Submersible Fluorometer Using LEDs and Photodiodes
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Solution Overview
Problem
Current active fluorometers for measuring photosynthetic activity are costly, power-intensive, and bulky due to the use of bright light sources and expensive photodetectors, making them unsuitable for researchers with limited budgets and requiring a more portable, low-power, and submersible solution.
Innovation Solution
A submersible active fluorometer using solid-state LEDs and a photodiode as light sources and detectors, respectively, with a microcontroller for control and data processing, reducing size, power consumption, and cost while improving ruggedness and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If bright light sources and photomultiplier tubes are used in active fluorometers, then measurement precision is improved, but device cost and power consumption increase
Solution Approach 1:
The patent replaces expensive, fragile photomultiplier tubes with inexpensive photodiodes that can be easily replaced if needed. This substitution dramatically reduces instrument cost while maintaining adequate measurement capability for aquatic photosynthetic organisms.
Solution Approach 2:
The patent changes the operational parameters by using pulse-width modulation (PWM) to control LED intensity rather than requiring continuously variable bright light sources. This allows precise control of excitation light levels, enabling accurate fluorescence measurements with lower-power LEDs instead of high-power lamps.
2Measurement precision
If flash lamps are used to provide bright light for active fluorescence measurement, then measurement precision is improved, but power consumption and device complexity increase
Solution Approach 1:
The patent replaces mechanical flash lamp systems with solid-state LED arrays controlled by PWM circuitry. This substitution eliminates the need for high-voltage power supplies, ballast circuits, and flash lamp synchronization mechanisms, dramatically reducing power consumption and simplifying the power delivery system.
Solution Approach 2:
The patent uses periodic pulsing of LEDs through PWM to deliver excitation energy in controlled bursts, similar to flash lamps but with much lower peak power requirements. The microcontroller manages the timing and duration of these pulses to achieve the necessary fluorescence excitation while minimizing overall power consumption.
3Measurement precision
If photomultiplier tubes are used as detectors, then measurement precision is improved, but device size and fragility increase
Solution Approach 1:
The patent replaces fragile, expensive photomultiplier tubes with robust, inexpensive photodiodes that are resistant to shock and vibration. While photodiodes have lower gain, the use of PWM-controlled LEDs provides sufficient excitation intensity to produce detectable signals, making the simpler photodiode detector adequate for the application.
4Illumination intensity
If complex support circuitry is used for bright light sources, then illumination intensity is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces complex light source control circuitry with simple PWM-based LED driver circuits. LEDs inherently provide sufficient brightness when properly driven, and PWM control allows precise intensity modulation using minimal circuitry - essentially a microcontroller output, resistor, and MOSFET or transistor switch, eliminating the need for complex voltage regulation and current control circuits required by traditional lamps.
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 solution enables efficient measurement of active fluorescence with reduced costs, size, and power consumption, allowing for multiple units to be deployed and providing reliable, real-time data in various aquatic environments.
Implementation Method 1
uses a photodetector that is a photodiode
Implementation Method 2
uses either a single LED or a few LEDs that are modulated to provide a measuring light source
Data Source
AI summary
A submersible fluorometer for measuring a fluorescence of a photosynthetic material in a liquid, the fluorometer includes a set of light emitting diodes (LEDs) for supplying light to direct towards the liquid and a photodiode for measuring a detected light emitted from the liquid. The light is used for measuring the fluorescence of the photosynthetic material in the liquid. The fluorometer also has a water-tight volume for protecting the photodiode from the liquid.