Analytical instrument optimum data acquisition method and apparatus
AssigneeVarian Associates, Inc.
InventorsStephen H. Smallcombe, Howard D. W. Hill
Life of this patent
Estimating the term…
Abstract
An analytical instrument employing ensemble averaging to improve the signal-to-noise ratio including means for determining the most efficient scaling factor and for controlling the instrument to maintain assurance of efficient averaging.
Claims18
Method for improving the signal-to-noise ratio of time averaged outputs derived from an analytical instrument, said time averaged outputs comprising the sum of a number of low level resonance outputs derived from a spectrometer which outputs, during an experiment, have both signal and noise portions comprising the steps of:
- determining a maximum sampling rate corresponding to the bandwidth of the frequency spectrum to be examined;
- examining the output of said spectrometer, said examining step including sampling said output noise from said spectrometer at a desired sampling rate not greater than said maximum sampling rate with an A/D converter for a plurality of points;
- determining a parameter m equal to a function of the ratio of the rms value of said plurality of points of said examined output noise to d, the value of the least significant bit of said A/D converter;
- and
- controlling said analytical instrument to maintain the said ratio greater than a predetermined value N during time averaging of the outputs of said spectrometer.
An analytical instrument comprising a spectrometer, a ensemble averaging computer including means for accumulating data to improve the signal-to-noise ratio of ensemble averaged low level resonance outputs derived from said spectrometer, said ensemble averaging computer including an A/D converter having a least significant bit value of d, a memory unit including scaling capability and storage of the scaling factor, an arithmetic unit, a logic and timing unit, said analytical instrument further including
- means for causing said A/D converter to perform a plurality of time displaced noise measurements and analogue to digital conversions of said noise measurements of the output of said spectrometer at a sampling rate less than a predetermined maximum sampling rate;
- means to cause said memory unit to store each said digital time noise displaced measurement in a separate channel of said memory;
- means for causing said computer to operate upon said plurality of digital time displaced readings to determine a factor m, wherein m is proportional to log kV'/d and where V' is the rms value of the said stored digital time displaced measurements, d is said least significant bit of the said A/D converter, and k is a constant;
- means for generating a parameter n, where n equals a function of m;
- means for causing said arithmetic unit to compare, in non-quiescent state operation, the number of said scaling operations to the parameter n;
- and
- means for discontinuing operation of said analytical instrument when said scaling factor exceeds the parameter n.
An analytical instrument comprising a spectrometer, a ensemble averaging computer including means for accumulating data to improve the signal-to-noise ratio of ensemble averaged low level resonance outputs derived from said spectrometer, said ensemble averaging computer including an A/D converter having a least significant bit value of d, a memory unit including scaling capability and storage of the scaling factor, an arithmetic unit, a logic and timing unit, said analytical instrument further including;
- means for causing said A/D converter to perform a plurality of time displaced noise measurements and analog to digital conversions of said noise measurements of the output of said spectrometer at a sampling rate less than a predetermined maximum sampling rate;
- means to cause said memory unit to store each said digital time displaced noise measurement in a separate channel of said memory;
- means for discontinuing accumulations of said analytical instrument responsive to a function of the ratio between the noise voltage represented by said plurality of said time displaced measurements and the said A/D converter least significant bit value d.
An analytical instrument comprising a spectrometer, a ensemble averaging computer including means for accumulating data to improve the signal-to-noise ratio of ensemble averaged low level resonance outputs derived from said spectrometer, said ensemble averaging computer including an A/D converter having a lease significant bit value of d, a memory unit including scaling capability and storage of the scaling factor, an arithmetic unit, a logic and timing unit, said analytical instrument further including;
- means for causing said A/D converter to perform a plurality of time displaced noise measurements and analog to digital conversions of said noise measurements of the output of said spectrometer at a sampling rate less than a predetermined maximum sampling rate;
- means to cause said memory unit to store each said digital time displaced noise measurement in a separate channel of said memory;
- means for adjusting the amplitude of said low level resonance outputs of said analytical instrument responsive to a function of the ratio between the noise voltage represented by said plurality of said time displaced measurements and the said A/D converter least significant bit value d.
Dependencies are inferred from the claim text.