Sensors are the "core perception center" of the Sartorius balance, and their type directly determines the accuracy, stability, and adaptability to application scenarios of the balance.
The Sadolis balance mainly adopts two technical architectures: strain gauge sensors and electromagnetic force balance sensors, with customized sensor modules for some special scenarios.
This article will break down the technical characteristics and classification differences of two types of core sensors, and extract the key points of fault handling based on frontline maintenance experience, providing practical technical guidance for industry maintenance personnel.

1、 Classification and Technical Principles of Core Sensors

（1） Strain gauge sensor

The working principle of strain gauge sensors is based on the correlation effect between the deformation of metal elastomers and the change in strain gauge resistance. When the weighing pan carries a heavy object, the elastomer undergoes slight deformation,
The strain gauges pasted on its surface stretch or compress accordingly, causing a change in resistance value. The resistance signal is then converted into a voltage signal through a Wheatstone bridge, amplified and converted into digital to analog data to output weight data.

（2） Electromagnetic force balance sensor

Electromagnetic force balance sensors follow the principle of Lorentz force balance. When a heavy object is loaded, it will drive the lever linkage coil to produce displacement in the magnetic field of the permanent magnet,
The position sensor captures the offset signal and feeds it back to the servo amplifier. The coil generates electromagnetic force with precise current, forming a dynamic balance with gravity. The magnitude of the current is proportional to the weight, and the specific value is displayed after signal processing.

Sartoris divides these sensors into multiple categories based on accuracy levels, including precision types with a range ≤ 8.2kg and a resolution of 0.001-0.01g, and analytical types with a range ≤ 600g and a resolution of 0.1mg,
Semi micro/micro type with a range of ≤ 240g and a resolution of 0.001-0.01mg, as well as explosion-proof customized type that meets ATEX/IECEx standards. This type of sensor is widely used in high-precision scenarios such as laboratory research and development, pharmaceutical testing, etc., with a resolution of over 1 billion.
Its core technical feature is the use of closed-loop control and temperature dynamic compensation design, with a built-in temperature sensor that can real-time correct changes in the magnetic induction intensity of the magnet steel,
The temperature drift coefficient is as low as 2ppm or below, and it supports fully automatic internal calibration function. Some models integrate built-in weights, which can independently complete accuracy calibration. Its stability and anti-interference ability are significantly better than strain gauge sensors.

2、 Key performance differences between two types of sensors

In terms of accuracy range, strain gauge sensors have an accuracy of ≤ 0.01% and a resolution of ≤ 200000; The electromagnetic force balance sensor has an accuracy of ≤ 0.001% and a resolution of over 1 billion, with the latter having a significant advantage in accuracy.

In terms of stability, strain gauge sensors adopt open-loop control, which is easily affected by temperature and elastic deformation, and there is a high risk of numerical drift after long-term use;
The electromagnetic force balance sensor, with its closed-loop feedback and temperature dynamic compensation design, can effectively counteract environmental interference and has excellent stability performance.

The difference in calibration methods is that strain gauge sensors only support external weight calibration, and the operation process is relatively cumbersome; Electromagnetic force balance sensors have both external calibration and fully automatic internal calibration functions. Some models can start calibration with one click, greatly improving operational efficiency.

In terms of temperature drift coefficient, the strain gauge sensor is about 8ppm, and frequent calibration is required when the ambient temperature fluctuates greatly; The temperature drift coefficient of the electromagnetic force balance sensor is controlled below 2ppm, which has stronger adaptability to temperature.

3、 Common faults and maintenance techniques of sensors

（1） Common fault handling

When encountering zero position jumping or numerical drift problems, priority should be given to investigating foreign objects in the scale pan, airflow interference, and power stability, as these external factors are often the main causes of faults.
If the fault still persists after excluding external factors, the strain gauge sensor needs to check whether the elastic adhesive is aging, and the electromagnetic force sensor needs to clean the dust inside the magnetic cylinder. When disassembling, the coil connection wire should be disconnected first to avoid the spring plate breaking under force.

（2） Exclusive fault repair

One of the common faults of strain gauge sensors is excessive corner error, which is often caused by deformation of the elastic body or displacement of the strain gauge. During maintenance, the installation position of the sensor needs to be recalibrated,
When replacing damaged strain gauges, it is necessary to ensure that the adhesive thickness is uniform and the curing process meets the standards. When there is a weak signal problem, it is necessary to check the balance state of the Wheatstone bridge, detect the consistency of the strain gauge resistance through a multimeter, and replace the strain gauges with excessive resistance deviation in a timely manner.

If the electromagnetic force sensor reports errors of "L/E" or "CH2", it is mostly due to abnormal coil displacement. You can first reposition the scale and lightly press it to reset, and observe whether the fault is eliminated;
If it is ineffective, it is necessary to check whether the lever spring plate is broken and whether the coil is stuck. During the disassembly process, special tools should be used to avoid damaging the magnetization performance of the magnetic steel.
When there is a sudden drop in accuracy, priority should be given to fully automatic internal calibration. If internal calibration fails, it is necessary to check whether the built-in weights have shifted and whether the magnetic induction intensity of the magnetic cylinder has decreased. If necessary, contact the original factory for magnetic steel magnetization or coil calibration.

（3） Core Precautions for Maintenance

When disassembling sensors, it is necessary to perform anti-static operations throughout the process to avoid static electricity from penetrating sensitive components such as coils or circuit boards. The core components of electromagnetic force sensors, such as coils and magnetic cylinders, must not collide, and the elastic spring should avoid excessive force to prevent irreversible deformation.

After maintenance, calibration needs to be completed according to the Sartorius standard process. Strain gauge sensors require four point calibration using standard weights to ensure that the errors at each weighing point meet the requirements; Electromagnetic force sensors need to undergo internal calibration and external weight comparison to double verify whether the accuracy meets the standards. The calibration results must meet the JJG verification standards.

After repairing explosion-proof sensors, the explosion-proof sealing performance needs to be re verified. It is strictly prohibited to change the circuit layout or replace non original accessories without authorization to avoid damaging the explosion-proof structure and causing safety hazards.

4、 Conclusion

The classification design of Sartorius balance sensors fully considers the accuracy requirements and cost control of different scenarios. Strain gauge sensors cover the general market with high cost-effectiveness,
In the maintenance practice of electromagnetic force balance sensors, it is necessary to first clarify the sensor type and core technical characteristics, conduct targeted troubleshooting of the root cause, and strictly follow the original factory maintenance specifications and calibration standards,
To restore device performance to the maximum extent possible. In the future, as Sartorius sensor technology upgrades towards intelligence and miniaturization, maintenance work also needs to pay attention to the application of module integration maintenance and software calibration technology, continuously improving maintenance professionalism and efficiency.