Printed Four-Wire Strain Measurement Device for Accurate In-Situ Monitoring
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Solution Overview
Problem
Existing strain measurement devices have structural limitations that distort resistance measurements, particularly when used in high-precision applications, and are costly due to vacuum-based production methods, making them unsuitable for precise strain monitoring in shaping processes like draping or deep drawing.
Innovation Solution
A strain measurement device with a carrier film and conductive printing ink that allows for four-wire sensing, printed measuring loops, and a microprocessor, enabling accurate strain measurement without line and connection resistances, and can be produced inexpensively without vacuum processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain measuring strips are produced using vacuum-based sputtering methods, then high measurement precision can be achieved, but production cost increases significantly
Solution Approach 1:
The patent replaces vacuum-based sputtering (a complex mechanical/vacuum system) with a printing process using conductive printing paste. This substitution eliminates the need for expensive vacuum equipment while achieving comparable measurement precision through the printed resistance grid pattern on the carrier film.
Solution Approach 2:
The invention changes the production method from vacuum sputtering to printing technology, fundamentally altering the manufacturing parameter space. This allows for lower-cost production while maintaining the electrical resistance characteristics necessary for accurate strain measurement through the use of conductive printing materials.
2Reliability
If conducting tracks are soldered in the immediate vicinity of the measuring element, then connection reliability is improved, but structural height increases and measurement accuracy deteriorates due to line and connection resistances
Solution Approach 1:
The patent employs an asymmetric layout where the measuring element is positioned at one end of the carrier film while the conductor connections are located at the opposite end. This asymmetric arrangement separates the measurement function from the connection function, eliminating the interference of connection resistances on measurement accuracy while maintaining reliable electrical connections through the extended conducting tracks.
Solution Approach 2:
The invention divides the strain measurement device into functionally separate regions: a measurement region containing the measuring element and a connection region containing the conductor connections. This segmentation allows each region to be optimized independently, with the measuring element positioned away from connection points to eliminate parasitic resistance effects.
3Length of stationary object
If the strain measurement device is made with low structural height, then it can be used in tight spaces during shaping processes, but connection reliability may be compromised
Solution Approach 1:
The patent transitions from a three-dimensional stacked configuration to a two-dimensional planar layout. The conductor connections are arranged in the same plane as the measuring element, connected by conducting tracks that extend across the carrier film surface. This dimensional change maintains low profile height while ensuring reliable electrical connections through the extended track length.
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 solution provides accurate, low-profile strain measurement capable of withstanding high strains, allowing in-situ monitoring during shaping processes, and can be used as a disposable sensor, with integrated energy and communication systems for real-time data processing and control.
Implementation Method 1
The strain measuring strip is likewise expanded as a result of the strain of the body, thus altering the electrical resistance of the strain measuring strip
Data Source
AI summary
A strain measurement device (10) for electrically determining a strain of a basic body, having a carrier film (12) which can be applied to the basic body (40), an electric measuring loop (14) printed onto the carrier film (12) of conductive printing paste/printing ink, which has a measuring element (16) for generating an electrical signal based on the strain and which has four conducting tracks (18) connected to the measuring element (16) for four-wire sensing, the four conducting tracks (18) each having an electrical conductor connection (22), the conducting tracks (18), the conductor connections (22) and the measuring element (16) being printed with the same printing paste. Furthermore, an overall device (38) with such a strain measurement device (10), the strain measurement device (10) being connected to a base unit (44) which has an evaluation unit (46) and an energy supply unit (48).