Corrosion measurement with secondary temperature compensation
AssigneeRohrback Corporation
InventorsRex V. Rhoades, James L. Geer
Life of this patent
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Abstract
An electrical resistance type corrosion measuring probe has a test element exposed to a corrosive environment and an adjacent reference element protected from the environment. Electrical circuitry is connected to the elements for measurement of resistance ratio. This provides a corrosion output signal having a first order of temperature correction provided by the reference element. Secondary temperature compensation for dynamic or short term variation of temperature of the corrosive environment is provided by thermocouple measurement of temperatures of the test and reference elements and compensating the corrosion signal in accordance with the directly measured short term temperature difference of the elements.
Claims18
In an electrical resistance type corrosion measuring instrument having test and reference elements in a probe adapted to be placed in an environment of which corrosive characteristics are to be measured, and having means for providing a corrosion signal representing corrosion of said test element, said signal having a primary temperature compensation for temperature of the environment of said probe elements, said elements having different thermal responses to temperature fluctuations of said environment,
- the improvement comprising apparatus for further compensating said signal for fluctuation of environment temperature, said apparatus comprising
- means for measuring temperatures of both said elements and generating a secondary temperature compensation signal representative of the temperature of said elements relative to each other, and
- means for combining said corrosion signal with said secondary temperature compensation signal to provide an output signal representative of corrosion of said test element and compensated for temperature fluctuation of said environment.
A corrosion probe comprising
- a test element adapted to be exposed to an environment of which corrosive characteristics are to be measured,
- a reference element mounted adjacent said test element and protected from corrosion by said environment,
- resistance responsive means for generating a corrosion signal having a first compensation for temperature of said elements,
- means for measuring the difference in temperature between said test and reference elements, and
- means responsive to said temperature difference measuring means for compensating said corrosion signal for temperature differences of said test and reference elements.
In a corrosion probe having test and reference elements and means responsive to resistances of the elements for generating a primary corrosion signal having a primary compensation for temperature, the improvement comprising means for providing additional temperature compensation for said corrosion signal, said last mentioned means comprising
- first and second temperature sensing devices connected to sense temperatures of said test and reference elements respectively,
- means responsive to said devices for generating a secondary temperature compensation signal in accordance with the difference between sensed temperatures of said test and reference elements, and
- means for combining said temperature compensation signal with said primary corrosion signal.
The method of providing temperature compensation of a corrosion probe of the type having a test element arranged for exposure to a corrosive environment, a reference element protected from the corrosive environment and means for measuring electrical parameters of the elements to obtain a corrosion signal indicative of corrosion of the test element, said method comprising
- sensing temperature of said test element,
- sensing temperature of said reference element,
- generating a signal representing the difference between the sensed temperatures, and
- employing said signal to compensate the corrosion signal.
In a corrosion probe wherein a reference element protected from a corrosive environment is employed together with a test element to be placed in the corrosive environment, and wherein electrical parameters of the elements are measured to provide a corrosion signal compensated for changes in said electrical parameters caused by relatively static temperature of the corrosive environment, the method of providing further temperature compensation comprising the steps of
- directly sensing temperature of said test element,
- directly sensing temperature of said protected reference element, and
- employing the sensed temperatures to compensate said corrosion signal for temperature differences between said test and reference elements.
Dependencies are inferred from the claim text.