Single-Sided Strain Gauge With Unbalanced Wheatstone Bridge
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Solution Overview
Problem
Single sided strain gauge sensors fail to provide accurate results due to negligible differential signal when all resistors are on the same side of the substrate, as stress changes are minimal and do not produce a measurable voltage difference.
Innovation Solution
A single sided strain gauge design featuring a balanced Wheatstone bridge arrangement of equal resistance resistors on one surface and an unbalanced Wheatstone bridge arrangement of unequal resistance resistors, connected in parallel, with the latter being remotely located to avoid equivalent strain forces, enabling a differential voltage output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If all resistors are positioned on the same side of the substrate in a single sided strain gauge, then the device structure is simplified and easier to manufacture, but the differential signal becomes negligible and measurement accuracy deteriorates
Solution Approach 1:
The strain gauge is segmented into two distinct Wheatstone bridge arrangements: a first bridge with equal resistance resistors and a second bridge with unequal resistance resistors. This segmentation allows each bridge to serve a specific function - the first bridge provides a stable reference while the second bridge generates the differential signal, thereby maintaining measurement precision while keeping all components on one side of the substrate.
Solution Approach 2:
Different regions of the substrate are assigned different functional qualities. The first Wheatstone bridge arrangement uses equal resistance resistors optimized for stability, while the second arrangement uses unequal resistance resistors optimized for generating differential signal. This local differentiation of resistor properties enables both ease of manufacture and measurement precision within the single-sided configuration.
2Ease of manufacture
If a balanced Wheatstone bridge with equal resistance resistors is used, then the bridge is stable and easy to manufacture, but it cannot generate a measurable differential voltage output when force is applied
Solution Approach 1:
The patent merges two Wheatstone bridge arrangements into a single functional system. The first bridge with equal resistance resistors provides manufacturing simplicity and stability, while the second bridge with unequal resistance resistors provides the necessary voltage differential output. By connecting these two bridges appropriately, the system combines the advantages of both configurations.
Solution Approach 2:
While the first Wheatstone bridge maintains symmetry with equal resistance resistors for ease of manufacture, the second bridge introduces asymmetry through unequal resistance resistors. This asymmetry is essential for generating a measurable voltage differential when force is applied to the substrate, as the unequal resistors create imbalanced current paths that produce the required output signal.
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 configuration generates a significant voltage differential between output nodes, allowing for accurate and precise measurement of applied forces, overcoming the limitations of prior art single sided strain gauges.
Implementation Method 1
the strain, stress, or tension on the resistors 4a and 4b (disposed on the top side of the test specimen 3) changes with respect to the strain, stress, or compression on the resistors 5a and 5b (disposed on the bottom side of the test specimen 3). As a result, the resistance of the resistors 4a and 4b changes with respect to the resistance of the resistors 5a and 5b.
Data Source
AI summary
Disclosed herein is a strain gauge including a substrate, with a first Wheatstone bridge arrangement of resistors disposed on a first surface of the substrate, and a second Wheatstone bridge arrangement of resistors disposed remotely from the first Wheatstone bridge arrangement of resistors. The resistors of the first Wheatstone bridge arrangement are equal in resistance to one another, while the resistors of the second Wheatstone bridge arrangement are unequal in resistance to one another and unequal to those of the first Wheatstone bridge arrangement. The first Wheatstone bridge arrangement of resistors are electrically connected in parallel with the second Wheatstone bridge arrangement of resistors such that each resistor of the first Wheatstone bridge arrangement is electrically connected in parallel with a different resistor of the second Wheatstone bridge arrangement.