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US 5,326,447 AGranted
Oxygen analyzer
AssigneeThe Foxboro Company
InventorKenneth S. Fletcher
Life of this patent
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Abstract
An analyzer for detecting a selected chemical (such as oxygen) in a process fluid includes a plurality of electrodes that are separated from the fluid by a membrane that is permeable to the selected chemical, each of the electrodes when energized producing a signal in response to the selected chemical in the fluid. The selected chemical level in the process fluid is determined based on the signal produced by a first one of the electrodes, and the determined level is used with the signal produced by a second one of the electrodes to detect whether the membrane has become faulty (e.g., fouled by materials in the process fluid).
Claims47
Apparatus for detecting a selected chemical in a fluid, comprising
- a plurality of electrodes separated from said fluid by a membrane that is permeable to said selected chemical, each of said electrodes when energized producing a signal in response to said selected chemical in said fluid,
- a power source for energizing said electrodes,
- means for determining a level of said selected chemical in said fluid based on said signal produced by a first one of said electrodes, and
- means for comparing said determined level with said signal produced by a second one of said electrodes, and means for detecting whether said membrane is faulty based on said comparing.
1 more element
Apparatus for detecting a selected chemical in a fluid, comprising
- a housing that is adapted to be inserted in said fluid, said housing having an end over which a membrane that is permeable to said selected chemical is disposed, said end having a surface disposed substantially parallel to said membrane for supporting a plurality of electrodes adjacent to said membrane and separated from said fluid by said membrane,
- a first one of said electrodes being adapted to be energized for first duration of time which enables said first electrode to produce a first signal that indicates a level of said selected chemical in said fluid,
- a second one of said electrodes being adapted to be energized for a second duration of time which enables said second electrode to produce a second signal that when compared with said first signal provides an indication of whether said membrane is faulty.
A method for detecting a selected chemical in a fluid, comprising
- providing a plurality of electrodes separated from said fluid by a membrane that is permeable to said selected chemical, each of said electrodes when energized producing a signal in response to said selected chemical in the fluid,
- energizing said electrodes,
- determining a level of said selected chemical in said fluid based on said signal produced by a first one of said electrodes,
- comparing said determined level with said signal produced by a second one of said electrodes, and
- detecting whether said membrane is faulty based on said comparing.
2 more elements
A method for detecting a selected chemical in a fluid, comprising
- providing a plurality of electrodes separated from said fluid by a membrane that is permeable to said selected chemical, each of said electrodes when energized producing a signal in response to said selected chemical in the fluid,
- energizing said first electrode for a first duration of time which causes said signal produced by said first electrode to reach a steady-state value,
- energizing said second electrode for a second duration of time which does not cause said signal produced by said second electrode to reach a steady-state value, said first duration exceeding said second duration,
- allowing a user of said apparatus to select said first duration and said second duration,
- determining a level of said selected chemical in said fluid based on said signal produced by a first one of said electrodes,
- analyzing said signal produced by said second electrode during said second duration to derive an expected level of said selected chemical, and
- detecting that said membrane is faulty if said determined level differs from said expected level by more than a selected amount.
4 more elements
A method for detecting a selected chemical in a fluid, comprising
- providing a plurality of electrodes separated from said fluid by a membrane that is permeable to said selected chemical, each of said electrodes when energized producing a signal in response to said selected chemical in the fluid,
- energizing said electrodes, said step of energizing including energizing said second electrode for a selected duration of time,
- determining a level of said selected chemical in said fluid based on said signal produced by a first one of said electrodes,
- analyzing said signal produced by said second electrode during a portion of said selected duration to derive an expected level of said selected chemical, said step of analyzing including integrating said signal produced by said second electrode during said portion of said selected duration to produce said expected level, said section duration being based on a calibrated ratio between said determined level and said expected level, and
- detecting that said membrane is faulty if said determined level differs from said expected level by more than a selected amount.
2 more elements
A method for detecting a selected chemical in a fluid, comprising
- providing a plurality of electrodes separated from said fluid by a membrane that is permeable to said selected chemical, each of said electrodes when energized producing a signal in response to said selected chemical in the fluid,
- energizing a first one of said electrodes for a time which causes said signal produced thereby in response to said selected chemical to reach a steady-state value and determining a level of said selected chemical based on said signal produced by said first electrode,
- energizing a second one of said electrodes for a time which does not cause said signal produced thereby in response to said selected chemical to reach a steady-state value, and
- detecting whether said membrane is faulty based on comparing said signal produced by said second electrode with said determined level.
1 more element
Dependencies are inferred from the claim text.