Hanna Instruments HI 9146-04 - Manual (Page 8)

14 15
• Make sure that the rubber O-ring is seated
properly inside the membrane cap.
• With the sensor facing down, screw the
membrane cap clockwise. Some electro-
lyte will overflow.
The Platinum cathode sensor (#8 in the Func-
tional Description on page 2) should always be
bright and untarnished. If it is tarnished or
stained, which could be due to contact with
certain gases or extended use with a loose or
damaged membrane, the cathode sensor
should be cleaned. Use a clean, lint-free card-
board or cloth. Rub the cathode very gently
side to side 4-5 times. This will be enough to
polish and remove any stains without damag-
ing the platinum tip. Then, rinse the probe with
deionized or distilled water. Install a new mem-
brane and fill it with fresh electrolyte following
the instructions above. Recalibrate the instru-
ment.
Important: In order to have accurate and
stable measurements, it is important that the
surface of the membrane is in perfect condi-
tion. This permeable membrane isolates the
sensor elements from the environment but
allows oxygen to enter. If any dirt is deposited
on the membrane, rinse it carefully with dis-
tilled or deionized water. If any imperfections
are observed, or any damage is evident (such
as wrinkles, tears or holes), the membrane
should be replaced. Make sure that the O-Ring
is properly seated in the membrane cap.
PROBE & MEMBRANE MAINTENANCE
The oxygen probe body is made of reinforced
polypropylene for maximum durability.
A thermistor sensor measures temperature of
the sample. It is recommended that the protec-
tive cap be always kept on the probe when the
probe is not in use.
To replace the membrane or refill it with
electrolyte, proceed as follows:
• Remove the protective cap by gently twist-
ing and pulling it off the
probe (see fig. 1).
• Unscrew the membrane
by turning it counterclock-
wise (see fig.2)
• Wet the sensor by soak-
ing the bottom 2½ cm
(1") of the probe in elec-
trolyte (HI 7041S) for 5
minutes.
• Rinse a new membrane
(HI 76407A) with elec-
trolyte while shaking it
gently. Refill with clean
electrolyte.
• Gently tap the sides of
the membrane with your
finger tip to ensure that
no air bubbles remain
trapped. Do not directly
tap the bottom as this
may cause irreparable
damage to the mem-
brane.
TWIST
AND
PULL
fig. 1
UNSCREW
fig. 2