Temperature-Compensated Deflection Sensor for Truck Weighing
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Solution Overview
Problem
Conventional onboard weighing systems for trucks using deflection sensors suffer from inaccurate weight readings due to temperature fluctuations and the thermal coefficient of expansion of structural members, requiring complex calibration and additional wiring, making them impractical for widespread use.
Innovation Solution
A temperature-compensated deflection sensor system that calculates load weight values using both load and temperature sensor outputs, applying statistically-generated compensation factors to provide accurate weight measurements across varying temperatures and loads, with programmable controllers and integrated circuitry for reduced noise and easier installation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional deflection sensors are used for onboard weighing, then weight measurement capability is provided, but measurement precision deteriorates due to temperature fluctuations and thermal expansion
Solution Approach 1:
The patent converts the harmful thermal effects into a useful compensation signal by measuring the temperature with a temperature sensor and using it to calculate compensation values. The temperature-dependent output changes are not merely corrected but utilized to determine the actual load by comparing against pre-stored reference values, turning the previously harmful thermal expansion and sensor drift into a measurable parameter for accurate compensation.
Solution Approach 2:
The patent introduces a temperature sensor as an intermediary element that measures the ambient temperature affecting the deflection sensor. This temperature measurement serves as a mediator between the thermal environment and the load measurement system, enabling the controller to retrieve appropriate compensation factors from memory and apply them to correct the deflection sensor output, thereby isolating the load measurement from temperature influences.
2Measurement precision
If zero-offset temperature-compensating resistors are added to strain gauge circuitry, then temperature compensation is provided for no-load case, but measurement precision deteriorates under loaded conditions
Solution Approach 1:
The patent replaces the static zero-offset compensation approach with a dynamic compensation system that adapts to different load conditions. Instead of using fixed resistors that only compensate for no-load temperature effects, the system dynamically retrieves temperature compensation factors from memory based on the current temperature reading and applies them to the actual load measurement, enabling accurate compensation across the entire load range from zero to full capacity.
Solution Approach 2:
The patent changes the compensation parameters from fixed resistor values to variable compensation factors stored in memory. These factors are selected based on temperature measurements and applied dynamically to correct the sensor output for different load conditions. This parameter change enables the system to adapt the compensation level according to both temperature and load state, overcoming the limitations of fixed zero-offset compensation.
3Measurement precision
If individual sensor calibration over temperature and weight range is performed, then measurement precision is improved, but device complexity and manufacturing time increase
Solution Approach 1:
The patent creates a master calibration dataset that captures the temperature-dependent behavior of deflection sensors across the full load range. Instead of requiring individual calibration of each sensor, the system uses this pre-established reference data (stored in memory) to compensate for temperature effects in production and field sensors. This copying approach allows manufacturing teams to deploy pre-calibrated compensation algorithms without performing time-consuming individual sensor calibrations, significantly reducing manufacturing complexity while maintaining full-span accuracy.
4Measurement precision
If temperature sensors are added adjacent to each deflection sensor, then measurement precision is improved through local temperature compensation, but device complexity increases due to additional wiring and programming
Solution Approach 1:
The patent implements a universal temperature compensation approach where a single temperature sensor serves multiple deflection sensors in proximity. Rather than dedicating one temperature sensor to each deflection sensor, the system uses one temperature measurement to compensate for multiple sensors operating in the same thermal environment. This multi-functional use of the temperature sensor reduces wiring complexity and programming requirements while maintaining accurate local temperature compensation for all sensors in the group.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system achieves accurate weight measurements with error rates less than ±0.5% of the load range in explicit mode and ±2% in approximate mode, effectively compensating for thermal effects and lot-to-lot variations, ensuring reliable operation from -40°C to 85°C and full load ranges.
Implementation Method 1
parasitic weighing systems, including the system shown in the '049 patent, function by mimicking the deflection of the structural member to which they are attached through a calibrated linear function. That structural member has its own thermal coefficient of expansion, which has a further effect on the sensor output that is not indicative of the load on the structural member
Implementation Method 2
Strain gauges bonded to the sensor are read by a related electronics system
Data Source
AI summary
A method for temperature-compensated weight measurement includes receiving a first output signal from a load sensor device coupled to a structural member, receiving a second output signal from a temperature sensor device, and calculating a load weight value by using the first output signal and the second output signal, and applying a statistically-generated temperature compensation factor.