There are several types of instruments that enable us to measure the ozone content in different conditions (in the outdoors, in moving platforms, in industrial buildings, etc.). They operate on the basis of different physical and chemical processes and have different values of parameters such as sensitivity, accuracy, response time, etc. The model of photometer for measuring the ozone concentration is described below. The instrument acts due to selective absorption of UV-radiation by ozone molecule. The distinguishing peculiarity of this device is the use of radioluminescent source (RLS) with very high long-term temporal emission stability instead of the generally used unstable mercury lamp. The RLS emission power is 3 (DOT) 1011 quantum/s. Three subsystems (optical, gas-flow, and electronic) making up this photometer are described in detail. The approximate estimates of photometer threshold sensitivity and accuracy are made and the possible means for improving these parameters are outlined.