The beam position monitoring (BPM) system for the storage ring of the
Beijing Electron Positron Collider (BEPC) has been upgraded. The short
-term reproducibility of the measurement is better than 10 microns. Th
e measurement time for scanning all BPMs is about 11 seconds. The dyna
mic rang of the system is over 81 dB and the minimum measurable beam i
ntensity is less than 0.5mA. The reliability of the measurement is ass
ured by the self-consistency check.