Temperature and humidity compensation for gas detection apparatus
AssigneeThe Standard Oil Company
InventorsStephen C. Pyke, Donald L. Boos, Milton L. Brouwer
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Abstract
The use of multiple field effect transistors, wherein only one transistor is sensitive to the presence of a particular element, is disclosed whereby similar responses to temperature and/or humidity fluctuations may be subtracted yielding a response to a particular element that is relatively insensitive to temperature and/or humidity variations.
Claims14
A compensated apparatus for monitoring the concentration of at least one selected gas comprising:
- a first three terminal field-effect transistor sensor that is responsive to at least one of changes in temperature and humidity and to at least one selected gas;
- at least a second field-effect transistor sensor that is responsive to the same at least one of changes in temperature and humidity that said first sensor is and is substantially unresponsive to said at least one selected gas;
- means for adjusting the response of at least one of said first and second sensors so that the responses of said sensors to said at least one of said changes in temperature and humidity are essentially the same;
- and
- means for subtracting the response of the second sensor from the response of the first sensor to compensate for the response of said first sensor to changes in the at least one of temperature and humidity.
A method of monitoring changes in gas concentration that is substantially insensitive to changes in at least one of temperature and humidity comprising:
- sensing the concentration of at least one selected gas with a first three terminal field-effect transistor sensor that is responsive to changes in at least one of temperature and humidity and to said at least one selected gas;
- sensing the change in said at least one condition with a second field-effect transistor sensor that has the same response to the same at least one of changes in temperature and humidity that said first sensor has and is substantially unresponsive to said at least one selected gas;
- adjusting the responses of at least one of said first and second sensors so that the responses of said sensors to said at least one of said changes in temperature and humidity are essentially the same;
- subtracting the response of said second sensor from the response of the first sensor to compensate for the response of the first sensor to changes in the at least one of temperature and humidity;
- and
- monitoring the compensated response of said first sensor to detect changes in the concentration of the at least one selected gas.
Dependencies are inferred from the claim text.