Touch sensor, sanitary fitting with touch sensor and method for detecting the touching of an electrically conducting surface

Touch sensor with a sensor surface insulated from ground potential, wherein the sensor surface is connected via a measuring resistor with an AC voltage generator, and wherein the voltage applied to the measuring resistor serves as Differenzmeßsignal. At least one touch sensor can advantageously be integrated into a sanitary fitting and serve to control solenoid valves to water inlets of the valve. An operating element of the fitting serves as a sensor surface and is connected via a connecting cable with a control electronics of the sensor. A method of detecting the contact of an electrically conductive surface using a capacitive touch sensor that detects the complex conductance of a human body. The touch detection is performed by measuring and evaluating a current flow in the direction from the sensor to the person who touches the sensor surface and / or in the direction of the person in the sensor.