A microcontroller uses a combination of several synchronized PWM outputs to generate a low distortion sine wave by summing the PWM outputs and filtering the summed signal. The sine wave is used as a guard voltage. The unknown impedance is measured by impinging the guard voltage on the sense electrode by a transistor connected in common base configuration and then transferring the sense current through the common base connected transistor to a transimpedance amplifier made out of a second transistor connected in common emitter configuration. The output voltage at the collector of the second transistor is measured by an ADC input of the microcontroller. The microcontroller translates the ADC output values into the unknown impedance to be measured by doing a software demodulation of the ADC output values. A reference impedance can be connected in parallel to the unknown impeder to eliminate gain errors of the signal sensing circuit.


    Zugriff

    Download


    Exportieren, teilen und zitieren



    Titel :

    Low-Cost Complex Impedance Measurement Circuit for Guard-Sense Capacitive Sensors Operated in Loading Mode


    Beteiligte:

    Erscheinungsdatum :

    14.12.2017


    Medientyp :

    Patent


    Format :

    Elektronische Ressource


    Sprache :

    Englisch


    Klassifikation :

    IPC:    B60R Fahrzeuge, Fahrzeugausstattung oder Fahrzeugteile, soweit nicht anderweitig vorgesehen , VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR / B60N SEATS SPECIALLY ADAPTED FOR VEHICLES , Sitze besonders für Fahrzeuge ausgebildet / G01D MEASURING NOT SPECIALLY ADAPTED FOR A SPECIFIC VARIABLE , Anzeigen oder Aufzeichnen in Verbindung mit Messen allgemein





    LOW-COST, HIGH MEASUREMENT SPEED CAPACITIVE SENSING CIRCUIT FOR LOADING MODE OPERATION OF CAPACITIVE SENSORS

    LAMESCH LAURENT / JUSTINGER TOBIAS / PÜTZ MICHAEL et al. | Europäisches Patentamt | 2024

    Freier Zugriff

    Method for determining a sense impedance in a guard-sense capacitive sensor

    LAMESCH LAURENT | Europäisches Patentamt | 2020

    Freier Zugriff

    METHOD FOR DETERMINING A SENSE IMPEDANCE IN A GUARD-SENSE CAPACITIVE SENSOR

    LAMESCH LAURENT | Europäisches Patentamt | 2018

    Freier Zugriff