Device for measuring the concentrations in a measuring liquid
First Claim
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1. A device for measuring the concentration of ions in a measurement liquid, comprising:
- at least one ion sensitive field effect transistor (pH-ISFET) having a drain provided in the measurement liquid;
a bridge circuit having at least three resistors, said bridge circuit provided with feed points having a feed voltage and a diagonal voltage, said bridge circuit connected to said pH-ISFET;
an operational amplifier having a p-input and an n-input, said operational amplifier connected to said bridge circuit, said diagonal voltage of said bridge circuit being between said p-input and said n-input of said operational amplifier, said n-input connected to said drain, the output of said operational amplifier being fed back to said bridge circuit; and
a reference electrode provided in the measurement liquid;
wherein an output signal is produced by the device which measures the ion concentration of the measurement liquid, said output signal formed as the output voltage from the difference of the drain potential of said pH-ISFET on said n-input and the reference potential of said reference electrode.
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Abstract
The invention relates to a device for measuring the concentration of ions, notably of hydrogen ions, in a measuring liquid using at least one ion-sensitive field effect transistor which is integrated into an electric circuit within the device in such a way that said circuit emits an output signal which serves as measure of the ion concentration in the measuring liquid. To provide a circuit which is as simple as possible and in particular comprises as few components as possible, the invention provides for the at least one pH-ISFET to be bridge-connected with at least three resistors.
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Citations
12 Claims
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1. A device for measuring the concentration of ions in a measurement liquid, comprising:
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at least one ion sensitive field effect transistor (pH-ISFET) having a drain provided in the measurement liquid;
a bridge circuit having at least three resistors, said bridge circuit provided with feed points having a feed voltage and a diagonal voltage, said bridge circuit connected to said pH-ISFET;
an operational amplifier having a p-input and an n-input, said operational amplifier connected to said bridge circuit, said diagonal voltage of said bridge circuit being between said p-input and said n-input of said operational amplifier, said n-input connected to said drain, the output of said operational amplifier being fed back to said bridge circuit; and
a reference electrode provided in the measurement liquid;
wherein an output signal is produced by the device which measures the ion concentration of the measurement liquid, said output signal formed as the output voltage from the difference of the drain potential of said pH-ISFET on said n-input and the reference potential of said reference electrode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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Specification