Abstract: An arrangement for measuring conditions within a cement kiln in which the metallic body of the kiln is used as a wave guide for radio waves used for the measurement. An antenna with radio frequency energy applied thereto, runs through the kiln, and measuring antennas are located at predetermined points along the length of the kiln. The prevailing field strength measured by the measuring antennas is indicative of the conditions, particular temperature, which prevail within the kiln. Each of the measuring antennas may lie in a plane perpendicular to the kiln access, and a stationary link is inductively coupled to each measuring antenna. The stationary link travels around the kiln in a plane perpendicular to the axis thereof.