Multi average ratemeter

In the core of a nuclear reactor, neutron detection is a random process. Any measurement based on observing the neutron counts is affected by some degree of statistical fluctuation, particularly in star-up condition. Moreover, the mean value of the neutron count rate evolves with time and follows an exponential law expressed by ψ(t) = ψ0.eφt. The ratemeter estimates the mean value of neutron count rate (ψ0) and the relative variations (φ). As was showed in an earlier paper the statistical error (related to the counts number) and the dynamic error (associated with the counting time) are the two main contributions to the overall error of a single measurement. Traditional approach was an analogue integrator-differentiator with different time constant, manually selectable. In the real word it is needed a measurement as precise and soon as possible. In this paper, a method to solve the trade-off between speed and precision will be described; the goal is to obtain stable readings and response time better than 50 msec. (author)