Most states prefer to collect taxes based on the weights of goods in transit as determined at weigh stations. Weigh stations also help the government to monitor weights of trucks to ensure safety on the road. How much weight you can legally carry on a truck varies from one state to another; a common standard is 34,000 pounds (15,400 kilograms).

The weight of a truck is typically calculated in two measurements; axle weight and gross weight. Axle weight is the amount of weight carried by each axle while gross weight is the combined weight of all axles.

Truck Scales Truck weights are measured using truck scales. Truck scales are built to withstand enormous amounts of abuse.  For instance, some modern scales can handle gross weights of more than 80,000 pounds (36,000 kilograms) each day at rates of more than 200 trucks a day, 365 days a year.

Commonwealth Industrial’s truck scales can support up to 200,000 lbs which shows just why we are the preferred weigh station in Virginia.

Types Of Truck Scales

All truck scales are built from steel, concrete, or a combination of both. However, different weigh scales work differently. Load cell scales are the most common. Here, each cell is made from a durable material such as steel or concrete with at least one strain gauge attached to or embedded in the cell. A strain gauge basically consists of one or more wires that transmit mild electric current. When you subject the cell to weight, the wire(s) inside the cell is/are slightly compressed or altered. The signal from each cell is then sent to a nearby junction box where sensors measure variations in current. This variation is what is used to calculate the amount of weight sitting on the scale.

There are two types of strain gauges; compression and tension. Compression gauges rely on how much the scale cells compress when under pressure while tension gauges depend on slight changes in cell shapes.

Bending Plate Scales

These scales use metal plates attached to strain gauges. When you apply weight, the plates are subjected to stress. Strain gauges only need to determine how much stress is exhibited at each plate to determine how much weight is sitting on the plate. The sum of measurements from each gauge gives the total weight at that axle.

Piezoelectric Scales

These scales use a series of piezoelectric sensors. When subjected to weight, pressure within the scale alters the voltage of the charge flowing through the electrical conductor onto which the sensors are embedded. The sensors measure the voltage variation and use it to calculate the weight on the scale. The results from all sensors are added together.

Methods of Weighing Trucks

Apart from the different weigh scale technologies, there are 3 different ways of weighing trucks;

1. One-axle – a truck drives over a single scale, stopping every time a set of wheels rest on the scale. The total for all sets of wheels is added to obtain the gross weight.
2. Onestop weighing – a set of scales positioned strategically and connected to a single electronic controller combine the axle weights to give the gross weight straight away.
3. Weigh in motion (WIM) – a series of embedded sensors calculate the weight at each axle as the truck drives over a sensor pad. The truck doesn’t need to come to a stop.