ELSD Photodiode Dynamic Gain Control
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Solution Overview
Problem
Current evaporative light scattering detectors (EDDLs) face issues with high costs due to the use of photomultipliers and loss of time and sensitivity when reaching saturation, as well as the inability to adjust gain with photodiodes, limiting their detection range and efficiency.
Innovation Solution
Incorporating an automatically controlled light detector with a photodiode or photomultiplier coupled to an automatic dynamic management unit with capacitors for adjustable current accumulation, allowing for dynamic adjustment of signal acquisition frequency to mimic gain adjustment, thereby extending the detection range without user intervention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a photomultiplier is used in the detection chamber, then detection sensitivity is improved, but device cost increases
Solution Approach 1:
The patent replaces the expensive photomultiplier with a cheaper photodiode, accepting that the photodiode has inherent limitations (inability to adjust gain) and compensating through software-based signal processing and dynamic accumulation time adjustment to achieve comparable detection performance at lower cost
Solution Approach 2:
The patent replaces the photomultiplier's electronic gain adjustment mechanism with a software-based accumulation time control system, where the microprocessor dynamically adjusts the accumulation time of the integrator to compensate for the photodiode's fixed gain characteristic, effectively substituting hardware adjustment with software control
2Measurement precision
If photomultiplier gain is increased to improve detection limit, then sensitivity is improved, but saturation occurs more easily
Solution Approach 1:
The patent implements dynamic adjustment of the accumulation time based on the detected signal intensity. The microprocessor continuously monitors the signal level and automatically adjusts the accumulation time to keep the signal within the optimal range, preventing both saturation and excessive noise amplification, thereby maintaining reliable measurements across varying concentration levels
Solution Approach 2:
The patent employs a feedback mechanism where the detected signal intensity is used to control the accumulation time. The system monitors the output signal and adjusts the accumulation parameter in response to signal levels, creating a closed-loop control system that automatically prevents saturation while maintaining sensitivity for low-concentration samples
3Reliability
If photomultiplier high voltage is adjusted manually to prevent saturation, then measurement reliability is improved, but analysis time increases
Solution Approach 1:
The patent implements an automatic control system where the microprocessor autonomously adjusts the accumulation time based on the detected signal intensity without requiring user intervention. The system self-regulates to prevent saturation and optimize sensitivity, eliminating the need for manual parameter adjustment and maintaining measurement reliability across different sample concentrations
Solution Approach 2:
The patent performs preliminary signal assessment and automatically configures the optimal accumulation time before full measurement begins. The system evaluates the signal characteristics and pre-adjusts the integration parameters to prevent saturation, ensuring reliable measurements from the start of analysis without requiring intermediate manual interventions
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 enhances sensitivity by maximizing detection range and preventing saturation, allowing for continuous and sensitive measurement without manual adjustments, reducing costs by using less expensive photodiodes and maintaining chromatogram integrity.
Implementation Method 1
a photodiode which will deliver a measurement signal in the form of a current proportional to the intensity of the luminous flux received by said photodiode
Implementation Method 2
an integrator with a series of capacitors of defined capacitance which can be individually switched in an adjustable manner and which will fulfil the function of an analogue/digital converter with current input and digital output allowing the accumulation of the current delivered at the output of the light detector
Implementation Method 3
a nebulization gas making it possible to transform the sample into an aerosol
Implementation Method 4
an evaporation chamber in which the carrier liquid is evaporated in order to retain only microparticles of the compounds to be analyzed
Data Source
AI summary
Light scattering evaporative detector (LSED), characterized in that the electronically controlled light measurement device equipping the detection chamber of the LED comprises a light detector, in particular a photodiode coupled to an automatic dynamic management unit with integration, in particular equipped with a series of capacitors of defined capacitance that can be individually switched in an adjustable manner and fulfilling the function of an analog/digital converter with current input and digital output allowing the current delivered at the output of the light detector, in particular the photodiode, to be accumulated for a very short period that can be automatically set internally by a control firmware.