As the block diagram indicates, Li-ion batteries / AC charger provides the DC voltage to the
electronic unit.
The regulated voltageof +12V are generated by switching regulator and regulated voltages of
+5V is generated by LDO MAX883.
Positive high voltage used for powered by +12V supplies. The high voltage for the PMT is set
at+750 to 800V DC. The Alpha detector ZnS(As) when exposed to alpha particles light
scintillations are provided.
This signal is detected and a -ve tail pulse is produced by the PMT. This signal is amplified by
the hybrid -ve Tail to TTL circuit. The TTL pulse thus produced is fed to display board for
counting and further analysis.
The display board essentially compreses of 20X4 LCD, micro-controller and other
peripherals like BCD counter, RTC, E
2
PROM, UART to USB connector, keypad etc.
The counts recieved from the Tail to TTL connector are fed to the 6 digit BCD conter. The
counts are readout by the micro-controller periodically for counts / count-rate calculations
and display on 20X4 LCD display also reads / sets micro-controller RTC device and displays
on LCD current time and date. The instrument settings area configured through 2X2 front
panel keypad and stored in the E
2
PROM.
Acquisition for palm is initiated on optical sensor transition and goes on uninterrupted until
there is transition in optical sensor status.
At the end of acquisition, result is diplayed on LCD and depending on alarm status, audio
alarms are generated for contamination event.
Acquisition data is stored in the E
2
PROM and it can be transferred to PC through USB port.
