WIDE RANGE MONITOR

PURPOSE:To widen the effective measuring range of a campbell measuring system, by controlling the level shift of the amplified gain and logarithmic output of a logarithmic campbell signal component by a shift circuit. CONSTITUTION:A preamplifier 13 for a logarithmic compbell is changed over to a low gain when the effective output of a logarithmic campbell circuit 14 reaches a full-scale value P by a shift circuit 17 responding to a change-over level detecting circuit according to the increase of a neutron flux level with the increase in the output of a nuclear reactor. At the same time, the circuit 17 allows the logarithmic output from the logarithmic converter circuit 14b of the circuit 14 to shift over a level change portion p-q corresponding to gain change. Therefore, upper and lower limits are widen and the outputs (a), (b) of the circuit 14 is sufficiently overlapped with the neutron source (SRM) measuring output (c) of a (SRM) region from a logarithmic counting rate counter circuit 3 through a synthesizer circuit 15 as well as also well overlapped with the intermediate output (IRM) of an IRM region from a linear campbell circuit S. As a result, monitoring and measuring accuracy due to a neutron flux wide range monitor is enhanced.