Eberline RO-2 - Maintenance and Troubleshooting; Preventive Maintenance; Calibration; Disassembly and Reassembly

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MODEL КО-2
. SECTION IV
MAINTENANCE
A.
PREVENTIVE
MAINTENANCE
1, Replace the bátteries when, during battery check,
the
meter
indicates
at
or
below
the
left
end
of
the
BATT
OK line on the meter face. The batteries are accessible
when
the
cover
assembly
is
separated
from
the
case
and
the
desiccant
box
is
unstrapped.
The
batteries
may
be
changed
separately
or
in
pairs.
BAT
1
checks
the
right
hand
battery
and
BAT
2
checks
the
left
hand
battery
(viewed
from
the
top).
Center
battery
BT3
powers
the
ion
chamber
current
only
and,
therefore,
lasts
for
an
in-
definite
amount
of
time
(shelf
life).
It
is
not
checked
by
the
internal
battery
checking
circuits.
It
is
a
good
prac-
tice,
whenever
a
new
battery
is
required
for
BT1
or
BT2,
to move the center battery to that position and install
the new battery in the center position. In this way, the
full power available from fresh batteries is utilized (no
shelf life decay) and a fresh battery always powers the
chamber. Turn the RO-2 off before changing batteries.
2.. Remove the batteries if the instrument is to be
inactive for a long period.
3. Dry or replace the desiccant crystals when they first
begin to turn clear or pink in color. To remove the desic-
cant box, separate the cover assembly and case and open
the nylon retaining straps that hold the box. Remove the
tape from around the box lid. When new or dried crys-
tals are in place in the box, retape the lid to the box and
reinstall. Do not seal the box completely with tape.
Leave a small space so that air can enter and leave the
box. The desiccant crystals can be repeatedly dried by
heating to 250 °F for twelve hours ог to 400 °F for one
hour. Do not heat the plastic box. The desiccant life will
be prolonged if the box is placed in a small plastic bag
with a rubber band closing the bag around the plastic
hose.
NOTE
It is very important that the inside of the
chamber assembly be kept dry to avoid
leakage currents due to moisture. If the
desiccant becomes saturated and the unit
becomes erratic due to moisture, renew the
desiccant crystals and cycle the instrument
between room temperature (or lower) and
+140 °F three or four times to flush the
chamber air across the desiccant.
CHANGE 4
B. CALIBRATION
For maximum accuracy, the RO-2 should be calibrated
at approximately the same temperature and air pressure
as is expected for its use. If the conditions for calibra-
tion and for use are necessarily different, an offset may
be used during calibration so that the instrument will
read properly when put in use. Tables 2-1 and 2-2,
Section 11, may be used to select the proper offset in this
case,
To calibrate, remove the calibration control locks and
position the RO-2 so that the ion chamber is in a gamma
field of known intensity. The effective center of the
chamber is marked by case indentations. Adjust the
calibration control (corresponding to the range switch .
position) for the proper meter indication. For best ac- .
curacy, choose a calibration field strength that will
cause the meter to read around the four mark when
calibrated. Repeat the procedure for all four ranges.
To avoid errors, the entire ion chamber of the RO-2
must be in the у field when calibrating. The effective
center of the chamber is marked by indentations at the
front and sides of the case.
WARNING
The у field intensities required for the com-
plete calibration of the RO-2 are potentially
hazardous to personnel. Observe proper
precautions to prevent injury.
C. DISASSEMBLY
1. The cover assembly and the case may be separated
by unfastening the front and rear latches and lifting the
instrument from the case.
NOTE
The chamber face is very thin and easily.
damaged. If the case is to be off for an ex-
tended period, protect the face with card-
board or other covering.