
SECTION
14. INSTALLATION
AND
MAINTENANCE
14.2
POWER
REQUIREMENTS
The 21X
operates
at a nominal12V
DC. Below
9.6 or above 16 volts
the 21X
does not operate
properly.
The
21X is diode
protected
against
accidental
reversal
of the
positive
and
ground
leads
f rom'
the
battery. Input voltages
in excess
of 18V
may
damage the 21X
and/or
power
supply. A
transzorb
provides
transient
protection
by
limiting voltage
at
approximately 20V.
System operating time for
the batteries can be
determined
by dividing the battery
capacity
(amp-hours)
by the average system
current
drain. The 21X draws 1.0 mA in
the
quiescent
state, 25 mA while
processing,
and 60 mA
during an analog measurement;the
length of
operating
time
for
each datalogger instruction is
listed
in Section 3. Typicalcurrent
for
common
21X
peripherals
are
given
in Table
14.2-1
:
14-2
FIGURE
14.3-1. 21X Battery
Pack and Panel
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