Liquid Level Sensing Using Interdigitated Heaters
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Solution Overview
Problem
Existing liquid level sensing devices are complex and expensive to manufacture, often requiring costly materials and complex manufacturing processes, and are not well-suited for sensing corrosive liquids without using expensive corrosion-resistant materials.
Innovation Solution
A liquid level sensing system that uses a strip with a series of heaters and sensors, where the heaters emit heat pulses to be sensed by the sensors, allowing for low-cost detection of liquid levels without the need for expensive materials, and is adapted for use with corrosive liquids by employing a wide range of temperature coefficient of resistance materials and interdigitated heater-sensor configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional liquid level sensing devices are used, then liquid level detection is achieved, but manufacturing cost and device complexity increase
Solution Approach 1:
The sensing device is divided into multiple discrete heating elements arranged in a linear array, each capable of independent operation. This segmentation allows the system to determine liquid level by identifying which specific heating elements are in contact with the liquid, providing precise measurement while maintaining simple individual component design
Solution Approach 2:
The invention utilizes changes in electrical resistance of the heating elements as they transition from air-cooled to liquid-cooled states. By monitoring resistance parameter changes rather than using complex mechanical or optical sensors, the system achieves accurate liquid level detection with simpler and more cost-effective components
2Measurement precision
If conventional liquid level sensing devices are used, then liquid level detection is achieved, but manufacturing cost increases
Solution Approach 1:
The heating elements are constructed from inexpensive materials such as conductive paint or thin metal traces that can be easily fabricated and replaced if needed. This approach uses low-cost materials to achieve the sensing function, dramatically reducing manufacturing costs while maintaining adequate measurement precision
Solution Approach 2:
By utilizing the inherent electrical resistance changes of simple heating elements when exposed to liquid, the invention eliminates the need for expensive specialized sensors. The same resistive element serves both as a heater and a sensor, reducing component count and manufacturing complexity
3Reliability
If standard materials are used in corrosive liquid environments, then liquid level detection is achieved, but material cost increases due to corrosion resistance requirements
Solution Approach 1:
The heating elements are implemented as thin flexible traces or painted conductive layers that can be applied directly to the sensing surface. These thin-film constructions minimize material usage and can be formulated with corrosion-resistant properties, providing reliable performance in harsh environments at low cost
Solution Approach 2:
The sensing device utilizes composite construction combining a substrate material with conductive paint or coating layers. This allows the base material to provide structural support while the conductive layer provides sensing functionality with inherent corrosion resistance, achieving both reliability and cost-effectiveness
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 system provides a cost-effective means to accurately detect liquid levels, including in corrosive environments, with high heat dissipation and temperature stability, using refractory metals and their alloys, and offers improved manufacturing efficiency and reduced material costs.
Implementation Method 1
the heater is to emit a heat pulse and the sensor is to sense the heat pulse
Implementation Method 2
a temperature sensor of the series of temperature sensors is to sense a temperature resulting from the dissipation of the heat pulse
Data Source
AI summary
In some examples, a liquid container comprises a chamber forming a volume containing a liquid, an elongated strip extending into the volume containing the liquid, a plurality of heaters supported by the strip along the strip, and a plurality of temperature sensors supported by the strip along the strip. The temperature sensors output signals indicative of dissipation of heat from the heaters to indicate a level of the liquid in the volume.