Abstract: A measuring apparatus for the determination of medical, electro-chemical measured values relevant to organic or metabolic functions comprises a sensor head, a coupling, to which the sensor head is exchangeably secured, and a microprocessor-controlled base instrument, which is provided with a central control unit, with a data detection and evaluation unit to detect and convert the measuring signals forwarded by the coupling in accordance with an in each case associated calibrating regulation, with a display to display the measured values and with a keyboard to enter measuring-relevant data.

Abstract: A sensor for measuring the activity of ions by means of ion-selective membranes (4) improves the measuring possibilities and reduces the dimensions of the sensor in that a plurality of such membranes are held in a common carrier (3) and are electrically insulated and protected against the penetration of moisture. Shunts (2) are provided in a sensor body (1) of the carrier. The carrier and sensor body are connected to one another. The invention is also directed to a method for producing such a sensor. Moreover, the invention is concerned with sensors and a respective arrangement for hemodialysis.