How to Determine Load Cell Accuracy

Load Cell Accuracy: 5 Factors Affecting Load Cell Precision

In the precision-demanding world of industrial metrology, understanding and ensuring the accuracy of your load cell system is paramount. The load cell often is the cornerstone of weight measurement, and is crucial across various sectors, from manufacturing to logistics.

Fortunately, with Arlyn Scales, you aren’t alone. With this guide, we’ll help you understand load cell accuracy and the factors that affect it, which empowers you to determine precision and find the resolution of your load cell.

Understanding Load Cells and Their Role in Metrology

A load cell is a transducer that converts force into an electrical output signal, serving as a critical component in weighing systems. Understanding how load cells function and the different types available is essential.

At the heart of a load cell is its ability to accurately measure weight or force. When a load is applied, the cell deforms slightly, and this deformation is converted into an electrical signal, which can be measured and interpreted.

Various industries utilize different types of load cells, each suited to specific applications. Bending beam load cells, for example, are commonly used in tank weighing and industrial scales. Each type has its unique characteristics in terms of load capacity, sensitivity, and environmental suitability.

The Importance of Load Cell Accuracy

Accuracy in load cell measurements is a critical aspect that can significantly impact the overall efficiency and reliability of commercial operations. Understanding why load cell accuracy is essential and recognizing the potential consequences of inaccuracies is crucial for any industry relying on precise weight measurements.

The accuracy of a load cell determines how closely its output signal reflects the actual weight or force applied. This is vital in industries where precision is key, such as in manufacturing processes, quality control, and safety systems.

Inaccurate load cell readings can lead to several problems, including production errors, quality control failures, and safety issues. For instance, in the pharmaceutical industry, incorrect measurements can result in improper dosages of medications, while in construction, it could mean the failure to detect structural overloads.

5 Factors Affecting Load Cell Accuracy

While people can calculate accurate load cell output in theory, in real life there have to be accommodations for error. Due to the strain gauges being extremely sensitive, they can easily be damaged or skew the results.

Some basic factors include the weight indicator and how it is used, the environment in question, and the other control systems within the same area. Temperature extremes and damp environments, for example, can cause damage to the load cell if not monitored.

The interaction can interfere with the signal, especially if radio or electromagnetic waves are close in range. That’s why you need to properly ground and shield your load cells.

1. Load Cell Repeatability

Repeatability means that you consistently receive the same output when the same item is weighed on a regular basis. This is of particular importance for check weighing, which involves moving weights along an assembly line, such as with mail and luggage.

2. Percent of Rated Output (%RO)

The Percent of Rated Output indicates the margin of error, or variance. For example, if you have a 10,000-kilogram scale and the %RO is .10%, then the ideal resolution would be +/-10 kilograms.

3. Temperature Range

Arlynguard S

Some scale series, like our new Arlynguard S, are designed to handle extreme heat and cold in a variety of environments. When load cells aren’t built to endure, it can become a problem as mass expands when exposed to heat, and contracts as it cools.

In the case of water, it expands when cold, so the temperature affects water droplets as well. There is a temperature effect on output, which causes various fluctuations. The same goes for temperature condensation ranges, in which the cell is maintained.

When you work in temperature extremes, the condensation range can help you calculate the margin of error due to fluctuations from heat or cold. You can use it to measure the shifts in the load cell’s sensitivity as well as the amount of zero shift during weighing.

4. Load Cell Creep

If you are weighing the same item continuously over a long time, factor in potential load cell creep. Load cell creep is when output fluctuations happen as the same load is applied to a strain gauge over a long amount of time.

The intervals, in this case, are thirty minutes, and the creep errors are represented by percentages FSO. You can use the percentages of the error to calculate the correct amount.

This isn’t as important when you remove the items and loads immediately. However, it is if the items are weighed for more than thirty minutes.

5. Output & Input Voltage

Many load cell signals involve electrical currents that come through cables. Excitation fluctuation may vary, and this will also affect the readings from the cell. A proper load cell that matches the voltage should have a more consistent output.

Calibration: The Key to Accurate Load Cell Readings

Calibration is an essential process in maintaining the accuracy of a load cell. It involves adjusting the load cell to ensure that its output accurately reflects the applied force or weight. This process is crucial for counteracting the factors that can lead to inaccuracies in load cell measurements.

Calibration typically involves applying known weights to the load cell and adjusting its response until the output matches the applied weight. This ensures that the load cell’s output signal accurately corresponds to the actual force or weight, accounting for any environmental, mechanical, or electrical factors that may affect its performance.

Regular calibration is important because a load cell’s accuracy can drift over time due to factors like wear and tear or environmental changes. Regular calibration helps to maintain consistent output and ensures that the load cell remains reliable throughout its operational life.

For industries that depend on precise measurements, such as pharmaceutical manufacturing or material testing, regular calibration of load cells is a critical part of quality control processes. For more information about calibration, you can read this article on how to calibrate load cells.

Testing Load Cell Accuracy

Regular testing of load cell accuracy is crucial for ensuring reliable measurements. This process helps identify any deviations in accuracy and necessitates recalibration if needed. Here’s a guide on how to test the accuracy of a load cell:

  1. Prepare for Testing: Ensure that the load cell is correctly installed and positioned. The testing area should be free from environmental factors that could affect the results, such as vibrations or air currents.
  2. Select Appropriate Weights: Use calibration weights that are suitable for the load cell’s capacity. These weights should be certified and traceable to national or international standards.
  3. Apply Weights Sequentially: Place the weights on the load cell one at a time, observing the output signal after each weight is added. It’s important to apply the load centrally and uniformly to avoid errors.
  4. Record the Readings: Note the readings for each weight. The load cell should respond linearly as weights are added. Any non-linearity or inconsistency in the readings could indicate a problem.
  5. Compare with Known Standards: The readings should be compared with the known weights to assess the load cell’s accuracy. If there is a significant discrepancy, recalibration might be necessary.
  6. Check for Repeatability: Remove and reapply the weights multiple times to check the repeatability of the readings. Consistency in repeated measurements is a key indicator of a load cell’s precision.

By conducting regular accuracy tests, you can ensure that your load cell system remains reliable and precise. This is essential for maintaining the integrity of your measurements and the quality of your operations.

Interpreting Load Cell Accuracy Specifications

Understanding and interpreting the accuracy specifications of a load cell are crucial for ensuring that it meets your measurement needs. These specifications, typically found on load cell data sheets, provide valuable information about the performance and limitations of the load cell.

  • Rated Output: The rated output of a load cell indicates the electrical signal produced per unit of force or weight. It’s important to ensure that the load cell’s rated output aligns with the requirements of your measurement system.
  • Combined Error: This specification refers to the load cell’s accuracy in terms of the maximum deviation from a straight line during loading and unloading. A lower combined error indicates a more accurate load cell.
  • Non-Repeatability: Non-repeatability is a measure of the load cell’s ability to maintain consistent output under identical loading conditions. It is an important aspect of precision.
  • Understanding Terms Related to Accuracy: Other terms that often appear on load cell data sheets include ‘creep’ (change in output over time while under load), ‘hysteresis’ (difference in output readings for the same applied load during loading and unloading), and ‘temperature effect’ (impact of temperature changes on the load cell’s performance).

By carefully reviewing and understanding these specifications, you can make informed decisions about the suitability of a particular load cell for your application. This understanding is key to ensuring that your load cell system can achieve the required precision and accuracy for your specific measurement tasks.

Find Your Full-Scale Load Cells At Arlyn Scales

At Arlyn Scales, we believe that all weighing equipment should have precision and accuracy for regular business operations. You can trust us to ensure that each product is top-of-the-line and designed for your specific business need.

Our engineers have redesigned strain gauges so that load cells can handle potential shock overload. With our diverse catalog and advanced manufacturing, you’re empowered to decide which in our newest series is right for you, with the proper temperature range or the hazards involved in the workplace.

Best of all, we can help regardless of the load specifications involved or the loads applied to the weighing systems. To find out more about our load cells and how to determine their accuracy, reach out to our team today.