How accurate are the weighments at your truck scale? Outdated technology, heavy use, and time between calibrations can lead to performance degradation and inaccurate weighments.
A bulk grain facility recently realized its scale was off by 50 kg. per weighment, resulting in a loss of over $1,000 a day, or $20,000 per month! Fortunately, they discovered solutions like smart digital load cells and professional calibrations.
The weight accuracy of a truck scale can easily be taken for granted, but accuracy is crucial when buying or selling goods by weight. Throughout every weight-based transaction, your business relies on the ability of your scale to weigh as accurately and consistently as possible.
The Impact of Accuracy
Profit margins, inventory levels, and quality management are all directly affected by the accuracy of your scale. Many business owners are shocked to discover how many full truckloads worth of goods they could be giving away over time due to legally acceptable scale errors. Most truck scales are designed only to meet the minimum legal requirements. In many cases, they are calibrated to within +/-30 kilograms (or 60 pounds) of weighing error at full truckload values - and that error will grow in the time between calibrations. That much error can have a significant negative impact on your business. Modern technological advances now empower some vehicle scales to maintain a much higher accuracy level.
Influences on Scale Accuracy
Scale accuracy is influenced by several factors. Understanding them can help scale owners like you determine the best calibration schedule for your truck scale. All vehicle scales used for business transactions must be periodically calibrated to ensure they weigh within legal accuracy tolerances, as the accuracy of most scales drifts outside the specified ranges over time. Adequately maintaining your weighbridge reduces your overall cost of ownership and maximizes the operational life of your scale. Calibrations determine the accuracy of your scale, and accuracy impacts the profitability of your operation.
Advanced Technology
Understanding the basic differences between types of load cells can also help you understand the nature of the weighing system. Businesses that rely heavily on their scale may benefit from upgrading or converting to a more modern load cell system.
I never considered that my truck scale could give me inaccurate measurements. When I called METTLER TOLEDO to calibrate my scale, I quickly learned that I had been losing profits for months. After upgrading to POWERCELL PDX, I can finally know that my profits and my reputation are protected.
Sam, Facility Manager
Achieving Accuracy with Your Existing Truck Scale
The load cells in your scale may be a limiting factor of accuracy. If so, you can consider more frequent calibrations, or upgrading to a more advanced load cell system.
Discover Types of Load Cells
Analog Load Cells
Analog load cells have been in use since the 1980s and remain relatively unchanged. They are passive devices that measure weight through minuscule changes in electrical resistance. Although they can be calibrated to meet legal-for-trade accuracy standards, they can lose accuracy between calibrations. Analog load cells are highly susceptible to factors that can disturb accuracy, such as temperature, moisture, and electrical interference.
Hydraulic Load Cells
Hydraulic load cells use fluid to transmit the force of the load on the scale to a single analog load cell. They are intended to be physically resilient but still reflect the limited accuracy of analog technology. Hydraulic systems face unique challenges, such as maintaining the purity of the hydraulic fluid. With lengthy amounts of plumbing and many connections, leaking fluid is a common source of inaccuracy.
Digital Load Cells
Digital load cells transmit information using a stream of binary data, which is more stable than the small electrical current transmitted by analog load cells. Processing of the weight information only occurs once the signals reach the scale indicator. This means that the weight readings from the scale are only as good as the weakest load cell.
POWERCELL® Load Cells
POWERCELL load cells are active devices, that expand on the benefits of digital load cells by incorporating processing capacities at each load cell. These load cells can compensate for variables that affect weight readings using patented algorithms. The calibration procedure is also more precise; POWERCELL factory calibrations are computed digitally, with infinite coefficients. This means that the scale is much closer to "zero error" than possible with other technologies.
Achieving Accuracy with Weighbridge Maintenance
In commercial or legal-for-trade applications, scales must be regularly recertified by weights and measures authorities. Many scale owners assume that these recertifications ensure sufficient accuracy, but the error tolerances for minimum requirements can be significant. Even a recently certified scale could still be losing money.
Calibration standards can vary by location, however, the goal is the same – ensure the scale reading reflects the actual weight applied. If the readings fall outside of tolerance, the scale is adjusted and calibration is performed again. Even though legal-for-trade scales are periodically calibrated, many factors can be detrimental to the scale's accuracy.
Truck Scale Maintenance Steps
Visual Inspection
Preventative maintenance maximizes the life of your scale, preventing unforeseen breakdowns. After a thorough inspection, a scale condition report details the status of scale components, including the foundation, weighbridge, load cells, cables, junction box, and suspension or checking system.
Eccentricity (Shift) Test
An eccentricity test evaluates the ability of the scale to weigh the same load consistently, regardless of the placement of the load on the scale.
Error of Indication (Linearity) Test
An error of indication test is conducted to determine how the scale is weighing along a specified range, usually from zero to a certain percentage of the scale's capacity, using certified test weights
Strain Load Test
A strain load test determines a scale's performance in use. The technician places a large load on the scale and then adds the known load of certified test weights, verifying that the weight increases by the correct value.
Repeatability Test
The repeatability test determines if a known load applied to the scale will indicate the same value each time. For each repeated weighing, the indication value is recorded and compared against the first indication.
Download the free white paper for everything you need to know about the weighment accuracy and calibration of your truck scale. This white paper explores topics like determining the proper calibration period, evaluating calibration readings, making adjustments to improve accuracy, and more.
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