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.


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

Unlocking the Power of DAQ Webinar Recap

Interface hosted a technical seminar on the topic of data acquisition systems. With the demands for more data and faster processing with requirements to connect multiple devices in testing environments, there is an increasing need for high accuracy DAQ systems. Keith Skidmore and Dave Reardon detail the basics of DAQ, trends, products, software options and answer to questions in the webinar, Unlocking the Power of DAQ.

To start, a data acquisition (DAQ) system consists of hardware and software components designed to collect, process, and analyze data from various sources and convert it into digital format for further analysis and storage.

Components of DAQ Systems

  • Input:  Sensors (Ex: Force, Torque), Digital Signals (Ex: DIO, Counters), Timing Signals (Ex: IRIG, GPS) and Serial Streams (Ex: RS-232, RS-422)
  • Signal Conditioning Circuitry: Excitation, Amplifier, Voltage Offsets, and Filters
  • Analog-to-Digital Converters (ADC)
  • Digital-to-Analog Converters (DAC)
  • Hardware and Software for processing, analyzing, display and recording
  • Output Signal: prior to ADC, after DAC, or even after processing

Analog data acquisition systems acquire and process analog signals. Analog signals can include sensors that measure load, force, torque, strain, temperature, pressure, voltage, current, and many other physical or electrical qualities.  Digital data acquisition systems acquire and process digital signals. Digital signals can include on and off states, counters, serial streams, text data, video, GPS signals, and other advanced options.

 Key Considerations for DAQ Systems

  • Features
    • Supported range of inputs mV/V, VDC, mA, partial bridge, encoder, pulse, frequency
    • Included software and related functionality
  • Form factor
    • Bench top, rack mount, portable, ruggedized and others
  • Sample rate
  • Connectivity
  • Power supply
  • Channel count and cost per channel

Interface DAQ Products

Interface offers a range of solutions for DAQ systems. The top products for DAQ include:

During the webinar, Keith and Dave detail a series of product groups for the Interface Data AQ Packs.

Data AQ Pack Brochure

Watch the webinar and learn more about product options, software, applications and best practice tips.

Interface Instrumentation Definitions

The new Interface Instrumentation Selection Guide is a great way to get started in choosing the right instrumentation for your next project or lab. To serve as additional resources, here are key instrumentation definitions that can also help you make the best decision regarding the type and model of instrumentation that will work best with your sensor.

Instrumentation Selection Guide Definitions

A Wheatstone bridge-based sensor, such as a load cell, requires excitation voltage to operate. The excitation voltage is typically 10V; however, many instruments supply lower voltage, an 2.5V, 5V, and others. Since these sensors are ratiometric, Interface instrumentation devices are designed to pair with these types of sensor products.

The output signal from a load cell is expressed in terms of mV output per V of excitation, at capacity. For example, a 100 lb capacity load cell rated for 2 mV/V output will have 20mV output at 100 lb, when excited with 10V. Because the output signal is directly affected by input voltage, it’s important to maintain a stable excitation voltage, which our instrumentation does.

Signal Conditioners
A signal condition provides stable excitation voltage to the sensor and amplifies the low-level sensor signal to a high-level output such as +/-5V, +/-10V, 0-20mA, 4-20mA, 0-5V, or 0-10V.
Many of our products include filtering, which can help reduce noise in the output signal.

Data Acquisition Systems
A complete data acquisition system consists of DAQ hardware, sensors and actuators, signal conditioning hardware, and a computer running DAQ software. Interface provides DAQ instrumentation that are ideal for completing a sensor-based system. Many data acquisition systems require high-level inputs such as +/-10V and don’t work very well with low level mV signals. Interface instrumentation solutions do work well with DAQ systems. The DAQ doesn’t necessarily supply a stable excitation voltage like the Interface sensors do.

Interface Modules
An interface module converts the low-level mV/V sensor signal to a digital format that can be transmitted to a computer, (PC or laptop). Popular interface modules provide USB, wireless USB, or Bluetooth data transmission. Software is normally provided and allows data display, logging and graphing. The interface modules are commonly used when data needs to be logged to computer and you are not using an existing data acquisition system. The interface module advantages over standard data acquisition is ease of use and they are normally plug-n-play. Considerations when selecting this type of instrumentation include bit resolution, number of channels, sample rate, software features and type of output.

Interface indicators provide stable excitation voltage and converts the sensor signal to a digital display. Commonly available features include analog or digital output, selectable digital filtering, peak and valley monitoring and set point outputs. Things to consider when selecting an indicator are internal sample rate and update rate of analog output.

Wireless Telemetry System (WTS)
Wireless is very popular today. Interface’s Wireless Telemetry System is easy-to-use providing wireless data communication between a load sensor and a receiving indicator. The WTS is capable of receiving multiple inputs and is fully compatible will all Interface force sensors. The WTS comes calibrated, tested and ready-to-run. The charge lasts up to three months using AA batteries.  You can see the complete WTS and Bluetooth Telemetry System comparison here.

When selecting the type of instrumentation you need to pair with your measurement device, some additional things to consider are power supply requirements, amount of filtering, fixed or adjustable filtering, input range, scalability and zero adjustment range. Our instrumentation can accommodate these requirements. To get started on picking the instrumentation solution that fits your requirements, go to the Interface Instrumentation Selection Guide.

We’ve provided a quick visual reference of Interface’s instrumentation types and correlating models.

All Interface Instrumentation product details are listed by product model name. You can find product specifications, as well supporting datasheet for each product by going here.


Additional Resources

Instrumentation Analog Versus Digital Outputs

Introducing New Interface Instrumentation Selection Guide

Advancements in Instrumentation Webinar Recap

Recap of Inventive Multi-Axis and Instrumentation Webinar

Recap of Instructional on Instrumentation Webinar

Digital Instrumentation Brochure

Instrumentation Brochure


Interface Load Cell Indicators 101

At Interface, our claim to fame is that we offer the most accurate and reliable force measurement devices on the market, from load cells to torque transducers and everything in-between. However, no test is complete without the system used to gather the data to evaluate performance results. That’s why we provide a wide variety of instrumentation solutions that include signal conditionersoutput moduleshigh speed data loggersportable load cell indicators, and weight indicators to complete any testing system.

Among the Interface instrumentation products, the most frequently purchased with a force measurement devices are our load cell indicators in various models including handheld, digital, wireless, multichannel, programmable, output modules, analog and bidirectional.

What is a load cell Indicator?

A load cell indicator is a high-accuracy device connected to the output of a load cell to amplify and display the value of the measured load force and weight. Load cell indicators are often needed where the force, load, or weight measurement needs to be visually displayed for the user and displaying the results on a PC is not feasible or desired in the testing environment. For example, testing in the field or confined spaces can make it impossible to connect directly to a PC. In these situations, indicators are used to quickly review and capture force data in real-time.

A few key benefits of load cell indicators include that they provide stable excitation voltage and converts force measurement sensor signals to a digital display. Commonly available features include analog or digital output, selectable digital filtering, peak and valley monitoring and set-point outputs. Additionally, each load cell indicator can be used to connect to four (or more) digital load cells and can display individual readings or the sum of all connected load cells.

Need a load cell indicator?

Interface offers a wide variety of load cell indicators in multiple configurations. Interface indicators come in single to multi-channel weight transmitters and can be found in handheld and portable designs. Things to consider when selecting an indicator are internal sample rate and update rate of the output. A few of our most popular indicators include:

9890 Strain Gage, Load Cell, & mV/V Indicator

Model 9890 is a powerful multipurpose digital load cell meter ideal for weight and force measurement applications. With a max current of 350 mA at 10 V, it can support up to 12 load cells making it perfect for multipoint weight measurement purposes. The dual-scale capability allows for displays in two different units of measure. See a demonstration video here.

9320 Battery Powered Portable Load Cell Indicator

Model 9320 is a bipolar 7-digit handheld meter featuring two independently scalable ranges, peak and valley monitoring, display hold, mV/V calibration, and a power save feature. Typical battery life exceeds 45 hours of continuous use and 450 in low power mode. IEEE1451.4 TEDS Plug and Play compliant.

482 Battery Powered Bidirectional Weight Indicator

Model 482 is battery powered, bidirectional, and comes in a NEMA 4X stainless enclosure. Standard options include 523,000 internal counts, 0.8-inch LCD 6-digit display and a measurement rate that goes up to 40 Hz. Available options include analog and relay outputs.

1280 Programmable Weight Indicator and Controller

The Interface 1280 Series programmable digital weight indicator with color touchscreen, web server view and multiple protocol types delivers uncompromising speed for today’s operations and expansive options for tomorrow’s requirements.

INF4-Ethernet IP Weight Transmitter and Indicator

The Interface INF4-Ethernet IP weight transmitter and indicator has a six-digit red LED display (8 mm height), space-saving compact design, four buttons for the system calibration, and a six-indicator LED.

See all the indicator options here.

Load Cell Indicator Application Note

The application note below provides an example of the benefit of a load cell indicator in real-world use within the medical industry.

A pharmaceutical tablet producer wanted to monitor the forces applied by the tablet forming machine to understand the relationship between raw material, die set, forming force, and motor-cycle speed. The goal was to improve productivity and efficiency of the tablet forming process while reducing losses, such as cracked tablets or voids, by adding a dimension of feedback that could be used to assign specific press adjustment criteria for given inputs.

An Interface Model WMC Sealed Stainless Steel Mini Load Cell (10K lbf Capacity) was mounted in the section of the downward press bar. The machine was modified to accomplish this. The load cell was then connected to a Model 9320 Portable Load Cell Indicator to collect the needed data.

The indicator was selected as the data collection device because a laptop could have interfered with the test cycle due to space restrictions. The output of the load cell was connected to the 9320 Portable Load Cell Indicator and set aside so that the cable did not interfere with the cycle and no snagging would occur. A cable tie was used to stow aside the cable and to ensure there was enough clearance for the entire cycle.

After analyzing the data, the tablet producer was able to quantify adjustment levels by monitoring which forces produced the most optimal results for a given cycle speed, die set, and raw material. Productivity and efficiency were greatly improved by the enhancement of the data feedback.

To learn more about Interface load cell indicators and for a complete list of products, you can download our instrumentation brochure here. You can also read more about instrumentation options in test and measurement in this post.

Multi-Axis Sensor Applications

For more than 50 years, Interface has proven itself as the premier provider of load cells, with the most accurate and reliable products on the market. As the technical landscape has evolved, we have invested heavily in new technology to suit the growing needs of our customers. One of the most important innovations we’ve brought to market over the past few years is our lineup of wide-ranging multi-axis sensors.

Interface Multi-Axis Sensors are designed to measure a multitude of forces and moments simultaneously with a single load cell sensor. These sensors provide multiple bridges that precisely measure the applied force from one direction with minimal crosstalk from the other axes.

Multi Axis Sensor 3AXX 3 Axis Load Cells -

Interface Multi-Axis Sensor 3-Axis Load Cell

Interface offers 3-axis, 6-axis, and axial torsion load cells, which provide the ultimate in force and torque measurement. We can measure forces simultaneously in three mutually perpendicular axes, with the 6-axis load cells also measuring torque around those axes. In addition, we offer multiple data acquisition and amplifier systems which make graphing, logging and displaying data easy enough for any experience level.

Our customers work in a wide variety of industries, and we are continually seeing new applications of our range of multi-axis sensors. These sensors are used in aerospace, automotive, medical and more.

The following application examples provide a clearer picture of the benefit of this force measurement and sensor technology.

Rocket Structural Testing – In rocket and aerospace testing, there are a million different considerations to ensure a proper launch. One of the vital force tests that need to be conducted is on the connection between the rocket and the launch vehicle. There are force and moment in multiple directions at the connection point. Interface Multi-Axis Sensors can be used to test not only the strength of the connection but also ensure a safe disconnection between the rocket and launch vehicle.

Drone Testing – One of the most interesting applications of our multi-axis sensors is in the drone industry and in areas of urban mobility. Our sensors are used to test the drone’s rotor. The drone will always pull on the sensor to create the most significant force; however, there is also a slight amount of moment that needs to be accounted for. We were able to calibrate a semi-custom load cell to account for both the large pull force and the small moment force to provide the most accurate data possible.

Prosthetics – Another impressive application of our multi-axis sensor technology is in the medical industry. We helped to test the multiple force and torque data necessary to build a strong and reliable prosthetic knee joint and spine. Each of these prosthetics has multiple motions on many axes. To measure the quality of the prosthetic and to ensure it doesn’t fail when implanted in a patient, medical OEM’s need to be able to collect data on each of these axes simultaneously.

The need for measurements on multiple axes has grown over the last couple of years because of the desire to use big data to create better products. Interface Multi-Axis Sensors provide the accurate measurements our customers need and the ability to collect those measurements simultaneously, which has created a significant boost in efficiency.

To learn more about Interface’s expanding lineup of multi-axis sensors and data acquisition systems, please contact our team of experienced Application Engineers or visit /product-category/multi-axis-sensors/.

Contributor: Keith Skidmore, Regional Sales Director at Interface