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Load Cell Simulator 101

A load cell simulator is a device that mimics the electrical signal of a load cell. This allows technicians to test and calibrate measurement systems without applying physical force or weight to the load.

By generating a range of input signals using a load cell simulator, technicians can assess the instrument’s linearity, sensitivity, and accuracy, ensuring it meets the required specifications.

The two most common uses for load cell simulators are troubleshooting and calibration. Load cell simulators can effectively troubleshoot force measurement systems, detecting and isolating faults or malfunctions. By simulating various load conditions and injecting fault conditions, technicians can pinpoint the source of the problem, such as a broken wire or a faulty load cell.

Load cell simulators are essential for calibrating force measurement devices, ensuring they accurately translate applied force into a measurable electrical signal. By generating a controlled force signal, technicians can compare the displayed value to the known input signal, identifying discrepancies and adjusting the device accordingly.

Interface load cell simulators are part of our accessories product line. They are an essential accessory and valuable investment for any testing lab or research facility frequently using load cells. These simulators can help to improve safety, reduce downtime, improve accuracy, lower costs, and increase convenience.

Why Use a Load Cell Simulator?

  • Testing and monitoring force measurement systems: Load cell simulators can test instrumentation performance used in force measurement systems, such as hydraulic presses, assembly machines, and material testing machines. By simulating forces that the system would typically encounter, the simulator can help identify potential problems with the instrumentation, ensuring that the system operates safely and efficiently.
  • Verifying proper indicator setup: Load cell simulators can be used to verify that an indicator is configured correctly for the type of load cells being used. This includes checking the scaling and the instrument’s linearity.
  • Cable checks: One of the first troubleshooting tips for any load cell application is to check the cables and connectors. A load cell simulator is valuable for checking cables.
  • Scaling: Load cell simulators are crucial for scaling force measurement devices, enabling precise calibration, troubleshooting, and testing. They play a vital role in ensuring the accuracy and reliability of force measurements across various industries.
  • Calibrating scale indicators: Load cell simulators can generate a precise mV/V signal corresponding to a specific weight. This allows technicians to calibrate scale indicators to ensure that they are displaying accurate weight readings.
  • Application evaluation: Load cell simulators can be used to develop and troubleshoot force-related applications, such as medical devices, prosthetics, and exercise equipment. By simulating forces that users would typically apply, the simulator can help to ensure that the application is safe, effective, and operational.
  • Research and product development: Load cell simulators can be used to research new force measurement applications.
  • Technician training: Load cell simulators can educate and train technicians on the proper use and calibration of load cells.

Interface Load Cell Simulators

CX SERIES PRECISION MV/V TRANSFER STANDARD LOAD CELL SIMULATOR 

CX SERIES PRECISION mV/V TRANSFER STANDARDModel CX Series Precision mV/V Transfer Standard is the market’s most accurate load cell simulator. This NIST Traceable product is commonly used to calibrate and check instruments in accredited labs.

  • Most accurate load cell simulator
  • Special low thermal EMF construction
  • Each unit is individually calibrated, aged, and recalibrated
  • Strong, rugged design
  • Instrument substitution testing

In the series, models CX-0202, CX-0610, CX-0440, CS-0330, and CX-0220 are used to set up and check the Gold Standard® System Hardware. CX-0440, CX-0330, and CX-0220 are single-step mV/V transfer standards providing precision outputs of ±4, ±3, and ±2 mV/V respectively. CX-0610 is a multi-step unit that allows the user to go from -6 mV/V to +6 mV/V in 1 mV/V steps. Model CX-0404 is specifically designed for instrument substitution testing as per ASTM E74.

EVALUATOR 3 LOAD CELL SIMULATOR 

Evaluator 3 Load Cell SimulatorThe Evaluator 3 variable range simulator is well suited for basic troubleshooting needs, offering nine fixed intervals from -5 mV/V to +4.5 mV/V.

  • ABS plastic case
  • Weighs less than 1 lb (0.45 kg)
  • Fixed rotary switch, -0.5 mV/V to 4.5 mV/V in 9 steps of 0.5mV/V per step
  • Used in testing and troubleshooting mV/V instrumentation

IF500 LOAD CELL SIMULATOR 

The new model IF500 is a 5V or 10V excitation-only load cell simulator with a state-of-the-art microprocessor-based design. It is a cost-effective simulator with advanced instrumentation capabilities. The instrument excitation supply powers the IF500 and requires no batteries.

  • Set “ANY” mV/V value within ±5mV/V
  • State-of-the-art, microprocessor-based design
  • Sleep mode eliminates digital clock noise
  • Powered by instrument excitation supply… No batteries
  • Buffered Ratiometric output
  • 350-ohm bridge configuration
  • Stores up to 10 settings with sequential recall
  • Digital zero trim and storage
  • Low noise, low quiescent current, low-temperature coefficient, high stability amplifiers
  • Compatible with instruments using 5V or 10V excitation, including Interface’s instrument models 9820, 9840, 9860, 9870, 9890, CSC/CSD, DMA/DMA2, DCA, INF1/INF4, ISG, SGA, and VSC
  • Options include: NIST Traceable Calibration Certificate, Screw Terminal Adapters for the BNC Connectors and Cable Adapters

Application Examples for Load Cell Simulators

Manufacturing: Load cell simulators are essential for calibrating and testing force measurement devices used in manufacturing processes, ensuring accurate force control and product consistency. ADDITIONAL RESOURCE: Manufacturing Solutions.

Food Processing: Load cell simulators are critical in calibrating and troubleshooting force measurement devices, ensuring precise portion control, and maintaining food safety standards.  ADDITIONAL RESOURCE: Force Measurement for Efficiency in Food Processing and Packaging

Construction: Load cell simulators are employed for testing and calibrating force measurement devices used in construction applications, such as crane load monitoring and material testing. ADDITIONAL RESOURCE: Construction Solutions

Medical Devices: Load cell simulators are utilized for calibrating and verifying the accuracy of force measurement devices in medical applications, such as patient weighing scales and rehabilitation equipment. ADDITIONAL RESOURCE: Medical and Healthcare

Interface load cell simulators are indispensable tools for scaling force measurement devices, providing a safe, efficient, and cost-effective means to ensure the accuracy and reliability of force measurements across diverse industries. Their ability to calibrate, troubleshoot, and test force measurement devices contributes to product quality, process control, safety, and regulatory compliance, making them essential for maintaining the integrity of force measurement systems.

Excitation Voltage 101

Excitation is an electrical signal. The excitation voltage is represented by the volts direct current (VDC). The direct current flows in one direction only. Alternating current (AC) changes direction at times.

Load cell excitation provides a voltage to generate an output signal, sometimes referred to as ‘powering’ the load cell. An output signal from a load cell is typically minimal, so an excitation voltage is needed to power the load cell and ensure the output signal is accurate. The magnitude of the output signal is proportional to the amount of force applied to the load cell. The greater the force, the greater the output signal.

Interface load cells contain proprietary strain gages applied to a Wheatstone bridge, essentially an electrical circuit that changes resistance when subjected to strain. The Wheatstone bridge is comprised of strain gages that are arranged in a specific configuration. When a load is applied to the load cell, the strain gages deform, and their resistance changes. This change in resistance causes the output voltage of the Wheatstone bridge to change.

Interface provides electrical performance data on all specifications represented as VDC MAX, when applicable.  The data for excitation voltage is listed under the electrical section of a transducer model’s specification datasheet, along with other factors, including rated output, bridge resistance, and zero balance.

Sensor Power and Excitation Tips

Load cell excitation is necessary to ensure the accuracy and reliability of load cell measurements.  Here are a few tips to consider regarding excitation and power signals when designing a force measurement system:

  • The output signal from a load cell is expressed in millivolt output per Volt (mv/V) of excitation at capacity.
  • The excitation voltage also affects the magnitude of the output signal. A higher excitation voltage will produce a higher output signal.
  • The output signal is directly affected by the input voltage. It’s essential to maintain a stable excitation voltage.
  • Interface load cells all contain a full bridge circuit. Each leg has a typical bridge resistance of 350 ohms, except for models like our 1500, which have 700 ohm legs.
  • The preferred excitation voltage is 10 VDC, which guarantees the closest match to the original calibration performed at Interface before it is shipped from our factory.
  • A DAQ system won’t always provide stable excitation voltage. Consider using a signal conditioner or DAQ with specific bridge inputs.

Why Load Cell Excitation Matters

Excitation matters in force measurement applications because it provides the power needed to operate the load cell and ensure an accurate output signal. The load cell cannot generate an output signal without excitation, and the force measurement will be inaccurate. In addition, it does influence accuracy, noise, and range.

Accuracy: The excitation voltage powers the load cell and ensures an accurate output signal.

Noise Reduction: The excitation voltage can help to reduce noise in the output signal.

Range: The excitation voltage can help extend the load cell’s measurement limit.

The excitation voltage should be applied to the load cell in a balanced manner. This means the excitation voltage should be applied to both sides of the load cell. The excitation voltage should be stable. This means that the voltage should not fluctuate or drift over time. The excitation voltage should be filtered. This means that any noise in the excitation voltage should be removed.

Excitation 101 in Force Measurement

The excitation voltage determines the sensitivity of the load cell. A higher excitation voltage will result in a more sensitive load cell, which means it can measure smaller forces.

The excitation voltage influences the frequency response of the load cell. A higher excitation voltage will result in a broader frequency response, meaning the load cell can track changes in force more accurately.

Linearity measures how accurately the load cell converts force into an electrical signal. A higher excitation voltage will result in a more linear load cell, meaning the output signal will be more proportional to the applied force.

The excitation voltage is well-regulated to reduce measurement errors. Variations in excitation voltage can cause a slight shift in zero balance and creep. This effect is most noticeable when the excitation voltage is first initiated. The solution is to allow the load cell to stabilize by operating it with a 10 VDC excitation for the time required for the gage temperatures to reach equilibrium. The effects of excitation voltage variation are typically not seen by users except when the voltage is first applied to the cell.

For tips like this, please consult Interface’s Load Cell Field Guide. We also detail remote sensing of excitation and temperature. Download your copy for free here.

It is essential to carefully select the excitation voltage for a load cell application to ensure that it can provide accurate and reliable measurements.

Demystifying Specifications Webinar

Interface’s technical force measurement webinar Demystifying Specifications details descriptions, terms, values and parameters found in product datasheets for load cells, torque transducers, instrumentation and specialty products. Learn from our experts what specifications need critical review, recommendations based on product categories, and the insider point of view on what is most important in terms of specifications for different use cases and tests.

Calibration Curve 101

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

Load Cells Versus Piezoelectric Sensors

Load cells and piezoelectric sensors are used in all types of measurement applications. While both types of sensors are used to measure similar physical quantities, they work on different principles and have distinctive characteristics.

By simple definition, load cells measure the amount of force or weight being applied to them. The amount of force a load cell is engineered to measure is numerated by the capacity of the model specification and design, such as 50lbf (pounds-force) or 5kN (kilonewton). When a force is applied to the load cell, the metal body deforms slightly, which changes the resistance of the strain gages. This change in resistance is then measured and used to calculate the amount of force being applied to the load cell.

Piezoelectric sensors work on the principle of piezoelectricity. They are made of materials that generate an electric charge in response to mechanical stress, such as pressure or vibration. Piezoelectricity is a property of certain materials that allows them to generate an electric charge in response to applied mechanical stress, such as pressure or vibration. The word “piezo” comes from the Greek word for “squeeze” or “press,” which refers to the fact that these materials generate an electric charge when they are squeezed or pressed. When a force is applied to a piezoelectric sensor, it generates a voltage proportional to the amount of force being applied. This voltage can then be measured and used to calculate the force or weight being measured. Piezoelectric sensors are most often used in vibration and pressure tests.

Load cells are more suitable for applications where high accuracy is required, as they are more sensitive than piezoelectric sensors in detecting smaller changes in force. Load cells are characteristically more robust and can withstand higher loads without being damaged. Piezoelectric sensors, on the other hand, can be more fragile and may require more careful handling to avoid damage.

Load Cell Advantages

  • Higher accuracy: Load cells are more accurate than piezoelectric sensors, especially when measuring low loads. Load cells can provide precise and reliable measurements with minimal error, making them ideal for applications that require high accuracy. Read: Specifying Accuracy Requirements When Selecting Load Cells
  • Lower sensitivity to temperature changes: Load cells are less sensitive to temperature changes than piezoelectric sensors. This means that load cells can maintain their accuracy even when the temperature changes, while piezoelectric sensors may need to be calibrated frequently to maintain accuracy. Read: Understanding Load Cell Temperature Compensation
  • Better linearity: Load cells have a more linear response than piezoelectric sensors, which means that their output is more predictable and easier to calibrate. This is particularly important in applications where accurate and repeatable measurements are critical.
  • Higher durability: Load cells are more robust and can withstand higher loads without being damaged. This makes them suitable for applications where high loads are present, such as in heavy machinery or construction.
  • Lower cost: Load cells are often less expensive than piezoelectric sensors, making them a more cost-effective choice, especially for OEM use cases.

Piezoelectric sensors are used in a wide range of applications that require the measurement of vibration or acceleration. For example, piezoelectric sensors can be used in machinery and equipment to monitor vibrations and detect potential problems, such as imbalances or misalignments. They are the sensors used in cars to measure pressure, such as in tire pressure monitoring systems or fuel injection systems. Piezoelectric sensors are found in ultrasound imaging to generate and detect sound waves and in musical instruments, such as electric guitars or electronic drum kits, to convert vibrations into electrical signals for amplification.

In selecting the right load cell for any project, check out our new Load Cell Selection Guide. It is a useful resource to determine the capacity, capability and design features that are best suited for your applications. You can also check out How to Choose the Right Load Cell.

Load cells and piezoelectric sensors have distinctive characteristics and advantages, thus specific application requirements will determine the choice of sensor. For questions about selecting the right sensor for your application, contact our solutions engineers.

Additional Resources

How Do Load Cells Work?

LowProfile Load Cells 101

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

Load Cell Basics Sensor Specifications

Interface Load Cell Field Guide

 

 

Load Cell Stiffness 101

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

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

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

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

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

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

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

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

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

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

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

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

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

ADDITIONAL RESOURCES

Interface Load Cell Field Guide

How Do Load Cells Work?

LowProfile Load Cells 101

Load Cell Basics Sensor Specifications

Load Cell Basics Webinar Recap

Load Cell Sensitivity 101

Load cell sensitivity refers to the relationship between the input force applied to a load cell and the output signal it generates. It is a measure of the load cell’s responsiveness to changes in the applied force and is expressed in units of mV/V (millivolts per volt) or micro-volts per volt.

When determining the accuracy of a load cell, load cell sensitivity is an important parameter. A higher sensitivity means that even small changes in the applied force will result in a larger change in the output signal, making the load cell more sensitive and accurate.

It is critical to understand that load cell sensitivity and accuracy are closely related. A high sensitivity load cell will generate a larger output signal for the same applied force, which can increase the accuracy of the measurement. In general, the accuracy of a load cell is a combination of its sensitivity and the quality of its design and construction. Interface specializes in precision accuracy, which is important when considering the use case for your load cell.  As defined by the specifications, a high-quality load cell with appropriate sensitivity will provide accurate and consistent measurements, while a load cell with low sensitivity or poor quality may provide less accurate measurements.

Most load cells are designed to measure force in one certain direction, which is determined by the way the load cell is mounted. Inappropriate loading will cause side and eccentric load, which risks reducing the life of load cells and distorting measurement results.

Eccentric load sensitivity is measured by eccentric load, which is any load applied parallel to but not concentric with the primary axis. Side load is any load at the point of axial load application at 90 degrees to the primary axis.

To achieve a desired level of accuracy, it is important to choose a load cell with the appropriate sensitivity for the application. Load cell sensitivity can be affected by factors such as temperature, temperature gradients, and environmental conditions, so it is important to take these factors into account when selecting a load cell.

What conditions impact load cell sensitivity? Load cell sensitivity can be impacted by several factors, including:

  • Temperature: Changes in temperature can cause thermal expansion or contraction of the load cell material, affecting the output signal and reducing accuracy.
  • Temperature gradients: The presence of temperature gradients within the load cell can cause differential expansion or contraction of different parts of the load cell, further affecting the output signal and reducing accuracy.
  • Environmental conditions: Exposure to harsh environments, such as moisture, vibration, and shock, can cause damage or degradation to the load cell, reducing its sensitivity and accuracy.
  • Load cell orientation: The orientation of the load cell can impact the output signal, especially in applications where the load is applied at an angle.
  • Mechanical stresses: The presence of mechanical stresses, such as bending or twisting, can affect the output signal and reduce accuracy.
  • Aging: Over time, the load cell may experience degradation or wear and tear, reducing its sensitivity and accuracy. This is where regular calibration plays a role in the lifetime of your load cell.

It is important to consider these factors when selecting a load cell and to properly maintain and calibrate the load cell to ensure optimal sensitivity and accuracy over time.

Calibration is a process that involves adjusting the output signal of a load cell to ensure that it accurately reflects the applied force. Calibration improves load cell sensitivity by correcting for any errors or inaccuracies in the output signal, ensuring that the load cell provides accurate and consistent readings over time.

During calibration, a series of known loads are applied to the load cell, and the corresponding output signals are measured. These measurements are used to create a calibration curve that represents the relationship between the applied force and the output signal.

Calibration helps to correct for various factors that can affect load cell sensitivity, such as temperature, environmental conditions, and mechanical stresses. By adjusting the output signal to accurately reflect the applied force, calibration helps to ensure that the load cell provides accurate and consistent readings, even in challenging conditions. Interface recommends calibration of every load cell at least once a year for regular sensitivity maintenance.

Interface engineers design high accuracy, quality load cells with appropriate sensitivity that provides accurate and consistent measurements. It is important to consider both sensitivity and accuracy when selecting a load cell for an application and to regularly calibrate the load cell to ensure that it continues to provide accurate and reliable measurements over time.

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.

 

The Five Critical Factors of Load Cell Quality

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

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

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

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

Five Most Critical Factors of Load Cell Quality

#1 Repeatability

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

#2 Longevity

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

#3 Accuracy

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

#4 Sensitivity to Off-Axis Loads

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

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

#5 Access to Prominent Force Measurement Experts

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

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

Contributor:  Ken Vining, Chief Engineer and Head of Quality