A device for determining a physical value of a liquid flowing in a pipe, without contact with the liquid. The device includes: a sensor for the physical value; a connector to insert into the pipe and including: an internal passage extending between two apertures, a flexible membrane for a pressure sensor, forming a wall of the internal passage; and a fastening mechanism for fastening the sensor onto the connector. The sensor is a temperature sensor fastened to the connector with the sensitive part of the sensor turned towards the membrane.