Maybe you were driving by a weigh station and saw a bunch of semi-trucks in line waiting to drive over the scale or perhaps your company owns a 70 foot long truck scale. Or, maybe you are curious about buying a truck scale to weigh your vehicles. Either way, you’ve probably wondered at some point just how accurate are truck scales?
Truck Scale Accuracy
The truck scales that we offer are designed to meet NTEP Certification per Handbook 44 and they are NTEP Class IIIL. The scales are typically listed as 120,000 x 20 lb for example. The 120,000 lb is the max capacity of the scale and the 20 lb is the increment amount (graduation) that the scale displays weight in.
The scale is tested from zero to at least 12.5 % of scale capacity using known test weights and then to at least 25 % of scale capacity using either a substitution or strain load test that utilizes known test weights of at least 12.5 % of scale capacity. Whenever practical, a strain load test should be conducted to the used capacity of the scale. When a strain load test is conducted, the tolerances apply only to the test weights or substitution test loads.
Methods of Adjusting the Truck Scale
From time to time, truck scales will become inaccurate and need to be tested, adjusted, and calibrated. In most truck scales, individual load cells are adjusted and scale sections are adjusted by potentiometers in junction boxes. There may be as many as three truck scale junction boxes, usually located inside the truck scale weighbridge. The overall span adjustment for the scale system is usually done through the vehicle scale weight indicator.
So, How Accurate are Truck Scales?
Ok, so what is the actual answer to the question, how accurate are truck scales? The tolerance that we adhere to for accuracy is 0.1 of one percent of the applied weight. For example, if we place 25,000 pounds of weight on the scale, we are allowed +/- 25 pounds. Please see our entry on truck scale basics for more truck scale fundamentals.