Magnetic Displacement Sensor for Syringe Drug Reservoirs
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Solution Overview
Problem
Existing displacement sensors for monitoring liquid levels in syringe-type drug reservoirs face challenges such as mechanical wear, high manufacturing costs, and limited sensitivity, making them unsuitable for accurate and reliable drug delivery.
Innovation Solution
A linear capacitance displacement transducer with fixed cylindrical capacitor plates and a movable dielectric structure within the space between them, which alters the capacitance signal output, providing robust and cost-effective measurement without requiring moving electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a potentiometric sensor is used to measure displacement, then the device can provide displacement measurement, but mechanical wear and frictional resistance occur in the wiper action
Solution Approach 1:
The patent replaces the mechanical potentiometric sensor with a magnetic field-based sensor system. A permanent magnet is attached to the movable element, and a magnetic sensor (such as a Hall effect sensor or magnetoresistive sensor) measures the displacement by detecting changes in the magnetic field. This substitution eliminates mechanical contact, thereby removing wear and frictional resistance while maintaining measurement capability.
2Object-affected harmful factors
If an LVDT with separate shielding coils is used, then low noise measurement is achieved, but the device length is at least twice the measurement distance and manufacturing cost increases
Solution Approach 1:
The patent combines the measurement coil and shielding function into a single integrated structure. The sensor head includes a permanent magnet for generating the magnetic field and a magnetic sensor for detection, with integrated shielding elements that eliminate the need for separate shielding coils. This merging reduces the overall device length to be comparable to the measurement distance while maintaining low noise performance through proper magnetic shielding design.
3Measurement precision
If optical encoders or ultrasonic devices are used for displacement measurement, then measurement capability is provided, but manufacturing cost increases and application flexibility is restricted
Solution Approach 1:
The patent employs a cost-effective magnetic sensor system that uses readily available permanent magnets and magnetic sensors (such as Hall effect sensors or magnetoresistive sensors). This approach avoids the high manufacturing costs associated with optical encoders and ultrasonic devices. The magnetic field-based measurement is robust, requires no complex alignment, and can be manufactured using standard processes, making it suitable for cost-sensitive applications while maintaining adequate measurement precision.
4Measurement precision
If capacitance based sensors with moving plates are used, then displacement measurement is achieved, but manufacturing challenges increase
Solution Approach 1:
The patent replaces the mechanically complex capacitance sensor with a magnetic field-based sensor system. Instead of using moving capacitor plates that require precise alignment and fabrication, the invention uses a permanent magnet attached to the movable element and a magnetic sensor in the sensor head. This substitution eliminates the manufacturing challenges associated with precision capacitor plate fabrication while maintaining displacement measurement 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 solution enables accurate and reliable monitoring of fluid levels in syringe-type reservoirs, enhancing the sensitivity for detecting erroneous drug delivery while maintaining a robust and inexpensive design.
Implementation Method 1
a permanent magnet attached to the movable element
Implementation Method 2
a magnetic sensor in the sensor head that measures the position of the movable element
Data Source
Figure 1~2
Figure 3
AI summary
A linear capacitance displacement transducer (1 ) comprising first (2) and second (3) fixed capacitor plate and a dielectric structure (5) moveable longitudinally within a space (4) between the first (2) and second (3) capacitor plates, the dielectric structure (5) being operatively coupled to a moveable element (8). The capacitor plates and the dielectric material may be cylindrical and disposed coaxially and concentrically. The transducer (1) enables a displacement sensor that is capable of monitoring liquid levels in a syringe type drug reservoir (101) with sufficient sensitivity as to allow detection of erroneous drug delivery. The sensor is inexpensive to manufacture and provides reliable performance through robust design.