Load Cell Bridge Circuit for Balance and Temperature Compensation
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Solution Overview
Problem
Load cells with strain gauges having large element resistance values and temperature dependency face challenges in adjusting initial balance while compensating for temperature characteristics, particularly in applications like six-component force detectors for vehicle wheels, where sensitivity varies by direction and temperature fluctuations are significant.
Innovation Solution
A load cell configuration with a bridge circuit incorporating first and second chip resistors for initial balance adjustment, a thermistor for temperature compensation, and additional adjustment resistors to correct deviations, connected in series and parallel configurations within the bridge circuit paths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a strain gauge with large element resistance value and temperature dependency is used to achieve large output, then the output sensitivity is improved, but the difficulty of adjusting initial balance while compensating temperature characteristics increases
Solution Approach 1:
The adjustment circuit is segmented into multiple independent components: chip resistors for initial balance adjustment, thermistors for temperature compensation, and adjustment resistors for deviation correction. Each component handles a specific aspect of the adjustment, making the overall system manageable despite the complexity introduced by using strain gauges with large element resistance values and temperature dependency.
Solution Approach 2:
Chip resistors and thermistors are introduced as intermediary elements between the strain gauges and the bridge circuit output. These intermediaries facilitate the adjustment of initial balance and temperature compensation without requiring direct modification of the strain gauge characteristics, thereby enabling manageable adjustment processes while maintaining high output sensitivity.
2Reliability
If temperature compensation is implemented using a thermistor, then temperature characteristics are compensated, but the device complexity increases due to additional components and adjustment steps
Solution Approach 1:
The thermistor for temperature compensation is combined with adjustment resistors in a unified adjustment circuit configuration. This merging allows temperature compensation and initial balance adjustment to be performed through an integrated circuit design, reducing the overall device complexity compared to having separate independent circuits for each function.
Solution Approach 2:
The adjustment circuit is designed with multi-functionality, where chip resistors serve both initial balance adjustment and temperature compensation functions, and adjustment resistors can correct deviations in both initial balance and temperature characteristics. This universal design reduces the need for additional specialized components, thereby limiting the increase in device complexity while achieving reliable temperature compensation.
3Measurement precision
If multiple adjustment resistors are added to correct initial balance deviation after thermistor installation, then the initial balance is adjusted, but the manufacturing process becomes more complex
Solution Approach 1:
Chip resistors with predetermined resistance values are selected and installed before the thermistor to establish an initial balance baseline. Adjustment resistors are then added subsequently to correct any deviations. This preliminary action approach allows the manufacturing process to proceed in manageable stages, reducing overall complexity by preparing the circuit in a logical sequence rather than requiring all adjustments to be made simultaneously.
Solution Approach 2:
The manufacturing process utilizes parameter changes by selecting chip resistors and adjustment resistors with specific resistance values to achieve the desired initial balance. By changing resistance parameters through component selection rather than through complex circuit configurations, the manufacturing process is simplified while still achieving precise initial balance adjustment.
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
Enables easy adjustment of initial balance and compensation for temperature characteristics without additional sensors or software, enhancing the reliability of load cell outputs, especially in multi-component force detection.
Implementation Method 1
a thermistor configured to compensate for a temperature characteristic of the bridge circuit
Implementation Method 2
a strain gauge, which changes in resistance in accordance with strain generated by a load
Data Source
AI summary
A load cell includes a bridge circuit that converts and outputs a change in resistance of a strain gauge, which changes in accordance with a load. The load cell includes, in a first path on one side of the bridge circuit, a first chip resistor that adjusts an initial balance of the bridge circuit, and a thermistor that compensates for a temperature characteristic of the bridge circuit and a first adjustment resistor that adjusts a deviation of the initial balance with the thermistor being provided, which are connected in series with the first chip resistor and connected in parallel. The load cell includes, in a second path on another side of the bridge circuit, a second chip resistor that adjusts the initial balance, and a second adjustment resistor that adjusts the deviation caused by providing the first adjustment resistor and is connected in series with the second chip resistor.