Portable pH detector
First Claim
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1. A portable pH detector, comprising:
- a ISFET having a sensing film for immersion in a solution;
a signal detection unit to maintain a drain-source voltage and a drain-source current of the ISFET in a constant condition, and to detect the gate voltage of the ISFET as an output signal;
a gain control and level shift unit to adjust the level of the output signal as a first signal;
a A/D converter to convert the first signal into a first digital signal; and
a microprocessor coupled to the A/D converter to compare the first digital signal with a relational table to obtain the pH of the solution.
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Abstract
A portable pH detector. A pH-ISFET is immersed into a solution, and the gate voltage of the pH-ISFET is detected by a signal detection unit. The level of the detected voltage is adjusted by a gain control and level shift unit and is converted by an A/D converter circuit and then output to a 8051 microcontroller to compute the pH of the solution, with the computed result displayed on a LCD.
7 Citations
18 Claims
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1. A portable pH detector, comprising:
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a ISFET having a sensing film for immersion in a solution;
a signal detection unit to maintain a drain-source voltage and a drain-source current of the ISFET in a constant condition, and to detect the gate voltage of the ISFET as an output signal;
a gain control and level shift unit to adjust the level of the output signal as a first signal;
a A/D converter to convert the first signal into a first digital signal; and
a microprocessor coupled to the A/D converter to compare the first digital signal with a relational table to obtain the pH of the solution. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method for measuring pH of a solution, compatible with a portable pH detector having a pH-ISFET with a sensing film, a signal detection unit to maintain a drain-source voltage and a drain-source current of the ISFET in a constant condition and detecting the gate voltage of the pH-ISFET, a gain control and level shift unit, a A/D converter and a microprocessor, the method comprising:
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measuring a first solution with a first determined pH and a second solution with a second determined pH to obtain a first reference value and a second reference value by the pH-ISFET respectively;
creating a relational table according to the first reference value and a second reference value;
measuring a solution by the pH-ISFET to obtain a first digital value; and
comparing the first digital value and the relational table to determine the pH of the solution. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18)
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Specification