A device for determining a physical value of a liquid flowing in a pipe, without contact with said liquid, said device comprising: a sensor (3) for said physical value; a connector (2) to insert into said pipe and comprising: an internal passage (13) extending between two apertures (11, 12), a flexible membrane (6) for a pressure sensor, forming a wall of said internal passage (13); and means (27, 62) for fastening said sensor (3) onto said connector (2); characterized in that said sensor is a temperature sensor (3) fastened to said connector (2) with the sensitive part of said sensor (3) turned towards said membrane (6).