Multi-Load Cell Calibration via Transfer Function Mapping
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing measurement devices with multiple sensors face challenges in balancing and calibrating load cells, leading to inaccurate readings and complex calibration processes, especially when dealing with large or massive objects, as the weight distribution among sensors is difficult to achieve evenly, resulting in unstable results and requiring frequent maintenance.
Innovation Solution
A calibration method and apparatus that uses multiple load cells with a simplified mechanical system, allowing for the characterization of linear transfer functions of multiple sensors while coupled together, requiring minimal test readings, and utilizing a microcontroller with an ADC to process signals from load cells, springs, and instrumentation amplifiers to distribute weight evenly across sensors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If multiple load cells are used to measure large objects, then the measurement capacity is improved, but the calibration complexity increases
Solution Approach 1:
The system performs preliminary calibration by placing test weights at specific locations on the platform before actual measurements. This preliminary action characterizes the linear transfer functions of all load cells and determines calibration constants, so that when multiple load cells are used for large object measurement, the calibration complexity has already been resolved in advance.
Solution Approach 2:
The system uses feedback from test weight measurements at multiple locations to automatically calculate calibration constants for each load cell. The microcontroller processes signals from all load cells, compares them against known test weights, and computes the calibration constants that balance the weight distribution across all sensors, eliminating manual calibration complexity.
2Reliability
If multiple load cells are used to distribute weight, then the measurement reliability is improved, but the weight distribution uniformity deteriorates
Solution Approach 1:
The system applies local quality by determining individual calibration constants for each load cell based on its specific position and characteristics on the platform. Instead of treating all load cells uniformly, the system characterizes each one's linear transfer function separately and applies location-specific calibration factors, enabling uniform weight distribution across all sensors despite their different positions.
3Measurement precision
If traditional calibration methods are used with multiple sensors, then the measurement precision can be maintained, but the calibration time increases
Solution Approach 1:
The system uses partial action by performing calibration with test weights placed at a limited number of strategic locations on the platform rather than exhaustive calibration at every possible position. This partial calibration approach is sufficient to characterize the linear transfer functions of all load cells and determine the necessary calibration constants, significantly reducing calibration time while maintaining measurement precision.
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
This approach simplifies the calibration of multiple sensors, reduces the need for mechanical components, and allows for precise weight measurement with fewer calibration readings, making it easier to use inexpensive sensors in various applications, including robotic systems, and enables field calibration and repair with minimal disruption.
Implementation Method 1
The load cells are usually fabricated from a block of metal such as steel or aluminum. The cells are set up so that they are supported by a fixed structure by bolts on one end. The weight to be measured is coupled to bolt holes at the other end. Over the range of weights that the cell is designed to work with, the block slightly buckles or deforms under the weight.
Implementation Method 2
The support structure usually transfers the weight from the platform to the sensor through springs. Springs allow the weight to transfer and to apply to the sensor vertically.
Implementation Method 3
The weight sensors are typically load cells that use a strain gauge coupled to a Wheatstone bridge to produce a resistance proportional to weight.
Data Source
AI summary
An electronic measurement device or electronic scale including an arrangement of multiple low-cost sensors to measure a physical property of an object is disclosed. The electronic measurement device or electronic scale utilizes an accurate and effective calibration method that compensates for the idiosyncrasies of using individual sensors. The electronic measurement device positions a plurality of sensors at predetermined observational locations to provide sensor output signals in response to sensing physical characteristics of the physical property of the object to be measured and combines the different sensor output signals by applying a combined calibration transfer function that represents a calibration function for each of the plurality of sensors to provide a cumulative measurement signal that represents the measurement of the physical property of the object. A centroid of the mass of the object is computed and used to execute different applications.