A device for examining liquids. A precise examination of liquids has until now only been possible where there are permanently installed evaluation devices. This disadvantage can be avoided with the device for testing liquids. It is equipped with a sensor, which has a measuring device with which any liquid can be examined. The sensor is able to be electrically and mechanically connected to a structural unit which is only slightly larger than a mobile radio telephone. Integrated into the structural unit are an evaluation device and an interface module. The measuring signals of the sensor are registered by the interface module and stored, evaluated and displayed on a display device in the evaluation device.