Fluid sensor, system for testing a sample and process

Analysis system for testing a biological sample, the analysis system comprising an analysis device for receiving a cartridge including a fluid system having a sensor portion, the analysis device including a fluid sensor for detecting a content change in a sensor portion responsive to a content change of a fluid system with which the sensor portion is associated,

• wherein the fluid sensor includes at least one sensor electrode, the sensor electrode having an electrode potential and a capacitive behavior, the sensor electrode configured to store electrical energy in an electrical field formed by the sensor electrode when being charged causing the electrode potential to change accordingly, wherein a capacitance value of the sensor electrode varies when the content changes,
• wherein the fluid sensor includes evaluation electronics for detecting a change in electrical properties of the sensor portion when a content change of the fluid system takes place using the sensor electrode, the evaluation electronics including a unidirectional electrical device, in the following referred to as UED, and an AC source,
• wherein the AC source is coupled via the UED to the sensor electrode to charge the sensor electrode, and
• wherein the evaluation electronics comprises a discharge path coupled to the sensor electrode for discharging the sensor electrode through a lowpass filter to output the content change and an energy storage coupled to the sensor electrode such that charge from the sensor electrode is shareable with said energy storage.

A process for detecting a content change in a sensor portion of a fluid system with a fluid sensor for detecting a content change in a sensor portion of a fluid system, wherein the fluid sensor includes at least one sensor electrode, the sensor electrode having an electrode potential and a capacitive behavior, the process comprising:

• storing electrical energy in an electrical field formed by the sensor electrode when being charged causing the electrode potential to change accordingly, wherein a capacitance value of the sensor electrode varies when the content changes,
• wherein the fluid sensor includes evaluation electronics for detecting a change in electrical properties of the sensor portion when a content change of the fluid system takes place using the sensor electrode, the evaluation electronics including a unidirectional electrical device, in the following referred to as UED, and an AC source,
• wherein the AC source is coupled via the UED to the sensor electrode to charge the sensor electrode,
• wherein the evaluation electronics includes a discharge path coupled to the sensor electrode for discharging the sensor electrode through a lowpass filter to output the content change;
• and an energy storage coupled to the sensor electrode such that charge from the sensor electrode is shareable with said energy storage, and
• wherein the evaluation electronics of the fluid sensor repeatedly charges the sensor electrode with the AC source via the UED to a predefined electrode potential and automatically discharges the sensor electrode by means of the discharge path starting from the predefined electrode potential approximating the electrode potential to the reference potential or sharing charge of the sensor electrode with an energy storage each time after charging is finished.