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Counters recycling

The memory allocated to the 1s ratemeters and to each energy spectra channel is 16 bit. This means that if the counts in one ratemeters bin or PHA channel exceeds 216=65536, the counter will be reset to 1 and restart counting. The result will be that if the counter recycles n times, the true measured count rate or count per PHA channel will be equal to the final counter value summed to n 65536.
Counters recycling affected the GRBM measurements of SGR1900+14 outburst (August,27 1998) in the first 2 seconds. The recycling was apparent from the comparison with other experiments results and also by counts in the GRBM and AC ratemeters. In this case the recycling heavily affected also the HRTP, making it impossible to reconstruct the real high time resolution event profile in the first second.



Lorenzo Amati
8/30/1999