Load cells are used across a wide range of industries and applications and are the most critical component found in every digital scale made today. They are used in laboratory balances, bench scales, floor scales, truck scales, custom weighing systems and beyond. In this article, we cover everything there is to know about load cells including the different types, where they are used, how to troubleshoot them and the technical specifications that outline their capabilities. 

Don't forget to download your free PDF copy of "The Ultimate Load Cell Guide" at the end of this article.

What is a Load Cell?

A load cell, also referred to as a force sensor or weight sensor, is a device that measures weight or force by converting a physical force to an electrical signal. When a load or object is placed on a load cell, it changes shape slightly, and this change is converted into an electrical signal. That signal can then be read and displayed to show how much force is being applied.

Types of Load Cells

There are several common types of  load cells, each with their own unique design characteristics suitable for specific weight measurement applications.

Single Point Load Cells

Single Point load cells are usually flat and rectangular, sometimes with a slight curve. They have a single central point for mounting underneath the weighing platform. The strain gauges are often located near the center or along the body to measure the deformation caused by the applied load. They are designed to be installed singularly underneath a weighing platform and are commonly used in bench scales, medical scales, and other smaller capacity weighing systems (generally under 1,000lbs). 

Installation

While they are relatively easy to install, it's crucial to follow certain installation guidelines. These may include proper alignment, secure mounting, and ensuring the load is evenly distributed on the platform. As only a single point is required, corner error adjustment may be done to ensure proper weighing anywhere on a loading platform.

Limitations

Generally, there are limits to the size and capacity of the weighing platform when using a single point load cell. They are best suited for smaller scales where the load will be placed at a fixed point.

Single Ended Beam

Single Ended Beam load cells are typically shaped like a straight metal block or a slight curve with a single mounting hole or bracket at one end. They are often used in industrial applications and are ideal for floor scales, hopper scales, and other weighing systems where medium and heavier loads are involved (often between 500lbs to 20,000lbs). 

Installation

These load cells are typically mounted on one end, with the other end left free to move. This allows the load cell to flex under the weight, providing accurate measurements. Proper mounting and alignment are crucial for accurate readings. 

Limitations

Due to their design, single ended beam load cells are generally not suitable for applications requiring high precision over a wide range of small and large loads. They are more focused on higher capacity weighing.

S-Beam

S-Type load cells have an 'S', with attachment points at the top and bottom. The curved shape allows the cell to handle both tensile and compressive forces, and strain gauges are usually located at the bends to measure the force.  S-Beam load cells are versatile and can handle both tensile and compressive loads. They are commonly used in hanging scales, simple compression weighing platform scales, and tension measurement applications (generally under 10,000lbs to each load cell). 

Installation

These load cells are typically installed using rod ends or eye bolts to suspend the load. Proper alignment is crucial to ensure accurate readings. They often come with anti-rotational links to ensure that the load cell doesn't rotate, which could affect the readings. 

Limitations 

S-Type load cells are sensitive to side loads and may require additional hardware or shielding to protect against environmental factors like wind or vibration. They are generally not recommended for high capacity weighing applications.

Double Ended Beam

Double Ended Beam load cells are elongated blocks of metal, usually with mounting holes or brackets at both ends. The middle section is designed to flex under load, and strain gauges are typically located here to measure the deformation. They are designed for center mounting and are often used in truck scales, tank and hopper weighing, and other industrial applications.  Double-ended beam load cells are highly durable and can handle very heavy loads in the hundreds of tons. 

Installation

These load cells are mounted at both ends and loaded in the center, allowing for greater flexibility and movement, which can improve accuracy. They are generally installed in sets and connected to a single readout, requiring careful calibration to ensure uniform loading. 

Limitations

Double Ended Beam load cells are more complex to install than other types and may require a more rigid mounting structure to ensure accurate measurements. They are also generally more expensive due to their robust design and higher capacity.

Tension Links

Tension link load cells are elongated, usually straight or slightly curved, with attachment points at both ends. They look like a metal link and are designed to be inserted into a chain or cable system.  Tension link load cells are designed specifically for inline tension measurement. They are commonly used in crane scales, lifting systems, and winch force measurement applications. 

Installation

These load cells are straightforward to install, usually requiring only shackles or other connecting elements to link them into the system. The orientation is important; they should be aligned with the direction of the force to ensure accurate measurements. 

Limitations

Tension link load cells are specialized for tension measurement and are not suitable for compressive loads. They may also be sensitive to side-loading and bending forces, which could affect their accuracy.

Load Pins

Load pins are cylindrical in shape, resembling a thick rod or shaft, and are designed to fit into existing holes in machinery. They usually have a flange at one end for secure mounting and may have grooves or other features to lock them into place. Load pins replace existing shafts, axles, or pins in machinery or equipment, effectively becoming a load-bearing element that can measure force. They are often used in pulley systems, shackles, and various types of lifting gear. 

Installation

Load pins are designed to fit into existing systems, so installation usually involves removing the current pin or axle and replacing it with the load pin. Calibration is crucial, as the load pin must accurately measure the force exerted on it within the system. 

Limitations

Load pins are highly specialized and must be custom designed to fit into existing systems, making them more expensive. They are also generally limited to the specific type of application for which they were designed, such as shear or axial force measurement.

Compression Canister & Compression Disk

Compression canister load cells and compression disk load cells are cylindrical in shape, resembling a can or a barrel. They are designed to handle very high loads and are often used in truck scales and industrial weighing systems. The top and bottom of the cylinder have flatter surfaces for mounting. 

Installation

These load cells are generally installed vertically and are loaded in compression. They often come with a rocker pin or a load button to ensure proper force distribution. 

Limitations

Due to their design, they are generally not suitable for applications requiring high precision or for measuring tensile forces. They are more focused on high-capacity weighing though are generally not as sturdy as double ended beams.

Planar Beam

Planar Beam load cells are flat, low-profile load cells that are often rectangular or square in shape. They are designed for use in multi-load cell applications like platform scales and are ideal for low-clearance or tight-space installations. 

Installation

These load cells are usually installed in sets and are placed flat under the weighing platform. They are designed to distribute the load evenly across all cells in the system. 

Limitations

While they are versatile, they are generally limited to lower-capacity applications. They may also require more complex wiring and calibration when used in multi-cell configurations.

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Load Cell Mounts

Load cell mounts, also commonly referred to as  weigh modules, are designed to provide a strong stable base for a load cell. They are built from strong materials and typically include a lower and top plate for mounting the load cell to an apparatus. Load cell mounts are often used with larger structures like tanks and silos, as well as custom systems that require specialized mounting.

Types of Load Cell Mounts

Compression Mounts

Used primarily for compression load cells, these mounts are designed to withstand heavy loads and are commonly used in truck scales and industrial applications.

Tension Mounts

These are used for tension load cells, often found in hanging scales or crane scales. They usually include eye bolts or rod ends for secure mounting.

By understanding these additional load cell designs and mounts, you can further refine your selection process. Whether you're dealing with light loads in controlled environments or heavy loads in rugged conditions, there's a load cell design suited for your specific application. Always consult manufacturer guidelines or professionals in the field to make the most informed choice.

What Are the Benefits of Load Cell Mounts? 

Secure Mounting & Alignment

Load cell modules provide a secure and stable platform for the load cell, ensuring that it remains in the correct position even under heavy loads or vibrations. Proper alignment is critical for accurate weight measurement. Mounts help in aligning the load cell correctly with the weighing platform. 

Load Distribution

Mounts help in evenly distributing the load across the load cell, reducing the risk of overload or uneven wear and tear. This is especially important in heavy-capacity or bulk weighing applications where loads may be off-center or variable. Take for example a grain silo. As the grain is dispensed, there may be a difference in weight from side-to-side within the silo.

Ease of Installation and Maintenance

Good mounts simplify the process of installing and replacing load cells, making it easier to maintain the weighing system. This is especially important when working with large structures like tanks, hoppers and silos. They allow easy access to the load cell, making troubleshooting and replacements much easier.

Environmental Protection

Some load cell mounts come with features like rubber seals or corrosion-resistant materials to protect the load cell from environmental factors like moisture, chemicals, and dust.

Where Are Load Cell Mounts Commonly Used?

Load cell mounts are used in a wide range of industrial applications. Some of these applications include: 

• Tanks, hoppers and silos
• Conveyor and belt systems 
• Truck and vehicle scales 
• Floor scales
• Custom weighing systems and automation

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How a Load Cell Works

Load cells work by converting a specific type of mechanical force—typically tension, torque, compression, or pressure—into an output signal. This output signal is then transmitted via a load cable to the scale’s indicator where the precise weight can be measured and read by the operator. 

Most modern load cells use a wired system of four strategically placed strain gauges for maximum measurement accuracy. When an object is placed on the scale, the resistance of each strain gauge will vary, causing a fluctuation in output voltage. It’s this change in output voltage that gets measured and converted into a digital value for the scale operator to read. 

Strain gauge load sensors are by far the most common and can be found in nearly every type of scale manufactured today. 

A strain gauge is typically constructed of a very fine wire or metal foil that’s arranged in a grid-like pattern. They can take the weight of the object acting on the load cell and convert it into an electrical signal.

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Load Cell Construction

Load cells are generally constructed out of aluminum, alloy steel, and stainless steel. Each have varying characteristics, advantages, and shortcomings. For most applications however, the material that is chosen is generally due to the degree of corrosion resistance needed, with aluminum being the most susceptible and stainless steel being least susceptible.

Aluminum

Aerospace aluminum is a type of aluminum that is specifically designed for use in the aerospace industry. It is known for its high strength-to-weight ratio, excellent corrosion resistance, and ability to withstand extreme temperatures. These properties make it ideal for use in load cells. Load cells are often subjected to extreme conditions, such as high temperatures and heavy loads, so the use of aerospace aluminum allows them to maintain their accuracy and reliability under these conditions.

Alloy Steel

Load cells are often made from alloy steel, which is a type of steel that is composed of iron and one or more other elements, such as carbon, manganese, silicon, nickel, or chromium. The specific type of alloy steel that is used to make a load cell will depend on the intended application and the desired properties of the load cell. 

Carbon Steel

Carbon steel is an alloy steel that contains a relatively high amount of carbon, typically around 0.6-1.4% by weight. It is known for its high strength and hardness, making it ideal for use in load cells that are subjected to high loads or pressures. 

Stainless Steel

Stainless steel is an alloy steel that contains a minimum of 10.5% chromium by weight. It is known for its excellent corrosion resistance, making it ideal for use in load cells that will be exposed to corrosive environments. 

Nickel-based Steel

Nickel-based steel is an alloy steel that contains a relatively high amount of nickel, typically around 10-30% by weight. It is known for its high strength, toughness, and resistance to wear and tear, making it ideal for use in load cells that are subjected to heavy loads or high levels of stress. 

Nickel plating can be used to improve the appearance of alloy steel and aluminum, as well as to provide a protective coating that helps to prevent corrosion. The process involves applying a thin layer of nickel to the surface of the metal using an electroplating technique, in which an electrical current is used to deposit the nickel onto the surface of the metal. The resulting coated metal has a smooth, shiny finish and is resistant to corrosion, making it suitable for use in a variety of applications.

Stainless Steel

2Cr13 and 17-4PH are both types of stainless steel commonly used in load cell manufacturing, but they have some key differences in their composition and properties. 2Cr13 is a martensitic stainless steel that contains 13% chromium and 2% carbon. It is known for its good hardness and wear resistance, as well as its ability to be hardened by heat treatment. 17-4PH is a precipitation hardened stainless steel that contains 17% chromium, 4% nickel, and 4% copper. It is known for its high strength and excellent corrosion resistance, as well as its ability to be hardened by aging. 

In terms of their use in load cells, the main difference between these two types of stainless steel is their strength and hardness. 2Cr13 is typically used in load cells that are subjected to lower loads or less demanding conditions, while 17-4PH is used in load cells that are subjected to higher loads or more demanding conditions. The higher strength and hardness of 17-4PH allow it to withstand greater loads and stresses without deforming or failing, while the good hardness and wear resistance of 2Cr13 make it well-suited for load cells that may be subjected to wear and tear.

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How To Choose the Right Load Cell

Application

Before any further decisions or choices can be made, it is important to know what the weighing application is. This helps to guide further questions and expectations when choosing the appropriate load cell. 

Industry Requirements

Some industries have specific requirements or regulations that dictate performance guidelines, which helps to further narrow down the load cell type that is most appropriate for the job.

• Retail:  Frequently requires legal-for-trade approved weighing systems
• Food Processing:  Washdown environments require higher IP ratings in these hygienic environments.
• Chemicals and Energy:  Often requires intrinsic safety due to the hazardous environments that exist.
• Vehicle Weighing:  High safety factors and digitized output such as CANBUS are required.
• Agricultural:  Harsh environments including corrosion protection against salt and fertilizers.

Performance Expectations

Minimum Resolution

What is the minimum resolution that can be accepted for the application?

Load cells have performance ratings based on projected and tested resolutions. This can be expressed in percentages or more commonly in the weighing industry, divisions (d). For example, a resolution of 0.1kg for a 500kg capacity scale can be expressed as 0.02% or 5000 divisions.

Safety Factor

What is the required safety factor?

There is typically an inverse relationship between capacity and resolution. Certain applications are more prone to overloading, shock loading, or require uplift protection. There are load cells that offer higher safety factors while others are designed for sensitivity. It is imperative to take this into consideration when selecting the load cell type, model, and capacity.

Environmental Protection 

Environmentally protected load cells are designed to withstand exposure from mild to moderate environmental challenges without compromising their functionality. These load cells feature robust construction and specialized coatings, potting or seals that offer resistance to moisture, dust, humidity, and other contaminants commonly encountered in industrial settings. While they may not provide the same level of complete sealing as hermetically sealed load cells, they offer sufficient protection for many applications where the environment is not extremely harsh. 

The housing of environmentally protected load cells is typically constructed from durable materials such as stainless steel or aluminum alloy, providing mechanical strength and resistance to corrosion.

Hermetically Sealed

Hermetically sealed load cells are precision instruments designed for accurately measuring force or weight in various industrial applications where environmental conditions can be challenging. These load cells are constructed with a special sealing technique that completely encloses the internal components, providing a barrier against moisture, dust, chemicals, and other contaminants. This hermetic sealing ensures reliable and accurate performance even in harsh operating environments. The hermetic sealing process typically involves welding or bonding the load cell housing to create a completely airtight and watertight seal. This prevents any ingress of external elements that could potentially compromise the functionality and accuracy of the load cell.

One of the primary advantages of hermetically sealed load cells is their enhanced durability and longevity. By preventing exposure to moisture and other corrosive substances, these load cells are better able to maintain their performance over time, reducing the need for frequent maintenance or replacement.

Welded Seal

Welded seal load cells are precision instruments designed for demanding industrial environments. They feature a specialized construction technique where the load cell housing is sealed using welding methods to create a robust and durable barrier against some environmental contaminants. They are not suited for high moisture, steam, or direct washdown applications.

The welding process involves fusing together the various components of the load cell housing, such as the top and bottom plates, using high-precision welding techniques. This creates a seal that effectively prevents the ingress of minimal moisture, dust, and other contaminants that could potentially affect the performance and accuracy of the load cell.

Welded seal load cells are commonly constructed from materials such as stainless steel or aluminum alloy, which offer excellent mechanical strength and corrosion resistance. Additionally, they may feature protective coatings or treatments to further enhance their resistance to corrosion and abrasion.

Surge Protection

Load cells with surge protection,or may also be referred to as lightning protection, are designed for applications that could see excessive voltage. No electronics are designed to take a direct lightning strike, however, with additional surge protection, load cells are protected in the event of an indirect voltage surge.

Surge protected load cells are often used for outdoor applications, especially truck scales. These load cells are designed with built-in protection to withstand voltage surges without damaging the load cells critical electronics. In most load cells, a voltage surge would immediately damage the load cell’s strain gauges which are the most susceptible.

IP Ratings

An IP Rating, or ingress protection rating, defines how well an electrical device’s enclosure will keep water and debris from getting inside. The IP rating of a load cell is directly related to how well it is protected when used in harsh or wet environments. This is especially important for any load cells that are used outdoors, such as truck scales, and in harsh industrial environments such as chemical manufacturing.

How to Read IP Ratings

The first digit rates the enclosure's effectiveness at blocking intrusion from SOLID particles on a scale of 0 to 6 (with a rating of 6 offering the most protection). 

The second digit rates for LIQUID protection on a scale of 0 to 8 (with a rating of 8 providing the most protection).

 IP Ratings Explained

Approval Requirements

Legal for Trade Approvals

Any commercial applications where product is sold by weight generally requires that the weighing equipment is ‘legal for trade’ approved. In most jurisdictions, this typically means that the load cells used must be certified by a national and/or international body. An applicable legal for trade requirement helps to narrow down the viable options available for consideration.

• NTEP (US-specific) — Requires that all load cells used in commercial weighing applications to be NTEP certified.
• OIML (International) — Common global standard that load cells may be certified legal for trade and recognized in over 50 countries around the world, including most of Europe, Asia, and South America.
• Measurement Canada (Canada) — Legal for trade measurement systems must be certified by an accredited inspector and use either NTEP or OIML-certified load cells.

Intrinsically Safe Certifications

In environments with explosive atmospheres, it’s critical that all electrical equipment, including weighing systems and load cells, adheres to stringent safety standards. These certifications ensure that the equipment is designed and manufactured to avoid risk of any possible ignition sources in hazardous environments.

• ATEX (Europe) — A mandatory certification for equipment intended for use in explosive atmospheres within the European Union. ATEX-certified load cells are rigorously tested to ensure they do not initiate an explosion due to electrical sparks or high temperatures.
• IECEx (International) – An international certification that facilitates the global trade of equipment used in explosive environments. IECEx-certified load cells meet the highest international safety standards, ensuring their safe operation in hazardous conditions worldwide.
• FM (US) (North America) — Factory Mutual Global certification, recognized in the US and Canada (cUS marked), ensures that load cells are safe for use in specified hazardous environments. This certification confirms that the equipment has been tested for safety and performance according to North American standards.

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How to Read Load Cell Data Sheets

Load cell datasheets provide a wealth of information essential for selecting the right load cell for your weighing application and ensuring its proper installation and use. Whether you are looking for a replacement load cell to service an inoperative scale or looking for a load cell to suite your weighing needs, it is important to understand how to interpret load cell datasheets. 

The following is an example of a standard load cell datasheet (courtesy of Anyload):

Dimensions

The dimensions of a load cell are the most critical attribute that you must consider first. If a load cell cannot fit into your installation, there is little that can be done to fix it. A single load cell model often has multiple sets of dimensions as there are different sizes depending on its rated capacity.

Take care to refer to the dimensions corresponding to the rated capacity that you are looking for. Alphabetical letters are commonly used to represent a specific dimension (e.g., “H” represents height, “W” for width, “W1 for width including the removeable side plates, “T” for bolt thread size).

Specifications

Manufacturers will list, to varying levels of detail, specifications of its products: excitation, output, accuracy (in ideal conditions), cable color code, material, and more. Some are more critical than others, depending on your needs.

Highlighted in red are critical figures that must be accounted for when installing a load cell into a new or existing system. In existing systems with multiple load cells, they must match. Highlighted in yellow are important figures to take note of and may or may not be critical to the functioning of a weighing system.

Definitions

The remaining specifications are important to consult and may be important considerations in some specific applications but are not generally critical to the basic functioning of a weighing system. The following is a basic explanation of each of these metrics:

Full Scale Output

The electrical output signal generated by the load cell when it is subjected to its maximum rated load expressed in millivolts per volt (mV/V). 

Zero Balance

Output signal of the load cell when there is no load applied. Crucial for accurate measurements and is usually close to zero. 

Non-Linearity

Deviation between the load cell’s actual output and its expected linear output represented as a percentage of full-scale output. 

Repeatability

Load cell’s ability to consistently provide the same output when the same load is applied under identical conditions. Crucial for ensuring consistent measurements. 

Hysteresis Error

The difference in output when a specific load is applied and then removed, measured in both ascending and descending paths, expressed as a percentage of the full-scale output. 

Creep in 30 min

The change in output occurring over 30 minutes while under constant load, expressed as a percentage of full-scale output. 

Input Resistance

Resistance measured across the load cell’s excitation terminals expressed in ohms (Ω) and is important for the compatibility with the instrumentation. 

Output Resistance

Resistance measured between the signal output terminals, also expressed in ohms (Ω). It impacts the quality of the signal transmission. 

Element Material

The material used for the element (metal body) of the load cell. This affects the load cell’s durability and environmental suitability. 

Recommended Excitation

The optimum voltage needed to power the load cell for accurate and stable readings. Exceeding this value may result in errors or damage. 

Insulation Resistance

The electrical resistance between the load cell’s body and its electrical circuitry, between the bridge circuit wires and shield wire, bridge circuit wires and body, and shield and body. Insulation resistance is usually measured in megaohms. A high value indicates good insulation. 

Compensated Temperature Range

The range of temperatures within which the load cell can operate without significant errors or a drop in performance.

Safe Overload

The maximum load that can be applied without causing permanent deformation or affecting performance. It is usually expressed as a percentage of the rated capacity. 

Breaking Overload

The point beyond which the load cell will physically fail or break. It is also expressed as a percentage of the rated capacity. This value is critical in systems where safety is a significant concern. 

Seal Type / IP Rating

The level of environmental protection offered by the load cell, such as to dust and water. It is often expressed as an IP rating. 

Cable Color Code

The color scheme used for the load cell’s wires. Review this before connecting any load cell to ensure that each wire is connected to the correct terminal.

Certifications 

Certified weighing systems generally require a certified load cell to maintain its certified status. Using a load cell without the proper certification may void the entire system’s certification. In the US, legal-for-trade scales should be serviced with NTEP (National Type Evaluation Program) certified load cells. Likewise, an FM approved facility should use FM-certified load cells according to your class and divisional requirements.

What is NTEP?

Interchangeable Reference

Since load cells are frequently swapped out, and a few common industry-standard designs make up most of the load cells used in North America, many manufacturers will provide a basic interchangeable table. Such tables list out other common load cell models of other suppliers against which a load cell has been checked to be interchangeable with. As some information in these tables can become outdated, and full interchangeability depends on many factors that may not be critical in most applications, you are still encouraged to carefully cross-reference both datasheets and consult an expert if you are uncertain.

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How to Connect a Load Cell to a Scale

Bench scales and floor scales are often sold separately from an indicator (also commonly referred to as a “scale head”). This guide will walk you through the basic steps of connecting a load cell wire to a weighing indicator. 

Note: Always follow the manufacturer's guidelines and safety measures while performing these steps. This guide serves as a general overview and your hardware might have specific requirements.

What You’ll Need

• Load cell cable or home run cable from a load cell junction box 
• Weighing Indicator 
• Screwdrivers (Phillips and regular) 
• Wire strippers 
• Multimeter (optional)

Step 1: Identify Load Cell Wires

Typically, a load cell or load cell junction box cable has 5 or 7 wires:

* Actual color of the wire can vary significantly from manufacturer to manufacturer. Please take care to verify this with the datasheet and product.

Step 2: Turn Off Power

Make sure the  scale indicator and any other connected devices are switched off to prevent electrical hazards. You may use the multimeter to double check.

Step 3: Prepare Wires

Use a wire stripper to expose about ¼ inch of the wire ends if they aren’t already prepared. Take care not to fray the wires.

Step 4: Open the Indicator

A wrench or screwdriver may be needed to open the back of your indicator. If you encounter any stickers or wires sealing the back of the indicator, check that you are not working with a legal-fortrade certified unit. Breaking any seals may void any such legal-for-trade certifications as they require an accredited technician to service.

Step 5: Locate Indicator Terminals

The indicator will have labeled input terminals corresponding to the load cell wires. Look for the terminals labeled:

• EX+ or VCC
• EX- or GND
• SIG+ or OUT+
• SIG- or OUT-

Some indicators will also have a terminal for the shield wire, usually labeled as SHLD or GND.

Step 6: Connect Wires

Thread the cable through the cable gland at the back, side, or bottom of the indicator. Using a small screwdriver, loosen the screws on the terminal blocks on the indicator. Insert the respective load cell wires into its corresponding terminals, and then tighten the screws. Make sure that the conductive metal of the wire establishes direct contact with the terminal's internal conductive component.

Step 7: Turn on Power and Calibrate

Turn on the indicator and follow the manufacturer’s calibration procedure to ensure accurate readings.  Calibration weights are generally required to perform this procedure. Certified calibrations such as ISO 17025 or State-level legal-for-trade certifications must be performed by an accredited technician. 

These are the general guidelines on how to set up most indicators: 

Power On: Turn on the indicator by pressing the designated power button or switching on the main power supply. Allow a few moments for the system to initialize. 

Enter Configuration Mode: Once the indicator displays its welcome or home screen, you'll need to access the configuration or setup menu. This is often done by pressing a 'Menu', 'Setup', or 'Config' button on the front panel, or by holding down a specific key combination as indicated in your user manual.

Password Protection: Some indicators have password-protected settings for added security. If prompted, enter the password to proceed. Default passwords are generally found in the user manual. 

Calibration Settings: Use the navigation buttons (often labeled as Up, Down, Left, Right, or similar) to scroll through the menu options. Look for an option labeled 'Calibration', 'Calibrate', 'Zero Balance', or something similar and select it. 

Tare the Scale: The first step in calibration is usually zeroing the scale, also known as 'taring.' Remove any weight from the scale and select the option to 'Zero' or 'Tare' the scale. 

Apply Known Weight: Now, you will be prompted to apply a known weight for calibration. This is often a weight that has been certified for its accuracy. Place the weight gently on the scale. 

Enter Known Weight Value: The indicator will usually ask you to enter the value of the known weight. Do so using the keypad. 

Calibration Confirmation: After the known weight is applied and its value is entered, the indicator will process this information to calibrate itself. You may see a message like 'Calibration Successful' once the process is complete. 

Save Settings: It's essential to save your calibration settings, which is usually done by selecting an option like 'Save', 'Apply', or 'Confirm'. 

Exit: Navigate back to the main menu or home screen by selecting 'Exit', 'Home', or a similar option, or by pressing the appropriate button.

Step 8: Test Scale

To verify that the calibration was successful, place the known weight back onto the scale and observe if the indicator provides the correct reading. Adjust settings or repeat the calibration steps if necessary. Additional functions on your indicator such as filtering options, unit conversions, data logging, print formats, and more can be fine-tuned at this stage to better suite your application needs. After making any adjustments, it is advisable to perform another test with a test weight to confirm that all settings are configured accurately for reliable and precise measurements.

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Troubleshooting Load Cells

Troubleshooting a load cell doesn't have to be a daunting task, even if you're not a tech whiz. Think of the load cell as the engine of your scale—it's the component that powers the weight measurement. Just like you'd listen to your car's engine for unusual sounds to diagnose issues, you can "listen" to your scale by keeping an eye out for irregular readings or behaviors. If your scale starts acting up, the issue could be with the load cell, like how engine problems can affect your car's performance. But it could also be something else entirely, like the setup of the scale or even external factors such as electrical interference. 

The key to effective troubleshooting is to take a step-by-step approach. Start by isolating the problem. Is the issue consistent or does it come and go? Are the readings off by a little or a lot?Once you have a handle on the symptoms, you can start digging deeper. And don't worry, you don't need an engineering degree to do this. Most of the time, a few simple checks can tell you a lot about what's going on. 

Remember, a scale is a tool, and like any tool, it needs to be maintained. A malfunctioning scale can throw off your entire operation, causing expensive downtime and costly repairs. So, let's get down to business and figure out what to look for when your scale starts giving you headaches.

Common Causes of Failure

Understanding the most common causes for scale and load cell failures can help you take preventative measures, reducing the risk of needing to repair or replace your weighing system. 

Overloading

Overloading occurs when a weight or force applied to the scale exceeds its maximum capacity. This can lead to permanent deformation of the load cell, affecting its ability to accurately measure weight and potentially causing it to fail. Significant overloading by >2-4x the rated capacity of the scale can by be a safety issue.

• Always be aware of your scale’s maximum weight capacity and avoid exceeding it 
• Purchase a higher capacity scale than needed if you expect to regularly overload a scale 
• Use overload stops or alarms to alert operators when they are nearing the scale’s limit

Shock Loading

Shock loading is the sudden and forceful application of weight onto the scale, as opposed to a gradual or gentle placement. Dropping a load, such as a box, from a few feet above the scale can easily cause more than 10x the amount of weight of the box. Doing so can instantly and irrecoverably damage the load cell.

• Always place items gently onto the scale 
• Use shock-absorbing materials or pads on top of the scale to minimize impact

Physical Damage

Any external force that harms the scale or load cell's structural integrity, such as forklifts swiping the feet of a scale, rodents chewing through the cables, etc. Damage to the cable is one of the most common sources of failure for load cells.

• If possible, keep the scale area clear of heavy machinery and potential hazards 
• Use protective casing for cables to prevent damage from rodents or other external factors 
• Do not lift or handle a load cell by grabbing onto its cable

Water Damage

Moisture ingress into the load cell, causing short circuits and corrosion inside the load cell or scale. Even humid environments can cause load cell failures over time due to condensation entering through microscopic cracks.

• Use scales and load cells rated for the operating environment 
• Avoid keeping scales and load cells in high moisture environments 
• Keep power sources and cables away from water

Surge Damage

Electrical surges, often caused by lightning or sudden changes in the electrical supply, can lead to immediate and severe damage to the load cell’s internal circuitry, along with damage to all other electronics.

• Use surge protectors on the power supply to mitigate the risk of electrical surges 
• Ground the scale and load cell system properly to disperse electrical charges safely 
• If possible, disconnect the scale from the electrical supply during storms or when not in use for extended periods 
• Avoid all welding, if possible, on or in proximity to your scales. Otherwise, ensure proper grounding and insulation is used

Corrosion Damage

Corrosion occurs when metal components of the load cell or scale come into contact with corrosive substances like acids, salts, or even moisture over an extended period. This can lead to the deterioration of the load cell's material and internal circuitry, affecting its accuracy and eventually causing it to fail.

• Use load cells made from materials that are resistant to corrosion, especially if used in harsh or outdoor environments 
• Keep the scale and load cell clean and avoid accumulation of substances that could lead to corrosion, such as water, dust, or chemical residues 
• Consider using hermetically sealed load cells that facilitate cleaning and prevent the ingress of corrosive agents

Troubleshooting Procedures

Scales can often be installed or located in hazardous environments. Under no circumstances should you attempt to troubleshoot a scale in such an environment if you are not qualified, authorized, and taking all necessary safety precautions. 

General Evaluation

• Visually inspect for any damage 
• If possible, safely clear any debris from under the scale 
• Check for force shunts (any obstructions or diversions of load away from the load cell) above and below the scale 
• Tighten any bolts, screws, and other mounting hardware if they may have come loose 
• Use a level to ensure that the weighing platform and the load cell are aligned 
• Inspect all the cables for disconnections, or any abrasion, punctures, cuts, and other damage

Scale Evaluation

• Check your indicator for any faults, defects, or damage
• Look for error messages or codes displayed on the screen 
• If possible, cycle power, reset and recalibrate your indicator. This can often resolve minor software glitches or calibration issues 
• Test the scale with a reliable test weight to verify its accuracy. Record the specific readings and note how it is different from the expected readings 
• Check for environmental factors like temperature, humidity, or electrical interference that could affect the scale’s performance 
• Consult any user manuals with the scale or indicator

Note: Scales can often be installed or located in hazardous environments. Under no circumstances should you attempt to troubleshoot a scale in such an environment if you are not qualified, authorized, and taking all necessary safety precautions.

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Load Cell Evaluation

⚠ DO NOT attempt to perform these evaluations if you are unable to take all proper safety precautions, are not confident in your ability to reassemble the scale, or are unfamiliar with operating a multimeter. 

⚠ DO NOT cut the load cell’s cable. Doing so will generally void any manufacturers’ warranties.

• Make sure to power off the entire system, that all work in the area is halted, and the load cell is disconnected from the scale. 
• You will need a high-quality multimeter and the means to safely remove the load cell.

Load cells operate by using strain gauges, which are essentially variable resistance sensors. These strain gauges are bonded to the material of the load cell, usually a metal, and they measure the strain (deformation) that occurs when a force is applied to the load cell. 

A strain gauge is a thin, conductive material arranged in a specific pattern (often a zigzag or meander pattern). When this material is stretched or compressed, its electrical resistance changes. Specifically, when the material is stretched (tension), the resistance increases; when compressed, the resistance decreases.

Wheatstone Bridge Circuits

Load cells typically use a Wheatstone bridge circuit, which is an electrical circuit used to measure an unknown electrical resistance by balancing two legs of a bridge circuit. A complete Wheatstone bridge circuit usually consists of four strain gauges: two in compression and two in tension. 

When you apply an excitation voltage to the load cell, it generates a millivolt (mV) signal through the output terminals. 

This signal is proportional to the force applied to the load cell and can be calculated using the following equation:

A complete Wheatstone bridge circuit typically uses four strain gauges. When it applies excitation voltage to the load cell it gives mV signal through the output terminals and the calculation works as below.

Load Cell Wiring

Excitation +/- 

These two terminals supply the voltage to the load cell. Regular analogue load cell can work between 5-15 VDC and 10VDC is typically recommended.

Signal +/- 

These two terminals give the mV signal out from the load cell.

Sense +/- 

When the load cell or junction cable is long (>20m/65ft) it’s recommended to use a load cell with 6-wire cable as it drops the actual excitation voltage due to the resistance of the cable.

Load Cell Testing

Test 1: Visual Inspection 

• Check for any damage to the load cell (e.g., abrasion, punctures, fatigue/wear, corrosion, dents, fissures, deformations, etc.) 
• If troubleshooting a new installation, check that the wires of the load cell cable are connected securely and to the correct terminal blocks in the junction box and/or indicator 
• Use a level to check if the load cell has been overloaded. If there are any detectable bends. A load cell that is overloaded might show visible deformations if the overloading was severe

Test 2: Check Terminal Resistance

Check the terminal resistance measurements against the load cell’s specifications.

Test 3: Zero Balance

Check zero balance measurement against the specifications.

Test 4: Check mV/V Stability 

Check the stability of the mV/V reading at no-load-applied conditions. If the load cell is unstable, there may be a loose connection or the internal circuit has been damaged, potentially by moisture ingress, or there may be a manufacturing defect or other issue.

Test 5: Check Positive Loading and Zero Return

Secure the load cell and manually apply gradual pressure at the live end of the load cell (the side that normally receives the load) in the direction of the load Pressing the load cell towards the positive loading direction should generate an increase in the mV/V reading. Release the pressure and it should return to zero after releasing

Test 6: Check Insulation Resistance

Check insulation resistance measurements against the load cell's specifications.

Quick Guide for Common Issues

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Need Expert Advice?

Scales Plus is a leading distributor of weighing equipment with one of the largest selections in the industry. If you need help choosing the right load cell, are looking for technical specs, need wiring diagrams, or advice about configuring a custom weighing system, you've come to the right place. Our team includes trained and licensed scale technicians that work in tandem with our sales support staff, providing a one-stop solution for everything weighing.

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Special Thanks to Anyload

Anyload is a leading manufacturer of load cells and weight sensors, with innovative solutions used across industries for critical weighing tasks. Scales Plus is an authorized distributor for Anyload, and as one of our closest partners, they worked with us on creating this comprehensive load cell guide.

Anyload Load Cells

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