Thermo EPD Mk2, Technical Handbook

Page: 54 / 115

EPD/HB/40521/000
ISSUE 5
EPD TECHNICAL HANDBOOK Page 44
4.2 Electrical Description
4.2.1 Electrical Characteristics
Power Supply: One AA Lithium Thionyl Chloride (LTC) battery 3.6 V), giving
typically 5 months continuous operation at an average dose
rate <5
µ
Sv/h with the alarm sounding <5 hours total during
battery life.
or:
One standard AA Alk aline battery (1.5 V), giving typically 55
days continuous operation at an average dose <5
µ
Sv/h with
the alarm sounding <2 hours total during battery life.
Confidence Test: Activated on start-up and by the button when the
CONFIDENCE TEST mode is called-up (see Section 3.5.7).
Detector Test: Performed during the start-up sequence and as a
background test, and under demand via the IR interface.
Battery Test: Configurable time interval between 1 to 60 minutes.
(15 minutes recommended).
Alarm sounder : 98 dB(A) to 101 dB(A) at 20 cm (loud mode)
75 dB(A) to 85 dB(A) at 20cm (quiet mode)
with multiple modes.
4.2.2 Battery Management
The EPD circuitry is designed to operate at 3.6V DC. The EPD can be powered by
either a 3.6V Lithium Thionyl Chloride (LTC) (Sulphurous Oxychloride, SOCL
2
)
battery or a standard 1.5V AA Alkaline type battery. If a 1.5V Alkaline battery is
installed the EPD automatically switches-in a step-up converter to maintain the 3.6V
operating voltage. The step-up converter is also switched in as the LTC battery runs
down. However, the EPD will not start up if it is fitted with a LTC battery that has been
discharged sufficiently to require the step-up converter to operate.
Operationally, as the voltage from either battery type falls, a series of preset voltage
thresholds operate as follows:
(i) The internal step-up converter is switched in to mainta in the voltage at the
EPD’s operating level.