Ion concentration measuring apparatus
First Claim
1. An ion concentration measuring apparatus comprising:
- a container for holding a test liquid containing at least one kind of ion whose concentration is to be measured;
means in contact with the test liquid for maintaining the test liquid at a constant potential;
at least one ion sensitive field effect transistor having a gate portion which is selectively sensitive to said ion, drain and source;
at least one measuring circuit comprising a constant voltage supply source which is not connected to the earth and which applies a constant voltage across the drain and source of the ion sensitive field effect transistor, a reference resistor connected to the constant voltage supply source and the drain or source, a potential control circuit having inputs connected across the reference resistor and an output connected to the drain or source for controlling a potential at the drain or source in such a manner that a voltage across the reference resistor remains a predetermined value, and a voltmeter for measuring a variation of the potential at the drain or source as a measure of the concentration of ion.
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Accused Products
Abstract
An apparatus for measuring a concentration of a specific ion contained in a test liquid held in a container with the aid of a reference electrode and an ion sensitive field effect transistor having a gate portion selectively sensitive to the specific ion, including a series circuit of a reference resistor and a constant voltage supply source connected across drain and source of the ion sensitive field effect transistor, a potential control circuit having inputs connected across the reference resistor to detect a potential difference across the reference resistor for controlling a source or drain potential of the ion sensitive field effect transistor in such a manner that the potential difference remains at a predetermined value and a voltmeter for measuring the source or drain potential as a measure of the ion concentration.
143 Citations
8 Claims
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1. An ion concentration measuring apparatus comprising:
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a container for holding a test liquid containing at least one kind of ion whose concentration is to be measured; means in contact with the test liquid for maintaining the test liquid at a constant potential; at least one ion sensitive field effect transistor having a gate portion which is selectively sensitive to said ion, drain and source; at least one measuring circuit comprising a constant voltage supply source which is not connected to the earth and which applies a constant voltage across the drain and source of the ion sensitive field effect transistor, a reference resistor connected to the constant voltage supply source and the drain or source, a potential control circuit having inputs connected across the reference resistor and an output connected to the drain or source for controlling a potential at the drain or source in such a manner that a voltage across the reference resistor remains a predetermined value, and a voltmeter for measuring a variation of the potential at the drain or source as a measure of the concentration of ion. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification