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What is Proof Testing and Why Does it Matter?

Proof testing determines that the failure of critical components and parts could result in costly damage to equipment and even injury in severe cases. Our measurement products are designed to be used in proof testing applications.

In proof testing applications, testing and measuring an object’s performance under extremely intense conditions, often above the specified operational use, is critical. This allows testing engineers to ensure the object can handle its rated load and go above and beyond to understand maximum performance and failure.

Interface load cells and data acquisition systems are frequently used for proof testing, which determines the strength and integrity of a test subject by applying a controlled, measured load to it. It is commonly used for general test and measurement applications for stress, fatigue, and materials testing. It is frequently used by industries such as construction, natural resources, infrastructure, heavy machinery, and manufacturing to verify the strong point and durability of objects and structures.

Top Three Reasons Why Proof Testing Matters

#1 Safety: Proof testing qualifies and quantifies the safety of equipment and structures that sustain substantial loads. Identifying weaknesses or defects is preventative, as failure can result in catastrophe. Proof testing for safety is standard for applications that include lifting equipment, rigging gear, structural supports, and components in aircraft or spacecraft.

#2 Quality: Proof testing is common during quality control to verify that equipment or materials meet the required specifications. Whether it is the equipment used in manufacturing equipment or the materials used to construct a building, proof testing is essential in defining and measuring adherence to quality standards.

#3 Reliability: Proof testing provides accurate data on the performance and trustworthiness of the tested objects. By understanding how it reacts under stress, product engineers and testing labs can validate the lifespan of a specific component or product. It is also used to define preventative maintenance requirements. It impacts production lines, product versioning, inspections, and, ultimately, the customer’s user experience.

Proof tests provide vital safety and performance measurements for equipment or structures with significant loads. It helps to prevent accidents, improve reliability, and ensure the quality and integrity of the tested item. Consult Interface Application Engineers to determine the best measurement devices for proof testing.

Proof Testing Using Load Cells

Step One: Load Cell and Set-Up

The starting point is selecting the proper measurement tool, in this case, a load cell. Consider the object’s size, expected load range, and accuracy requirements. Choose a load cell with a capacity slightly exceeding the maximum anticipated load during use.

TIP! Use Interface’s Load Cell Selection Guide

Mount the load cell and object in a stable, controlled environment. Ensure proper alignment and distribution of force on the load cell. Connect the load cell to the data acquisition system with a dedicated readout unit, computer software, or data logger, depending on your needs.

Step Two: Pre-Test and Zeroing

Most test engineers will run a pre-test at low load. This is done by applying a small force and monitoring the readings to ensure everything functions correctly and there are no extraneous signals. Zeroing the load cell to set the baseline measurement without any applied force is important. READ: Why Is Load Cell Zero Balance Important to Accuracy?

Step Three: The Test

When you start the proof test application and data recording, most technicians will increase the load gradually. As defined in a test plan, follow a preset loading schedule, typically in increments, until reaching the desired test load. This could be a static load held for a specific time or a cyclic load simulating real-world conditions. Next, using your load cell measurement instrumentation, monitor the load cell readings, object behavior, and any potential visual deformations throughout the test.

Step Four: Analysis

The proof testing provides data that can be used to analyze the load-displacement curve, identifying any deviations from expected behavior, excessive deflections, or potential failure points. Based on the data, determine if the object met the strength and performance requirements or exhibited any unacceptable flaws. This is why a high-performance, accurate load cell matters in proof testing. It determines the quality of your analysis. As with any testing, it is valuable to maintain records of the test procedure, data, and conclusions for future reference or further analysis. This step is crucial for regulatory and product liability requirements.

The specific requirements and procedures for proof testing will vary depending on the product, equipment, structure, industry standards, and regulations.

Proof Testing Example

The most straightforward solution, where it is necessary to measure the load in a tension cable subject to safety considerations, is to enclose the load cell in a compression cage, which converts tension into compression. The compression cell is trapped between the two plates. Thus, the load cell’s only overload failure mode is in compression, allowing a motion of 0.001″ to 0.010″ before the load cell becomes solid. Even if the load cell is destroyed, the compression cage cannot drop the load unless it fails. Therefore, the cage can be proof-tested with a dummy load cell or an overload-protected cell, and the risk of injury to personnel is avoided.

TIP! This example is detailed in our Interface Load Cell Field Guide. Get your copy here.

The nature of proof testing applications requires a diverse line of performance measurement tools. Interface products extend from overload capabilities for our precision LowProfile load cells to complete DAQ systems. These options provide perfect testing solutions when necessary to push the limits on a product, component, or part.

ADDITIONAL RESOURCES

Enhancing Structural Testing with Multi-Axis Load Cells

Fatigue Testing with Interface Load Cells

Load Cells Built for Stress Testing

Benefits of Proof Loading Verification

Manufacturing: Furniture Fatigue Cycle Testing

Data AQ Pack Guide

Interface Solutions for Consumer Products

How Does Tensile Testing Work?

Tensile testing, also known as tension testing, is a type of mechanical test used to determine how a material responds to a stretching force. This test helps evaluate the mechanical properties of an object, such as metals, polymers, composites, and various other materials.

Performing a tensile test applies a load to specimen, and gradually increasing the load sometimes until failure or destruction. The tensile data is analyzed by using a stress-strain curve.

Interface stain gage load cells are commonly used in tensile testing due to their high precision and sensitivity. They work by measuring the strain in a material, which is directly related to the applied force. This strain data is then converted into force measurements. Learn more in Tension Load Cells 101.

Tensile testing is fundamental in test and measurement. It is used by researchers, testing labs, and engineers across industries including infrastructure, medical, manufacturing, aerospace, consumer goods, automotive, energy, and construction.

How Tensile Testing Works

Tensile testing is essential in materials science and engineering to understand the material’s behavior under tension and to ensure its suitability for specific applications.

First, a specimen of the material is prepared with a specific shape and dimensions. This sample is carefully controlled to meet testing standards based on the test plan.

Interface supplies a variety of load cells for these tests. The load cell is typically mounted in a tensile testing machine. The tensile test machine has two separate jaws, one of which will move away from the other at a controlled rate during the test. As it moves away, it is pulling on the material, stretching it until it the test is complete, or it breaks. This is also referred to as testing to failure or destruction. The controlled rate is called the strain rate, and materials will behave differently under different strain rates.

The specimen is then securely mounted in a testing machine, which is usually called a tensile testing machine or universal testing machine. The load cell is positioned in such a way that it bears the load applied to the specimen during the test.

Load cells are commonly used in tensile testing to measure and record the force or load applied to a specimen during the test. These sensor devices are crucial for accurately determining the mechanical properties of materials under tension.

The testing machine applies a pulling force (tensile force) to the specimen along its longitudinal axis. The force is gradually increased at a constant rate, causing the specimen to elongate.

As the tensile testing machine applies a pulling force to the specimen, the load cell measures the force in real-time. This force measurement is typically displayed on a digital instrumentation device or recorded by a data acquisition system.

The recorded data, including the applied force and the corresponding elongation or deformation of the specimen is usually plotted on a stress-strain curve for analysis. The stress-strain curve provides valuable information about the material’s mechanical properties, including its ultimate tensile strength, yield strength, Young’s modulus, and elongation at break.

Engineering Checklist for Tensile Test Plans

  • Identify the Purpose of the Tensile Test
  • Select the Material and Test Standard
  • Define the Mechanical Properties
  • Determine the Specific Mechanical Properties for Evaluation
    • Common properties include tensile strength, yield strength, modulus of elasticity (Young’s modulus), elongation, reduction in area, stress-strain curve characteristics
  • Establish Test Conditions
    • Include temperature, strain rate and testing environment
  • Define Sample and Specimen Requirements
  • Determine Measurement Accuracy Requirements
  • Prepare Instrumentation and Equipment
  • Plan for Data Recording and Reporting
  • Review Compliance Requirements and Safety Standards
  • Document Test Plan
  • Publish Verification and Validation Processes
  • Report Results

Defining measurement requirements for tensile tests by specifications is a crucial step in ensuring that the tests accurately and reliably assess the mechanical properties of materials.

Tensile Testing Terms to Know

Stress: Stress is the force applied per unit cross-sectional area of the specimen and is usually denoted in units of pressure. Stress is calculated by dividing the measured force by the cross-sectional area of the specimen. The load cell’s force measurement ensures that the stress values are accurate and precise. Simply, stress is the amount of force applied over a cross-cross-section.

Strain: Strain represents the relative deformation of the material and is the change in length (elongation) divided by the original length of the specimen. Strain is the amount of elongation in a sample as it is stretched or squashed.

Elastic Region: In the stress-strain curve, the initial linear region where stress is directly proportional to strain is known as the elastic region. Here, the material returns to its original shape when the load is removed.  As soon as a material is placed under any load at all, it deforms. Visually, the deformation may not be noticeable, but right away, the material is deforming. There are two types of deformation: elastic (not permanent) and plastic (permanent).

Yield Point: The yield point is the stress at which the material begins to exhibit permanent deformation without an increase in load. It marks the transition from elastic to plastic deformation.

Ultimate Tensile Strength (UTS): UTS is the maximum stress the material can withstand before breaking. It is the highest point on the stress-strain curve. If the material is loaded to its UTS, it will never return to its original shape, but it can be useful in engineering calculations, as it shows the maximum, one-time stress a material can withstand.  Load cells can detect the exact moment of specimen failure, such as fracture or breakage. This information is crucial for determining the ultimate tensile strength and other mechanical properties of the material.

Elongation at Break: Elongation at break is the amount the specimen stretches before it breaks, expressed as a percentage of the original length.

Load cells can also be used for real-time monitoring and control during the test. Test operators can set specific load or strain rate parameters to control the testing machine’s operation and ensure the test is conducted within specified conditions.

Load cells play a safety role by providing feedback to the testing machine’s control system. If the load exceeds a certain threshold or if the load cell detects an anomaly, the testing machine can be programmed to stop or take corrective actions to prevent damage to the equipment or ensure operator safety.

To discuss Interface products and experience in tensile testing, be sure to reach out to our global representatives in the field or contact us. We are always here to help!

Wireless Telemetry Systems 101

A wireless telemetry system enables the remote measurement and transmission of data from one location to another without the need for physical wired connections.  As technology advances, wireless telemetry systems are becoming increasingly sophisticated, reliable, and secure, enabling them to be applied in various industries and use cases for test and measurement applications.

Interface offers a wide range of wireless telemetry products. Components in wireless telemetry systems typically include sensors, transducers, instrumentation, communication modules, transmitters, displays, and printers.

The sensors measure tension, compression, weight, torque, or any other measurable quantity. Interface utilizes proprietary strain gage sensor technologies. Transducers convert analog signals from sensors into digital data that can be processed and transmitted to instrumentation.

Load cells are commonly used with wireless telemetry systems to measure and transmit data about the force or weight applied to an object. The load cell converts the force exerted on it into an electrical signal, which can then be wirelessly transmitted to a remote monitoring system.

The most popular Interface wireless load cells are our WTS 1200 Standard Precision LowProfile® Wireless Load CellWTSTL Wireless Tension Link Load Cell, WTSLP Wireless Stainless Steel Load Pin and WTSSHK-D Wireless Crosby™ Load Shackle. Interface works with our customers to develop engineered-to-order wireless solutions by request.

The analog output from the load cell may require signal conditioning to ensure accuracy and compatibility with the wireless telemetry system. Signal conditioning can also be required for amplification, filtering, and analog-to-digital conversion to convert the analog signal into a digital format.

Wireless communications modules are responsible for transmitting the data over wireless channels. It can use various communication technologies like Wi-Fi and Bluetooth, depending on the application’s requirements. The transmitter is responsible for wirelessly communicating the load data to the receiving end of the telemetry system.

There are various options for data collection. Data acquisition instrumentation is preferred in force measurement applications to collect vast amounts of data from sensors and transducers and prepare it for transmission.

At the receiving end of the telemetry system, another wireless communication module receives the data from the load cell’s transmitter. Once the data is processed, it can be analyzed, logged, and displayed on a user interface, such as a computer dashboard or a mobile app. This allows operators, engineers, or users to monitor the load values in real-time and make informed decisions based on the data

Interface Wireless Telemetry System (WTS) Solutions

The Interface Wireless Telemetry System (WTS) offers flexibility by eliminating physical connections, making deploying sensors in remote or challenging environments easier. Wireless telemetry systems offer more flexibility in sensor placement and system configuration.

The absence of physical wires allows for easier repositioning or adding new sensors without significant infrastructure changes. This setup is particularly useful in scenarios where it is challenging or impractical to use wired connections, such as in large-scale industrial applications or when monitoring moving or rotating machinery.

Wireless Telemetry System Components

Wireless Transducers

Wireless Transmitters

Wireless Receivers

Wireless Output Modules

Wireless Displays and Instrumentation

This is a list of what types of products are available. The Interface WTS offering continues to grow with added products to the line. Check out the Wireless Modular System Overview for more system details.

Wireless Telemetry System Benefits

The Interface WTS is a wireless telemetry system that transmits high-quality data to single and multiple devices. It offers a wide variety of benefits, including:

  • High accuracy: The WTS offers measurement accuracy of ±0.02% of full scale, ensuring you get accurate readings from your sensors.
  • High speed: A high-speed system can transmit data up to 1000 Hz.
  • High resolution: The WTS has a resolution of 10,000 counts, which means that you can measure even slight changes in force.
  • Multiple configuration options: The WTS can be configured to meet a wide variety of needs. You can choose from a variety of transmitters, output modules, receivers, antennas, and displays.
  • Easy to use: It is a modular system that can be easily expanded to meet the needs of your application. It is supported by our powerful WTS Toolkit configuration software, making it easy to set up and use.
  • IP-rated enclosures: The WTS transmitters and receivers are available in two different-sized enclosures that are rated to IP67, making them dustproof and waterproof.

A major benefit of wireless telemetry systems is the ability to adapt and expand by adding additional sensors or devices without the constraints of wires and cables. They are easy to integrate, and installation is fast for immediate benefits.

Wireless telemetry integrates with the Internet of Things (IoT) and cloud-based platforms, enabling centralized data storage, analysis, and easy access from multiple devices.

Read: Interface Wireless Telemetry System Review

Applications Using Interface Wireless Telemetry System Solutions

Aerospace: Wireless options are preferred for large projects that require careful movement and testing of aircraft, components, and systems. Providing flexibility in real-time data without the cable is a huge benefit. See these WTS solutions for Aircraft Engine Hoist and Airplane Jacking System

Industrial Automation: Load cells with wireless telemetry are commonly used in industrial environments for weighing large objects, such as in material handling, manufacturing, and logistics. Check out IoT Lifting Heavy Objects.

Medical and Healthcare: Wireless medical telemetry systems, such as wearable health devices, are used for patient monitoring. In medical settings, wireless load cells are used in patient lifts and hospital beds to monitor patient weight and movement. Learn more in our Patient Hoyer Lift application.

Agriculture: The agriculture industry uses WTS to monitor crop management programs and measure the weight of produce, animal feed, or livestock. Check out this use case: WTS Equine Bridle Tension System App Note.

Energy: The energy industry utilizes wireless load cells and telemetry products to remotely monitor oil wells, pipelines, and storage facilities. Check out Tank Weighing and Center of Gravity

Infrastructure: Civil engineers use WTS to assess the health and integrity of structures like bridges and dams. Monitoring loads on bridges and cranes to ensure safety and structural integrity. Check out Road Bridge Lift Monitoring.

Manufacturing: There are many examples of manufacturing WTS use cases. Wireless load cells are being used to monitor the weight of products as they move through the production line. This information can be used to ensure that products meet quality standards and identify any potential problems early on by fully utilizing the wireless telemetry capabilities.

Construction: In the construction industry, wireless load cells and telemetry systems monitor the load on beams and columns during construction to ensure that structures are safe and stable and to detect any potential problems before they cause an accident. Check out Jib Crane Tension Monitoring.

Transportation: In the transportation industry, wireless load cells are being used to monitor cargo weight on trucks and trains to ensure that loads are not overloaded and to comply with regulations. Read IoT Waste Management Container Weighing.

Automotive: The industry utilizes several machines and systems to test components used in the making of automobiles. Read how WTS is used in this brake testing application: WTS Brake Pedal Force Testing.

Entertainment: Protecting the artists, equipment, and attendees is top of mind for all venues. Wireless systems monitor environmental conditions, rigging, display mounts, and more. Read Multi-Stage Load Monitoring.

Integrating load cells with wireless telemetry systems provides a convenient and efficient way to monitor force or weight data remotely, allowing for real-time data analysis and enhancing the automation and safety of various processes.

If you are looking for a reliable and accurate wireless telemetry system, the Interface WTS is a great option. It is a powerful and versatile system that can be used in various applications. and industry use cases.

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