Capacitive Flow Sensor for Anhydrous Ammonia Phase Detection
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Solution Overview
Problem
Current flow sensing technologies for anhydrous ammonia and particulate matter in agricultural applications face challenges in accurately measuring flow rates, leading to non-uniform application and inefficiencies, particularly due to the presence of both liquid and vapor phases, which complicates the detection of flow rates and row-to-row variations.
Innovation Solution
A method and apparatus using electrical capacity measurements between conducting plates to determine the mass flow rate of substances, employing two sensing volumes to correlate density and velocity, and detecting the presence and path of particles, without requiring cooling towers or phase-change apparatuses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If cooling towers or cooling chambers are used to liquefy anhydrous ammonia for flow measurement, then the ammonia can be measured in liquid form, but the system complexity and cost increase significantly
Solution Approach 1:
The patent extracts the phase-change apparatus (cooling towers or cooling chambers) from the anhydrous ammonia application system and replaces it with a flow sensor that can directly measure both liquid and vapor phases without requiring phase transformation. This eliminates the complex cooling infrastructure while maintaining measurement capability.
Solution Approach 2:
The patent replaces the mechanical cooling system with an electrical field-based sensing system. Instead of using physical cooling towers or chambers to liquefy ammonia for measurement, the invention uses electrical capacity or inductive sensing to detect flow rates of both liquid and vapor phases directly in the hose.
2Measurement precision
If bleed off vapor is injected with measured ammonia to liquefy it, then flow measurement becomes possible, but over-application occurs due to injection of additional ammonia
Solution Approach 1:
The flow sensor enables the system to self-monitor its own ammonia consumption and delivery. By providing real-time feedback on actual flow rates in each hose, the system can automatically adjust or alert operators to prevent over-application, eliminating the need for bleed-off vapor injection which caused measurement errors and over-application.
3Manufacturing precision
If identical length hoses are used to maintain similar flow rates, then row-to-row uniformity improves, but the system cannot detect individual row variations or plugging
Solution Approach 1:
The patent divides the monitoring function into individual row-level sensors. Instead of a single aggregate measurement, each hose serving an individual row is equipped with its own flow sensor, enabling segmentation of the monitoring system to detect and report on individual row flow rates, plugging conditions, and uniformity issues.
4Speed
If liquid anhydrous ammonia is allowed to pool in low regions of hoses, then gravity assists flow, but differential flow rates occur between rows
Solution Approach 1:
The flow sensors provide real-time feedback on actual flow rates in each hose, enabling detection of differential flow caused by pooling or plugging. This feedback mechanism allows operators to identify and correct uniformity issues, transforming the uncontrolled pooling problem into a detectable and correctable condition.
Data Source
AI summary
An electric measurement method and apparatus for detecting a mass by an electric capacity (permittivity) or a material's dielectric constant, or alternatively, electric inductance (permeability). The mass may be any phase or combination of phases. The mass may be stationary or flowing. It may comprise discrete particles such as grain, or manufactured products such as ball bearings or threaded fasteners, etc. The mass may be a flow element in a rotameter or similar flow measurement device. The sensor comprises a volume which may be completely full or only partially full of the material. The material may be discrete components or a continuum. Sensor signals may be received by existing planter monitoring systems. In some embodiments the flow sensors are positioned external to the application port. In some embodiments sensors may be utilized which are responsive to the refractive index variation of specific chemicals.