How Truck Weighing Works

Some of the states in the US use truck weighing as a reference when calculating the taxes for transported goods but also to ensure that the weight of the truck transporting the respective good is within the specifications of the road system. The maximum weight may vary according to the characteristics of the road, but by some standards it cannot exceed the 15,400kg limit.

Basically there are two ways you can weigh a truck. One would be to measure the weight on each axle at a time, while the second method implies weighing the whole truck at once.

The most popular technology used to weigh trucks involves load-cell systems, which consists of a cell constructed out of a durable material such as steel, concrete, or a combination of both. One or more sensors - strain gauges - are attached or embedded in the cell. When load is applied the material the cell is made of is compressed or subjected to a tensioning force. The strain is then picked up by the sensors, which translate it into electrical resistance that can be measured in order to calculate the weight of the truck.

Another system regularly used for such applications is the bending-plate system, which only uses metal plates that have strain gauges attached to them. Again, when the metallic plate is subjected to stress the strain gauge measures the applied pressure to calculate the weight.

Alternatively, the strain gauges may be replaced with piezoelectric sensors. In this configuration, the load-cells must be made out of conducting material, so that when load is applied the electrical resistance through the material changes, allowing the sensors to calculate the weight of the load depending on the voltage of the current circulated through it.

Weighing systems can measure the load on one axle either during a stop or while the truck is in motion.

The one-axle method, involves gradually driving the truck across a series of load-cells that measure the load on each axle and then show the total weight by adding them together. One-stop systems weigh the whole truck at once on a scale containing a single strain sensor, while weigh in motion methods measure the load of the truck without the need for any stops. Such systems can even be installed directly into the road, monitoring all the traffic as it circulates at high speeds.