Stability and calibration of the analog RPC readout in ARGO-YBJ

The RPC charge readout, which is in operation on the entire central carpet (about 5800 m
²
) of ARGO-YBJ since December 2009, extends the energy range of measurement, allowing the study of the cosmic radiation up to PeV energies. Here we will describe the chain of steps that, starting from raw data, allows the measurement of the shower size by the ARGO-YBJ detector. Moreover, the effects of the environmental parameters and the stability of the analog readout are presented. Our first results on the high density shower selection will be also presented.