Amperometric sensor for low level dissolved oxygen with self-depleting sensor design
AssigneeRosemount Analytical Inc.
InventorChang-Dong Feng
Life of this patent
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Abstract
A dissolved oxygen sensor having a cathode and anode immersed in an electrolyte is designed to provide a low background current in the sensor when a potential is applied to the cathode. The background current is maintained at a desired level by selecting the area and length of a channel or path of diffusion of residual oxygen in the electrolyte to the cathode. The area (A) of the diffusion channel in relation to its length (L) is selected to be at or below a selected ratio, A/L.
Claims13
A sensor for sensing presence of a gas in a liquid comprising a housing having an interior chamber, a cathode mounted in said housing adjacent one end, an anode supported in said housing open to said chamber and spaced from the cathode, an electrolyte in the chamber, a membrane permeable to a gas having a section for separating the cathode, anode and the electrolyte from a sample medium, the cathode having a surface facing the membrane and spaced therefrom, a channel leading from the chamber to the space between the membrane and the cathode surface, the electrolyte filling the channel and the space, said channel having an area A and a length L, and the ratio A/L being below a selected amount for controlling maximum background current caused by residual amounts of the gas in the electrolyte.
In a dissolved oxygen sensor comprising a housing having an interior chamber and having at least one open end, a membrane overlying the open end, a cathode supported in the housing adjacent the open end with a space between the cathode and the membrane, a restricted channel extending from the space between the cathode and the membrane to the interior chamber and having an area and a length, and an anode mounted in said interior chamber, the interior chamber, the restricted channel, and the space between the membrane and the cathode being filled with an electrolyte, and a source of potential connected between the anode and the cathode, the improvement comprising forming the restricted channel to have a ratio A/L of the area (A) of the restricted channel relative to the length (L) of the restricted channel from the space to the chamber that is below a selected value to limit background current sensed between the cathode and anode.
A method of reducing the background current in a dissolved oxygen sensor having a chamber filled with electrolyte, a membrane covering an opening to the chamber and a cathode adjacent the membrane with a layer of electrolyte between the membrane and the cathode, comprising providing a restricted electrolyte filled channel from the chamber to the layer of electrolyte, applying a potential between the cathode and an anode in the chamber to reduce oxygen at the cathode so that residual oxygen in the electrolyte diffuses through the restricted channel to the cathode, and forming the restricted channel to have an area A and length L at a selected ratio of A to L to provide background current from dissolved oxygen in the electrolyte below a selected level.
Dependencies are inferred from the claim text.