Discharge Ionization Current Detector Noise Reduction
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Solution Overview
Problem
Existing gas chromatography detectors, such as FID and PDD, face challenges with low ionization efficiency, limited dynamic range, and noise interference from electromagnetic and thermo-electromotive forces, which hinder high-sensitivity and accurate detection of sample components.
Innovation Solution
A discharge ionization current detector utilizing a low-frequency dielectric barrier discharge with emission timing detection and signal extraction means to synchronize ion current detection with plasma emission, reducing noise interference and enhancing signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a low-frequency barrier discharge is used to create stable plasma, then plasma stability is improved, but ionization efficiency remains low (≤0.1%)
Solution Approach 1:
The patent applies periodic pulsed voltage to the dielectric barrier discharge electrode, creating periodic plasma discharge cycles. This periodic action allows the plasma to be formed and extinguished in controlled cycles, improving stability while maintaining sufficient ionization efficiency through optimized pulse parameters (frequency, duty cycle, voltage amplitude).
Solution Approach 2:
The patent optimizes multiple parameters of the low-frequency barrier discharge system including discharge frequency (1-100 kHz), applied voltage amplitude, gas flow rate, and pressure conditions. By carefully adjusting these parameters, the system achieves a balance between plasma stability and ionization efficiency, overcoming the limitation of conventional low-frequency discharge systems.
2Use of energy by moving object
If conventional PDD is used to achieve high ionization efficiency, then ionization efficiency is improved, but dynamic range decreases by one or more digits
Solution Approach 1:
The patent employs dynamic control of the discharge parameters, allowing the system to adapt to different sample concentrations. By dynamically adjusting pulse frequency, voltage amplitude, and duty cycle based on detected signal levels, the system maintains high ionization efficiency across a wide dynamic range, accommodating both trace and high-concentration samples.
Solution Approach 2:
The patent implements feedback control where the detected ion current signal is used to adjust discharge parameters in real-time. This feedback mechanism ensures that ionization efficiency is optimized for each measurement condition, allowing the system to maintain high performance across varying sample concentrations and expand the effective dynamic range.
3Duration of action of moving object
If continuous monitoring of ion current is performed, then detection coverage is improved, but noise from electromagnetic interference and thermo-electromotive force increases
Solution Approach 1:
The patent synchronizes ion current measurement with the periodic plasma discharge cycles. By measuring current only during specific phases of the discharge cycle when plasma is present and stable, the system achieves continuous monitoring coverage while minimizing noise from electromagnetic interference and thermo-electromotive force that would be present during non-discharge periods.
Solution Approach 2:
The patent applies preliminary filtering and synchronization techniques where the measurement system is pre-configured to detect signals only during expected plasma discharge windows. This preliminary action prepares the detection system to ignore noise periods and focus on signal periods, achieving continuous monitoring with reduced noise interference.
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 achieves improved detection sensitivity and accuracy by isolating the ion current signal during plasma emission, significantly increasing the signal-to-noise ratio and reducing noise interference, thereby enhancing the detection of sample components.
Implementation Method 1
a discharge ionization current detector using a low-frequency barrier discharge
Implementation Method 2
generating plasma from a predetermined gas by electric discharge
Implementation Method 3
a signal corresponding to an ion current detected by the current detection means at a timing synchronized with the plasma emission
Data Source
AI summary
A discharge ionization current detector using a low-frequency dielectric barrier discharge with an improved S/N ratio is provided. A current detector 20 is disposed between an excitation high-voltage power source 8 and a discharge electrode 5 to detect a discharge current flowing in pulses due to plasma generation. The detection signal of the current detector 20 and an output signal from a current amplifier 18 for amplifying an ion current are inputted into an output extraction unit 21. The output extraction unit 21 detects a precipitous-rise portion of the discharge current detection signal and generates a trigger signal, and then extracts an ion current signal for a predetermined time period from the trigger signal. This can remove an influence of a noise appearing in a signal during a time period where no plasma emission is generated, thereby improving the S/N ratio of the detection signal.