Method for processing a measurement signal from a pressure measurement cell, and a measurement cell arrangement
AssigneeInficon GmbH
InventorFelix Mullis
Life of this patent
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Abstract
Method for determining a pressure in a pressure cell, the method consisting in determining a measuring signal (x) that is at least proportional to a measured pressure in the pressure cell, generating an output signal (y) from the measuring signal (x) using a filter unit (10) comprising a transfer function by at least reducing, preferably eliminating, a noise signal contained in the measuring signal determining a change over time of the measuring signal (x), and setting the transfer function as a function of the change over time of the measuring signal (x). A measuring cell arrangement is also specified.
Claims21
A method of determining a pressure in a process chamber having a membrane pressure cell therein, in accordance with a specification of a vacuum process, wherein the method comprises:
- determining, in a signal processor a measuring signal that is at least proportional to a measured pressure in the membrane pressure cell,
- generating an output signal using a filter unit comprising a transfer function derived from the measuring signal by at least reducing a noise signal contained in the measuring signal, wherein the transfer function is defined by the formula
- yn=αxn+(1−α)yn-1
- wherein yn is a time-discrete output signal, xn is a time-discrete measuring signal, α is a variable whose value depends on the change over time of the measuring signal, and n is a time-dependent index,
- determining a change over time of the measuring signal, and
- processing, in the signal processor, the measuring signal in a fast path for generating an output pulse, wherein the output pulse of the fast path is active for at least as long as the determined change over time of the measuring signal over three sampling intervals is greater than the noise signal acquired in the same time period, which noise signal is contained in the measuring signal or in a measuring signal change acquired in the same time period,
- wherein the output pulse is provided by a control unit to a valve actuator, to control the pressure in the process chamber.
A measuring signal arrangement comprising a membrane pressure measuring cell operatively connected to a process chamber, the membrane pressure measuring cell comprising a filter unit generating a pressure-dependent measuring signal, which is applied to the filter unit and generating an output signal, wherein a change of the measuring signal is determined, and wherein the transfer function is adjusted as a function of the change over time of the measuring signal, the transfer function being defined by the formula:
- yn=αxn+(1−α)yn-1
- wherein yn is the time-discrete output signal, xn is the time-discrete measuring signal, α is a variable whose value depends on the change over time of the measuring signal, and n is a time-dependent index, wherein the measuring signal is applied to a fast path to generate an output pulse, the output pulse of the fast path being active at least as long as the determined change of the measuring signal during at least three sampling intervals is greater than the noise signal acquired in the same time period, which noise signal is contained in the measuring signal or in a measuring signal change acquired in the same time period.
Dependencies are inferred from the claim text.