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Load Cell Stiffness 101

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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

Interface New Product Releases Spring 2023

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Interface continues to expand our product offerings of force measurement solutions. We have added new high-accuracy load cells, Bluetooth data loggers, indicators and load cell base kits. The following product summaries highlight the latest additions, along with product features for each model.  We also have a new torque couplings technical guide.

In our Interface New Product Releases Winter 2023 updated, we featured our Pillow Block Load Bearing Load Cells (PBLC).  We are excited announce that our PBLC series are now available in multi-axis options. Reach out to our application engineers to learn more about Pillow Block Load Bearing Load Cells 2-Axis custom options.

If you have questions about our new products, capacities, capabilities, or application uses, please contact our application engineers.

SSLP STAINLESS STEEL LOW PROFILE UNIVERSAL LOAD CELL

The Interface Stainless Steel Low Profile Universal Load Cell SSLP model is a low profile, pancake-styled load cells. The internal construction is a diaphragm design, offering a lower cost solution with high natural frequency, low deflection and excellent resistance to side and torsion forces. There is an optional mounting base available, required if used in tension testing. It provides high stability and low height. The SSLP can be supplied calibrated as a complete system with associated instrumentation. View: SSLP Stainless Steel Low Profile Universal Load Cell

Primary SSLP features and benefits:

  • Capacities from 2.5 to 5000 kN (562 to 1,124K lbf)
  • Low profile with stainless steel construction
  • Environmentally sealed to IP67
  • Hose and conduit fitting at cable exit
  • High thermal stability
  • Base options, including custom bases and custom top plate
  • Load cap assembly optional
  • TED options
  • ATEX and submersible versions available
  • Options for internally amplified and multiple bridges

BX6-BT PORTABLE 6-CHANNEL HIGH-SPEED BLUETOOTH DATA LOGGER

Interface’s digital instrumentation data acquisition system BX6-BT Portable 6-Channel High Speed Bluetooth® Data Logger is a multi-channel measuring amplifier that offers a multitude of features in a convenient compact package. The BX6-BT first channel is for full-bridge strain gages, channels two through six are individually configurable as voltage input (single-ended) or strain gage bridge input, including half and quarter bridge configuration. View: BX6-BT Portable 6-Channel High Speed Bluetooth Data Logger

Primary BX6-BT features and benefits:

  • Simultaneous zeroing of all channels can be triggered via a digital input (tare)
  • Measurable temperature in the device and the battery voltage
  • Protected against vibration by full encapsulation housing
  • Configuration and acquisition of measurement data with BlueDAQ in the mode “BT Classic” with Serial Port Profiles (SPP)
  • Integrated Bluetooth module has its own microcontroller.
  • Connected 3.7V lithium-ion battery can be charged by an integrated charging circuit.
  • Power supply via a Li-Ion battery from 3.6V – 4.2V

9840C TEDS READ WRITE INTELLIGENT INDICATOR

Interface’s new digital instrumentation 9840C indicator is a CE compliant and versatile precision instrument intended for the digital readout of strain gage sensors, which includes load cells. It is TEDS Plug and Play Ready and IEE 1451.4 Compliant. View: 9840C TEDS Read/Write Intelligent Indicator

Primary 9840C Intelligent Indicator features and benefits:

  • Reads and writes calibration data and coefficients to the load cell
  • Stores load cell information and calibration data and coefficients for use with up to 20 load cells
  • 10-point linearization
  • Adjustable calibration curve
  • Bipolar and accepts 2, 3, and 4 mV/V load cell inputs
  • Remote sense excitation (6-wire load cells)
  • Fast direct analog output with +/-10 VDC scalable analog output — 16 bit
  • Full duplex RS232C communication
  • Eight selectable digital filters
  • Front panel shunt calibration with two selectable resistors

LOWPROFILE™ LOAD CELL BASE KITS

Interface’s standard LowProfile Load Cells are offered with bases. The base is a flat surface, guaranteed to provide optimum support for the flexure. Use of the base, or a support surface with its equivalent flatness and stability, is required to ensure the exceptional performance of the LowProfile® Series. Note that the threaded hole in the base is on center, and a plug is permanently installed to seal dirt and moisture out of the space between the bottom hub of the flexure and the flat surface of the base. Read more about the basics of base kits. View: LowProfile™ Load Cell Base Kits

Primary LowProfile Load Cell Base Kits features and benefits:

  • 14 model options in both U.S. and Metric thread
  • 15 stainless steel model options
  • Bases are all heat treated
  • High strength materials, including stainless steel options
  • Available in LowProfile standard sizes for Interface load cell models 1000, 1200, 2400, 3200
  • Standard thread size is the same as the mating load cell
  • Custom base options available
  • When the base and load cell are ordered together, a plug is supplied in both the cell and the base to prevent damage or errors caused by over engagement of mating parts

TORQUE COUPLINGS PLUS NEW TECHNICAL GUIDE

Interface is excited to introduce a complete summary catalog and technical guide of our extensive line of Torque ROBA® DS Couplings. These Interface torsional rigid shaft coupling transmits drive torques up to the nominal torque completely backlash-free and with permanently high torsional spring rigidity. Problems to be found on other commercially available couplings, such as denting the disks or overcoming the frictional locking, are not an issue when using our couplings. The specified shaft misalignments can be 100% utilized without affecting the transmittable torque. This guarantees unlimited use. View: Torque Couplings Technical Guide and Summary Catalog for all sizes, technical details, and installation instructions.

Primary Torque Couplings options and features:

  • Non-sensitive to alternating loads of up to 100% of the nominal torque
  • Low mass inertia due to high performance density
  • Completely backlash-free up to nominal torque
  • High misalignment compensation capability at low restoring forces
  • High torsional rigidity up to nominal torque
  • Completely wear and maintenance-free
  • Optimum construction shape due to large variant range

There are two main categories of couplings used in force measurement and the biggest difference in the two is the degree of freedom needed for the application. The categories are single-jointed and double-jointed. Read more in our Couplings 101 Series.

INF4-POWERLINK TWO, THREE, AND FOUR SENSOR WEIGHT TRANSMITTER AND INDICATOR

Expanding our INF4 series, we introduced the Interface INF4-POWERLINK Two, Three, and Four Sensor Weight Transmitter and Indicator. It has a six-digit red LED display (8 mm height), space saving compact design, four buttons for the system calibration. You can store up to 50 events, use multiple load cells in parallel and set alerts for value deviations. View: INF4-POWERLINK Two, Three, and Four Sensor Weight Transmitter and Indicator

Primary INF4-POWERLINK 2, 3 and 4 features and benefits:

  • Four independent channels for monitoring and direct management of individual load cells
  • Digital equalization
  • Four channel load distribution signaling with archive
  • Automatic diagnostics comparing recorded values plus alerts
  • Event log archives for calibrations, zero settings, errors, and equalizations
  • Excitation remote sense
  • 16 load cells in parallel
  • Tare weight zero setting, semi-automatic tare (net/gross weight) and predetermined tare
  • Connections to PLC via analog output or fieldbus and PC/PLC via RS485 up to 99 instruments with line repeaters, up to 32 without line repeaters
  • Direct connection between RS485 and RS232 without converter

INF1-POWERLINK SINGLE SENSOR WEIGHT TRANSMITTER AND INDICATOR

The INF1 series added the INF1-POWERLINK Single Sensor Weight Transmitter and Indicator. Like the version above, the options for this include a compact design, use with multiple load cells (up to 8) in parallel. View: INF1-POWERLINK Single Sensor Weight Transmitter and Indicator

Primary INF1-POWERLINK Single features and benefits:

  • Connection to PLC via analog output or fieldbus
  • PC/PLC via RS485 up to 99 instruments with line repeaters, up to 32 without line repeaters
  • Remote display via RS485
  • Excitation remote sense
  • Eight load cells in parallel
  • Digital filter to reduce the effects of weight oscillation
  • Theoretical calibration and real calibration with the possibility of weight linearization up to five points
  • Tare weight zero setting and automatic zero setting at power on

SPECIAL EVENT ALERT!

We are hosting Testing Lab Essentials: Today + Tomorrow on Thursday, April 6. We are diving into products and solutions used in all types of testing labs, along with tips and best practices for modernizing your test lab. Join the conversation.  All Interface webinars are recorded if you are not able to attend the live event.

ADDITIONAL PRODUCT RESOURCES

Interface is ready to help you get the exact product based on your unique requirements.  For engineered to order or custom solution options, please contact our experienced applications experts.

Load Cell Sensitivity 101

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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.

Mechanical Installation Load Cell Troubleshooting 101

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The performance of a load cell force measurement system is dependent upon the reliability of the physical installation, correct interconnection of the components, proper performance of the basic components which make up the system, and calibration of the system.

Interface provides installation instructions for our products. Review the installation guide and keep on hand for installation and troubleshooting. Load cells not mounted in accordance with the manufacturer’s recommendations may not perform to the design specifications.

Always start any troubleshooting with a physical inspection of the load or weighing sensor. Resistance results from numerous factors, creating an inaccurate reading of the measurement and potential overload. If there is any appearance of dents, bending, cracks or deformation it is likely the device will need to be repaired or replaced. If none of these conditions are visible, the next step is to troubleshoot the mechanical installation.

The following is a quick checklist to reference for mechanical installation troubleshooting:

  • Check the mounting surfaces for cleanliness, flatness, and alignment
  • Check the torque of all mounting hardware
  • Check the load cell orientation
  • Check use of proper hardware as required to connect the load to the load cell
  • Check cables or output devices

Orientation is of a load cell is defined by the “dead” end on mechanical reference or load forcing source and the “live” end connected to the load to be measured by the cell. Dead end is the end closest mechanically to the cable exit or connector. A fundamental requirement is that there be one, and only one, load path.  This load path must be through the load axis of the load cell. This may sound elementary; however, it is a commonly overlooked problem.

Check all hardware and accessories when troubleshooting during mechanical installation, including all connectors, cables, thread sizes, jam nuts, swivels, mounts, and bolts. It is always important to also thoroughly inspect the cables used in a system. Evaluate the cable to ensure there is no crimping, cuts, or exposed wires. This is a common cause of mechanical installation failure.

For a quick reference, here is a discussion about what a healthy load cell should look like, and any visual clues that may potentially be a sign for an improperly working load cell.

For more helpful guides and troubleshooting tips, please visit the Interface Technical Library. Interface provides technical support for additional questions related to installation or if there is help needed in troubleshooting any of our products. Contact us here and let us know how we can help.

Additional Resources

Force Measurement Installation Guides

I’ve Got a Load Cell, Now What Play List

Force Measurement Accessories 101

 

Strain Gage Design Under Eccentric Load WRSGC Presentation

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By Ashlesa Mohapatra, product design engineer, Interface

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Force Measurement Installation Guides

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Interface is a long-time provider of the world’s most accurate and reliable force measurement products. Our sensor and instrumentation solutions are used across industries to test and monitor everything from critical infrastructure and to advanced robotics. Innovators and engineers know that our quality is unmatched. However, any measurement device manufacturer nor superior quality of a product can save users from poor performance when making this one critical mistake, poor installation.

Proper installation is one of the absolute keys to reliable and accurate test data and successful measurement programs. This is true for any type of test and measurement protocol, in particular utilizing force measurement.

Preparing for any installation for any load cell force or weighing measurement system is dependent of the integrity of the physical installation, interconnection of the components, following proper performance of the system components, and calibration.

Installation success is such an important topic, we asked Interface engineers and application experts for their thoughts on the top reasons why proper installation is critical to a successful test or vice versa. They also shared helpful guidance on why improper installation can be so damaging.

  • Poor installation can lead to damaging the load cell, so to protect your investment follow the installation instructions that a accompany your product.
  • When we provide performance metrics on our product, it is based on our in-house calibration. When improperly installed, you will not be hitting the performance numbers you need during use.
  • Improper installation can cause overload which can not only damage the load cell, but also create unsafe working conditions.
  • Installation guides not only give you the proper installation techniques, but they also provide the correct order for installation.
  • And our favorite tip, and the most relatable, “Improper installation with ultimately lead to headaches!”

Installation can also vary widely between load cells and other force measurement solutions. Each product has different processes depending on the mounting components, the application being tested or monitored, the environment in which the application is being tested or monitored, and more. It is important to carefully review any materials provided with the instrumentation and sensor.

Interface provides a wide variety of installation guides, instructions and technical support online. You can find these instruction guides by visiting our support installation and manuals option.

In addition, we have resources providing clear explanation on installation and its importance. Recently, our video and blog series titled, I’ve Got A Load cell – Now What? Part 6 – Usage & Best Practices, includes in-depth information on installation and mounting.

Mechanical Installation Tips

Once you have your load cell hooked up and your instrumentation scale, it is time to put it to work. You want to review the attachment, including thread engagement and mounting. If you are threading into the live end, the center hub on the low profile load cell, make sure you have enough threads engaging into the load cell itself. We recommend that you thread it into where the studs bottom out, then back up a half a turn. Next step is to preload tension load by about 130% of capacity and jam the jam nut. We want to ensure that we do not have any repeatability issues due to thread engagement of the flexure. If you cannot provide a preload, reference the torque values in the installation guide.

Mounting to Base, Structure or Plate Tips

  • Use Grade 8 or Better Hardware
  • Mount to Total Flatness of .002″
  • R30-33 Hardness Scale
  • Follow the star patter to proper torque values
  • Preinstalled Bases

Interface bases help in making integration to any assembly much easier. Interface manufactures bases with the same high-performance materials and specifications for hardness and flatness as our load cells. The bases offer threaded holes, which make it easier for mechanics like hydraulic actuators.

We also offer several references for troubleshooting. Two important considerations to review during set-up are the mechanical and electrical installation requirements.

Mechanical Installation Troubleshooting: Load cells not mounted in accordance with the manufacturer’s recommendations may not perform to specifications. It is important to review the mounting surfaces, hardware, and orientation during the installation.

Electrical Installation Troubleshooting: Proper load cell performance is depending upon the electrical system. The areas to inspect during any install are the connections, cables, settings of excitation voltage and loading of the bridge circuit.

We urge that to get the most out of your new load cell to reference the materials provided in the installation guides. If you have any questions, Interface is also here to help. Feel free to reach out to your local representatives and distributors or call us directly at 480-948-5555 to speak with an engineer to help solve your installation challenges.

LowProfile Load Cells 101

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In the field of force measurement, load cells are defined by a set of specifications attributed to a configured shape and size of the flexure model. These models are engineered to meet requirements in weight, size, cost, accuracy, use life, rated capacity, extraneous forces, test profile, error specs, temperature, altitude, pressure, and materials.

Of all the flexure models available, the low profile load cell is the most common force measurement sensor model used for general test and measurement applications.

Did you know that Interface is known for creating the first low profile load cells more than 50 years ago? Our founder first introduced the low profile in 1969 and later trademarked as the first of its kind precision LowProfile® Load Cell by Interface. With this invention, Interface became with market leader of precision load cells. In fact, our 1200 Standard Precision LowProfile® Load Cell, designed for eccentric load compensated tension and compression, remains our most popular product today.

This pancake-style shear beam cell design is world-renowned for durability, accuracy, and performance. The LowProfile design resembles two shear beam cells end-to-end, exhibiting the stability of a doubled-ended shear beam and augmented by the fact that the circular design is equivalent to four double-ended cells. Thus, it provides stability in eight directions at the center point.

The LowProfile designs include a base, bolted to the flexure around its outside rim. The base is a flat surface, guaranteed to provide optimum support for the flexure. The use of a base ensures the exceptional performance in the Interface LowProfile series, as each load cell is built, evaluated, and calibrated with the base.

Advantages of all Interface LowProfile design include:

  • Higher output
  • Better fatigue life
  • Better resistance to extraneous loads
  • Shorter load path
  • Extremely low compliance with higher stiffness
  • Option for compression overload protection integral to the cell
  • Proprietary strain gages
  • Customization

One process step that is standard in the LowProfile series is the adjustment to extraneous load sensitivity. Although the design itself cancels out the built of this sensitivity, Interface goes one step further and adjusts each cell to minimize it even more.

The Interface LowProfile Series is available in compression-only, tension and compression and calibration grade. There are high and low-capacity options, flange-style, amplified, as well as fatigue rated models. Various features are available through hundreds of configurations to accommodate the wide range of testing profiles, such as connectors, wireless, additional bridges, and overload protection.

The LowProfile Series has three major classifications: precision, ultra precision and fatigue rated. The basic construction of all the cells in the series is quite similar. The major differences are in the number of shear beams and the number of gages in the legs of the bridge.

LowProfile Precision Series: Standard capacities of the precision low profile designs can measure up to 2M lbf. The gaged sensors in every load cell are individually inspected and tested and certified to meet our rigid standards. With greater stiffness, respectable static error band specifications and resistance to extraneous loads, this is Interfaces number one line of products.  The standard 1200 is by far the most sought after low profile today.

1200 Precision LowProfile Load Cell Standard Series features:

  • Proprietary Interface temperature compensated strain gages
    Performance to .04%
    High output – to 4 mV/V
    0.0008%/°F (.0015%/°C) temperature effect on output
    Low deflection
    Shunt calibration
    Barometric compensation

This 1200 Standard Precision LowProfile® Load Cell standard model is available through our QuickShip48 expedited delivery service. Click here to order now. For additional low profile capacities of the Model 1200 series, base options, connectors, bridge options and overload protection availability, go here for the specifications datasheet, model options, drawings and technical specifications.

LowProfile Ultra Precision Series: Engineers at Interface designed this series to meet the demands of sophisticated testing labs with precision performance in the critical parameters such as static error band, non-linearity, hysteresis, non-repeatability, and extraneous load sensitivity. The models in the 1100 Ultra Precision LowProfile® Load Cell are the most popular of this design.

LowProfile Fatigue Rated Series: This series guarantees fatigue life of 100 million fully reversed load cycles.  This series has tighter specifications on resistance to extraneous loads and offers stiffer compliance. Interface’s fatigue rated load cells typically have static overload rating of 300% in both tension and compression modes. Originally designed for aerospace testing, the Interface 1000 Fatigue-Rated LowProfile® Load Cell are the most used fatigue-rated low profiles.

Interface also provides very high-grade low profiles for calibration. The LowProfile Gold Standard Calibration Series: Interface sets the standard in precision load cells. The model 1600 Gold Standard® Calibration LowProfile® Load Cell are uniquely designed for calibrating other load cells to the highest levels of quality and accuracy used in test and measurement. The Interface Model 1600 provides both tension and compression in one unit. It also has the options for a second and third bridge, as well as overload protection.

1600 Gold Standard® LowProfile® Tension and Compression Load Cell Standard Series features:
• 0.01% creep
• High Output to 4 mV/V
• High-Precision Installed Base
• ±0.0008%/˚F Max Temperature Effect on Output
• Low Deflection
• Shunt Calibration
• Barometric Compensation
• Calibration Adapter
• 3-Run NIST Traceable ASTM E74 Calibrations
• 4% Lower Load Limit per ASTM E74

Low profile load cells are used for all types of testing. There are many options and designs available as standard models. We also provide engineered to order, custom and OEM solutions for all our load cells. As with all our standard load cells, we do offer various capacities, modifications, and custom options.

One thing that is for certain, the Interface LowProfile is a standard across the force measurement industry. They are common in testing rigs, designed in as components, often found in the best metrology labs throughout the world.  Industry leaders in manufacturing, aerospace, automation, food processing, medical and biosciences, energy and transportation choose LowProfiles for the meticulousness required in high-performance force measurement testing.

Low-Profile-Load-Cell-Brochure

Faces of Interface Featuring Sean Malone

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In today’s Faces of Interface, we talked with Sean Malone who is responsible for calibrating and repairing our customer’s force measurement equipment. As our esteemed warranty coordinator, his important role requires extensive knowledge of force measurement technologies. This is because not only do we support the products we make, we also calibrate and repair force measurement products from a wide variety of other manufacturers.

Throughout his life, Sean has always had a propensity for working with his hands. Hi family owned a locksmith business, so he grew up to become very mechanically proficient. In fact, Sean worked for the 35-year family-run business for 25 years before the family decided to sell it. Sean also went to school at ITT Tech during that time and received his associates in computer networking and science.

After leaving the locksmith business, Sean investigated a new role where he could continue to work with his hands every day. This desire led him to Interface. He began his career at Interface as a repair technician in our production facility, then he moved on to become a calibration finalist, and the manager of the service department before settling into his current role as warranty coordinator.

His journey through Interface’s service department gave him a great deal of knowledge about the business and the ins and outs of a load cell. This allows him to perform his current role to the highest degree and aptitude. He’s also a great resource for questions and support for our team members and global network. His position today includes being a single point contact for service customers, performing root cause analysis, fixing load cells, calibrating them, and ensuring items sent in for services get back to the customer in premium working order.

Sean says that he’s caught his professional stride at Interface and really enjoys the fact that he is learning something new every day. He also remarked that the people he comes to work with make the job and the company that much more enjoyable. We’re glad to have you here too Sean, as you represent the best in ForceLeaders.

In his free time, you won’t find Sean anywhere else but at the golf course. Being an Arizona native, he has grown up with a passion for the U.S. golf capitol of the world and all it has to offer for an avid golfer. His skills in the sport also extend to a little bit of frisbee golf from time to time. All things golf, all the time. That’s the way Sean winds down.

We’re incredibly honored to have Sean on the team and his work is critical to keeping our customers products operating at the highest standards of accuracy and reliability, today and for many years to come.

To learn more about the outstanding team at Interface, check in to our blog each month for our Faces of Interface series.

Specifying Accuracy Requirements When Selecting Load Cells

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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