Hanna Instruments HI 9142 User Manual

Page 16

The Platinum cathode (#8 in the Functional Description at page 4)
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
should be cleaned. Use a lint-free cardboard or cloth and rub the
cathode very gently side to side 4-5 times. This will be enough
to polish and remove any stains without damaging the platinum
tip. Afterwards, rinse the probe with deionized or distilled water
and install a new membrane cap using fresh electrolyte. Recalibrate
the instrument.

Important: In order to have accurate and stable measurements,
it is important that the surface of the membrane is in perfect
condition. This semi-permeable membrane isolates the sensor
elements from the environment but allows oxygen to enter. If any
dirt is observed on the membrane, rinse carefully with distilled or
deionized water. If any imperfection still exists, or any damage is
evident (such as wrinkles or tears), the membrane should be
replaced. Make sure that the O-Ring is properly seated in the
membrane cap.

PROBE AND MEMBRANE MAINTENANCE

The oxygen probe body is made of reinforced plastic for maximum
durability.
A thermistor temperature sensor provides temperature measurement
and compensation. When not in use, it is always recommended to
protect the probe against damage and dirt using the supplied cap.

To replace the membrane or refill with electrolyte, proceed as
follows:

• Remove the protective cap by gently

twisting and pulling it off (see fig. 1).

• Unscrew the membrane by turning

it counterclockwise (see fig. 2).

• Wet the sensor by soaking the

bottom (2.5 cm) of the probe in
HI 7041S electrolyte solution for
5 minutes.

• Rinse the new membrane (

HI 76407A supplied with the

meter) with some electrolyte while shaking it gently. Refill
with clean electrolyte.

• Gently tap the sides of the membrane

with your finger to ensure that no air
bubbles remain trapped inside. Do
no directly tap the bottom as this
will damage the membrane.

• 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
electrolyte will overflow.

TWIST

AND

PULL

fig. 1

UNSCREW

fig. 2