Measuring and testing – Liquid level or depth gauge – Hydrostatic pressure type
Reexamination Certificate
2001-10-30
2003-04-01
Williams, Hezron (Department: 2856)
Measuring and testing
Liquid level or depth gauge
Hydrostatic pressure type
C073S29000R
Reexamination Certificate
active
06539796
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid level sensor, an ampoule, and a liquid amount detection method which are used in a so-called liquid source bubbling system.
2. Related Background Art
There are cases where liquid level sensors are used in so-called liquid source bubbling systems in which a bubbling gas is introduced into an ampoule so as to generate bubbling in a liquid, thereby producing a desirable process gas. Known as an example of the liquid level sensors is one in which a sensor probe is directly immersed in a liquid contained in an ampoule, so as to detect the level of the liquid.
SUMMARY OF THE INVENTION
However, from the viewpoint of quality control, the above-mentioned liquid source bubbling systems have been desired to monitor not only whether a liquid exists within the ampoule or not, but also whether the liquid decreases in a normal manner nor not, how much the liquid remains within the ampoule, and so forth.
It is an object of the present invention to provide a liquid level sensor, an ampoule, and a liquid amount detection method which can effectively monitor the state of the liquid.
The inventors conducted diligent studies and, as a result, have found that the number of bubbling periods of the bubbling gas and the bubbling time can be grasped in a liquid source bubbling system since the liquid within the ampoule is stirred during the bubbling of the bubbling gas, thus accomplishing the present invention.
Namely, the present invention provides a liquid level sensor for detecting a level of a liquid contained in an ampoule in which a bubbling gas is introduced, the liquid level sensor comprising a self-heating sensor probe and a temperature measuring sensor probe which are disposed within the ampoule; temperature difference detecting means for detecting a temperature difference between the self-heating sensor probe and the temperature measuring sensor probe; and bubbling count means for counting the number of bubbling periods of the bubbling gas according to the temperature difference.
When gas bubbles in an ampoule in which a liquid level sensor having a self-heating sensor probe and a temperature measuring sensor probe is disposed, the liquid within the ampoule is stirred, whereby the temperature difference (output potential difference) between the self-heating sensor probe and the temperature measuring sensor probe approaches zero. Therefore, the number of bubbling periods of the bubbling gas can be counted when the number of actions by which the temperature difference between the two sensor probes approaches zero is counted by the bubbling count means. As a consequence, how the liquid within the ampoule is reduced and the like can be grasped. For example, whether the liquid within the ampoule decreases normally or not can be grasped by seeing how many bubbling periods occur during when the liquid within the ampoule changes from a fulfilled state to an empty state.
Preferably, the liquid level sensor further comprises liquid level determining means for determining a level of the liquid according to the temperature difference. Such a liquid level sensor detects the number of bubbling periods of the bubbling gas together with the level of the liquid within the ampoule, thus being able to monitor the state of the liquid within the ampoule more effectively.
Preferably, the bubbling count means has pulse generating means for generating a pulse signal when the temperature difference decreases by a predetermined amount, and a pulse counter for counting the number of pulses generated by the pulse generating means. This can realize the bubbling count means by a simple configuration, and thus is advantageous in terms of cost.
Preferably, the liquid level sensor further comprises display means for displaying the number of bubbling periods counted by the bubbling count means. As a consequence, the operator can immediately grasp the number of bubbling periods by seeing the display means.
Preferably, a plurality of sensor probe sections each comprising the self-heating sensor probe and the temperature measuring sensor probe are provided, while the sensor probe sections have respective front end positions different from each other. As a consequence, how the liquid decreases within the ampoule can be grasped stepwise.
In another aspect, the present invention provides a liquid level sensor for detecting a level of a liquid contained in an ampoule in which a bubbling gas is introduced, the liquid level sensor comprising a self-heating sensor probe and a temperature measuring sensor probe which are disposed within the ampoule; temperature difference detecting means for detecting a temperature difference between the self-heating sensor probe and the temperature measuring sensor probe; and arithmetic means for determining a bubbling time of the bubbling gas according to the temperature difference and calculating an amount of use of the liquid in the ampoule from the bubbling time.
When gas bubbles in an ampoule in which a liquid level sensor having a self-heating sensor probe and a temperature measuring sensor probe is disposed, the liquid within the ampoule is stirred, whereby the temperature difference (output potential difference) between the self-heating sensor probe and the temperature measuring sensor probe approaches zero. Therefore, by using this characteristic, the arithmetic means calculates the bubbling time of the bubbling gas. Since the amount of use of liquid per unit bubbling time is assumed to be substantially constant, the arithmetic means calculates the amount of use of liquid in the ampoule from the liquid use amount data per unit bubbling time and the bubbling time of the bubbling gas. Since the total amount of liquid within the ampoule in the initial state is determined beforehand, the currently remaining amount of liquid can easily be seen when the amount of use of liquid is known. Since how much the liquid remains within the ampoule can be grasped in an analog fashion as such, it will be sufficient if only one set of self-heating sensor probe and temperature-measuring sensor probe exists, whereby the configuration of the liquid level sensor can be simplified.
Preferably, the liquid level sensor further comprises liquid level determining means for determining a level of the liquid according to the temperature difference. Since such a liquid level sensor detects the amount of the liquid remaining within the ampoule while detecting whether the level of the liquid within the ampoule is higher or lower than a predetermined level, it can monitor the state of the liquid within the ampoule more effectively.
Preferably, the arithmetic means stores liquid use amount data per unit bubbling time beforehand and calculates the amount of use of the liquid in the ampoule from the bubbling time of the bubbling gas and the liquid use amount data per unit bubbling time. In this case, the amount of use of liquid can be obtained without calculating the amount of use of liquid per unit bubbling time in the arithmetic means.
Preferably, the arithmetic means measures an interval from a falling timing period of the temperature difference to a rising timing period of the temperature difference, so as to determine the bubbling time.
Preferably, the liquid level sensor further comprises display means for displaying the amount of use of liquid or remaining amount of liquid in the ampoule calculated by the arithmetic means. As a consequence, the operator can immediately grasp the amount of use or remaining amount of liquid by seeing the display means.
In another aspect, the present invention provides a liquid level sensor for detecting a level of a liquid contained in an ampoule in which a bubbling gas is introduced, the liquid level sensor comprising a self-heating sensor probe and a temperature measuring sensor probe which are disposed within the ampoule; temperature difference detecting means for detecting a temperature difference between the self-heating sensor probe and the temperature measuring sensor probe; and arithmet
Murayama Yuji
Shirai Yoshikatsu
Applied Materials Inc.
Frank Rodney
Moser Patterson & Sheridan
Williams Hezron
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