Since more than a decade, several instruments using narrow field of view radiometers and applying time series, snapshots and scanning techniques have been developed to monitor down welling long wave radiations and by consequence cloud cover intensity. For regular monitoring of cloud cover, in atmospheric measurement networks the time series technique has already been used with ceilometric data and now with narrow field of view (NFOV) radiometers. In order to determine the best set of data for sampling frequency, zenith angle and also field of view, we built a numerical simulator calculating interactions between a measurement grid in the approximation of the parallel plan model and binarized cloud fields generated by the "Larges Eddies Simulation" method. We will present results obtained with various sets of radiometers with different geometries facing to cloud fields simulating a wide range of broken clouds conditions. As a conclusion, we provide recommendations for positioning and feature of NFOV radiometers and finally we will discuss potential improvements of these simulation techniques.