Flexible Sensor Head Isolating Strain Gauges from Mechanical Deformation
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Solution Overview
Problem
Existing pressure sensor technologies using strain gauges face challenges in accurately measuring fluid pressure without mechanical interference from bending, stretching, compression, and twisting forces, which can lead to sensor destruction under high fluid pressures.
Innovation Solution
A sensor head design featuring a flexible connection between the centre and fastening portions, with strain gauges attached to an internal assembly surface protected by an end stopper, preventing deformation transfer and ensuring fluid isolation, allowing for accurate pressure measurement without direct fluid exposure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauges are placed directly on the item to measure pressure, then measurement capability is achieved, but mechanical forces from bending, stretching, compression and twisting of the item interfere with the pressure measurement
Solution Approach 1:
The sensor head is divided into a centre portion (carrying strain gauges) and a fastening portion (attached to item), connected by flexible connection elements. This segmentation isolates the measurement function from the mounting function, preventing mechanical forces from the item from reaching the strain gauges.
Solution Approach 2:
Flexible connection elements act as intermediaries between the fastening portion and the centre portion. These elements selectively transmit only fluid pressure forces while blocking mechanical forces from the item, thereby protecting the strain gauges from harmful mechanical interference.
2Stability of the object's composition
If the sensor head is rigidly connected to the item, then structural stability is improved, but deformation from item twisting and bending is transferred to the strain gauge assembly
Solution Approach 1:
Different parts of the sensor head have different mechanical properties: the fastening portion provides stable attachment to the item, while the flexible connection elements provide isolation from harmful deformations. This local differentiation of mechanical properties allows simultaneous stability and measurement accuracy.
3Adaptability or versatility
If the centre portion is exposed to high fluid pressure beyond the sensor's range, then pressure measurement capability is extended, but permanent destruction of the sensor head occurs
Solution Approach 1:
The end stopper is positioned beforehand to prevent over-compression of the flexible connection elements. When excessive pressure is applied, the centre portion contacts the end stopper, which cushions the overload and prevents permanent destruction of the sensor head, thereby protecting reliability while maintaining extended pressure range capability.
4Loss of information
If cables are routed through the item to connect strain gauges to distant apparatus, then measurement data transmission is achieved, but fluid pressure and mechanical forces may interfere with cable operation
Solution Approach 1:
The cable routing function is extracted from the pressurized fluid environment. Cables are routed through a centre bore in the end stopper and an adjacent channel in the item that is both fluid- and pressurewise separated from the pressurized fluid, thereby eliminating fluid and mechanical interference while maintaining data transmission capability.
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 design effectively isolates the strain gauges from external forces and fluid pressure, preventing damage and maintaining measurement accuracy even under pressures exceeding the sensor's initial range, while ensuring fluid-tight sealing and protection from mechanical stress.
Implementation Method 1
the connection of the centre portion to the fastening portion through one or more flexible connection elements in such a way that a deformation of the fastening portion provided by twisting, bending, compression or stretching of the item is not transferred to the centre portion
Implementation Method 2
A strain gauge is a device used for measuring very small deformations in a surface to which the strain gauge is attached, that is deformations appearing in the order of size of a few μm. Strain gauges are coupled into measuring bridges which are connected to an apparatus registering changes in electrical resistance in the strain gauges.
Implementation Method 3
the periphery of the assembly surface which is arranged inside of the centre portion, abuts supportingly against an end surface of an end stopper, typically formed as a circular, upwardly protruding portion of the item, when an outer sensor head surface is exposed to a fluid pressure exceeding the level which the flexible connection element can withstand
Data Source
AI summary
Device for measurement of fluid pressure by means of an arrangement of strain gauges provided on a sensor head arranged on an item arranged to be exposed to a pressurized fluid against an external sensor head surface, where the sensor head comprises a fastening portion attached to the item, and a center portion connected to the fastening portion by means of at least one flexible connecting element, the arrangement of strain gauges is attached to the center portion of the sensor head on an internal assembly surface arranged in close proximity to a contact face on an end stopper which in an active condition encircles the arrangement of strain gauges, and the assembly surface is inexposable for the pressurized fluid.