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I’ve Got a Load Cell – Now What? Episodes 5 and 6

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Reviewing the test and measurement video I’ve Got a Load Cell – Now What?, today we are highlighting Episodes 5 and 6 in the favored series.

These two installments highlight instrumentation and installation tips with best practice recommendations for the most popular load cell, the 1200 LowProfile, in addition to the 1100 LowProfile, SM S-Type and WMC Stainless Steel Miniature Load Cell products.

Once you have selected measurement device, it is equally important to review your instrumentation options. You will need a way of interpreting the output or the voltage from the load cell. This requires connecting to some type of instrumentation. If you already own an instrumentation device, you need to ensure that it is useable with any new force measurement device.

Interface offers a large line of instrumentation, from simple indicators to more complex multi-channel data acquisition systems used with multi-axis sensors, load cells and torque transducers. In addition to watching the video, be sure to check out our Instrumentation Selection Guide.

If you are selecting new instrumentation, there are a few questions to help qualify what will work best. For example, do you need a simple device to read analog outputs or advanced wireless instrumentation used with calibration-grade equipment? What type of software will you need to analyze the output data? Will you be connecting the instrumentation to a computer? As discussed in, I’ve Got a Load Cell Episode 5, here are some basic considerations for instrumentation.

Instrumentation Selection

Step 1: Electrical Wiring – Review the electrical wiring diagrams (also available on each product page). If you need to review the wiring based on engineered-to-order or custom options, contact our application engineers.

Step 2:  Signal Leads – Are you using a 4 or 6-wire configuration? A 6-wire lead provides sense. Some instrumentation options will support 6-wire signal leads. Most applications allow you to just pair with excitation.

Step 3: Cables – Identify the type of cable required with the right number of leads. For example, our standard 6-wire cable will support the sense function. We recommend shielded conductors when you order your cables.

Step 4: Grounding – Avoid ground loops in any wiring.

Step 5: Excitation Voltage – Review the sensor’s voltage of excitation on the datasheet to identify the load cell calibration. We recommend to properly match with the instrumentation’s capabilities in voltage with the load cell.

Step 6: Set-Up – Once you connect your instrumentation, you need to scale it. Review your options in the installation instructions. Some instrumentation options will take an mV entry and others will require a known load or shunt calibration. Reference your device’s calibration certificate.

In the I’ve Got a Load Cell, Now What? series Episode 6, we highlight some important diagnostics, installation tips and best practices. This video highlights examples of installation for some of our most popular load cells.

During the selection of your load cell, which usually begins with capacity and capabilities requirements, it is important to consider performance influencing factors and installation.

Use Case Considerations

  • Environmental Considerations and Exposure
  • Fatigue or Non-Fatigue
  • Overload Protection Needs
  • Off-Axis Loads
  • Dimensions
  • Mounting and Base Requirements
  • Output
  • Installation Set-Up

If you already have an older load cell, we recommend doing some back load cell health checks before putting it back into use. How can you evaluate the health of your load cell? You can do some simple diagnostics with load cells. Here are three recommended diagnostics:

  1. Zero Balance Check – If the load cell has been in use for some time, it is good to determine if there has been any potential overload or damage to the load cell. If the zero balance has shifted up or down from the nominal, that is an indication the load cell should be evaluated or repaired prior to using it in test applications.
  2. RCal or Shunt Calibration Check – Any shift from the specifications or certificate requires further evaluation.
  3. Bridge Evaluation – Some instrumentation will allow you to do a bridge evaluation. If you have any concerns on the performance or accuracy of the output, contact Interface to discuss tools that you can use to evaluate the bridge of the load cell.

The next section of Episode 6 highlights the 1200 LowProfile features, installation tips, and mounting options for assembly.

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.

Brian Peters and Elliot Speidell continue to detail the assembly and best practices for three additional products. You can watch more installation tips and recommendations related to the 1100 Model Ultra Precision Compression Only LowProfile Load Cells, SM S-Type Tension and Compression Load Cells and our popular WMC Sealed Stainless Steel Miniature Load Cell.

Interface publishes all our installation guides, diagrams and resources for support online. Go to our support resources for additional help.

Be sure to subscribe to our YouTube channel to get the latest videos on products, applications and user tips.

Interface Plays a Role in Testing Bicycles

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Interface sensors are used in a never-ending list of products, from heavy machinery to miniature medical devices. In the spirit of the Olympics, we thought we would share how our force and torque technologies are used in the test and measurement of bicycles, whether used for extreme off-road racing or speeding around the track. Interface has a role in helping to get bikes on the road and performing at optimum speeds.

Road, mountain and e-bikes present a fantastic use case for our products because everything from the force a rider puts on a bike’s suspension, shocks and frame when sitting on it, to the torque of the pedals and tires need to be carefully tested before a bike is ready for action. In the application notes below, we outline different parts and kinds of bikes that utilize measurement testing in design and actual use, along with the specific Interface force sensors used in each case.

Mountain Bike Shock Testing

In this application example, when a manufacturer wanted to test the durability of the forks on the front of their bikes, the rear shocks, front suspension, and ensure that the bikes shocks absorption is working properly for bike riders, we had a solution. Interface suggested installing the 1000 High Capacity Fatigue-Rated LowProfile™ Load Cell in a fatigue frame using the company’s bike forks. The forks undergo a fatigue test for several hours. Test results from the 1000 High Capacity Fatigue-Rated LowProfile™ Load Cell will be sent to the INF-USB3 Universal Serial Bus Single Channel PC Interface Module where the customer can view, log, and graph the results on their PC computer or laptop with provided software. Using this solution, the customer was able to test the bike’s front and rear shocks using Interface’s products. They determined if there were any weak spots in the forks or if it was working properly.

E-Bike Torque Measurement

e) manufacturer needed to test the torque on their electronic bicycles. They also needed a torque sensing system that measures how much force the bike rider is pedaling onto the pedals, because this determines how much electric power the bike’s motor generates. To address this challenge, Interface suggested installing the Model T12 Square Drive Torque Transducer where the pedal assist sensor would normally be. The T12 Square Drive Torque Transducer’s results could then be recorded, graphed, and logged using the SI-USB4 4 Channel USB Interface Module when connected to the customer’s PC. This allows the e-bike manufacturing company to successfully test the torque on their electronic bicycles with Interface’s products and instrumentation.

Bike Power Pedals

For a bike manufacturer testing the functionality of its power pedals, Interface supplied a full wireless system solution to measure how much force the cyclist pushes down onto the bike pedals. The solution included four Model SML Low Height S-Type Load Cells installed within the bike’s pedals. The four SMLs were paired with our Wireless Telemetry System components, two WTS-AM-4 Wireless Strain Bridge Transmitter Modules, which transmit the force data from the cyclist to the WTS-BS-6 Wireless Telemetry Dongle Base Station Dongle connected to the customer’s PC or laptop. Interface also provided the software needed with their wireless products. Using this system, the bike manufacturer was able to measure the pedal power applied by the cyclist. The customer was also able to measure and log the data wirelessly transmitted to their PC computer.

Bike Load Testing

In this example, another mountain bike manufacturing company wanted a system that measures their bike frames load capacities and vibrations on the frame, and to ensure the bike’s high quality and frame load durability during the final step of the product testing process. Interface suggested installing Model SSMF Fatigue Rated S-Type Load Cell, connected to a WTS products, the WTS-AM-1E Wireless Strain Bridge, between the mountain bike’s seat and the bike frame. This measured the vibrations and load forces applied onto the bike frame. The results are then captured by the WTS-AM-1E and transmitted to the customer’s PC using the WTS-BS-6 Wireless Telemetry Dongle Base Station. Using this solution, the mountain bike manufacturing company was able to gather highly accurate data to determine that their bikes met performance standards through this final testing.

Bike Frame Fatigue Testing

Fatigue testing is critical for bike design engineers. Our customer wanted to perform a fatigue test on their bike frames and analyze the strength of their bike frames in order to ensure durability and high-quality standards, turned to Interface for a solution. We suggested installing Model 1000 Fatigue-Rated LowProfile™ Load Cell to the customer’s bike frame fatigue tester. This load cell provides the customer with highly accurate results through the fatigue cycling. These results are collected using the INF-USB3 Universal Serial Bus Single Channel PC Interface Module and displayed on the customer’s PC or Laptop with Interface’s provided software. With this solution, the bike manufacturing company successfully had their bikes undergo fatigue frame testing, receiving highly accurate results with Interface’s load cell and instrumentation.

This deep dive into bicycle testing is just the beginning in demonstrating how many applications of Interface products can be used to improve the quality and reliability of the final design. When you consider bicycles, testing is critical whether it’s being used in the Olympics, for recreation or even transportation. Bicycle safety is fundamental to any design. Testing the performance and durability are essential before any bicycle is approved to be used on the road.

For a preview of all the application we have and can possibly work on, continue following the Interface IQ Blog at http www.interfaceforce.com/blog/. Each month we provide analysis and insight on new and interesting use cases and application examples.

Load Cell Test Protocols and Calibrations

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In the Interface Load Cell Field Guide, our engineers and product design experts detail important troubleshooting tips and best practices to help test and measurement professionals understand the intricacies of load cells and applications for force measurement devices. In this post, our team has outlined some helpful advice for testing protocols, error sourcing and calibrations.

The first step in creating test protocols and calibration use cases is to define the mode you are testing. Load cells are routinely conditioned in either tension or compression mode and then calibrated. If a calibration in the opposite mode is also required, the cell is first conditioned in that mode prior to the second calibration. The calibration data reflects the operation of the cell only when it is conditioned in the mode in question.

For this reason, it is important that the test protocol, which is the sequence of the load applications, must be planned before any determination of possible error sources can begin. In most instances, a specification of acceptance must be devised to ensure that the requirements of the load cell user are met.

Typical error sources in force test and measurement are usually identified as being related to:

  • Lack of protocol
  • Replication of actual use case
  • Conditioning
  • Alignment
  • Adapters
  • Cables
  • Instrumentation
  • Threads and loading
  • Temperature
  • Excitation voltage
  • Bolting
  • Materials

In very stringent applications, users generally can correct test data for nonlinearity of the load cell, removing a substantial amount of the total error.  If this can’t be done, nonlinearity will be part of the error budget.

An error budget is the maximum amount of time that a technical system can fail without service level consequences. In force test and measurement, it is sometimes referred to as uncertainty budget.

Nonlinearity is the algebraic difference between output at a specific load and the corresponding point on the straight line drawn between minimum load and maximum load.

Nonrepeatability is essentially a function of the resolution and stability of the signal conditioning electronics.  Load cells typically have nonrepeatability that is better than the load frames, fixtures and electronics used to measure it.

Nonrepeatabillty is the maximum difference between output readings for repeating loading under identical loading and environmental conditions.

The remaining source of error, hysteresis, is highly dependent on the load sequence test protocol.  It is possible to optimize the test protocol in most cases, to minimize the introduction of unwanted hysteresis into the measurements.

Hysteresis is the algebraic differences between output at a given load descending from maximum load and output at the same load ascending from minimum load.

There are cases when users are constrained, either by requirement or product specification, to operate a load cell in an undefined way that will result in unknown hysteresis effects. In such instances, the user will have to accept the worst-case hysteresis as an operating specification.

Some load cells must be operated in both tension and compression mode during their normal use cycle, without the ability to recondition the cell before changing modes. This results in a condition called toggle, a non-return to zero after looping through both modes. The magnitude of toggle is a broad range. There are several solutions to the toggle problem, including using a higher capacity load cell so that it can operate over a smaller range of its capacity, use a cell made from a lower toggle material or require a tighter specification.

ONLINE RESOURCE: INTERFACE TECHNICAL INFORMATION

For questions about testing protocols, conditioning, or calibration, contact our technical experts. If you need calibration services, we are here and ready to help.  Click here to request a calibration or repair service today.

Testing for Commercial Drones and Parcel Delivery

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Drone parcel delivery, and the use of drones in general, has expanded rapidly throughout the world. A technology that was once relegated to science fiction and imagination is becoming a real-world asset and making a huge impact on many commercial use applications in military and defense, consumer goods, logistics and inventory management, industrial automation, construction, security, agriculture, healthcare, imaging and surveying, as well as shipping and fulfillment.

To give you an idea of the impact of drones, take a look at recent numbers published by the FAA on registered drones in the U.S.:

  • 1,710,159 Drones Registered
  • 495,909 Commercial Drones Registered
  • 1,210,751 Recreational Drones Registered
  • 195,346 Remote Pilots Certified

There is a significant role for test and measurement as well as embedded sensors in this growing industry, which is expected to reach of $6B in size in the next few years. Load cells play a huge part in the design and development of this specialized aircraft technology and ongoing monitoring while in flight. Drones are classified as unmanned aerial vehicles. Basically, an aircraft without a human pilot. Successful operation of a UAV is dependent on a system, including the vehicle, a ground-based controller, and communications components, all of which must pass rigorous performance testing standards and constant data feedback.

The knowledge and tools we apply to test and measure airplanes and spacecraft performance can be transferred at a smaller scale to drones. Drone OEMs need to collect data points on thrust and velocity in test, and they also need to collect real-time sensor data on drones in-use. In fact, a large variety of sensor types are used for drone applications, including: force sensors, gyroscopes, barometers, and accelerometers.

Most recreational drones have passed significant testing during the engineering and design phase to ensure safety for anyone on the ground. Early applications and adoption sparked immediate regulation and safety requirements. We are now seeing the fastest expansion of this technology into commercial use. The future of drone technology for wide-scale business use has several of the world’s largest companies engaged in expansive development and deployment in use of UAVs for package delivery, including Alphabet (Google), Amazon, UPS, CVS and Walmart.

Commercial applications require substantially more rigorous testing in all use cases, in particular for transportation of objects. Most developed countries have defined commercial use requirements and regulations, such as the FAA in the U.S. Not only is the safety of those on the ground important critical, so is protecting the value of the goods in transport.

In demonstrating how force measurement solutions are used with drone technology, Interface created animated application note showcasing how a force solution is necessary for real-time monitoring of drones used in the shipping and fulfillment markets. Testing beyond flight, there is a level of complexity present when you introduce the weight of a package to a drone.

DRONE TESTING USE CASE

Customer Challenge:

A customer approached Interface to deliver a force solution capable of weighing a “payload” and using that data in real-time to tell the propeller motors to compensate for weight shifting or uneven weight distribution. The purpose of the force solution was to help the drone lift the payload and fly normally to reach its destination.

Interface Force Measurement Solution:

To solve this challenge, Interface supplied four WMC Sealed Stainless Steel Miniature Load Cells, which were used to measure the weight of the payload and detect weight shifting and distribution in flight. As shifting and uneven distribution occurred, the load cells send a signal to the necessary propeller motors to compensate.

How it Works:

The four miniature load cells are connected independently to each of the four landing gear legs. The load cells are then connected to the drone’s processor, which allows the load cell to communicate the weight of the payload and store the information. As the drone flies and weight shifts, the load cell can then relay the information to the processor in real-time so that the individual motors increase in RPM to balance the shifting weight.

Subscribe to Interface’s YouTube Channel to see our latest animated application notes. This new series of animated application notes give viewers a better sense of how force measurement products are applied to real-world challenges to collect and analyze data. So far, we have produced three animated application notes, which we have linked below:

 

Interface Solutions for Industrial Markets

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The industrial market is vast. The industry classification covers everything from manufacturing and assembly to mining and agriculture. The highly regulated environments involved in industrial applications often require advanced equipment and technologies for product design and development, as well as after market performance management. Force and torque products are critical sensor components used in industrial applications.

Interface has been a partner to industrial customers for more than 50 years. We engineer, build, and supply force and torque sensors and acquisition devices designed to provide industrial engineers and manufacturers with high quality data that monitors and confirms the design and in-action processes of their equipment. Applications for industrial markets involve everything from heavy machinery to weighing solutions. The accuracy of these devices is critical to high-quality outcomes, low-costs and most importantly, worker safety.

INDUSTRIAL APPLICATIONS 

An example of an industrial process that requires an accurate force sensor is a crane application used in lifting heaving objects. Interface engaged with a customer who needed to measure the lifting capabilities of a crane using an Interface load shackle. The purpose of the shackle was to ensure the crane wasn’t lifting more than it could handle, putting worker safety at risk and potentially damaging the machine.

Interface model WTSSHK-B Wireless Load Shackle was connected to a crane load string to measure forces. A model WTS-BS-1-HA Battery Powered Handheld Display was used to wirelessly receive load information and display results. Using this solution, the customer was able to successfully measure lifting and reading weight wirelessly on a handheld display while the crane was in action.

Another great example of the industrial industry’s use of force applications can be seen in manufacturing automation. One of the growing trends in marketing automation is the use of robotics to replace repetitive human tasks. Robotic arms are often found on assembly lines and they carry out a single task over and over. If the robotic arm isn’t properly calibrated, it can ruin an entire production line and lead to significant losses. To qualify the accuracy, many OEM’s use load cells and torque transducers to continuously measure the intricate movements of a robotic arm.

One Interface customer used a robotic arm to close packaging on a production line. If the arm wasn’t accurate, it could apply to much force and crush the packaging or not close the packaging as intended, leading to losses in shipping.

Interface supplied a 6-Axis Load Cell with a model BX8 Data Acquisition and Amplifier System. The Interface Multi-Axis 6-Axis Load Cell was able to measure all forces and torques on every axis and the BX8 8-Channel Data Acquisition System was able to log, display, and graph these measurements while sending scaled analog output signals for these axes to the robot’s control system.

READ MORE HERE: FORCE MEASUREMENT IS REDUCING WASTE AND AUTOMATING THE CONSUMER PACKAGING INDUSTRY

Another consideration for specialized industrial applications is in harsh environments. There are hundreds of thousands of engineers and manufacturers that spend their days working in these environments. Whether its operating inside of facilities with large machines and intricate moving parts, working hundreds of feet in the air repairing a bridge, or deep within a mine shaft, these professionals put themselves in danger every day by the nature of their work. As engineers and manufacturers, many of us are also tasked to solve for safety challenges and keep these professionals protected in any environment.

One of the ways we contribute to industrial safety is with the development of our Interface Ex Rated Load Cells, also known as Interface Intrinsically Safe Products. These specialized load cells and force measurement solutions are designed and manufactured so that the materials and electronic components are safe for use in hazardous gas and dust environments when installed per applicable installation instructions. These components are designed for those applications found in dangerous environments in particular industries like oil and gas, mining, aerospace, automotive and more.

The applications for industrial vary widely because the industry is diverse. Interfaces designs and manufacturers force and torque products for hundreds of different industrial use cases and applications every year. Our team of engineers can even create custom solutions for new and innovative industrial requirements. Included below are examples of some of the products typically used by our industrial customers.

  • 2400 Load Cell Series – The 2400 is a stainless-steel load cell designed for applications requiring a hermetic seal for use in general industrial applications.
  • 3200 Load Cell Series – The 3200 precision stainless steel load cell series has all the features of the Interface Model 1200 LowProfile® (one of Interface’s most popular products) and in addition it is stainless steel and hermetically sealed for harsh applications.
  • SSMH Load Cell Series – Model SSMH S-type load cell provides a suitable force measurement sensor for applications in coal mining and transfer and other heavy industries where explosive dusts and environment conditions are potentially explosion-hazard rated. SSMH capacities available that provide intrinsically safe certification.
  • Stainless Steel Load Buttons – Interface’s load button load cells are designed for customers who require the measurement of forces in a very confined space. They are designed to provide the most accuracy in as little space as possible.
  • 5400 Series Reaction Torque Transducer Series – Model 5400 series features a rugged flange-style designed with thru-holes, low deflection, high torsional stiffness and the ability to withstand large overhung moments.
  • Wireless Telemetry System (WTS) – High accuracy, high quality measurement is interfaced with simple yet powerful configuration and monitoring software. The WTS gives sensor manufacturers and integrators the complete flexibility to build their own sensor modules around it. The system easily replaces wired systems, reducing installation and maintenance costs.

These are just a few examples of Interface applications notes and products designed for industrial applications. For more information on Interface solutions design for the Industrial industry, contact our experienced application engineers.

 

Introduction to Interface Application Notes

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Interface has a long history of sharing valuable resources to help our fellow colleagues and customers with various use cases for test and measurement applications. Whether it be with our in-depth technical library, the Interface Load Cell Field Guide, free access to design files for our breadth of products, or industry case studies highlighting how our customers use Interface products. Access to all of these resources is available on Interface’s website www.interfaceforce.com.

A frequently visited area of these online resources is our Interface Application Notes archive. These resourceful explainers are of interest to engineers, new product designers, metrology and engineering students, as well as T&M industry professionals.

Interface created a large collection of App Notes to showcase how Interface load cells, torque transducers, accessories and instrumentation are used by OEMs and for various test and measurement projects across all types of industries.

Each Interface App Note has the following details:

  • Name of the App Note with Primary Product
  • Industry
  • Summary of the Application Use Case Need or Challenge
  • Interface Solution
  • Results
  • Materials
  • How it Works
  • Visual Representation of the Application

Interface App Notes are great conversation starters. They help to showcase how various Interface products and systems are used across all types of industries including medical, automotive, energy, industrial automation, consumer products testing, and aerospace. Additionally, several application notes highlight specific test and measurement lab projects.

Interface Top 10 Application Notes

  1. Race Car Suspension Testing
  2. Aircraft Wing Testing
  3. Surgical Stapler Force Verification
  4. Drone Parcel Delivery
  5. Bluetooth Brake Pedal
  6. Medical Bag Weighing
  7. Seat Testing Machine
  8. Industrial Automation Friction Testing
  9. Vascular Clamp Testing  
  10. Bolt Fastening and Torque

We have many more for you to check out. Visit the entire library of Interface Application Notes here. We are adding new application notes on a regular basis, so check back frequently.

Be sure to check out the full line of Interface solutions here. If you have questions or would like to talk with our application engineering experts, drop us a note or give us a call.