Abstract: A sensor cap for an electrochemical sensor for determining the concentration of an analyte in a measurement medium, includes a main part, which extends along a first axis and has a first end, which has a first opening, and a second end, which is opposite the first end and has a second opening, wherein an electrolyte chamber extends between the first opening and the second opening and a connecting unit is formed at the second end in order to connect the sensor cap to a sensor body of the electrochemical sensor, a membrane unit having a first membrane element and a second membrane element, wherein the first membrane element is permeable to the analyte and the second membrane element comprises a material that is impermeable to the analyte, wherein the second membrane element has a through-hole.

Abstract: A method for calibrating an amperometric sensor at a stationary measuring point, comprises the following steps: providing a mobile calibration device comprising a stabilized calibration fluid at the stationary measuring point; activating the stabilized calibration fluid and providing an activated calibration fluid; calibrating the amperometric sensor by means of the activated calibration fluid; and a mobile calibration device.