Liquid Dispensing Device with Density Calculation
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Solution Overview
Problem
Existing methods for dispensing a liquid with a target weight are inadequate when the density of the liquid is unknown, as they rely on known density values.
Innovation Solution
A dispensing device and method that use a pipette and a controller to discharge a liquid sample with a tentative volume based on a tentative density, measure the weight of the discharged liquid, calculate the actual density, and then adjust the volume for accurate dispensing of the target weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a known density value is used to calculate the volume of liquid to be dispensed, then the dispensing process is simple and quick, but the accuracy of the target weight dispensing cannot be guaranteed when the liquid density is unknown
Solution Approach 1:
The system performs preliminary density measurement by dispensing a small test volume (e.g., 10 μL) and measuring its weight before the actual dispensing operation. This preliminary action establishes the actual density value needed for accurate subsequent dispensing, resolving the contradiction by preparing the necessary parameter in advance without complicating the main dispensing workflow.
Solution Approach 2:
The system implements feedback by measuring the weight of the test liquid, calculating actual density, and using this information to adjust and determine the precise volume for the target weight dispensing. This closed-loop feedback mechanism ensures accurate target weight dispensing while keeping the process integrated and manageable.
2Reliability
If volume-based management is used for liquid dispensing, then the process is straightforward, but environmental temperature variations significantly affect the accuracy of the dispensed weight
Solution Approach 1:
The system replaces volume-based mechanical dispensing with weight-based measurement and control. By using a balance to measure liquid weight directly and calculating volume from measured weight and density (volume = weight/density), the system achieves temperature stability while maintaining operational simplicity through automated calculations and control.
Solution Approach 2:
The system changes the fundamental parameter from volume to weight for the primary dispensing control. By managing liquids based on weight rather than volume, and dynamically adjusting volume calculations based on measured density, the system achieves reliability against temperature variations while keeping the interface simple for users.
3Measurement precision
If the density of the liquid is assumed to be a standard value (e.g., 1 g/mL), then the calculation is simple, but the accuracy deteriorates when the actual density differs from the assumed value
Solution Approach 1:
The system performs a minimal partial measurement (small test volume dispensing and weighing) to obtain the density value needed for the complete task. This partial action provides sufficient accuracy for the subsequent full dispensing operation without requiring excessive time or resources, resolving the contradiction between precision and time loss.
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 dispensing of a liquid with a target weight even when the density is unknown, while also reducing the influence of environmental temperature variations compared to volume-based management.
Implementation Method 1
information about a weight z (in grams) of the liquid sample discharged in the first liquid discharge processing
Data Source
AI summary
A dispensing device that dispenses a liquid sample with a target weight x (in grams) includes: a pipette that discharges the liquid sample into a vessel; and a controller that controls the pipette. The controller performs: first liquid discharge processing in which the controller discharges the liquid sample with a volume of (x/ρ0×y) milliliters (mL) into the pipette, where y is a numeric value greater than 0 and smaller than 1, and ρ0 is the tentative density (in grams per mL) of the liquid sample; first weight acquisition processing in which the controller acquires information about the weight z (in grams) of the liquid sample discharged in first liquid discharge processing; density calculation processing in which the controller calculates the density p (in grams/mL) of the liquid sample according to the expression ρ=z/(x/ρ0×y); and second liquid discharge processing in which the controller discharges, into the pipette, the liquid sample with a volume based on the density ρ, weight z, and target weight x.