Digital Waveform Ion Mobility Spectrometer
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Solution Overview
Problem
Current differential mobility spectrometers using transformer-based electronic circuits produce voltage pulses with varying mobilities over time, compromising the resolving power of ion separation due to non-constant electric fields, which affects the clarity of mobility spectra.
Innovation Solution
The implementation of electronically controlled fast-varying potentials creating a high-frequency multipole field with a sawtooth-like dipole field and a constant DC offset, using switched voltages to maintain constant fields during high-frequency pulses, allowing independent control of pulse heights and widths.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If transformer-based electronic circuits are used to produce voltage pulses, then high voltage pulses can be generated, but the electric field varies over time causing varying ion mobilities which compromises resolving power
Solution Approach 1:
The patent replaces transformer-based electronic circuits with a digital waveform generator that produces voltage pulses through electronic switching. This substitution eliminates the temporal variation in electric field strength that occurs with transformer-based systems, providing a constant electric field during each pulse phase. The digital generator uses solid-state switching components to create clean, stable voltage pulses with precise control over amplitude and duration, thereby maintaining constant ion mobility throughout the measurement period and improving resolving power.
Solution Approach 2:
The patent implements independent control of pulse heights and widths through the digital waveform generator. By separately controlling the amplitude (voltage height) and duration (pulse width) parameters, the system can optimize the electric field conditions for specific ion separation requirements. This parameter independence allows the electric field to be maintained at optimal constant values during each pulse phase, preventing the mobility variations that occur when voltage changes over time, thus improving the precision of ion mobility measurements.
2Measurement precision
If high voltage pulses are applied to separate ions by mobility, then ion separation is achieved, but voltage breakdown risks increase
Solution Approach 1:
The patent employs dynamic control of voltage pulses through the digital waveform generator, which can precisely adjust pulse amplitude, duration, and timing. The system applies high voltage only during the specific time intervals when ion separation is required, rather than maintaining continuous high voltage. This dynamic approach allows the system to achieve effective ion separation when needed while minimizing the overall exposure to high voltage stress, thereby reducing the probability of voltage breakdown and improving system reliability.
Solution Approach 2:
The patent uses periodic voltage pulses with controlled duty cycles to drive the ion mobility separation process. Instead of applying continuous high voltage, the system applies high voltage in repeated short bursts separated by lower voltage or zero voltage intervals. This periodic action achieves the necessary ion separation effect during the high-voltage phases while allowing the system to recover and dissipate stress during the low-voltage phases, significantly reducing the cumulative risk of voltage breakdown and enhancing operational reliability.
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 approach enhances the resolving power of ion separation by ensuring only ions with specific mobilities reach detectors, reducing peak widths and increasing separation distance, while minimizing voltage requirements and potential high-voltage breakthrough risks.
Implementation Method 1
a high frequency periodic asymmetric waveform of potentials causes, for a short time, a high-field, and for a longer time, a low-field, which forces the ions to oscillate normal to the direction of the carrier gas flow
Implementation Method 2
The velocity of motion of these ions is proportional to the electrical fields, and the proportionality factor is 'ion mobility'
Implementation Method 3
If the electric field acts perpendicularly to the direction in which the ions are moving with the carrier gas, the ions are deflected; the deflection distance is characteristic of the sizes of the ions and their interactions with the supporting gas atmosphere
Data Source
AI summary
A method for differential mobility separation of ions using digital-drive based high voltage fast switching electronics. The digital waveform delivered to the spectrometer is characterized by at least two substantially rectangular pulses of different amplitude and polarity. The control circuitry allows for waveform frequency, duty cycle and pulse amplitudes to be varied independently. Balanced as well as unbalanced asymmetric waveforms can be designed for optimum differential mobility separation of ions. The digital drive is designed for differential mobility spectrometers including parallel plate and segmented plate multipoles of planar symmetry, as well as multipoles of cylindrical symmetry, which may optionally be arranged in series. The use of the digital drive establishes alternating electric fields during which the displacement as a result of ion oscillation is determined by mobility coefficients.