The disclosure relates to a measurement sensor (10) intended in particular for determining the oxygen content in exhaust gases from internal combustion engines. The sensor comprises a sensor element (14) mounted in a metal housing (13, 30) and attached to connecting cables (18) leading out of the housing (13, 30). The cables are enclosed in a cable sheath (12) and a reference atmosphere for the sensor element (14) can be introduced into the housing (13, 30). The cable sheath (12) is provided at least in areas of its outer surface with at least one gas-permeable section through which the reference atmosphere can penetrate into the interior of the cable sheath (12) and from there into the housing (13, 30). A porous PTFE tube is especially suitable as the cable sheath.