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Load Cell Mounting 101

Properly mounting a load cell ensures the sensor provides the most stable readings and accurate measurements. Although a load cell will function no matter how it is oriented and operated in tension or compression mode, mounting instructions are specific to each sensor model.

Interface provides complete product datasheets and drawings to locate the features for mounting. Our instructions include model, material, capacity, mounting holes, threads and dowel pins, and pilot specifications for live and dead-end use.

All load cells have a “dead” end and a “live” end. Commonly, the dead end is the mounting end directly connected to the output cable or connector by solid metal. Conversely, the live end is separated from the output cable or connector by the strain gage area of the flexure.

This concept is significant because mounting a cell on its live end makes it subject to forces introduced by moving or pulling the cable. However, mounting it on the dead end ensures that the forces coming in through the cable are shunted to the mounting instead of being measured by the load cell.

SPECIAL INTERFACE LOAD CELL MOUNTING TIP: The Interface load cell nameplate reads correctly when the cell sits on the dead end on a horizontal surface. Therefore, the user can employ the nameplate lettering to specify the required orientation to the installation team explicitly. For example, for a single-cell installation holding a vessel in tension from a ceiling joist, the user would specify mounting the cell so that the nameplate reads upside down. For a cell mounted on a hydraulic cylinder, the nameplate would read correctly when viewed from the end of the hydraulic cylinder.

WATCH: MOUNTING TIPS FROM OUR LOAD CELL BASICS WEBINAR

DEFINING YOUR MOUNTING REQUIREMENTS

Mechanical mounting is one of the most critical aspects determining your application’s success. This is a sensor-based decision, as load cell models have different features that can be used for various mounting requirements.

First, define how you will attach your load cells.  Are they going to be using threaded connections? Are you going to have the load cells press up against a surface? Are you using an actuator, rod-end bearings, or clevises?

Other considerations regarding mounting are the objects used to secure the sensor. Will you use adhesive? Will it be secured inline, or do you need a through-hole for mounting? Will you be using mounting plates, and what is the geometry of the plates? The material used and the stiffness of the mounting components can affect the measurement’s performance and accuracy. READ: Interface Sensor Mounting and Force Plates

The direction of the load will impact your decision on the best approach.  All load cells have a live end and a dead end. It is not a single direction; some live ends may be at the top or the bottom.  The live-end and dead-end design will influence your cable and wireless management.

If you apply torque when installing fasteners, it is important not to twist the sensor. Tip: Hold the load cell at the same end where you are installing a fixture to prevent damage to the device.

Load Cell Mating Surface Tips

  • The surface must be clean and flat
  • The mounting surface must be flat to 0.0002 total indicator reading
  • Suitable thickness and material
  • Recommended hardness of Rc 30 or higher
  • Mounting bolt torque according to specifications

Installation Care

Make sure the threaded connections are tight and preloaded, if possible. Pre-loading removes the system’s slop and prevents wear, which is critical when using the sensor for fatigue testing. It is also essential to pre-load to get the performance as designated in the calibration certification.

For compression loading, you want one flat surface and one radius surface. Make sure you only have one curved surface. Typically, the load cell will have a radius surface, so you will want to load it against a flat surface. Identifying the load point is harder if you have two flat surfaces. If you have two radius surfaces, they will tend to slide apart. This can create bending and be dangerous to the technician.

Interface offers load cells with and without bases. When supplied together, the base is engineered to be an appropriate and “matching” mating surface for the sensor.  If you are using a load cell without a base, it is important to mount it to something like the base in flatness, stiffness, and thickness so they do not deform under load. This is critical to get the most accurate measurement.

QUICK REVIEW: MOUNTING CHECKLIST

  • Load Cells not mounted by the manufacturer’s recommendations may not perform to the manufacturer’s specifications.
  • Make sure that mounting surfaces are clean, flat, and aligned.
  • Torque of all mounting hardware to specifications.
  • Always confirm the load cell orientation: the “dead” end on mechanical reference or load forcing source and the “live” end connected to the load to be measured. Typically, the dead end is the end closest mechanically to the cable exit or connector.
  • Use proper hardware (thread sizes, jam nuts, and swivels) to connect the load to the load cell.
  • It is fundamental to have one and only one load path.
  • This load path must be through the load axis of the load cell. This may sound elementary; however, it is a commonly overlooked problem.

Utilizing best practices in mounting is also extremely important. Deflections in the system can introduce errors and apparent crosstalk into the sensor measurement.

ADDITIONAL RESOURCES

Universal Load Cells 101

Mounting Tips for Multi-Axis Sensors

Mounting Plates

6A Mounting Tightening Torques

3A Mounting Instructions

Flange Style Load Cells and Torque Transducers 101

Basics on Load Cell Base Kits

LowProfile™ Load Cell Base Kits

 

 

Interface Cable Assemblies 101

Force measurement cables and connectors are far more integral than a cable. Unlike cables for many electronics, they are not just power or data transfer sources. Instead, cables and connectors play a significant role in the total force measurement systems.

Specific cables and mating connectors are used for different applications, environments, frequency and power requirements, and paired measurement devices. This includes sensor considerations as well as instrumentation.

What are cable assemblies? 

A cable assembly for a load cell essentially acts as the lifeline between the load cell and the analog output instrumentation, transmitting the electrical signals generated by the load cell to be interpreted and measured. It’s not just a simple cable but a carefully constructed unit designed to maintain signal integrity and protect against external interference.

Interface cable assemblies are used for connecting transducers to instrumentation. Our cable assemblies are designed for easy integration with Interface measurement devices and instrumentation. Interface cables maintain the specification of the product. We provide standard cable assemblies and custom lengths, depending on your application. Shielded cables are available from Interface. Our line of cables is part of the diverse line of Interface Accessories.

Cable Assembly Basics

  • Shielding protects the signals from noise and ensures accurate readings.
  • Twisted pairs are individual conductor pairs twisted together to reduce noise interference and crosstalk between signals.
  • The material and gauge are chosen to minimize voltage drop and signal loss over the cable length.
  • Durable jackets protect the internal components from physical damage and environmental factors like moisture and abrasion.
  • Mating connectors should be compatible with the load cell and instrumentation, often sealed to prevent moisture ingress.
  • Strain relief prevents damage to the cable near the connectors from pulling or moving.
  • Proper shield grounding is crucial for effective noise mitigation.

In essence, a load cell cable assembly is engineered to ensure the fidelity and accuracy of the load cell’s signal, ultimately contributing to reliable and precise measurements in your system. Remember, the specific design and features of the cable assembly can vary depending on the type of load cell, application requirements, and environmental considerations. C

Essential Tips for Selecting a Cable

  • Length: One of the most critical considerations when selecting the suitable cable for your application is cable length. Minimize cable length to reduce signal loss and maintain accuracy. Consider the extra length needed for routing flexibility; however, it is not recommended to use extra long cables if it is not necessary.
  • Temperature range: Ensure the cable is rated for your environment’s expected operating temperature range.
  • Moisture resistance: Consider waterproof cables for outdoor or wet environments to prevent corrosion and signal degradation.
  • Flexibility: Choose a cable with appropriate flexibility for your installation. Stiffer cables are more durable but more challenging to maneuver in tight spaces.
  • Shielded or unshielded? Choose shielded cables in environments with electrical noise from motors, power lines, or radio frequencies. Unshielded cables are sufficient for cleaner environments.
  • Twisted pair or single conductor? Use twisted pairs for improved noise rejection, especially in long cable runs. Single conductors are cheaper but more susceptible to interference.
  • Number of conductors: Match the number of conductors to your load cell configuration. 4-wire for basic setups, 6-wire for advanced measurements. Consult with your application engineer to define your requirements.

TIP: For constant voltage excitation, two effects of significance can affect accuracy. An effect on the sensitivity due to voltage drops over the cable length.  An effect on the thermal span characteristics of the load cell due to the change of cable resistance with temperature.

Cable Length Effects

If the load cell is purchased with a cable of any length, the sensitivity is determined with the installed cable in calibration, and this is not a problem. For load cells with connectors, or if a cable is added that is not designed for the exact use, there will be a loss of sensitivity of approximately 0.37% per 10 feet of 28 gauge cable and 0.09% per 10 feet of 22 gauge cable. This error can be eliminated if a six-wire cable is run to the end of the load cell cable or connector and used with an indicator with sense lead capability.

Temperature Effects

Since cable resistance is a function of temperature, the cable response to temperature change affects the thermal span characteristics of the load cell cable system. For 6-wire systems, this effect is eliminated. For 4-wire cables, the effect is compensated for in the standard cable lengths offered with the load cells if the load cell and cable are at the same temperature simultaneously. For non-standard cable lengths, there will be an effect on thermal span performance. The impact of adding 10 feet of 28 gauge cable is to cause a decrease in sensitivity with a temperature equal to 0.0008%/°F. For an added 10 feet of 22 gauge cable, the effect is to decrease the sensitivity by 0.0002%/°F. In some cases, it is tolerable to degrade performance since Interface standard specification is extremely tight. However, this can be a significant factor for long cable runs or high-accuracy applications. The best way to eliminate the problem is to run six wires to the end of the standard cable length and sense the excitation voltage.

Wireless Versus Cable Key Considerations

  • Type of Sensor – is there a wireless option?
  • Type of Sensor Output
  • Communication Protocol
  • Accuracy Impact 
  • Types of Errors Subject to Wireless Devices
  • Servicing Limitations with Power (Battery)
  • Line of Sight for Wireless
  • Data Rate Can Decline with Wireless Transmissions
  • Synchronization of Data

With a growing demand for wireless solutions, it is crucial to consider the results and environment before cutting the cable.

The application is vital in your cable evaluation. With a growing demand for wireless solutions, it is essential to consider the results and environment before cutting the cable. With an increasing demand for wireless solutions, it is vital to consider the results and environment before cutting the cable. Not all cables are the same. We can look at the oil and gas industry as an example of specific cable considerations. We have many oil and gas industry customers who need force measurement solutions to deal with the heat and pressure in a downhole application. The cables and connectors for this project often need custom braiding and coating to ensure the wiring won’t melt or corrode in this environment. We also have submersible solutions in which the connection between the submersible load cell and the connector must be sealed tightly to prevent water damage to the components.

At Interface, our accessories use only the highest-quality components and materials. Our engineers will also work with you to find the accessories that fit your needs. We can work with you to create a custom solution if we don’t offer the necessary connectors and cables in-house. We also provide various options depending on the data requirements, whether permanent monitoring or portable solutions, and different cables based on data type for the type of instrument.

To learn more about our cables, visit our accessories.

ADDITIONAL RESOURCES

Understanding Cable Length and Temperature Effects

Force Measurement Accessories 101

Accessories-Brochure-2

Why Is Load Cell Zero Balance Important to Accuracy?

Several factors go into the accuracy and consistent performance of a load cell. These factors include non-linearity, hysteresis, repeatability, creep, temperature, environmental effects, and zero balance.

Every Interface load cell’s design and specifications account for all these factors. Understanding each of these factors is important, especially considering the use case.

Specifications are detailed descriptions that outline the characteristics, features, and qualities of our products, systems, or services. Product specifications detailing performance, capabilities, capacities, and dimensions are included on all datasheets. Products have internal specifications tested during manufacture, typically with full traceability.

Zero balance is considered an electrical load cell specification value. It is essential to consider when selecting the type of load cell for any application.

Load cell zero balance is the signal of the load cell in the no-load condition. It is defined as the output signal of the load cell with rated excitation and no load applied. It refers to the amount of deviation in output between true zero and an actual load cell with zero load. It is usually expressed in the percentage of rated output (%RO). Zero balance is a test that can be done to understand calibration on a load cell.

Load cells constantly reset to zero after every measurement to maintain accuracy. If it does not, then the results will prove to be inaccurate. The zero balance must be within the error margin indicated on the calibration certificate. Interface sensors are typically +/-1.0%.

This is important to test because zero balance will tell you if a load cell is in working order or has been damaged or overloaded. A computed zero balance of 10-20% indicates probable overload. If the load cell has been overloaded, mechanical damage has been done that is not repairable because overloading results in permanent deformation within the flexural element and gages, destroying the carefully balanced processing that results in performance to Interface specifications.

While it is possible to electrically re-zero a load cell following overload, it is not recommended because this does nothing to restore the affected performance parameters or the degradation of structural integrity. If the degree of overload is not severe, the cell may sometimes be used at the user’s discretion. However, some performance parameters may violate specifications, and the cyclic life of the load cell may be reduced.

To perform a zero balance test, The load cell should be connected to a stable power supply, preferably a load cell indicator with an excitation voltage of at least 10 volts. Disconnect any other load cell for multiple load cell systems. Measure the voltage across the load cell’s output leads with a millivoltmeter and divide this value by the input or excitation voltage to obtain the zero balance in mV/V. Compare the zero balance to the original load cell calibration certificate or the datasheet. Every Interface product has a detailed datasheet available on the product page of the sensor.

ADDITIONAL TECHNICAL DEFINITIONS

Zero float is the shift in zero balance resulting from a complete cycle of equal tension and compression loads. It is normally expressed in the units of %FS and characterized at FS = Capacity.

Zero stability is the degree to which zero balance is maintained over a specified period with all environmental conditions, loading history, and other variables remaining constant.

Learn more about the specification values that define load cell accuracy in this short clip from our  Demystifying Specifications Webinar.

Get your free copy of the Interface Load Cell Field Guide to learn more about factors affecting load cell accuracy. If you are concerned about the zero balance of your Interface load cell due to inaccurate results or recent damage, please get in touch with us at 480-948-5555.

ADDITIONAL TECHNICAL RESOURCES

Interface Technical Support Information and Troubleshooting

Interface Product Selection Guides

Interface Installation Guides and Operation Manuals

Interface Software and Drivers

Interface Product Catalogs

Interface 101 Blog Series and InterfaceIQ Posts

Interface Industry Solutions and Applications

Interface Recorded Webinars

Load Cell Simulator 101

A load cell simulator is a device that mimics the electrical signal of a load cell. This allows technicians to test and calibrate measurement systems without applying physical force or weight to the load.

By generating a range of input signals using a load cell simulator, technicians can assess the instrument’s linearity, sensitivity, and accuracy, ensuring it meets the required specifications.

The two most common uses for load cell simulators are troubleshooting and calibration. Load cell simulators can effectively troubleshoot force measurement systems, detecting and isolating faults or malfunctions. By simulating various load conditions and injecting fault conditions, technicians can pinpoint the source of the problem, such as a broken wire or a faulty load cell.

Load cell simulators are essential for calibrating force measurement devices, ensuring they accurately translate applied force into a measurable electrical signal. By generating a controlled force signal, technicians can compare the displayed value to the known input signal, identifying discrepancies and adjusting the device accordingly.

Interface load cell simulators are part of our accessories product line. They are an essential accessory and valuable investment for any testing lab or research facility frequently using load cells. These simulators can help to improve safety, reduce downtime, improve accuracy, lower costs, and increase convenience.

Why Use a Load Cell Simulator?

  • Testing and monitoring force measurement systems: Load cell simulators can test instrumentation performance used in force measurement systems, such as hydraulic presses, assembly machines, and material testing machines. By simulating forces that the system would typically encounter, the simulator can help identify potential problems with the instrumentation, ensuring that the system operates safely and efficiently.
  • Verifying proper indicator setup: Load cell simulators can be used to verify that an indicator is configured correctly for the type of load cells being used. This includes checking the scaling and the instrument’s linearity.
  • Cable checks: One of the first troubleshooting tips for any load cell application is to check the cables and connectors. A load cell simulator is valuable for checking cables.
  • Scaling: Load cell simulators are crucial for scaling force measurement devices, enabling precise calibration, troubleshooting, and testing. They play a vital role in ensuring the accuracy and reliability of force measurements across various industries.
  • Calibrating scale indicators: Load cell simulators can generate a precise mV/V signal corresponding to a specific weight. This allows technicians to calibrate scale indicators to ensure that they are displaying accurate weight readings.
  • Application evaluation: Load cell simulators can be used to develop and troubleshoot force-related applications, such as medical devices, prosthetics, and exercise equipment. By simulating forces that users would typically apply, the simulator can help to ensure that the application is safe, effective, and operational.
  • Research and product development: Load cell simulators can be used to research new force measurement applications.
  • Technician training: Load cell simulators can educate and train technicians on the proper use and calibration of load cells.

Interface Load Cell Simulators

CX SERIES PRECISION MV/V TRANSFER STANDARD LOAD CELL SIMULATOR 

CX SERIES PRECISION mV/V TRANSFER STANDARDModel CX Series Precision mV/V Transfer Standard is the market’s most accurate load cell simulator. This NIST Traceable product is commonly used to calibrate and check instruments in accredited labs.

  • Most accurate load cell simulator
  • Special low thermal EMF construction
  • Each unit is individually calibrated, aged, and recalibrated
  • Strong, rugged design
  • Instrument substitution testing

In the series, models CX-0202, CX-0610, CX-0440, CS-0330, and CX-0220 are used to set up and check the Gold Standard® System Hardware. CX-0440, CX-0330, and CX-0220 are single-step mV/V transfer standards providing precision outputs of ±4, ±3, and ±2 mV/V respectively. CX-0610 is a multi-step unit that allows the user to go from -6 mV/V to +6 mV/V in 1 mV/V steps. Model CX-0404 is specifically designed for instrument substitution testing as per ASTM E74.

EVALUATOR 3 LOAD CELL SIMULATOR 

Evaluator 3 Load Cell SimulatorThe Evaluator 3 variable range simulator is well suited for basic troubleshooting needs, offering nine fixed intervals from -5 mV/V to +4.5 mV/V.

  • ABS plastic case
  • Weighs less than 1 lb (0.45 kg)
  • Fixed rotary switch, -0.5 mV/V to 4.5 mV/V in 9 steps of 0.5mV/V per step
  • Used in testing and troubleshooting mV/V instrumentation

IF500 LOAD CELL SIMULATOR 

The new model IF500 is a 5V or 10V excitation-only load cell simulator with a state-of-the-art microprocessor-based design. It is a cost-effective simulator with advanced instrumentation capabilities. The instrument excitation supply powers the IF500 and requires no batteries.

  • Set “ANY” mV/V value within ±5mV/V
  • State-of-the-art, microprocessor-based design
  • Sleep mode eliminates digital clock noise
  • Powered by instrument excitation supply… No batteries
  • Buffered Ratiometric output
  • 350-ohm bridge configuration
  • Stores up to 10 settings with sequential recall
  • Digital zero trim and storage
  • Low noise, low quiescent current, low-temperature coefficient, high stability amplifiers
  • Compatible with instruments using 5V or 10V excitation, including Interface’s instrument models 9820, 9840, 9860, 9870, 9890, CSC/CSD, DMA/DMA2, DCA, INF1/INF4, ISG, SGA, and VSC
  • Options include: NIST Traceable Calibration Certificate, Screw Terminal Adapters for the BNC Connectors and Cable Adapters

Application Examples for Load Cell Simulators

Manufacturing: Load cell simulators are essential for calibrating and testing force measurement devices used in manufacturing processes, ensuring accurate force control and product consistency. ADDITIONAL RESOURCE: Manufacturing Solutions.

Food Processing: Load cell simulators are critical in calibrating and troubleshooting force measurement devices, ensuring precise portion control, and maintaining food safety standards.  ADDITIONAL RESOURCE: Force Measurement for Efficiency in Food Processing and Packaging

Construction: Load cell simulators are employed for testing and calibrating force measurement devices used in construction applications, such as crane load monitoring and material testing. ADDITIONAL RESOURCE: Construction Solutions

Medical Devices: Load cell simulators are utilized for calibrating and verifying the accuracy of force measurement devices in medical applications, such as patient weighing scales and rehabilitation equipment. ADDITIONAL RESOURCE: Medical and Healthcare

Interface load cell simulators are indispensable tools for scaling force measurement devices, providing a safe, efficient, and cost-effective means to ensure the accuracy and reliability of force measurements across diverse industries. Their ability to calibrate, troubleshoot, and test force measurement devices contributes to product quality, process control, safety, and regulatory compliance, making them essential for maintaining the integrity of force measurement systems.

Small in Dimension and Precise in Measurement

The world of force measurement is vast. Interface products are used across industries and in a wide range of applications. From the measurement of minute forces in catheter stint testing to jumbo load cells for massive structural testing of rockets, Interface load cells provide highly accurate measurement no matter the size of the load cell.

One of the many benefits of Interface products is the extensive range of measurement capacities and dimensions we offer, including our Mini Load Cells used for small and precise measurements. Interface Mini™ load cells are ideal for light touch, weight, or limited space test and measurement applications. The Mini Load Cells provide remarkably accurate measurements like our LowProfile load cells. With capacities available as low as 0.11 lbf / 0.5 N and as high as 100 kN, there are various miniature load cells for testing and options for custom OEM solutions.

TIP: Explore your options with our Mini Load Cell Selection Guide

Typical applications for measuring tiny, accurate forces are within the medical, manufacturing, robotics, and consumer product industries.

Medical device manufacturers are working to provide handheld point-of-care devices for patients. Additionally, medical devices used within the human body must provide extremely delicate forces to achieve their intended purpose without harming the patient.

Take something that seems relatively simple, like a vascular clamp. These types of delicate instruments are used on heart valves. If they provide too little force, they cannot do their job. However, providing too much force could severely harm the patient. Medical device manufacturers of these surgical tools use miniature load cells to measure the clamping force to ensure precise accuracy to toe the line between too much and too little force, which is a very precise number.

In the pharmaceutical industry, very small load cells are crucial for accurately measuring the force applied to the pills (tablets) during the press marking phase and other manufacturing processes to ensure consistent dosage and tablet integrity.

With consumer products, precision force measurement is critical to various manufacturing processes and real-time monitoring. A load button load cell is the right size for testing the durability of a smart device by applying a force to the screen and measuring the amount of force the screen can withstand before cracking or breaking. Read: Touchscreen Force Testing App Note

A miniature load cell can measure the force required to open a food package. This information can be used to ensure that the packaging is easy for consumers to open and secure enough to protect the food from damage. In food processing, load cells measure the force applied to food during mixing, blending, and other processes to ensure consistent product quality and prevent damage to the food itself. For instance, load cells can monitor the force applied to a dough mixer to ensure the dough is correctly mixed without becoming overworked or tough.

MINIATURE LOAD CELLS FOR SMALLER, MORE PRECISE FORCE MEASUREMENT APPLICATIONS

CONVEXBT LOAD BUTTON LOAD CELL

ConvexBT Load Button Load CellThe ConvexBT Load Button Load Cell is superior to any other load button. Constructed from heat-treated stainless steel and environmentally sealed with integral temperature compensation. Learn more about ConvexBT on our YouTube channel here: https://youtu.be/l4xEKNjKREw

  • 5 lbf to 1,000 lbf, 22.24 N to 4.44 N
  • Integral temperature compensation
  • Enhanced eccentric load rejection
  • Multi-point calibration
  • Integral load button
  • Minimal diameter

SMTM MICRO S-TYPE LOAD CELL

Model SMTM is the miniature overload-protected S-type load cell and is excellent to use where size is a constraint.

  • Capacity 5, 25, 50 lbf (20, 100, 200N)
  • It can be used in tension and compression
  • Micro-sized 3/4” x 3/4” x 1/4”
  • Excellent temperature compensation (0.005%/°F Temp Effect on Output)
  • Overload protected

SUPERSC S-TYPE MINIATURE LOAD CELL

The SuperSC is an economical general-purpose load cell with a high force in a compact design. The SuperSC is environmentally sealed and insensitive to off-axis loading. The proprietary form factor is 80% smaller and 50% lighter than other models of s-type load cells. READ: New Technical White Paper Analyzes SuperSC S-Type Miniature Load Cells

  • 25 to 1000 lbf (100 N to 5 kN)
  • High force in a compact design
  • Environmentally sealed
  • High stiffness
  • Low deflection

ULC ULTRA LOW CAPACITY LOAD CELL

ULC ULTRA LOW CAPACITY LOAD CELL

The Interface model ULC is the world’s most accurate ultra-low capacity load cell measuring loads from 0.1 to 2 N (10.2 grams to 500 gmf).

  • Proprietary Interface temperature compensated strain gages
  • Highest performance low capacity load cell in the world
  • Overload protected
  • Safe side load overload to 5X capacity
  • Low extraneous load sensitivity
  • Low-temperature effect on zero (0.002%/°F)
  • Tension and Compression
  • 5 ft integral cable included

MBP OVERLOAD PROTECTED MINIATURE BEAM LOAD CELL

Model MBP series load cells perform similarly to the famous Model MB series with the added safeguard of internal overload protection.

  • 5 lbf to 10 lbf
  • Proprietary Interface temperature compensated strain gages
  • 10x overload protection
  • Low height – 0.99 in (25.1 mm)
  • 0008%F temp. effect on output
  • 5′ Integral Cable (custom lengths available upon request)
  • NIST Traceable Calibration Certificate

SMALL AND PRECISE MEASUREMENT APPLICATIONS

SPECIMEN RESEARCH

In the medical industry, medical experts need the best equipment to research multiple specimens. In this case, a medical researcher needs to monitor the load force of their linear actuator that uses a needle to collect material from the desired specimen. Interface’s SuperSC S-Type Miniature Load Cell can easily be installed into the linear test stand. A needle with a gripper on the end is installed on the lower end of the SuperSC. As the needle is pushed to collect specimen material, the load feedback is captured using the 9330 Battery Powered High-Speed Data Logging Indicator through an SD card or another laptop. Read: Specimen Research App Note

AIRBAG CONNECTOR TESTING

Testing airbag connectors functionality is needed to ensure perfect deployment in case of a car crash. Eight to twelve connectors are installed in each vehicle, and tests must be made to clarify whether the connectors are working effectively. These connectors usually work when latched, but that does not ensure the electrical properties are performing. The amount of force needs to be tested to see when an electrical current is connected. Interface’s solution is to attach the WMC Sealed Stainless Steel Miniature Load Cell to the actuator of the test rig. The airbag connector is placed at the test rig’s bottom. Forces are applied and measured using the 9330 High-Speed Data Logger as the connector is pushed down to latch together. When connected to a computer, results can be logged, downloaded, and reviewed.

COBOT MONITORING SYSTEM

Collaborative robots, or cobots, are offering more manufacturing operations in the industrial packaging industry. Protective cages or fences are no longer needed for safety purposes, but safety testing is still required to ensure humans and robots can work together. Four 3-axis Force Load Cells (creating one 6-axis Force Plate) are installed between two metal plates at the base of the cobot. Interface suggests installing a 6-axis force plate under the cobot and two ConvexBT Load Button Load Cells in the pinchers of the cobot. If a human were to knock into the cobot or have any object stuck in the pincher, the cobot would sense the force measured from the load cells and be programmed to stop immediately.

Interface can serve a wide range of test and measurement applications from millions of pounds force to the most minute. If you want sensors with small, more precise measurement capabilities, please check out our miniature load cell selection guide.

Interface Load Cells for Press Machines

Press machines are designed to measure and apply force for various reasons. Hydraulic presses can be used to shape materials or crush objects. Stamping presses make a visible impression or stamp onto materials, such as a pharmaceutical tablet or logo on a food product. Even sandwich presses follow many of the characteristics of more industrial presses.

Press machines are used across automotive, aerospace, construction, consumer goods, medical, agriculture, mining, and other industries.  The presses produce consistent, cost-effective quality parts, tools, and products. No matter what kind of press machine, it must undergo rigorous testing during the machine-building process. During operation, there must be continuous monitoring of the press force used in each application.

NEW! Interface Solutions for Machine Builders

Interface load cells are critical to designing, testing, and using accurate and reliable press machinery. Interface load cells come in various shapes, dimensions, and capacities, allowing press machine builders and engineers to find the best solution for their specific machinery use case. Whether selecting a miniature load button load cell for a small press test or our WMC Load Cell to integrate into the machine, Interface has a range of products for press machine applications.

Benefits of using load cells in press machines:

  • Enhance Operator Safety
  • Prevention of Overloading
  • Improve Consistency
  • Avoid Damage to Equipment
  • Reduce Waste and Scrap
  • Increase Quality and Consistency of Work Product
  • Improve Process Control
  • Extend the Life of the Machine’s Operation
  • Increase Productivity

In a press machine test, the load cell is typically placed between the ram of the press and the die, where it can measure the force being applied to the object. The load cell is usually connected to a readout or display showing the operator the force applied to the part or material. This readout may be a simple analog or digital display, depending on the specific press and load cell being used in the machine. Review our Instrumentation Selection Guide to find the best option for your press.

There are numerous options for the types of load cells used for press machine applications. Hydraulic presses are some of the most common presses that use load cells. These machines are often built to form metal parts, such as gears, shafts, and bearings. The construction industry uses presses to assemble and test concrete structures. These presses are designed to crush and process minerals and ore in mining.

Mechanical presses are typically used for high-precision applications, such as metal stamping and forming. Miniature load cells are used in more precise applications that require smaller measurements. These use cases are often reserved for the medical or consumer goods industry, where the goal is to provide a stamping force for medicine or candy to label the product without crushing or damaging it. A precision Interface load cell ensures that the force applied to the material is consistent and accurate.

Another type of press using a sensor is known as a screw press which forms and compacts materials such as plastic and rubber. These press machines are found in chemical, food, and waste processing facilities.

Depending on the measurement capacity needed in the machine’s application, two popular Interface options are the Rod End Load Cells and Mini WMC Sealed Stainless Steel Load Cells. A rod end load cell is typically installed at the end of the piston or ram, where it can measure the tension or compression force being applied during the pressing operation.  These load cells provide accurate and reliable force measurement in various presses.

Press Forming and Load Monitoring

Press forming is a method to deform different materials. For instance, materials such as steel can be bent, stretched, or formed into shapes. A force measurement solution is required to monitor the forces being applied by the press-forming machine. This ensures quality control and traceability during the production process. Interface recommended installing the 1000 High Capacity Fatigue-Rated LowProfile™ Load Cell for large press forming machines. When the material is placed under the punch plate to form a shape, the 1000 series load cell measures the force applied. The captured force results were sent to the INF-USB3 Universal Serial Bus Single Channel PC Interface Module, where results could be graphed and logged on the customer’s PC using the provided software. Interface’s force measurement products and instrumentation accurately monitored and logged the force results of the press force machine, ensuring zero-error production performance.

Tablet Forming Machine Optimization

A pharmaceutical tablet producer wanted to monitor the forces the tablet forming machine applied to understand the relationship between raw material, die set, form, force, and the motor’s cycle speed. The goal was to improve the productivity and efficiency of the tablet-forming process while reducing losses (i.e., 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. After analyzing the data, the tablet producer could quantify adjustment levels by monitoring which forces produced optimal results for a given cycle speed, die set, and raw material. The enhancement of the data feedback significantly improves productivity and efficiency.

Candy Stamp Force Testing

Manufacturers of hard-shell candies often stamp text or logos on the candy shells. Stamping too hard breaks the candy shell and stamping too light results in an uneven or incomplete imprint. Using a test apparatus with an Interface Model WMC Mini Load Cell attached to hydraulic actuators was discovered to be an accurate way to measure the compression force required. Engineers determined the specific force needed to properly apply the imprint without breaking the candy shell using this solution.

Using Interface load cells on a press machine is a valuable investment that can help to improve the quality of the products being produced, extend the life of the press machine, and reduce the risk of accidents.

ADDITIONAL RESOURCES

Press Forming and Load Monitoring

Press Load Monitoring App Note

Hydraulic Press Machines and Load Cells

Metal Press Cutting Machine

Interface Solutions for Machine Builders

Force Measurement Sensors are Essential to Modern Industrial Machinery

 

Excitation Voltage 101

Excitation is an electrical signal. The excitation voltage is represented by the volts direct current (VDC). The direct current flows in one direction only. Alternating current (AC) changes direction at times.

Load cell excitation provides a voltage to generate an output signal, sometimes referred to as ‘powering’ the load cell. An output signal from a load cell is typically minimal, so an excitation voltage is needed to power the load cell and ensure the output signal is accurate. The magnitude of the output signal is proportional to the amount of force applied to the load cell. The greater the force, the greater the output signal.

Interface load cells contain proprietary strain gages applied to a Wheatstone bridge, essentially an electrical circuit that changes resistance when subjected to strain. The Wheatstone bridge is comprised of strain gages that are arranged in a specific configuration. When a load is applied to the load cell, the strain gages deform, and their resistance changes. This change in resistance causes the output voltage of the Wheatstone bridge to change.

Interface provides electrical performance data on all specifications represented as VDC MAX, when applicable.  The data for excitation voltage is listed under the electrical section of a transducer model’s specification datasheet, along with other factors, including rated output, bridge resistance, and zero balance.

Sensor Power and Excitation Tips

Load cell excitation is necessary to ensure the accuracy and reliability of load cell measurements.  Here are a few tips to consider regarding excitation and power signals when designing a force measurement system:

  • The output signal from a load cell is expressed in millivolt output per Volt (mv/V) of excitation at capacity.
  • The excitation voltage also affects the magnitude of the output signal. A higher excitation voltage will produce a higher output signal.
  • The output signal is directly affected by the input voltage. It’s essential to maintain a stable excitation voltage.
  • Interface load cells all contain a full bridge circuit. Each leg has a typical bridge resistance of 350 ohms, except for models like our 1500, which have 700 ohm legs.
  • The preferred excitation voltage is 10 VDC, which guarantees the closest match to the original calibration performed at Interface before it is shipped from our factory.
  • A DAQ system won’t always provide stable excitation voltage. Consider using a signal conditioner or DAQ with specific bridge inputs.

Why Load Cell Excitation Matters

Excitation matters in force measurement applications because it provides the power needed to operate the load cell and ensure an accurate output signal. The load cell cannot generate an output signal without excitation, and the force measurement will be inaccurate. In addition, it does influence accuracy, noise, and range.

Accuracy: The excitation voltage powers the load cell and ensures an accurate output signal.

Noise Reduction: The excitation voltage can help to reduce noise in the output signal.

Range: The excitation voltage can help extend the load cell’s measurement limit.

The excitation voltage should be applied to the load cell in a balanced manner. This means the excitation voltage should be applied to both sides of the load cell. The excitation voltage should be stable. This means that the voltage should not fluctuate or drift over time. The excitation voltage should be filtered. This means that any noise in the excitation voltage should be removed.

Excitation 101 in Force Measurement

The excitation voltage determines the sensitivity of the load cell. A higher excitation voltage will result in a more sensitive load cell, which means it can measure smaller forces.

The excitation voltage influences the frequency response of the load cell. A higher excitation voltage will result in a broader frequency response, meaning the load cell can track changes in force more accurately.

Linearity measures how accurately the load cell converts force into an electrical signal. A higher excitation voltage will result in a more linear load cell, meaning the output signal will be more proportional to the applied force.

The excitation voltage is well-regulated to reduce measurement errors. Variations in excitation voltage can cause a slight shift in zero balance and creep. This effect is most noticeable when the excitation voltage is first initiated. The solution is to allow the load cell to stabilize by operating it with a 10 VDC excitation for the time required for the gage temperatures to reach equilibrium. The effects of excitation voltage variation are typically not seen by users except when the voltage is first applied to the cell.

For tips like this, please consult Interface’s Load Cell Field Guide. We also detail remote sensing of excitation and temperature. Download your copy for free here.

It is essential to carefully select the excitation voltage for a load cell application to ensure that it can provide accurate and reliable measurements.

Demystifying Specifications Webinar Recap

Interface recently hosted an online technical seminar that detailed product specification basics, key values, terms to know, how to read a datasheet, what specs matter most in force measurement applications.

For Interface, specifications are detailed descriptions that outline the characteristics, features, and qualities of our products, systems, or services. Product specifications are included on all datasheets, detailing product performance, capabilities, capacities and dimensions. Products have internal specifications that are tested against during manufacture, typically with full traceability.

Throughout the webinar Demystifying Specifications, Brian Peters and Jeff White offered important tips on what to consider for high-speed, durability, precision, and specialty product requirements. They highlighted what to look for on the product datasheet when choosing a load cell or instrumentation device. This includes variables in specifications related to expected performance of transducers and instrumentation based on frequency, environment, and other critical testing application considerations. They also answered the most frequently asked questions of our applications engineers related to specifications and datasheets.

Demystifying Specifications Webinar Topics

  • Specification Basics
  • Specifications and Values in Force Measurement
  • Decoding Datasheets
  • Detailing Product Specs for Load Cells
  • Detailing Product Specs for Instrumentation
  • Detailing Product Specs for Specialty Sensor Products
  • Applying Specifications to Applications
  • Specification Tips
  • FAQs and Resources

The entire webinar, Demystifying Specifications, is now available to watch online.

Four Types of Specifications

Interface provides four types of specifications for every product we make and sell: functional, technical, performance and design.

  1. Functional specifications describe the intended functionality or behavior of a product, whether a sensor, instrument or accessory.  They outline what the product or system should do and how it should perform its tasks. Functional specifications typically include applications, product requirements, and expected use case results.
  2. Technical specifications provide detailed information about mechanical aspects of a product or system. They may include information about the materials, dimensions, technical standards, performance criteria, capacities, and other technical details necessary for the design, development, and implementation of the product or system
  3. Performance specifications define the performance requirements and criteria that a product or system must meet. This is critical in force and measurement. They specify the desired performance levels, such as speed, accuracy, capacity, efficiency, reliability, or other measurable attributes. Performance can be defined by a specific range, with maximum standards for peak performance. Performance specifications help ensure that the product or system meets the desired test and measurement goals.
  4. Design specifications outline the specific design criteria and constraints for a product or system. These specs provide guidelines and requirements related to the visual appearance and can also reference the model details found in a product’s engineering CAD STEP file. 

Specifications Commonly Found on Interface Product Datasheets

  • Models based on Form Factor
  • Measuring Range (Capacity)
  • Measurement Units: US (lbf) Metric (N, kN)
  • Accuracy (Max Error)
  • Temperature: Operating Range, Compensated Range, Effect on Zero and Effect on Output (Span)
  • Electrical: Rated Output, Excitation Voltage, Bridge Resistance, Zero Balance and Insulation Resistance
  • Mechanical: Safe Overload, Deflection, Optional Base, Natural Frequency, Weight, Calibration and Material
  • Dimensions
  • Options
  • Connector Options
  • Accessories

Key Force Measurement Specification Terms to Know

Nonlinearity: The algebraic difference between OUTPUT at a specific load and the corresponding point on the straight line drawn between minimum load and maximum load.  Normally expressed in units of %FS.

Hysteresis: The algebraic difference between output at a given load descending from maximum load and output at the same load ascending from minimum load. Normally expressed in units of %FS.

Static Error Band (SEB): The band of maximum deviations of the ascending and descending calibration points from a best fit line through zero output. It includes the effects of nonlinearity, hysteresis, and non-return to minimum load. Expressed in units of %FS.  SEB Output is a best fit straight line output at capacity.

Nonrepeatability: The maximum difference between output readings for repeated loadings under identical loading and environmental conditions.  Expressed in units of %RO. In practice there are many factors that affect repeatability that ARE NOT included in the nonrepeatability specification.

Creep:  The change in load cell signal occurring with time, while under load and with all environmental conditions and other variables remaining constant. Expressed as % applied load over specific time interval. Logarithmic effect that is also symmetric on load removal. Stated specifications may differ and are not for the same time interval.

Eccentric and Side Load Sensitivity: Eccentric Load – Any load applied parallel to but not concentric with the primary axis. Results in moment load. Side Load – Any load at the point of axial load application at 90° to the primary axis. Error influences are reported in terms % and %/in.

Watch the event to understand why these specification details matter and some of the important variables to consider when comparing, using or troubleshooting different measurement products.  During the event, we provided a list of resources that are helpful when looking for specification information or definitions. The complete list is below.

ADDITIONAL RESOURCES

Interface Product Selection Guides

Interface Technical Support Information and Troubleshooting

Interface Load Cell Field Guide (Free Copy)

Interface Installation Guides and Operation Manuals

Interface Software and Drivers

Interface Product Catalogs

Interface 101 Blog Series and InterfaceIQ Posts

Interface Industry Solutions and Applications

Interface Recorded Webinars

Load Cell Test Stands 101

Load cell test stands are important devices for manufacturers and testing engineers who need to measure the force or torque applied to an object, test specimen, or product. They are typically made up of a frame, one or more load cells, software, and data acquisition instrumentation.

How do load cell test stands work?

Interface load cells are sensors that convert force into an electrical signal. This signal is then amplified and sent to the test stand’s software, which displays and records the force data. The software can also be used to control the test stand, such as setting the speed and duration of a test.

Test stands are used to hold the test object or device and apply force or torque to it. They should be designed to provide a stable and consistent testing environment. It is typically designed to accommodate a wide range of objects of different sizes and shapes. Often a reconfigurable structure to adapt from test to test.

Test stands may have various components, such as a base or base plate, columns, a crosshead, and load introduction devices. Interface provides high-accuracy load cells, instrumentation and DAQ systems, software and accessories designed for use in various types of test stands.

What are the different types of load cell test stands?

There are two main types of load cell test stands: motorized and manual. Motorized test stands are more advanced and can be used for more demanding testing applications. They typically have features such as programmable speed and force control, as well as data logging capabilities. Manual test stands are less expensive and easier to use, but they are not as versatile as motorized test stands.

A test stand and a load frame are both mechanical structures used in materials testing, but they differ in their functions and designs.

The test stand can be a test bench or structure on a test bed plate. These assemblies are designed to rigidly hold an object while it is being subjected to external forces. These forces could be introduced from all angles and orientations and cover low cycle design limit to long duration fatigue cycle testing.

A load frame, on the other hand, is a machine that is specifically designed to apply and measure axial or torsion forces during material or small component testing.

Most Common Requirements for Load Cell Test Stands

Testing professionals, engineers and metrologists require a load cell test stand to perform accurate and precise measurements. The primary features of a test stand include:

  • High accuracy: The load cell test stand must be able to measure force or torque with a high degree of accuracy. This is important to ensure that the measurements are reliable and repeatable. Confidence in the data must be validated through accuracy of measurement.
  • Versatility: The load cell test stand must be able to be used for a variety of testing applications. Test lab professionals, engineers and metrologists need equipment that can perform a wide range of product and material tests. This also includes interchangeable sensors, depending on the capacity and type of test, such as tension or fatigue.
  • Repeatability: The load cell test stand must be able to repeat measurements with high precision. This is important to verify the accuracy of measurements over time, through continuous use and even high cycle counts.
  • Safety: The load cell test stand must be safe to use, even when testing products under high loads. Measurements are not compromised by safety concerns.
  • Ease of use: The load cell test stand must be easy to use, even for users with limited technical knowledge. This is important for testing professionals to be able to quickly and easily set up and use the test stand.

Load cell test stand requirements can vary based on the type of testing projects and materials. Many test stands are standard; however, complex testing programs often require custom test stands that are designed and calibrated for specific use cases. Interface provide load cells, instrumentation and software designed for use in test stands.

Test Stand Sensor Considerations

  • Ensure sensors are properly sized for capacity, cycle, and extraneous load considerations.
  • Multiple bridges are good feature for redundancy and data validation.
  • Thread adapters and connector protectors must be considered in choosing the sensor for a specific test stand application.
  • Multi-axis data capture often requires robust instrumentation to take full advantage of the data.
  • Invest in versatility and ruggedness to maximize return.

Additional Test Stand Options

  • Programmable speed and force controllers help to regulate the rate at which the load is applied to the product, as well as the maximum force that can be applied during a given test period or cycle.
  • Data logging instrumentation records the force data for each test. This data can then be used to analyze the results of the test and to make sure that the product meets the required specifications.
  • Remote monitoring and controls help with test stand use from a remote location. This can be useful to run tests without being physically present at the test stand.

There are many different types of load cell test stands, so it is important to choose one that is right for your specific needs. When selecting or building a load cell test stand, consider the weight or force that you need to measure, the accuracy and precision, the environment in which the test stand will be used and the equipment budget.  This is a topic we detailed in our Testing Lab Essentials Webinar. Watch this portion of the online technical seminar below.

Load Cell Test Stand Use Cases and Applications

  • Aerospace test stands are used to measure the strength of aircraft structures. Test stands are used to test the performance and durability of aircraft components, such as wings, fuselages, and engines. They are also used to test the structural integrity of aircraft materials, such as composites and metals.
  • Material test stands can be used to exam the strength, stiffness, and toughness of materials.
  • Structural test stands are used for small capacity testing, as well as large amounts of force to measure the structural integrity of buildings, bridges, and other formations.
  • Dynamic test stands are used to measure the performance of products under different environmental conditions, such as shock and vibration testing.
  • Medical manufacturers need to test the performance of medical devices. Test stands are used to test the performance and durability of medical devices, such as pacemakers and defibrillators. They are also used to test the accuracy of medical instruments and in-home medical equipment, as the safety of user is paramount to all other requirements.
  • Automotive labs use test the performance of engines, transmissions, brakes and other components. They are also used to test the durability of automotive materials, such as tires and plastics.
  • Consumer product manufacturers and OEMs must test the durability to ensure customer satisfaction and reliability of the product. Test stands are used in testing toys, appliances, tools, and electronic devices.
  • Industrial automation component makers and OEMs must test the strength of machine parts and materials used in product lines, machine tools, and robots. They are also used to test the safety of industrial equipment, such as forklifts and cranes.

Load cell test stands are an essential tool to accurately measure the forces acting on a test specimen. By using a load cell test stand, testing engineers can ensure that their equipment is operating within its design limits and that it is safe to use. If you have questions about building or upgrading your test stand, be sure to consult with our application engineers.