Wireless Charge Amplifier for Quasi-Static Piezoelectric Measurement
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Solution Overview
Problem
Existing piezoelectric sensors face challenges with cable installation in confined spaces due to limited space, exposure to harsh conditions, and leakage currents leading to measurement distortion, particularly in quasi-static applications with small measuring ranges.
Innovation Solution
A self-sufficient charge amplifier device with a housing containing a charge amplifier unit, power supply, and wireless communication, allowing for cable-free operation and wireless data transmission, along with a long time constant to minimize leakage currents and enable accurate quasi-static measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If cables are used to connect piezoelectric sensors to charge amplifiers, then electrical charges can be transmitted, but cable installation becomes difficult or impossible in confined spaces and cables are exposed to harsh conditions leading to premature aging and damage
Solution Approach 1:
The charge amplifier unit is extracted from the remote control unit and integrated directly into the sensor housing, eliminating the need for cables to connect the sensor to the amplifier. This allows the sensor to be placed in confined spaces without cable installation issues while maintaining reliable electrical charge transmission through the integrated circuit board connections.
Solution Approach 2:
A circuit board is introduced as an intermediary medium to replace cables for transmitting electrical charges from the piezoelectric sensor to the charge amplifier unit. The circuit board provides a more reliable and durable connection that is not susceptible to the same environmental degradation as cables, while also enabling shorter transmission paths.
2Adaptability or versatility
If multiple single-channel cables or multi-channel cables are used to measure multiple components of physical quantity simultaneously, then measurement capability is provided, but the number or diameter of cables increases further complicating or preventing cable installation
Solution Approach 1:
Multiple charge amplifier units are merged into a single integrated housing with the sensor, allowing multiple components of physical quantity to be measured simultaneously without requiring multiple separate cables. The circuit board integrates all amplifier connections, reducing cable complexity while maintaining full multi-component measurement capability.
Solution Approach 2:
The integrated charge amplifier device provides universal functionality for measuring multiple physical quantity components through a single unified system. The circuit board is designed to handle multiple sensor channels and amplifier units, enabling the system to measure various components (force, torque, acceleration) simultaneously without requiring separate cable assemblies for each component.
3Duration of action of moving object
If piezoelectric sensors are used for quasi-static applications with small measuring ranges, then long-term monitoring is enabled, but leakage currents interact with operational amplifier input offset voltage causing measurement distortion
Solution Approach 1:
The time constant of the charge amplifier unit is increased to at least 1000 seconds by adjusting the feedback resistor and capacitor values. This parameter change reduces the impact of leakage currents over time, allowing accurate quasi-static measurements to be maintained for durations of at least 10 seconds even with small measuring ranges, thereby extending the usable measurement duration without sacrificing 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
Enables accurate quasi-static measurements with minimal measurement error, up to 2%, over extended durations of up to 2*10^1 seconds, without the need for cables and reducing interference from high-pass filters.
Implementation Method 1
The sensor contains piezoelectric material that generates electrical charges when exposed to a physical quantity
Implementation Method 2
which capacitor is connected in parallel to the inverting input and the signal output, which capacitor has a capacitance and an electrical insulation resistance
Data Source
Figure 1
AI summary
A charge amplifier device for at least one piezoelectric sensor, which generates electrical charges under the action of a physical quantity to be measured, and which is electrically connectable to the charge amplifier device via a sensor cable; which charge amplifier device comprises a housing in which at least one charge amplifier unit, an electrical voltage supply unit, a control unit, and a wireless communication unit are arranged; wherein the piezoelectric sensor, when electrically connected to the charge amplifier device, discharges electrical charges to the charge amplifier unit via the sensor cable; which charge amplifier unit is configured to amplify discharged electrical charges into an electrical voltage; wherein the charge amplifier unit comprises an operational amplifier and at least one capacitor.wherein the operational amplifier has an inverting input and a signal output; wherein the inverting input has an electrical input resistance; wherein the capacitor is connected in parallel to the inverting input and the signal output; wherein the capacitor has a capacitance and an electrical insulation resistance; and wherein the charge amplifier unit has a time constant of greater than or equal to 103 s, preferably greater than or equal to 5*103 s.