A sensor (1) to determine the pressure in a milk transport system of an installation for milking animals, more particularly to determine to what extent a vacuum is present in the milk transport system. The sensor is provided with a first space (4), bounded by one first wall (2), which, in use, is in open communication with the milk transport system or is part of the milk transport system. The sensor is further provided with a first electrode (8) which is mechanically in contact with the first wall, a second electrode (12) and an electronic measuring circuit (16) for measuring a parameter which depends at least on the capacity formed by the first and the second electrode. The sensor is designed such that a distance between the first and second electrode varies as a function of a difference in pressure between the first space and the second space so that the parameter is a measure of the pressure prevailing in the first space relative to the pressure prevailing in the second space.
