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How to Choose the Right Load Cell

Load cells are used to test and confirm the design of hardware, components, and fixtures used across industries and by consumers. From the structural integrity of an airplane to the sensitivity of a smartphone touchscreen, there’s a load cell available to measure force. In fact, here at Interface we have over tens of thousands of products used in force measurement, for all types of different applications.

How do engineers and product designers go about choosing the right load cell for a specific application or testing project?

Have no fear, Interface has put together a short guide on choosing the load cell that is right for you. This blog will cover the basic questions to answer when selecting a product, as well the most important factors affecting load cell choice.  Be sure to watch the online video, Load Cell Basics, that highlights key factors of consideration when choosing the right load cell for additional insights.

The basic questions you need to consider when selecting a load cell include:

  • What are the expected loads? What is the minimum and maximum load you’ll be measuring?
  • Is there any potential for higher peak loads than what you intend to measure? What are these expected peak forces?
  • Is it tension, compression, or both?
  • Will there be any off-axis loads? If so, what is their geometry? Do you want to measure them too?
  • Will it be a static, dynamic or fatigue measurement?
  • What is the environment in which you’ll be conducting your test? Will the load cell need to be sealed?
  • How accurate do your measurements need to be? Do they need to be at the highest accuracy of ±0.02-0.05% or within ±0.5-1%?
  • What additional features, accessories and instrumentation does your application require to complete a test?
  • Do you need standard electrical connectors or customized options? What about additional bridges or amplifiers?
  • How are you planning to collect and analyze the data output from the load cell?

Next, these are the most important factors affecting accuracy, which will have a heavy influence over the load cell you choose. It’s important to understand how your application and the load cell will be affected by each of the factors, which include:

  • Mechanical – Dimensions and Mounting
  • Electrical – Output and Excitation
  • Environmental – Temperature and Moisture

One of the most important factors in choosing the right load cell is understanding how it will be mounted for testing or as a component within a design. There are a wide variety of mounting types including threaded connections, inline, through hole or even adhesive. Understanding the mounting type that suits your application is critical to getting the correct data because a poorly mounted load cell will distort the results and can damage the load cell.

The mounting process also requires you to understand which direction the load is coming from, in addition to any extraneous loads that may be present. The load cell mating surface is also an important factor. For example, when using our LowProfile® load cells without a pre-installed base, the best practice is to ensure that the mating surface is clean and flat to within a 0.0002-inch total indicator reading and is of suitable material, thickness, and hardness (Rc 30 or higher). Also make sure that bolts are torqued to the recommended level.

If you’re conducting a fatigue measurement, it’s also important to address the frequency and magnitude of load cycles with your load cell provider. Factors to address include single mode versus reverse cycles, deflection versus output resolution, and material types. Interface offers a wide variety of fatigue-rated load cells that are perfect for these types of applications.

Another consideration in choosing the right load cell is the electrical signal. Load cells work by converting force into an electrical signal. Therefore, it’s important to understand the electrical output type necessary for your application, which could include millivolt, voltage, current or digital output. You can find the excitation voltage data on our website for each of our load cells. Additional considerations include noise immunity, cable length and proper grounding.

The environment is also a critical factor in ensuring accurate performance of your load cell. Interface provides load cells in a variety of material types including aluminum, steel, and stainless steel. Each material has a variety of properties that make them more suitable for different environments. For a more in-depth perspective on the different strengths and weaknesses of materials, please read our blog titled, Considerations for Steel, Stainless Steel and Aluminum Load Cells. For applications where load cells need to be submerged in liquid or enter an explosive environment, we also have a variety of harsh environment and IP rated load cells, in addition to load cells suitable for high humidity or splash resistance. Learn more about our intrinsically safe load cells here.

Learn more about choosing the right load cell in these online resources:

WATCH: Load Cell Basics with Keith Skidmore

WATCH: How to Choose a Load Cell with Design Engineer Carlos Salamanca

READ: Load Cell Field Guide

VISIT: Interface Technical Library

To learn more about choosing the right load cell for any application, connect with our applications engineers about the force measurement needs for your next project at 480-948-5555.

Test Stand Applications for Force and Torque

In the world of test and measurement, test stands are essential equipment for manufacturers and testing engineers. The test stand provides a host of different testing products in a single “cabinet-like” structure. These systems have been used for a long time to gather data on various functions of products during the product test phase.

Test stands works like a mobile test lab, hosted by a frame and containing one or more force or torque sensor components, software, and data acquisition instrumentation and accessories. Force stands are typically motorized or manual.  Motorized test stands, also known as mechanical or electrical, have the advantages of controlling performance by applying modes such as speed, cycles, and time into the testing procedure. The more advanced testing stands are frequently used for repetitive high-performance testing requirements, validating accuracy and quality. Manual test stands are used for simple testing protocols and frequently used in education programs.

There are a wide variety of testing devices and sensor products that are used as part of the entire test process. As parts roll off the production line, the test stand will sit at the end of the line where the test engineer can immediately load the product into the test rig. Test stands help to streamline the test process by providing all available test functions in a single, mobile application.

Interface is a supplier of choice for precision components of various capacities and dimensions for test stand configurations requiring precision and accuracy in performance. Interface load cells, torque transducers, and instrumentation equipment are commonly used in numerous product test applications by engineers, metrologists, testing professionals and product designers around the world.

Included below are a few examples of specific test applications and the Interface components used in the different style testing stands.

Linear Test Stand

In this example, an Interface customer wanted to add a crush test to their test stand to measure the force it took to deform a piece of material. Interface provided an Model 1210 Load Cell with an internal amplification of 0-10VDC output.

The load cell was installed into the load string of the customer’s load frame, and the scaled analog output from the load cell was connected to the customer’s test stand instrumentation. When the force levels reached the crushing point, the customer’s software was able to read the output of the amplified load cell and record the value.

See the application note for the Linear Test Stand here.

Motor Test Stand

In the quality control lab at a major automotive manufacturing company, a test engineer needed to test, record, and audit the torque produced by a new motor design under start load. Interface supplied the new AxialTQ® Rotary Torque Transducer that connected between the motor and the differential, on the drive shaft, that could measure and record these torque values.

Based on the data collected using the AxialTQ transducer, along with the AxialTQ Output Module, and a laptop, the test engineer was able to make recommendations to optimize the amount of torque created by the new motor design.

See the application note for the Motor Test Stand here.

Verification Test Stand

In this application, a customer needed a test stand application to verify that its load cell was in good, working order. Interface helped to create a solution that used a load cell to verify the customer’s load cell. The solution involved the customer’s supplied verification load frame and an Interface Model 1210 Precision LowProfile® Load Cell connected with a Model SI-USB 2-Channel PC Interface Module.

The customer was able to install their load cell and Model 1210 Precision LowProfile Load cell into the verification load frame. Applied forces were displayed and recorded by Model SI-USB PC Interface Module for review and record keeping on customer’s computer. This allows the customer to have a proven load cell verification test stand at their disposal to ensure its test load cell is always in working order.

See the application note for the Verification Test Stand here.

These are just a few examples of the different types of test stands that Interface can provide off-the-shelf or custom force measurement solution components. If your project involves a mechanical test stand and you are interested in learning more about adding force sensors, please contact our application engineers.