Base line restoration circuit
AssigneeLeco Corporation
InventorTed J. Casper
Life of this patent
Estimating the term…
Abstract
Circuits for correcting base line shift of the detector coupling circuit of a TOFMS provide gain and impedance characteristics that compensate for the AC coupling effect of the detector. In one circuit, base line correction is achieved by injecting a current equal to that which flows due to the buildup charge in the detectors AC coupling network. In another circuit, the current source drives an integrator which is coupled to the signal path to reduce the detector AC coupling effects. In another circuit, a low noise amplifier utilizes a feedback network that reduces the detector AC coupling effects. In yet another circuit, an operational amplifier is employed to reduce the detector AC coupling effects.
Claims20
A base line restoration circuit for correcting shifts in output signals from the coupling circuit of an ion detector of a mass spectrometer comprising:
- an adjustable current source;
- a low pass filter having an input coupled to the output of the detector coupling circuit and an output coupled to said current source;
- and
- wherein said current source is coupled to the output of the coupling circuit of the detector to inject a current that offsets the voltage shift of the detector coupling circuit.
A base line restoration circuit for correcting shifts in output signals from the coupling circuit of an ion detector of a mass spectrometer comprising:
- a compensation circuit coupled to the output of the detector coupling circuit;
- wherein said compensation circuit includes a current source;
- and
- an integrator coupled between said current source and a termination impedance of the detector.
A base line restoration circuit for correcting shifts in output signals from the coupling circuit of an ion detector of a mass spectrometer comprising:
- a low noise amplifier having an input and an output;
- a feedback network that alters one of the gain and input impedance of said amplifier to result in base line restoration;
- and
- a bias circuit coupled to said amplifier for providing, at said output, signals which correct the shift in signals from the coupling circuit of the ion detector.
A time of flight mass spectrometer (TOFMS) comprising:
- a sample source including an ionization chamber;
- a flight tube coupled to said ionization chamber for acceleration ions from said source;
- an ion detector coupled to said flight tube;
- a detector coupling circuit coupled to said detector;
- and
- a base line restoration circuit coupled to said coupling circuit to correct for base line voltage shifts.
A base line restoration circuit for correcting shifts in output signals from the coupling circuit of an ion detector of a mass spectrometer comprising:
- an adjustable current source;
- a low pass filter coupled to said current source;
- and
- wherein said current source is coupled to the output of the coupling circuit of the detector to inject a current that offsets the shift of the coupling circuit.
A base line restoration circuit for correcting shifts in output signals from the coupling circuit of an ion detector of a mass spectrometer comprising:
- a compensation circuit coupled to the output of the detector coupling circuit;
- wherein said compensation circuit includes a current source;
- and
- an integrator coupled between said current source and a termination impedance of the detector.
Dependencies are inferred from the claim text.