Thermo Scientific SAM12, Manual

Page: 126 / 176

Technical Description - Circuitry Issue: 1.0
7-4 SAM12 User Manual Thermo Fisher Scientific
battery. Current and voltage monitoring (IC100/101) and
control circuitry (IC4) always ensure sufficient power is made
available to power the SAM12 (even when the battery is
exhausted) from the primary power source.
The transfer to battery is automatic. However the load will be
removed when the battery terminal voltage falls bellow
+10.5 V. This circuit is required to prevent the battery being
damaged by being deeply discharged. Hysteresis is built in to
this circuit to prevent oscillations. It does not allow the battery
to re-connect as soon as its terminal voltage recovers slightly as
a result of having the load removed from its terminals.
The user is signalled the pending shut-down in order that any
data can be saved.
A key switch is connected to the 5660A for manually switching
the power ON/OFF to the load.
The key-switch performs two operations.
Primarily it allows the instrument to be switched ON if either
the mains supply exists or the battery contains sufficient
charge, or both. This is achieved by turning the key clockwise
for at least 2 seconds.
Secondly, the instrument can be switched OFF should the
operating software fail to carry out the “Shut-down” task by
holding the key clockwise for at least 10 seconds.
FHT681 42543-0223 & 42543-0224
For more information regarding the Scintillation HV and
Amplifier Board, see
FHT681 Scintillation HV and Amplifier
Type 42543-0223 (page 2-3) .
For more information regarding the CCM Board, see FHT681
Coincidence Detector Card Type 42543-0224 (page 2-4) .
The Dual-Channel Scintillation HV and Amplifier board
provides the high voltages for two scintillation detectors. It
also receives charge pulses from two detectors, amplifies them
and discriminates between five energy levels. Independent
counter values (five for each channel) are generated every
100ms and stored in a 5 second buffer. In addition to that, 1s
values are built from the 100ms values. All these values can be
polled from the serial interface.
The HV sections are designed to provide independently
adjustable polarising voltages for two scintillation detectors
with working voltage ranges between 500V to 1400V.
Keyswitch operation
Scintillation HV & Amplifier