consistent readings. Over time, load cells can drift from their initial calibration due to environmental factors, wear and tear, and other factors. Regular calibration ensures that any deviations from the standard are detected and corrected, preventing inaccurate readings that can lead to errors in weighing and other measurements.

Load cells that are not calibrated regularly may experience premature wear and tear due to repeated use, leading to damage or failure. Calibration helps to identify any issues early on and prevent further damage, extending the lifespan of the load cell and saving on replacement costs.

Many industries and applications have strict standards and regulations for measuring weight and force. Regular calibration helps to ensure that load cells meet these standards and regulations.

Regular calibration can help load cells from going bad in multiple ways. It can help to prevent inaccurate readings, extend the lifespan of load cells, improve efficiency, and ensure compliance with standards and regulations. Accurate measurements are critical, and calibration helps to ensure that load cells is working properly. Request a repair or calibration service online.

ADDITIONAL SERVICES

Load Cell 101 and What You Need to Know

Load Cell Sensitivity 101

Can Load Cells Be Repaired?

Services & Repair

Mechanical Installation Load Cell Troubleshooting 101

How Do Load Cells Work?

Regular Calibration Service Maintains Load Cell Accuracy