Piezoelectric Sensor Impedance Matching for Viscous Fluids
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sensing devices with piezoelectric vibrators face reduced measurement accuracy when detecting substances in high viscosity sample solutions due to differences in impedance of conductive paths and circuit characteristics between oscillation circuits, leading to inconsistent frequency changes.
Innovation Solution
A sensing device with a common oscillation circuit for two piezoelectric vibrators, where the impedances of the conductive paths are kept uniform, ensuring that both vibrators oscillate time-dividedly with equal circuit characteristics, allowing for precise detection of substance absorption by minimizing the impact of viscosity on frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a common crystal piece with two crystal vibrators is used, then disturbance influence is shared similarly, but measurement accuracy deteriorates in high viscosity solutions due to impedance differences
Solution Approach 1:
The patent changes the electrical parameter (impedance) of the conductive paths by adjusting their length and configuration. Specifically, the conductive path to the first crystal vibrator is made longer than that to the second crystal vibrator, thereby equalizing the total impedance (crystal impedance + conductive path impedance) of both paths. This parameter adjustment eliminates the impedance difference that caused measurement errors in high viscosity solutions.
2Measurement precision
If separate oscillation circuits are used for each crystal vibrator, then circuit characteristics can be individually optimized, but device complexity increases
Solution Approach 1:
The patent merges two separate oscillation circuits into a single common oscillation circuit that serves both crystal vibrators. This is achieved by using one oscillation circuit with switching elements that connect it alternately to the first and second crystal vibrators. The merging reduces device complexity while maintaining measurement accuracy through the equalized impedance design.
Solution Approach 2:
The patent implements periodic switching between the two crystal vibrators using a switching element controlled by a switching signal. The switching occurs at regular intervals, allowing the single oscillation circuit to sequentially drive both vibrators. This periodic action enables one circuit to perform the function of two circuits while maintaining the ability to measure both frequencies accurately.
3Measurement precision
If conductive paths of different lengths are used, then impedance differences are compensated, but manufacturing precision requirements increase
Solution Approach 1:
The patent deliberately introduces asymmetry in the conductive path lengths, making the path to the first crystal vibrator longer than the path to the second crystal vibrator. This asymmetric design is intentional and calculated to compensate for the crystal impedance differences. The asymmetry is not a manufacturing defect but a designed feature that, when properly controlled, improves measurement precision by equalizing total impedances.
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 enables highly accurate detection of substances in high viscosity solutions by suppressing dispersion in characteristic vibration numbers, ensuring reliable measurement results.
Implementation Method 1
a sensing device using a piezoelectric vibrator whose characteristic vibration number changes by absorption of a substance to be sensed contained in a sample solution
Data Source
AI summary
A sensing device is configured that a first piezoelectric vibrator and a second piezoelectric vibrator, changing over a connection to an oscillation circuit, have the oscillation circuit in common, that an impedance of a conductive path including a first one-surface-side electrode constituting the first piezoelectric vibrator from the oscillation circuit and an impedance of a conductive path including a second one-surface-side electrode constituting the second piezoelectric vibrator from the oscillation circuit are uniform with each other, and that an impedance of a conductive path including a first other-surface-side electrode constituting the first piezoelectric vibrator from the oscillation circuit and an impedance of a conductive path including a second other-surface-side electrode constituting the second piezoelectric vibrator from the oscillation circuit are uniform with each other.