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Bending Beam Load Cell Basics

Bending beam load cells are a versatile and cost-effective solution for many weighing and force measurement applications. These types of miniature load cells are small in dimension, which makes them ideal solutions for compact testing environments and for embedding into machines or products for continuous performance measurement.

The use of bending beam load cells expands across industries and applications, for weighing scales, medical devices, industrial process controls, robotic designs, packaging machinery and civil engineering projects.

How Bending Beam Load Cells Work

A bending beam load cell converts a force applied to it into an electrical signal by measuring the flexure of the beam. This is done by attaching strain gages to the beam. When the beam bends, the strain gages change their resistance, which is then converted into an electrical signal by a Wheatstone bridge circuit. The output signal is proportional to the applied load.

The bending beam load cell is bolted to a support through the two mounting holes. Under the covers, you can see the large hole bored through the beam. This forms thin sections at the top and bottom surface, which concentrate the forces into the area where Interface’s proprietary strain gages are mounted on the top and bottom faces of the beam. The gages may be mounted on the outside surface, as shown, or inside the large hole.

The compression load is applied at the end opposite from the two mounting holes, usually onto a load button that the user inserts in the loading hole.

MB Miniature Beam Load Cell

MB MINI BEAM LOAD CELL

The Interface Model MB is a miniature beam load cell used in test machines and a variety of low capacity applications.

  • Standard Capacities are 5 to 250 lbf (22.2 N to 1.11 kN)
  • Proprietary Interface temperature compensated strain gages
  • Performance to 0.03%
  • Low height – 0.99 in (25.1 mm)
  • Eccentric load compensated
  • ±0.0008% /˚F – max temperature effect on output
  • Low deflection

MBI Overload Protected Miniature Beam Load Cell

Interface’s Model MBI Overload Protected Miniature Beam Load Cell has better resistance to off-axis loads then other similar load cells and is fatigue rated.

  • Standard capacities from 2 to 10 lbf (10 to 50 N)
  • Proprietary Interface temperature compensated strain gages
  • Performance to 0.03%
  • Low height – 1in max
  • ±0.0008% /˚F – max temperature effect on output
  • 10x overload protection

MBP Overload Protected Miniature Beam Load Cell

Our Model MBP series Mini load cells provide a similar performance to Model MB series with the added safeguard of internal overload protection. This patented overload protection is accomplished via hard stops that are EDM machined into the load cell flexure. This provides a greater overload protection (2.5-10lbf ±1000% of full scale capacity, 100 N ±500% of full scale capacity), giving the user added protection in more severe applications.

  • Standard capacities from 2 to 10 lbf (10 to 50 N)
  • Proprietary Interface temperature compensated strain gages
  • 10x overload protection
  • Low height – 0.99 in (25.1 mm)
  • ±0.0008% /˚F temp. effect on output
  • 5′ Integral Cable (custom lengths available upon request)
  • NIST Traceable Calibration Certificate

MBS Parallelogram Load Cell

The Interface MBS Parallelogram load cell is made of lightweight aluminum construction and highly suitable for medical and robotics applications.

  • Capacities from 2.2 to 10 lbf (9.8 to 44.5 N)
  • Lightweight
  • Nonlinearity error 0.02% FS
  • Ideal for OEM applications

Double Bending Beam Cells

A very useful variation on the bending beam design is achieved by forming two bending beams into one cell. This allows the loading fixtures to be attached at the threaded holes on the center line, between the beams, which makes the sensitive axis pass through the cell on a single line of action.

Bending Beam Load Cell Applications

Material testing is a common application for bending beam load cells. This type of miniature load cell measures the forces applied to materials with a high degree of accuracy to determine stiffness, strength and durability of the specimen.

It is quite common to find bending beam load cells in industrial automation machines and robots to precisely measure the forces required for control, safety and efficiency. In robotics specifically, bending beam load cells will measure the force applied to the robot’s arms and grippers. The data is used to control the robot’s movements and to ensure that it is not damaging the objects it is handling.

Aerospace engineering have long used bending beam load cells in design, testing and manufacturing of aircraft and spacecraft. Automotive engineering use bending beam load cells to design and test vehicles for safety and reliability.

Due to Interface’s ability to custom design bending beam solutions that meet strict size, capacity and accuracy requirements, our products are commonly used in medical and healthcare applications.

Bending Beam Application for Medical Device Testing

In this application, the medical device product lab needs to apply known forces to stent and catheters to ensure they pass all necessary strength and flexibility testing. MBP Overload Protected Beam Miniature Load Cell is placed behind the guide wire for the stent or catheter. The motor will spin the linear drive, push the load cell, and guide the wire through the testing maze. The bending beam load cell connects to the DIG-USB PC Interface Module to record and store testing data for analysis. Read more.

Bending Beam Application for Vertical Farming

Vertical farming is the production of produce in a vertical manner using smart technology systems, while indoors using an irrigation system. A wireless force measurement solution is needed to monitor the amount of water being used, to ensure the produce is being watered just the right amount. Interface suggests installing four MBI Overload Protected Miniature Beam Load Cells under each corner of the trays of the produce to accurate measure the weight during watering. A JB104SS 4-Channel Stainless Steel Junction Box connects to each bending beam cell and to a WTS-AM-1E acquisition module. The device wirelessly transmits the sum weight to the WTS-BS-1-HA Wireless Handheld Display for multiple transmitters, and the WTS-BS-6 Wireless Telemetry Dongle Base Station. Interface’s Wireless Telemetry System monitored and weighed the amount of water being used on the produce in this vertical farming system to increase yield and conversation. Read more here.

Additional Resources

How Do Load Cells Work?

The Basics Of Shear And Bending Beams

Interface Mini™ Load Cell Selection Guide

Introducing Interface Load Cell Selection Guides

The Anatomy Of A Load Cell

Mini Load Cells 101

Load Cell 101 And What You Need To Know

How Load Cells Can Go Bad

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

Basics on Load Cell Base Kits

As resilient and accurate as load cells are engineered, there is risk of damaging a load cell if they are not properly supported through mounting or mating to the test subject or test bench.

Load cell bases are designed to support and stabilize load cells. Load cell bases come in assorted sizes and configurations, depending on the intended application and the weight capacity.

Load cell bases are used with load cells that are frequently utilized in industrial equipment, test machines, and commercial testing labs. They may also be integrated into several types of equipment, such as weighbridges, conveyor systems, structural test stands, and packaging machines.

Interface publishes numerous guides on properly supporting a load cell during a test. However, for our LowProfile™ load cells, we provide complete Load Cell Base Kits to provide the engineered accuracy and necessary support for precision performance as intended in regular use. Bases minimize risks in damaging load cells from improper use.

Load cells with positive overload protection must be ordered with an Interface installed base. The positive overload option is useful when high overloads occur in applications such as: impact loads on weighing platforms; engine malfunctions during rocket or jet engine testing; transient overloads on engine dynamometers.

Interface’s Load Cell Base Kits are a type of mounting plate guaranteed to provide optimum support for the flexure. Using the base, or a support surface with its equivalent flatness and stability, is required to ensure the exceptional performance. They are heat treated and high strength bases, available in all standard sizes of our low profile models.

Standard thread size is the same as the mating load cell. Bases or flat mounting surfaces are required for all low profile load cell installations. A mounting surface that is flat to 0.0002″ T.I.R. (total indicator reading) is required, unless a base is installed.

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.

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. Center hub deflects under the load until it contacts the base which provides positive overload protection. The center tapped hole is sealed to keep overload surfaces clean.

When the base and load cell are ordered together, the base and plug are factory installed using the proper hardware tightened to the required torque specs. A plug is supplied in between the cell and the base to prevent damage or errors caused by over engagement of mating parts.

There are 14 model options in standard Load Cell Base Kits in both U.S. and Metric Threads. They are available for our standard 1000, 1100 and 1200 Load Cell Series of various capacities. We offer 15 stainless steel model options to be paired with our 2400 and 3200 Load Cell Series.

Load Cell Base Kits are an excellent accessory to ensuring the most out of your LowProfile Load Cells provide the performance as designed. For complete instructions on installations, please reference our Support section on the website.

ADDITIONAL RESOURCES

Accessories

Load Cell Basics Sensor Specifications

Interface Presents Load Cell Basics

Technical Library

Force Measurement Installation Guides

Mechanical Installation Load Cell Troubleshooting 101

Off-Axis Loading 101

Off-axis loading refers to a situation where a load cell, which is a device designed to measure force or weight, is subject to forces that are not aligned with its primary sensing axis. Load cells are typically designed to measure forces that are applied along a specific direction or axis, which is known as the primary sensing axis. When forces are applied to the load cell in other directions, this is referred to as off-axis loading.

Off-axis loading can affect the accuracy of load cell measurements, as the load cell may not be able to accurately distinguish between forces that are applied along the primary sensing axis and forces that are applied in other directions. This can result in errors in the measured weight or force.

To minimize the effects of off-axis loading, load cells are often designed with measures to reduce sensitivity to forces applied in other directions. These may include mechanical features such as strain relief structures or specialized materials that are more resistant to off-axis loading. Additionally, load cells are often installed and used in ways that minimize the likelihood of off-axis loading, such as aligning the primary sensing axis with the direction of the applied force. Be sure to carefully follow all Force Measurement Installation Guides provided with sensor.

What can be done to protect from off-axis loading?

Off-axis loading can affect the accuracy of load cell measurements, so it is important to take steps to protect against it. Here are a few ways to do so:

  • Use proper mounting and alignment: Load cells should be mounted and aligned in a way that ensures that the primary sensing axis is aligned with the direction of the applied force. This helps to minimize off-axis loading and ensure accurate measurements.
  • Use appropriate accessories: Using accessories such as adapters or mounting bases can help to ensure that load cells are properly aligned and oriented, minimizing the potential for off-axis loading.
  • Use anti-rotation features: Many load cells are equipped with anti-rotation features, such as bolt-hole patterns or keyway slots, which help to prevent the load cell from rotating around its mounting point. This can help to maintain proper alignment and reduce the effects of off-axis loading.
  • Use overload protection: Overload protection features, such as limit switches or stoppers, can be used to prevent load cells from being subjected to excessive forces or moments. This can help to prevent damage to the load cell and ensure accurate measurements.
  • Use a protective enclosure: Load cells can be placed in protective enclosures that shield them from external forces and environmental factors. These enclosures can help to protect against off-axis loading, as well as other types of interference.

By taking these steps, load cell users can help to protect against the effects of off-axis loading and ensure accurate and reliable measurements.

Product designs that mitigate off-axis loading

Engineers are constantly working to design new load cells that are more resistant to off-axis loading.  In fact, Interface product engineers have several products that are designed to protect from off-axis loading, including:

  1. ConvexBT Load Button Load Cell
  2. SuperSC S-Type Miniature Load Cell
  3. MBP Overload Protected Miniature Beam Load Cell
  4. MRTP Miniature Overload Protected Flange Style Reaction Torque Transducer
  5. MBI Overload Protected Miniature Beam Load Cell
  6. LBMP Overload Protected Compression Load Button Load Cell
  7. SMT Overload Protected S-Type Load Cell
  8. WMCP Overload Protected Stainless Steel Miniature Load Cell with Male Threads

By optimizing the mechanical design of load cells to minimize their sensitivity to off-axis loading this can include use of materials, such as composites or alloys, which are more resistant to deformation and strain. It also includes the use of specialized geometries that can help to distribute forces more evenly and reduce the effects of off-axis loading.

As well, engineers utilize built-in electronic compensation to correct for the effects of off-axis loading. This may involve using additional sensors or feedback loops to monitor the load cell’s response to external forces and adjust the output accordingly.

Interface engineers use a multi-disciplinary approach to designing load cells that are more resistant to off-axis loading. By combining advances in mechanical design, electronics, manufacturing, and simulation, they are creating load cells that are the most accurate in by classification in the world.

ADDITIONAL RESOURCES

ConvexBT – The Most Innovative Load Button Load Cell

Eccentric Loading Analysis for SuperSC S-Type Miniature Load Cell White Paper

Addressing Off-Axis Loads and Temperature Sensitive Applications

Benefits of Proof Loading Verification

How Do Load Cells Work?