Apparatus and method for compensating the drift of a local clock used as sampling frequency
AssigneeSercel
InventorsJérôme Laine, Jean-Paul Menard
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Abstract
The invention relates to an apparatus and a method for data acquisition, the apparatus being characterized in that it comprises an analog/digital converter (510) sampling at an imperfect frequency FE provided by a local clock (100) data acquired by a sensor (500) thus providing a series of sampled and dated data E[k], a time-stamping module (300) for measuring the frequency error of the local clock (100) by determining the sampling dates according to a universal time UTC(t), and a resampling module (400) for correcting the sampled and dated data E[k].
Claims15
Method of data acquisition comprising the steps of:
- sampling acquisition data at an imperfect sampling frequency FE provided by a local clock (100), thus forming a series of sampled and dated data E[k] having a time provided by the local clock (100);
- measuring the frequency error of the local clock (100) by determining the sampling dates according to a universal time UTC(t) and gauging the local clock (100) to a reference clock of a satellite-based positioning system (200);
- and
- collecting the sampled and dated data E[k] and turning on the satellite-based positioning system (200) so as to perform the gauging of the local clock (100);
- turning off the satellite-based positioning system (200) once the gauging of the local clock (100) has been performed;
- keeping the satellite-based positioning system (200) in the off state for the duration of validity of the gauging of the local clock (100).
Method according to claim l, in which the step of gauging of the local clock (100) comprises the steps of:
- metering in a first counter (310) of a time-stamping module (300) the number N1 of periods of the local clock (100) from a date UTC(SPS) provided by the reference clock of the satellite-based positioning system (200);
- determining in a second counter (320) of the time-stamping module (300) the frequency of the local clock (100) by gauging of the frequency of the local clock (100) to the frequency of the reference clock of the satellite-based positioning system (200);
- providing an operator (330) of the time-stamping module (300) with the data emanating from the counters (310) and (320) and the date UTC(SPS) so as to determine the sampling dates according to the universal time UTC(t).
Data acquisition apparatus, characterized in that it comprises an analog/digital converter (510) sampling at an imperfect frequency FE provided by a local clock (100) data acquired by a sensor (500) thus providing a series of sampled and dated data E[k] having a time provided by the local clock (100), a time-stamping module (300) for measuring the frequency error of the local clock (100) by determining the sampling dates according to a universal time UTC(t), a satellite-based positioning system (200) including a reference clock, the time-stamping module (300) being able to gauge the local clock (100) to the reference clock of the satellite-based positioning system (200), a resampling module (400) for correcting the sampled and dated data E[k], and a means for correcting the sampled and dated data E[k], turning on the satellite-based positioning system (200) so as to perform the gauging of the local clock (100), turning off the satellite-based positioning system (200) once the gauging of the local clock (100) has been performed and keeping the satellite-based positioning system (200) in the off state for the duration of validity of the gauging of the local clock 100.
Dependencies are inferred from the claim text.