Magnetic Sector Mass Spectrometer Magnet Control
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Solution Overview
Problem
Magnetic sector mass spectrometers face challenges in maintaining high stability and accuracy of the magnetic field, particularly during jumps between different magnetic flux densities, due to non-linearity and hysteresis effects, which affect instrument resolution and the ability to discriminate between adjacent ion masses.
Innovation Solution
A digital control system that uses a look-up table or functional relationship to select appropriate controller settings based on specific mass spectrometer parameters, including magnetic flux densities, acceleration voltages, and mass-to-charge ratios, employing a magnetoresistive sensor and temperature control to optimize PID settings and achieve faster and more stable magnetic field control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a magnetic sector mass spectrometer uses a magnet to separate ions by mass-to-charge ratio, then ion separation and detection capability is improved, but maintaining high stability and accuracy of the magnetic field becomes difficult due to non-linearity and hysteresis effects
Solution Approach 1:
The patent implements a feedback control system using a magnetoresistive sensor to continuously monitor the magnetic flux density and adjust the magnet current accordingly. The sensor output is fed to a controller that regulates the power supply to the magnet, creating a closed-loop system that compensates for drift and instability caused by non-linearity and hysteresis effects, thereby maintaining high magnetic field stability while preserving ion separation capability
Solution Approach 2:
The patent employs temperature control to stabilize the magnetoresistive sensor and compensates for non-linearity and hysteresis by implementing software-based calibration and dynamic adjustment of control parameters. The system adapts control parameters based on operating conditions to maintain accurate magnetic field control across different measurement ranges
2Adaptability or versatility
If the magnetic flux density is changed to scan multiple ion species, then the mass range detectable is improved, but the stability and accuracy of the magnetic field deteriorates
Solution Approach 1:
The patent implements dynamic control of the magnetic field by continuously adjusting the magnet current based on real-time feedback from the magnetoresistive sensor. The control system adapts to changing measurement requirements, enabling smooth scanning across multiple mass ranges while maintaining field stability through active compensation of non-linearity and hysteresis effects throughout the scanning process
3Reliability
If a Hall effect sensor or Field probe is used to measure flux density, then magnetic field control is achieved, but the system complexity and cost increase
Solution Approach 1:
The patent replaces traditional mechanical or complex electronic magnetic field sensing methods (Hall effect sensors, Field probes) with a magnetoresistive sensor that offers simplified integration and control. The magnetoresistive approach reduces system complexity by eliminating the need for complex signal conditioning and amplification circuits while maintaining accurate magnetic field measurement and control capability
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 stability and speed of magnetic field control, allowing for precise discrimination between ion species and improved instrument resolution, while reducing costs and logistical complexities by enabling the use of lower-quality magnets and calibrating out non-linearities and hysteresis effects.
Implementation Method 1
The variable input signal to the controller is derived from a magnetoresistive sensor in which a magnetoresistive element exhibits a change in electrical resistance in response to changes in magnetic flux density
Implementation Method 2
As the moving ions enter the magnetic field created by a magnet, charged ions of a particular mass to charge ratio m/z are deflected along a circular path of unique radius rm in a direction perpendicular to the direction of the applied magnetic field. The force due to the magnetic field (z.v.B, where z is the ionic charge, v is the ion velocity, and B is the magnetic field strength) balances the centripetal force mv2/rm.
Data Source
AI summary
A control system for controlling a magnet of a magnetic sector mass spectrometer comprises a magnetic field sensor for sensing the magnetic field of the magnet and generating an output representative thereof; a set point generator configured to generate an output representative of, or related to, a desired magnetic field of the magnet; and a digital controller configured to receive a variable digital input signal from the output of the magnetic field sensor and a set point digital input signal from the output of the set point generator, and to generate a digital output from which is derived a control signal for controlling a current to the magnet so as to control the magnetic field thereof. The control system is arranged to apply to the digital controller a selected one of a plurality of different controller settings, in accordance with the desired magnetic field of the magnet.