A method of detecting a gas bubble in a measuring chamber filled with a liquid. The electrical conductivity of the liquid or a variable derived therefrom is measured in the measuring chamber at a first pressure value p.sub.1, and a first measured value S.sub.1 is detected. The pressure in the measuring chamber is changed, the electrical conductivity of the liquid or a variable depending thereon is measured in the measuring chamber at at least a second pressure value p.sub.2, and a second measured value S.sub.2 is detected. The presence or lack of presence of at least one gas bubble in the liquid is detected by comparing the first measured value S.sub.1 to the second measured value S.sub.2.