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Choosing the Right Torque Transducer

Interface offers an extensive line of torque transducer models in different designs and capacities to fit all types of torque measurement testing requirements.  The first thing to understand when choosing the right torque transducer is how an actual torque transducer works in order to then determine the best type, style, model, mounting, capacity and special features for your requirements.

A torque transducer, like a load cell, consists of a metal spring element, or flexure. Strain gages are applied to the flexure in a Wheatstone bridge configuration. Torque applied to the sensor causes bending or shear strain in the gaged area, generating an output voltage signal proportional to torque.

To assist you in choosing the right torque transducer, get a copy of our Torque Measurement Primer for reference in your selection process.

Reaction or Rotary Type

There are also two different types of torque transducers: reaction and rotary. A reaction, also known as static, torque transducer measures torque without rotating, while a rotary torque transducer rotates as part of the system. A rotary sensor, also sometimes called dynamic torque, is merely a reaction sensor that is allowed to rotate. Normally, a reaction style sensor has a cable attached to it for supplying excitation voltage to the strain gage bridge and for output of the mV/V signal. Spinning of these sensors is prevented by the attached cable. To get around the issue of the attached cable, a variety of methods have been used for rotary sensors Some of those methods include slip rings, rotary transformers, rotating electronics, rotating digital electronics and radio telemetry.

Shaft or Flange Style

Torque transducers typically come in one of two major mechanical configurations, shaft or flange style. Shafts can be either smooth or keyed with keyed shafts coming in either single or double-keyed versions. Flange style sensors are typically shorter than shaft style, and have pilots on their flange faces as a centering feature.

Smooth shafts offer some advantages over their keyed counterparts, including more uniform introduction of the torque into the measuring shaft, ease of assembly and disassembly and zero backlash. A coupling designed for use with smooth shafts will have some method of clam ping to the shaft. This is commonly accomplished with split collars or shrink-disk style hubs. Shrink-disk style hubs usually include features to aid in their removal from the shaft.

Hubs for keyed shafts are simpler than those for smooth shafts and cost less but can suffer from wear due to backlash, especially in reciprocating applications. To prevent backlash, the hub must be installed on the keyed shaft with an interference fit, which is usually accomplished by either heating the hub before installation or pressing the hub onto the shaft.

Fixed or Floating Mount

There are also two main methods of mounting rotary torque transducers, fixed or floating. Fixed mount applies only to sensors with bearings and involves attaching the sensor housing to a fixed support. In floating installations the sensor is supported only by its drive and load side connections, which are typically single-flex style couplings. A flexible strap keeps the torque transducer housing from rotating. By definition, bearingless sensors are always floating mount.

Fixed mounting requires that the sensor housing have a means to attach it to the support. Sometimes the mount is an option on the sensor and sometimes the foot or pedestal mount is built as part of the sensor. The simplest fixed mount design sensors include a flat machined surface on the housing with threaded mounting holes. In fixed mount installations, double flex couplings must be used.

Capacity

Once you have determined the type, style and mount, how do you choose the right transducer for your project? One of the primary considerations is selecting the right capacity. On one hand, if you choose too large a range, the accuracy and resolution may not be enough for the application. On the other hand, if you choose too small a size, the sensor may be damaged due to overload, which is an expensive mistake. No manufacturer wants you to overload the sensor.

To select the proper size, first determine the amount of torque you want to measure. This can be easy or hard, depending on your application. An easy example would be a fastener torque application, where a certain amount of torque is to be applied to a fastener. A more difficult application might be trying to figure out how much torque is required for a new design wind turbine.

This is just a brief overview, there are many other variables to consider when choosing a torque transducer. To get a full rundown, check out our white paper Torque Measurement Primer. And as always, give us a call to speak directly with our applications engineers to learn more at 480-948-5555.

With more than 36,000 product SKUs in Interface’s extensive catalog, it can be a daunting task choosing the sensors that fit your exact needs. Fortunately, we’re here to work you through it! There is an abundance of content, including product brochures, white papers, case studies and application notes, for easy comparing of different product types and categories . These resources, as well as our model product datasheets with specifications can help navigate the options and along with common solutions by industry.

Our application engineers are just a phone call away and can help you determine the off-the-shelf products or custom solutions needed for your specific application. To learn more about our torque transducer selection, you can also visit www.interfaceforce.com/product-category/torque-transducers/.

ADDITIONAL RESOURCES

New Twist on Torque Webinar

AxialTQ

Latest Spin on AxialTQ

A Comparison of Torque Measurement Systems White Paper

Rover Wheel Torque Monitoring

Aircraft Yoke Torque Measurement

Insights in Torque Testing Featured in Quality Magazine

Torque Measurement for Electric Vehicles

 

Shunt Calibration 101

Calibration is a critical stage to ensure proper accuracy and reliability of any force measurement device. There are many ways to calibrate and different types of calibration. In the standards of maintaining our quality and precision requirements, Interface calibrates every test measurement device we manufacture including our load cells and torque transducers. Every device is shipped with the most detailed calibration certifications in the industry.

With our experience and expertise, we understand that sharing what we know is beneficial to our customers and partners in the test and measurement industry. One of the means by which we do this is through a series of technical white papers.  A popular white paper that was written years ago still stands the test of time, as it provides a deep dive on the topic of shunt calibration. Click on the title “Shunt Calibration for Dummies,” to access the full white paper.

What is Shunt Calibration?

Shunt calibration is a technique for simulating strain in a piezo-resistive strain gage Wheatstone bridge circuit by shunting one leg of the bridge. The bridge may be internal to a discreet transducer or composed of separately applied strain gages. The resulting bridge output is useful for calibrating or scaling instrumentation. Such instrumentation includes digital indicators, amplifiers, signal conditioners, A/D converters, PLC’s, and data acquisition equipment. Care must be taken to understand the circuits and connections, including extension cables, in order to avoid measurement errors.

Benefits of Shunt Calibration

The biggest reason to use shunt calibration is the flexibility and low-cost it offers the user. In this method of calibration, the bridge circuit is already there, and you don’t need to make and break cable connections to run it. This means that a shunt calibration can be applied conveniently and at any time during the test program. It is often used in situations where the user is calibrating control system equipment that will be communicating with a transducer or to confirm that the transducer is functioning properly.

Expected Shunt Calibration Repeatability in Modern Transducers

An important question that comes up regarding calibration is what type of repeatability can I expect from shunt calibration? Included below are the specifications outlining expected repeatability:

Procedure for a repeatability test performed:

  • 100 Klbf Load Cell specimen loaded in compression.
  • 12 test cycles of 4 mV/V hydraulically applied physical load and 1 mV/V Shunt Cal on two bridge legs.
  • Rb = 350 ohm, Rs = 88750 ohm, 20 ppm/°C, internal to load cell.
  • Measurements over 3 days.
  • Interface Gold Standard HRBSC instrumentation.

Results of test

  • Std Dev of physical load measurement: 0.004%.
  • Std Dev of Shunt Cal: 0.001% pos, 0.001% neg.

The topics that are illustrated in examples and discussion points for this white paper include:

  • Basic Bridge Circuit and Formulas
  • Resistor Examples
  • Tolerance
  • Cables
  • Errors
  • Permanent Zero Balance Shifts
  • Transducer Toggles
  • Instrumentation
  • Procedures for Repeatability in Tests

If this is a topic that of interest, download this technical reference guide for further exploration and calculation examples in shunt calibration.

As a leader in calibration services, Interface has an A2LA ISO 17025 accredited calibration lab located at the company’s headquarters in Arizona. Many depend on Interface for expert recalibration, which we recommend to do annually for optima maintenance. Our own calibration lab has the broadest capability and highest quality of calibration and repair services available. We understand the criticality of proper calibration and traceability and have the experience and expertise necessary to meet your exacting needs.

Additional Calibration Resources

Extending Transducer Calibration Range by Extrapolation

Additional Interface Calibration Grade Solutions

Gold Standard® Calibration System

This refreshed white paper is a tribute to the contributions of LaVar Clegg.

New Interface White Paper Highlights Turning an Active Component into a Sensor

The most common uses of force measurement in OEM (original equipment manufacturer) applications are when a force sensor is designed into a product that will be produced at mid to high volumes and provides real-time force feedback on certain product functions in use. Utilizing sensors as a feature enables data acquisition over time to monitor forces and understand how those forces effect product efficiency, safety, quality or all of these performance metrics. This ultimately is used to design a better product, in the current state and for future enhancements or to know when a product is performing best or risks breaking down.

Did you know that there is another application of force sensors in OEM applications that is playing a large role in the factory of the future? This is when we turn an active component into a sensor and use that data to create automated actions. This solution is used when there is a desire to take a moving component within a system and make it smarter, ultimately allowing it to make data-based decisions on its own.

For example, the manufacturing industry is using force sensors on machines within a production line that are responsible for picking components up for visual inspection. The sensor is integrated into the grabbing component and can tell the machine the exact force to use when picking up the component as not to damage it. This is a critical capability when dealing with expensive and delicate components that can break under too much force. In the past, a force measurement sensor would have been used only to test this functionality. When the sensor is designed directly into the machine, the user can both test beforehand and monitor and automate processes in real-time.

The need for this type of capability is growing rapidly amongst manufacturers across a wide variety of industry including aerospace and defense, industrial, medical, automotive, industrial automation, assembly and more. To further outline the potential for these types of solutions, Interface developed a new white paper that details  how sensor solutions for OEMs work with specific examples of the benefit of turning an active component into a sensor.

Included below is a brief intro to the recently released white paper. Get your copy by clicking on the link here. Additionally, if you’re interested in learning more about Interface solutions for OEM applications go here, or call us to speak to our OEM application experts at 480-948-5555. Ready to get started, let us know how we can help here.

WHITE PAPER EXCERPT

OEM SOLUTIONS: TURNING AN ACTIVE COMPONENT INTO A SENSOR

The age of industrial automation and big data is upon us. Manufacturers that fall behind in equipping their facilities and products with innovation that allows for automated processes, remote monitoring and better efficiency through technology, will quickly fall behind. This is due to the fact that automation helps to significantly improve process quality because it eliminates human error. It also creates long-term cost savings by speeding up several processes, or by helping to monitor products in use and in real-time to optimize performance and stability over time through better data collection.

Get your copy of the white paper to read more.

Special note, contributors to the white paper are Interface and sensor engineering experts, Brian Peters and Rob Fuge.

Additional Resources for OEM

Interface is a Critical Solutions Provider for OEMs

Making the Case for Custom Solutions Webinar Recap

 

The Role of Actuators in Force Measurement

One of the most common force measurement tests in the engineering and manufacturing world is called cycle testing. Cycle testing involves constant force being applied to a component or product over hours, days and even months. The goal is to test a product to find out how long it will last under the amount of force it will see in use in the real world.

Cycle testing is used throughout different industries. One of the most common applications of a cycle test is on something like airplane wings. The wings of an airplane are exposed to constant push and pull force to guarantee that they will hold up over many flights. Check out the wing fatigue testing application note here.

Another example is simple furniture tests, like a chair, to ensure it can withstand the weight of people of all sizes after years and years of use. These tests are designed to really push the limits on the product so engineers and manufacturers can confirm their designs and ensure safety and durability.

To carry out these tests, actuators are used to generate the force in cycle testing. An actuator is a component responsible for moving and controlling a mechanism or system. Actuators are small components that convert energy in a linear moment. There are a variety of different types of actuators including linear, rotary, hydraulic, pneumatic, and more. Each is designed to create force in different directions and on different axes.

Actuators are very important because force measurement is fed back into a control loop and the actuator allows you to accurately control how much force you’re putting on a test article. As a basic example, if you wanted to measure how much force it takes to close a door, you would use an actuator to provide the door closing force while the load cell measures the amount of force given off by the actuator.

Interface often integrates actuators into load cells for custom solutions to use in rigorous use and cycle testing. These types of custom solutions are used by equipment and product manufacturers, OEMs, as well as product design and testing labs. There is increasing frequency for OEMs to integrate actuators into load cells for testing their automated testing lines or products in use for continuous feedback.

For example, mobile device manufacturers use a miniature–sized load button load cell like the ConvexBT to test the pressure sensitivity of the touch screen. By using an actuator, phone manufacturers can set up an automated test lines with an actuator integrated in the load button load cell to test each screen as they go across a test line. You can read more about ConvexBT in this new white paper.

Another major application for actuators is in calibration machines. To test if a load cell is calibrated correctly, an actuator applies force to the load cell being tested and a calibration grade Gold Standard Load Cell simultaneously. These measurements can tell the user if the load cell needs to be recalibrated or not because the actuator allows the user to create a very precise force measurement. If measurements on the test load cell are not the same as the control load cell, the user knows it is off calibration and it’s time to schedule a calibration service.

From custom solutions to calibration, if actuators are necessary for your next project learn how Interface can work with you to find a solution that meets your precise needs.

Read more about Gold Standard Calibration Systems here.

Learn about how Interface is a preferred provider of OEM solutions here.

Interface Releases New ConvexBT White Paper

To meet the demand for the ever-evolving technological landscape, Interface is constantly gathers input from our customers across all industries and global network of test and measurement professionals to understand trends and sensor requirements for today and into the future. These valuable insights drive our new product introduction strategy and evaluations into how we can best solve your challenges.

In this new white paper, Ted Larson, VP Product & Project Management, and James Richardson, Mechanical Engineering Manager, highlight our recent introduction of a revolutionary load button load cell. We have captured the journey of our design story, along with detailing the innovative features, capacities, and benefits of our new ConvexBT Load Button Load Cell. Access the entire paper.

ConvexBT was introduced due to the growing trend of electronics miniaturization going on throughout nearly every hardware industry in the world. Original equipment manufacturers (OEMs) are packing more capabilities into smaller and smaller packages, and as product size shrinks testing sensors and equipment must downsize to match. ConvexBT is engineered to fit in tight spaces to test compression force with ultimate precision. It’s well-suited for industries like medical and industrial, where product miniaturization is prevalent throughout.

You can see some of the other recent ConvexBT highlights and use cases here:

[White Paper] ConvexBT The Most Innovative Load Button Load Cell

Advancing Load Button Load Cell Capabilities with ConvexBT 

Robotic Arm Application Note

Sensor Tips Magazine Highlight of ConvexBT

ConvexBT also includes some incredibly novel design choices that helps with rejection of misaligned loads, as well as temperature compensation. This makes it not only the most accurate load button load cell on the market, but also the most flexible. To learn more about ConvexBT and the unique design, capacity ranges, technical specification and more, download the white paper here.

Interface White Paper Highlights Contributing Factors to Load Cell Accuracy

Core to everything we do at Interface is within our foundational pillars of quality, service, accuracy, and innovation.

When it comes to precision load cells, our team of experienced engineers is fully committed to designing and building the best force measurement products in the industry. In fact, it is commonly known that with our published specifications, we often exceed them. It is why Interface products retain the industry-leading reputation for precision performance.

With innovation and imagination in our values, Interface team members look for ways to continuously test boundaries and explore possibilities, never losing sight of accuracy. We are students of the industry and understand the precise details and mechanics that go into force measurement product development to make our solutions are the most accurate on the market.

Critical to serving our customers is understanding the contributing factors of load cell accuracy and matching the products that best fit their requirements. There are many factors that can disrupt accuracy or skew data, such as the environment in which the load cell is being used, the type of load cell application use, even the mounting process.

All of these specifications must be correctly identified when choosing the right product for the project or product to ensure accurate results. To help our fellow community of engineers, manufacturers, and product designers to navigate the force measurement world, we have developed a new Contributing Factors to Load Cell Accuracy White Paper. Click here to get your copy today!

This Interface technical white paper includes a breakdown of the most critical factors of load cell accuracy, which includes:

  • Creep
  • Side and eccentric load
  • Temperature
  • Humidity
  • Mounting process

Chief Engineer Ken Vining provides valuable insights into some of the steps to take to avoid accuracy failure, such as:

  • Utilizing a golden part
  • Preventing load cell misuse
  • Setting a preventative maintenance schedule
  • Recalibration

This valuable resource provides a quick reference to understand load cells and the intricate details that come with their proper and accurate use. Included below is a link to access the downloadable PDF of the white paper. This technical white paper is an addition to our long-standing commitment to providing expert resources for those using or researching use case applications for load cells.

CLICK HERE TO ACCESS TO THIS NEW WHITEPAPER TODAY

The Interface Load Cell Field Guide is also available on Amazon.