Onboard weighing system is a highly demanded option among GPS tracking provides as the system helps to avoid heavy fines for overload, prevent cargo theft and unauthorized fleet usage. Due to the relative novelty of the solution, it is not so wide-spread, that gives an integrator a chance to stand out among competitors.

Basically, there are two possible ways to calculate axle load and cargo weight.

1. Server-based calculations. All possible calculations can be made on GPS tracking platform’s side. In this case, onboard hardware consists of a GPS tracker and axle load sensors only.

2. Onboard-based calculations. Let us say that customer’s requirements include onboard display with actual axle loads, gross and net cargo weight. It means we have to calculate all data onboard. The first generation of axle load sensors had only analog output. Thus the solution for a large number of axles and sensors required the introduction of an ADC module – eurosens Difference-T. The module is used to convert voltage to digital messages in RS485 or CAN bus.

Onboard weighing system components with onboard calculation (1st generation)

Latest axle load sensors already have RS485 or CAN bus interface. So one can connect any number of sensors directly to the GPS tracker using RS485 or CAN bus. Eurosens Display will collect data from all sensors, calculate total and cargo weight and provide data to the GPS tracker.

How to calculate the cost of the solution? The main factor here is the number of axle load sensors to be installed. Let’s go through the short questionnaire:

1. How many axles are there in a vehicle (and trailer)?

2. How many lifting axles are there?

3. Which type of cargo does the vehicle carry? The type of cargo defines the type of its distribution. See the difference between the even (front-rear, left-right) and a random distribution (the cargo can be placed anywhere).

The truck with even distribution requires only ONE sensor installed in the middle of the rear axle (one of rear axles). The vehicle with a random cargo distribution requires 2 sensors (front and rear) installed in the middle of the truck (otherwise, add left-right sensor).

Which accuracy it is possible to get?

For leaf spring suspension axle load can be calculated with 5-7% error from the maximum axle load. And total vehicle load can be calculated with 5-10% error from vehicle’s gross weight (or vehicle + trailer).

For air spring suspension: 2-3% error of the maximum axle load and 3-5% error from vehicle’s gross weight.

Example: Unloaded vehicle has 5000 kg weight, while loaded – 12000 kg. Measurement error for empty and full state will be approximately the same: +/-600-1200 kg error for empty and full state (leaf spring suspension vehicle) and +/- 240 kg (for air spring suspension).

Mechatronics’ team is working on adding extra features for on-board weighing, thus created several special modules for GPS tracking. One of them is for dump trucks and second one for garbage trucks.

New Eurosens axle load sensors with digital interface reduces the total cost of advanced onboard weighing system for truck+trailer combinations with a large number of axles.

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