Causes and Solutions of Temperature Drift in Weighing Sensors

By the assembly line in industrial production, when the ambient temperature rises from 20ºC in the early morning to 35ºC in the afternoon, the weighing data of the same batch of products may show continuous deviations. In cold storage warehouses, electronic scales in low-temperature environments can never return to zero when unloaded. In dynamic weighing systems on highways, high temperatures in summer may cause the weighing data of freight trucks to fluctuate unpredictably. Behind these phenomena lies a common problem — temperature drift of load cells. As the "nerve endings" of precision measurement, the temperature stability of load cells directly determines the reliability of the measurement system, and temperature drift has become one of the most hidden and influential error sources in industrial metrology.

The temperature drift of load cells is essentially the interference caused by changes in ambient temperature to the measurement system through two paths: material properties and structural stress. For load cells based on the strain gauge principle, their core working mechanism is to convert the mechanical deformation of the elastic body into measurable electrical signals through strain gauges, and both of these key components are extremely sensitive to temperature.

As a force-sensing component, the geometric dimensions and mechanical properties of the elastic body change significantly with temperature. The thermal expansion coefficient of ordinary steel is approximately 11.5×10⁻⁶/ºC. When the temperature changes by 10ºC, the length change of the elastic body may lead to a structural error of 0.01%~0.05%. This thermal expansion and contraction effect directly changes the deformation characteristics of the elastic body: when the temperature rises, the deformation under the same load decreases, resulting in a low output signal; when the temperature decreases, the deformation increases, resulting in a high output signal, forming a typical "structural temperature error". In high-temperature environments such as metallurgical workshops, this error may be further amplified because continuous high temperatures will reduce the elastic modulus of metal materials, causing the elastic body to produce greater deformation under the same load.

As a signal conversion component, the strain gauge has more complex temperature sensitivity. The resistance value of metal foil strain gauges (such as Constantan, Nichrome alloy) has a significant positive temperature coefficient. Even in the unloaded state, a temperature change of 10ºC may cause a zero drift of 0.02%~0.1% FS. More importantly, the sensitivity coefficient of the strain gauge (the resistance change rate corresponding to unit deformation) also fluctuates with temperature, resulting in changes in the output signal amplitude under the same deformation. Although semiconductor strain gauges have higher sensitivity, their resistance temperature coefficient is 10~100 times that of metal strain gauges, and the problem of temperature stability is more prominent. When the temperature gradient is unevenly distributed inside the sensor, the resistance changes of each arm of the bridge are not synchronized, which will further aggravate the degree of zero drift.

Temperature changes also affect measurement accuracy through indirect paths. The adhesive inside the sensor will age under the action of temperature cycles, leading to a decrease in the bonding strength between the strain gauge and the elastic body, introducing additional measurement lag. Cables will become hard and brittle in low-temperature environments and may have reduced insulation performance at high temperatures, both of which will increase noise interference in signal transmission. The voltage fluctuation of the power supply system due to temperature, although usually within ±1%, will also cause a 0.005%~0.01% change in the zero output. The superposition of these factors makes temperature drift a complex problem of multi-dimensional coupling.

 

Systematic Solutions: From Hardware Optimization to Intelligent Compensation
To solve the problem of temperature drift, a multi-level technical defense line needs to be established, combining hardware design optimization, circuit compensation, and intelligent algorithm correction to form a full-chain error control system. Modern weighing technology has developed a variety of mature and reliable solutions, which can be flexibly selected according to the accuracy requirements and environmental conditions of different application scenarios.
Temperature adaptation at the hardware level is the basis for controlling errors. Selecting materials with low temperature coefficients is the primary strategy. The elastic body can use low-expansion alloys such as Invar (with a thermal expansion coefficient of only below 1.5×10⁻⁶/°C). Although the cost is relatively high, it can significantly reduce structural temperature errors. For strain gauges, temperature self-compensating products can be selected. By adjusting the alloy composition to match the resistance temperature coefficient with the linear expansion coefficient of the elastic body, most temperature effects can be offset. In extreme environments, special sensor models need to be used: for high-temperature environments (>60°C), sensors with high-temperature resistant adhesives and wires should be selected, with an operating temperature of up to 150°C or even 300°C; for low-temperature environments (<-10°C), cold-resistant cables and low-temperature electrolyte components need to be used to avoid material embrittlement and performance degradation. In terms of mechanical structure design, adopting a symmetrical layout and thermal isolation measures can reduce the unbalanced stress caused by temperature gradients. For example, adding a thermal insulation pad between the sensor and the mounting base can reduce the environmental temperature conduction efficiency.
Circuit compensation technology provides a second layer of guarantee for error control. The most commonly used is the hardware compensation method, which offsets the temperature effect of the strain gauge by connecting temperature compensation resistors in series or parallel in the measuring bridge. Zero temperature compensation usually uses a compensation resistor different from the strain gauge material, utilizing its opposite temperature coefficient characteristic to neutralize zero drift; sensitivity temperature compensation adjusts the bridge excitation voltage by connecting a thermistor in series in the power supply circuit, reducing the temperature sensitivity of the output signal. For high-precision applications, a dedicated temperature compensation chip can be used to monitor the sensor temperature in real time and dynamically adjust compensation parameters. High-end sensors from manufacturers such as Futek have built-in multi-group compensation resistor networks, which can control the temperature error within 0.005% FS/10°C in the range of -40°C to 85°C.
Software algorithm compensation constitutes the third dimension of error control, especially suitable for scenarios with severe temperature fluctuations. The basic idea is to establish a temperature-error model, collect the ambient temperature in real time through a temperature sensor, and then correct the measured value according to a preset compensation curve. In microcontroller systems such as STM32, a temperature compensation data table can be established through experiments, and a linear interpolation algorithm can be used to achieve real-time correction. In a certain case, engineers established temperature compensation points at 10°C, 20°C, 30°C, 40°C, and 50°C, established a weight correction coefficient matrix, and reduced the temperature drift error by more than 60% under the condition of allowing the temperature to fluctuate.
The systematic environmental control measures are also indispensable. By means of air conditioning, heat insulation, and heat dissipation, the working environment temperature fluctuation of the sensor can be controlled within ±5°C, which can greatly reduce the pressure on the compensation system. In occasions with large vibrations, shock absorption devices need to be added to reduce additional temperature and stress interference caused by mechanical impact. Regular calibration can ensure the long-term stability of the compensation effect. It is recommended to carry out it when the environmental temperature changes greatly in different seasons, or use an intelligent weighing system with automatic calibration function, which can maintain measurement accuracy in an unattended situation.

 

Scenario-Based Application Cases: From Laboratory to Industrial Site
The solutions to temperature drift need to be deeply integrated with specific application scenarios. The measurement requirements and environmental characteristics of different industries vary greatly, which determines that the selection of technical solutions must be adapted to local conditions. From precision laboratories to harsh industrial environments, successful application cases provide us with valuable practical experience.
In the cold chain storage field of food and medicine, the problem of temperature drift is particularly prominent. A large cold storage found that when using ordinary load cells, there was a deviation of 2%~3% in the weighing of the same batch of goods every day between early morning (warehouse temperature about -18°C) and afternoon (warehouse temperature about -15°C), which seriously affected the accuracy of trade settlement. The technical team solved the problem through three steps: first, replaced it with a low-temperature resistant sensor, whose cable adopted cold-resistant polytetrafluoroethylene material to ensure flexibility even at -30°C; second, installed a PT100 temperature probe near the sensor, connected the temperature signal to the weighing indicator, and calibrated at different temperature points to establish a segmented compensation model. After the transformation, even if the warehouse temperature fluctuates between -20°C and -10°C, the measurement error can be controlled within 0.1%, completely solving the cold chain measurement dispute problem. This case shows that the combination of material adaptation and software compensation is an effective solution in low-temperature environments.
The high-temperature weighing scenario in the metallurgical industry faces completely different challenges. In the continuous casting production line of a steel plant, it is necessary to weigh the steel ladle online. The working environment temperature of the sensor is as high as 80°C~120°C, and ordinary sensors show obvious drift after one week of use. The solution adopts a three-layer protection strategy: at the mechanical level, a water-cooled jacket and a heat insulation baffle are added to the sensor to control the temperature of the sensor itself below 60°C; at the hardware level, high-temperature strain gauges (working temperature 150°C) and high-temperature curing adhesive are selected; at the software level, a dynamic compensation algorithm based on Kalman filtering is developed, combined with a furnace temperature prediction model to correct the temperature impact in advance. The transformed system maintained a measurement accuracy of 0.2% in continuous production, and the service life of the sensor was extended from 1 week to more than 6 months, significantly reducing maintenance costs. This demonstrates the importance of comprehensive protection in extreme high-temperature environments.
The high-speed highway dynamic weighing system faces the test of 剧烈 temperature fluctuations. In a certain province, at noon in summer, direct sunlight causes the temperature of the load cell to rise rapidly, differing from the ambient temperature by up to 30°C, resulting in a weighing data deviation of more than 50kg at different times of the same vehicle. The solution adds a synchronous reference channel to the weighing indicator, which corrects the weighing signal slope in real time by monitoring the temperature drift of the fixed resistor; at the same time, the sensor installation structure is optimized, using heat insulation materials to block direct sunlight and adding ventilation and heat dissipation design. After the improvement, the temperature drift of the system is reduced by more than 70%, and it has passed the dynamic accuracy certification of the National Institute of Metrology, effectively reducing toll disputes. This case proves that real-time hardware compensation technology has unique advantages in scenarios with rapid temperature changes.
The field of laboratory precision weighing has more stringent requirements for temperature stability. The electronic balance in a pharmaceutical research laboratory cannot pass the metrological verification when the ambient temperature changes by more than 2°C. The technical personnel adopted a solution combining environmental control and algorithm optimization: a micro constant temperature device was installed inside the balance to control the working temperature fluctuation of the sensor within ±0.5°C; a temperature-weight model based on a neural network was developed to predict and compensate errors through multi-point sampling. Finally, the system achieved a measurement accuracy of 0.001%, meeting the high-precision requirements of pharmaceutical research and development. This reflects the technical route of fine control in high-end metrological equipment.