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The Anatomy of a Load Cell

Have you ever stopped to think about what makes the things we use everyday work? At Interface, our engineers think about what makes up an Interface load cell on the production floor and in our design lab every day.

Whether we are manufacturing a new load cell or speaking to a customer about how it can help solve their test and measurement challenges, we are always thinking about what a load cell can do and how to perfect the process of building one that exceeds all customer expectations in performance, reliability and accuracy.

One thing that people ask us about all the time is, what does it look like inside the pioneering Interface blue load cell? In the photo below, you have a cross-section of a basic load cell identifying each of the components and how it all comes together to provide industries around the globe world-class force measurement solutions.

The first component to understand is the strain gage. This mechanism is embedded in the gage cavity and is a sensor that varies its resistance as it is stretched or compressed. When tension or compression is applied, the strain gage converts force, pressure, and weight into a change that can then be measured in the electrical resistance. You can read more in our recent strain gage 101 blog. Here at Interface, we manufacture our own strain gages in-house to ensure premium quality and accuracy.

The main features of a strain gage are illustrated in the following image:

  1. Grid Lines – strain sensitive pattern
  2. End Loops – provide creep compensation
  3. Solder Pads – used to solder interconnecting wire to the gage
  4. Fiducials – assist with the gage alignment
  5. Backing – insulates and supports foil and bonds the strain gage to the flexure

There are also multiple gage configurations depending on the type of load cell. These include:

  • Linear – measures the strain under bending (used in mini beam load cells)
  • Shear – measures strain under shear force (used in low-profile load cells)
  • Poisson – measures strain under normal stress (used in the Interface 2100 Series Column Load Cells)
  • Chevron – measures strain under torsion (used in the Interface 5400 Series Flange Load Cells)

The next component to understand is the load bearing component of the load cell. It is made up of the hub, diaphragm, outer ring, inner ring and base. This component deflects under load to allow the strain gages to send a signal through the connector to the data acquisition device. Customization can include changing the metal materials used to meet environmental or strength concerns and designing the beam height and thickness to meet certain size and stress considerations.

The mounting ring and connector are also incredibly important to the proper use of a load cell and accurate data collection. The mounting ring is the area in which the load cell is mounted to the test rig to measure force and collect data. It is important to pay attention to mounting instructions because an improperly mounted load cell can cause inaccurate results, as well as damage to the load cell. There are also mounting adapters available to fit a wide variety of test rigs.

The connector is the component that allows the load cell to connect to a data acquisition device. The connector is attached via a wire to the data acquisition device and force data is sent through this device to the user through ethernet or Bluetooth® depending on the load cell and data acquisition device configuration. Interface also sells a wide variety of data acquisition devices.

Load cells have many configurations and capacities. In fact, we have made tens of thousands of them over the years to meet standard, modified and engineered to order specifications. The load cell diagram above represents a popular low profile “pancake” load cell.  There are many other styles including miniature load cells, bending and dual bending beams, column-style, S-beam and load button load cells. However, even as the shapes and uses change, the anatomy remains relatively similar, with these main components acting as the workhorse of the load cell and providing accurate force data to the user.

For more information on Interface and our wide range of load cells, torque transducers and data acquisition devices check out our product categories on our site or download our product literature here.

Finding the Center of Gravity

Even after more than a half-century in the force measurement industry, Interface continues to find new  and innovative use cases for our precision products.

Recently, we were approached by a customer who needed help finding the center of gravity in order to optimize weight distribution and balance for a product in development. Our outstanding team here at Interface put our heads together to develop a unique testing method to help discover this critical data point.

One of the most rewarding experiences in managing our custom solutions is learning about a new customer challenge and developing a novel solution to address it.” Ken Bishop, Director of Sales and Customer Solutions, Interface, Inc.

For this specific use case, the customer had a cylindrical tank filled with material for which they needed to find the center of gravity. Because we were able to calculate the distance of the tank, we were able to understand the weight distribution and create a test to find the center.

The center of gravity of an object is calculated when the weight of the given object is concentrated into the center of the object. This is determined by measuring the weight seen by each of the four legs.  If the weight is distributed evenly, the material is in the center location.  This center location can also be referred to as the origin.

Utilizing a Model 1280 Programmable Weight Indicator and Controller, which is highly customizable instrumentation for any application, we were able to write a program to achieve our goal. We then placed two Model 1211 Standard Precision LowProfile® Load Cells on each end of the rack where the tank resided, using four load cells in total. Because we knew the distance of the object and had load cells to measure the weight at both ends, we were easily able to calculate and identify the origin point on the tank. In this case, the center of gravity.

Ken noted that during his tenured career at Interface, this was the first time he and the team had been tasked with finding the center of gravity in relationship to the distance for an object. As Interface’s team thought about how to develop the custom solution, they also considered additional applications in which this information could be beneficial.

The result of this successful test and measurement application, Interface considers the center of gravity analysis as a beneficial test to optimize flight performance of an airplane. This is important when there is that instant that a plane is not flying at max capacity. There may be open seats all around you, but in order to keep weight distribution in balance, the attendants may need to limit which seats are occupied during a flight. If planes were equipped with this type of sensor technology to calculate center of gravity, they could more evenly distribute weight and ensure optimal performance.  This same type of application can apply to any vehicle that moves on land, air or water with people or cargo.

SEE THE APPLICATION NOTE FOR CENTER OF GRAVITY TESTING

In the growing demands for urban mobility, unmanned vehicles and drone technologies, this type of testing application can help with vehicles, aircraft, space vehicles, boats and more with performance and safety.

Force measurement has a limitless number of applications to improve performance, maximize efficiency and even work in real-time to provide smart decisions. At Interface, we are discovering new ways to redevelop our load cell, torque and multi-axis sensor products for customized solutions to meet the growing demands for innovation.

Interface works with a wide range of industries, including aerospace, automotive, medical, metrology and industrial automation by teaming up to create unique use cases and applications that require our custom force measurement solutions. If you have a unique project that requires a custom solution, please visit the custom solutions page on our site at /custom-solutions/ or contact us at 480-948-5555.

Contributor:  Ken Bishop, Sales and Custom Solutions Director at Interface

Tank Weighing And Center Of Gravity App Note
Drone App Note

Interface Holiday Wish List

As we turn the corner on another great year at Interface, it comes with grace and gratitude to everyone that played part in our 2019 story. And with that, we wish everyone a very joyous holiday season.

To our customers, we appreciate your loyalty and trust. We know you rely on us to accomplish big things and ensure what you do is safe, reliable, durable and accurate. To our team members, our partners, our representatives, and distributors around the world, our success is your success. You are the faces of Interface and everything you do makes a difference.

Reflecting on the past year, we thought we would share what we know best. That’s what you like best!  We compiled a quick list of the top 10 products we sold this year to give you an idea of what’s hot and trending in force measurement.

Here are the items that were on the wish lists of engineers, testers, and lab technicians around the world by quantity of most frequently purchased.  By the way, this list excludes our calibration services and the unique solutions we design for our OEM customers.

BEST SELLING FORCE MEASUREMENT PRODUCTS OF 2019

  1. Mini Compression Load Button Load Cell – This top-selling Interface LBM load cell is available in capacities from 25 to 50K lbf, is environmentally-sealed and made of stainless steel.
  2. LW General Purpose Load Washer Load Cell – A big seller, the Interface Load Washer is available with a wide selection of OD, ID, heights and in various combinations. It is also made of stainless steel.
  3. SGA AC/DC Powered Signal Conditioner – Our SGA Signal Conditioner is a very popular instrumentation device that provides user-selectable analog output ±10V, ±5V, 0-10V, 0-5V, 0-20mA and 4-20mA as a single channel that powers up to four transducers.
  4. SM S-Type Load Cell – This high-demand S-Type Load Cell is for high-performance tension and compression testing. It utilizes proprietary Interface temperature compensated strain gages.
  5. 1200 Standard Precision LowProfile® Load Cell – The 1200 LowProfile Load Cell model series outsells all others. It is eccentric load compensated and has low deflection and shunt calibration. It can be used in tension and compression testing.
  6. T4 Standard Precision Shaft Style Rotary Torque Transducer – With more than 50 torque models available, this particular Interface T4 Torque Shaft Style Rotary Transducer has capacities from 0.1 Nm to 1K Nm (0.88 lbf-in to 8.85K lbf-in). It has contactless data transmission with digital electronics with on-shaft design.
  7. MB Mini Beam Load Cell – Our low capacity mini load cell has Interface temperature compensated strain gages with performance to 0.03%, low deflection and low height with 1-inch max.
  8. 1100 Ultra Precision LowProfile® Load Cell – The Interface model 1100, with a range of capacities, is selected among our best low profile load cells. It has very low nonlinearity, hysteresis, eccentric load sensitivity, and temperature sensitivity.
  9. 9320 Battery Powered Portable Load Cell Indicator – A very popular instrument, Interface’s 9320 Indicator is handheld and features two independently scalable ranges, peak and valley monitoring, display hold, mV/V calibration, and a power save feature. Typical battery life exceeds 40 hours of continuous use (450 hours in power-save mode), and is TEDS plug and play compliant.
  10. WTS 1200 Standard Precision LowProfile® Wireless Load Cell – Our most popular wireless load cell, often purchased as part of the entire Wireless Telemetry System (WTS), is compact in size and has capacities from 300 to 100K lbf (1.5 to 450 kN), with performance to 0.0425% and a 2.4 GHZ transceiver.

With thousands of products, we certainly have a diverse and broad selection of products and force measurement solutions. We didn’t include all our custom and OEM solutions or calibration services in our best selling list.

As we head into 2020, we look forward to working together to supporting your latest projects and unique applications, as well as helping to achieve your goals in the new decade!  We appreciate you and thank you for your business!

Happy Holidays from your Interface Team!

 

Compression Force Testing

Compression is a type of force that we apply every day often without thinking and compression is intensely tested in many of the products we use on a daily basis.

Compression force is defined as the energy generated from compressing an object or substance. Compressive force is simply the direction of the force applied to the load cell. The compressive strength of materials and structures is an incredibly important engineering consideration in both designs and build.

Whether you are clicking the keys on your laptop at work or slamming on your brakes to avoid an accident on your morning commute, you are using the compression force. Testing of the compression force is essential in developing a reliable and sturdy product that can withstand the pressure applied to it many times over. Often, safety is at the core of compression testing.

Load cells incorporated into the testing process work by measuring the pushing force of an application on a single axis. The strain gage compresses to measure the load applied. The deformation of the strain gage provides the measurement data. Application tests measure the total compression force the products or structures can handle, as well as the effects of compression over time through stress tests. In both cases, original equipment manufacturers (OEMs) need accurate measurements to guarantee their products can withstand compression in the short and long-term.

Interface supplies a variety of compression-focused load cells and accessories for all types of applications, both for test and measurement, as well as for inclusion in originally manufactured products and solutions. These compression load cells are often used in vehicles, industrial automation, aerospace, and defense industries. Applications are wide-ranging, from testing the impact of drones dropping packages to the material strength of bridges during an earthquake. Interface load cells are highly-rated to provide the most accurate data and reliability over time, which is why engineers rely on Interface compression-only load cells.

Here are a few of the compression load cells available from Interface:

1601 Gold Standard® Calibration Compression-Only LowProfile® Load Cells – Interface’s Gold Standard® Load Cells are designed for calibrating other load cells. The 1601 load cell is compression-only and has options available for a second and third bridge and overload protection.

1201 Compression-Only Standard Precision LowProfile® Load Cells – The Interface 1201 LowProfile® load cell provides a “compression-only” force measurement. Its spherical-shaped top surface helps provide minimal off-axis loading. 1201 is our most popular load cell designed for static applications and has a higher output than most competitive load cells.

2101 Dual Range Standard Compression-Only Load Cells – The Interface Model 2101 consists of lower and higher capacity model 1200 type load cells which are stacked with overload protection built into the lower capacity load cell permitting the high resolution to be obtained at both low and high levels of capacity. The Model 1201 is LowProfile® moment compensated.

LBM Compression Load Button Load Cells – The Interface LBM Compression Load Button is constructed from stainless steel and has a small size for all types of sensor apps and testing. This product is available in capacities that range from 25 lbf up to 50K lbf.

There is a variety of other standard compression-only load cells, including modified and custom Interface compression testing options in multiple capacities. For more information on our compression-only products or any of Interface’s industry-leading force measurement solutions, contact our Application Engineers.

Why Interface Load Cells Stand Out from the Competition

As you might expect, there’s a lot of care and attention to detail in our product development methods that allow Interface to create the most accurate and reliable force measurement tools on the market. Honed over our 51 plus years in the manufacturing of force measurement products, we have among the most refined and thorough processes in the industry. Today, we are going to reveal one of the unique testing processes in our LowProfile® load cell development which sets us apart from the competition, by a landslide!

It’s no secret, Interface LowProfile load cells are reliable and offer repeatable results. What isn’t widely known is this is because of the product’s overall capability to handle loads with minimum error due to misalignment. In plain English, these load cells are very forgiving to general misalignment when they are installed into the application. Why? Because of a process called moment compensation. This is one of the primary differentiators from other pancake load cells in the marketplace.

Moment compensation is one of the many production tests we run on our LowProfile load cells to guarantee minimal influence from off-axis loads known as “moments.” We compensate for moments by hanging a weight from a fixture and rotating it around the LowProfile load cell. The offset weights go around and take readings at specific locations. The computer records the data and identifies the highest readings and locations. The operator then modifies the geometry of the material from the beam to make the beamless stiff. Once this process is completed, we go around and repeat the process to confirm results until the product passes the specification criteria.

Moment compensation is performed on every individual Interface LowProfile load cell and most other Interface load cell models to ensure repeatability and accuracy. This is a big deal in the force measurement industry because most load cell manufacturers don’t test and compensate or have a specification for eccentric load sensitivity like we do.

Interface takes these extra steps because we understand that as product development becomes more complex, the margin for error gets smaller and smaller. Moment compensation also helps to maximize the operating life and minimize performance errors. With Interface LowProfile load cells, customers know that every step in our design and development process is conducted to ensure the premium quality which exceeds their needs and quality expectations.

Contributor: Carlos Salamanca, Interface Engineering

Are you a person that likes to learn visually? There’s an Interface video for that! Check out Interface’s Brian Peters explaining the process here:

For more information on Interface’s lineup up of our precision LowProfile load cells, please visit /product-category/load-cells/ or call to contact an Application Engineer at 480-948-5555.  You can also read about our entire line of load cells here.

Load Cell Brochure 6 Page

IoT Solution That Monitors Rigging and Lifting in Real-Time Showcased at OTC50

Interface, the world’s trusted leader in technology, design, and manufacturing of force measurement solutions is celebrating the 50th anniversary of the Offshore Technology Conference (OTC) by exhibiting at the global event.

In coordination with the event theme, The Next 50 Years of Offshore Developments, Interface will be highlighting their latest innovations that are advancing force measurement solutions specifically for the oil and gas industry. We will be gathering input from participants in our next-generation of downhole load cell and strain gage technology.

During OTC 2019, Interface is showcasing its proprietary wireless telemetry system (WTS) that measures force capacity in heavy machinery used by oil and gas support service. This innovation connects to software on a PC to handle enormous amounts of weight, preventing damage to both humans and equipment.

Interface’s solution is part of the most exclusive line of integrated wireless products on the market.” Ken Bishop, Director, Sales Engineering

Interface will also be discussing its line of ATEX approved products for use in extremely harsh environments, including its most popular product, the Interface LowProfile® load cell.  The company’s products are customizable to meet any customer specification.

Interface force measurement solutions are used in every facet of energy production from research and exploration to monitoring equipment. You can read more about Interface innovation in dry load cell technology here.  This advancement in force measurement provides unparalleled accuracy in a ruggedized package that will stand up to the harsh environments of a deep oil well. These design iterations increase product lifespans, with cost savings and consistency of using a single force measurement solution.

Attendees of OTC 2019 can find Interface team members at booth #7551, Hall C at NRG Park in Houston, May 6-8 from 9 a.m. to 5 p.m. and May 9 from 9 a.m. to 2 p.m. CST.