Effective management of cargo transportation today is impossible without accurate control of the mass of transported cargo. Installation weight sensors for a truck with air suspension is not just a way to avoid fines, but a necessity for optimizing logistics processes. Unlike mechanical springs, air springs provide stable body geometry, making them an ideal platform for integrating weighing systems. The accuracy of readings in such systems directly depends on the quality of the sensors and the correctness of their settings.
Modern monitoring systems allow the driver to see the current weight of each axle in real time right in the cab. This eliminates situations when the machine goes to the weight control with an overload, which is fraught with huge fines and downtime. In addition, electronic weighing systems Help distribute load evenly, extending the life of tires, brake pads and the suspension itself. Properly selected equipment pays for itself in several flights.
In this article we will analyze in detail the operating principle of such systems, consider the types of sensors and give step-by-step instructions for their implementation. You'll learn how to avoid common installation mistakes and why calibration is a critical step. Understanding the physics of a pneumatic system will help you choose the best solution for your fleet.
Operating principle of air suspended weighing systems
The basis of any weighing system on a truck with air suspension is the direct dependence of the air pressure in the air springs on the weight per axle. The heavier the load, the higher the system pressure required to hold the frame at a given height. Pressure sensorsinstalled in the highway, read these changes and convert them into an electrical signal. Then the control unit (indicator) converts this data into understandable kilograms or tons.
It is important to understand that the system does not weigh the load directly, like scales in a store, but calculates its mass based on pre-entered calibration coefficients. This is why initial setup with reference weighing is so important. Without precise reference points (zero weight and known reference weight), the readings will have a large error. Modern controllers are able to compensate for thermal expansion of air and non-linearity of the characteristics of rubber cylinders.
⚠️ Attention: The pressure in the pneumatic system may fluctuate (fluctuate) when the engine is running and driving on uneven roads. To obtain accurate readings, weighing should be carried out on level ground with the engine turned off or after the pressure in the receivers has stabilized.
There are systems that read data directly from the pillows, and those that cut into the common highway. The first option is often considered more accurate, since it eliminates the influence of pressure in other circuits if they are separated by valves. However, the second option is easier to install and maintain. The choice of a specific type depends on the design of the particular tractor or trailer and the requirements for measurement accuracy.
Types of sensors and their technical features
The market offers several types of sensors, each of which has its own advantages. Most common strain gauges, which are installed between the cushion and the frame or body. They measure the mechanical deformation of an element under load. Such systems are distinguished by high accuracy (error up to 1-2%) and independence from the state of the pneumatic system, but require more complex installation with body lifting.
The second popular type is pressure sensors (converters), which are mounted in the gap of the pneumatic line. They are cheaper to install and easier to replace. Modern models of such sensors are equipped with built-in microprocessors, which allows filtering pressure pulsations. For commercial vehicles, combined systems are often used, where pressure is monitored for the overall picture, and critical axles are equipped with strain gauges.
When choosing equipment, you should pay attention to the degree of protection of the housing. The truck is operated in harsh conditions: vibration, moisture, reagents on the roads, temperature changes. The optimal standard is IP67 or IP69K. Resistance to electromagnetic interference is also important, since there are many sources of radiation in the cab of a modern truck.
- 🔹 Strain gauges: high accuracy, installation complexity, high cost.
- 🔹 Pressure sensors: average accuracy, easy installation, affordable price.
- 🔹 Optical sensors: used less frequently, require clean surfaces, sensitive to dirt.
When purchasing pressure sensors, make sure that their operating range (eg 0-15 bar) corresponds to the maximum pressure in your pneumatic system, otherwise the sensor may fail when operating the floor level valve.
Criteria for selecting equipment for a vehicle fleet
Choosing a weighing system is a balance between budget and required accuracy. For internal warehouse operations where only a rough estimate is needed, simple pressure sensor-based systems are suitable. If your vehicle regularly undergoes state weight control and the risks of fines are high, it is better to invest in certified complexes with strain gauges. An important parameter is the presence verification certificate, if the system is used for commercial accounting of cargo.
The functionality of the indicator in the cockpit also plays a role. Basic models just show numbers. Advanced on-board computers are able to accumulate statistics, signal overload with sound, transmit data via Bluetooth to the dispatcher’s smartphone or integrate with satellite monitoring systems (GLONASS/GPS). This allows logisticians to see the weight of the vehicle in real time, without contacting the driver.
| System type | Accuracy | Difficulty of installation | Cost |
|---|---|---|---|
| Pressure sensors | 3-5% | Low | Low |
| Load cells | 1-2% | High | High |
| Combined | 2-3% | Average | Average |
| Optical | 2-4% | Average | High |
Don't forget about compatibility with the on-board voltage. Truck Standard - 24 V. Use of systems designed for passenger cars 12 V, will require additional converters, which reduces reliability. Also check the length of the wiring harnesses: on long trailers, the standard length may not be enough, and you will have to make extensions, which is a potential point of failure.
Effect of temperature on readings
During the cold season, the air in the pneumatic system is compressed, and the pressure drops at the same volume. High-quality controllers have temperature compensation, but cheap models can give an error of up to 5% in winter.
Installation technology: step-by-step instructions
System installation begins with careful preparation. It is necessary to turn off the car, relieve pressure from the system and provide access to the pneumatic frame and cylinders. If you install load cells, the body will need to be lifted, which requires a pit or lift. Installation of pressure sensors is simpler: they fit into standard tubes through tees going to the pillows.
Laying the wiring is the most critical stage. The cable must be protected with corrugation and securely secured with clamps to avoid chafing against moving parts of the suspension. All connections must be made using waterproof connectors. It is better to connect the power wires through a separate fuse in the mounting block, and not directly to the battery, in order to avoid problems during diagnostics.
☑️ Checklist before starting the system
After physical installation, the connection phase to the control unit follows. It is important to observe polarity here. The indicator is mounted in the cockpit so that the driver can see it without taking his eyes off the road, but it should not reflect on the windshield. It is often placed in the center console area or on the ceiling. The fixation must be rigid so that vibration does not damage the contacts.
⚠️ Attention: When drilling a frame or body to attach sensors, use only metal drills with high-quality sharpening and be sure to treat the holes with an anti-corrosion compound. Damage to the side member can have serious safety consequences.
System calibration and setup
The system will not display the correct weight immediately after installation. A calibration procedure is required. It consists of taking readings in two states: “empty” (car without load, full tank) and “standard” (car with a known load weight). Calibration allows the control unit to build a linear relationship between pressure and mass. The more accurately you know the weight of the reference load, the more accurately the system will work in the future.
The process usually looks like this: we drive an empty car, record the sensor readings for each axle. Then we load the car with a known weight (for example, on stationary scales) and enter this data into the indicator menu. Some modern systems allow calibration to be done on the fly, using data from government scales passed as reference points. This is convenient, but less accurate for initial setup.
It is important to periodically (every six months or season) check the readings. Air springs age and rubber changes its elasticity, which may shift the calibration curve slightly. If you notice that the system is consistently lying at a certain percentage, the calibration procedure must be repeated. It takes no more than 15 minutes.
High-quality calibration on a stationary scale with a known accuracy is the only way to guarantee the accuracy of the on-board weighing system.
Operation and common errors
During operation, drivers may encounter a number of problems. One of the most common is “walking” readings. This is often due to air leaks in the pneumatic system or a malfunction of the pressure sensor itself. If the pressure drops, the system thinks that the weight has decreased. Regular inspection of pneumatic lines for fistulas will help avoid false readings.
Another mistake is ignoring the difference in axle loading. The system can show total weight or weight by axle group, but does not always see misalignment. The driver must understand that even with normal total weight, overloading one axle (for example, due to shifting cargo) will result in a fine. Modern systems with individual sensors for each pillow help solve this problem by showing weight distribution in real time.
It's also worth mentioning the impact of suspension modifications. Installing additional lift axles, changing the rigidity of pneumatic elements, or replacing standard cylinders with tuning ones require recalibration of the system. The physical parameters of the system have changed, and the old coefficients are no longer relevant.
- 🔸 Regularly check the integrity of pneumatic tubes and fittings.
- 🔸 Do not allow water to enter the pneumatic system through the air compressor.
- 🔸 When replacing pneumatic cylinders, be sure to recalibrate the scales.
Usage weight sensors turns the truck into a smart logistics tool. This reduces risks, saves money on fines and fuel, and also extends the life of the equipment. The right choice, competent installation and timely maintenance are the three pillars on which the effectiveness of this system rests. Don’t skimp on the quality of sensors, because the cost of a mistake on the road can be very high.
Is it necessary to register the installation of weight sensors with the traffic police?
The installation of a weight monitoring system itself does not require changes to the vehicle design in the registration certificate, since this is an auxiliary equipment that does not affect traffic safety (brakes, steering). However, if the installation involves major intervention in the frame or air system, this could theoretically be considered a design change. In practice, if the sensors do not disrupt the operation of standard systems and do not change dimensions, inspectors do not have any questions.
Is it possible to connect sensors to a tachograph?
Technically possible, but difficult and rarely done routinely. Tachographs have strict certification requirements, and connecting third-party weight sensors may interfere with their sealing or operation. Typically, weight data is transmitted through a separate GLONASS/GPS tracker, which already transmits it to the dispatcher’s server, bypassing the tachograph.
How often should pressure sensors be replaced?
The service life of high-quality pressure sensors is 5-7 years or more. However, in conditions of an aggressive environment and constant vibration, the actual period may be shorter. It is recommended to diagnose their readings at each maintenance. If the readings begin to jump sharply or go to zero/maximum without changing the load, the sensor requires replacement.
Does the system work at -40°C?
Most industrial sensors have an operating range down to -40°C or even -50°C. However, in severe frosts, condensate in the pneumatic system may freeze, blocking the transfer of pressure to the sensor. Having an air dryer in the system is critical for winter operation of a truck with air suspension and scales.