User Guide

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PROBE AND MEMBRANE MAINTENANCE
The oxygen probe body is made of reinforced
plastic for maximum durability.
A thermistor temperature sensor provides tem-
perature measurements of the sample tested.
It is always recommended that the protective
cap be kept on the probe when the probe is
not in use to provide protection against dam-
age and dirt.
To replace the membrane or refill with
electrolyte, proceed as follows:
• Remove the protective
cap by gently twisting
and pulling it off the
body of the probe (see
fig. 1).
• Unscrew the membrane
cap by turning it coun-
terclockwise (see fig.2).
• Wet the sensor by
soaking the bottom 2½
cm (1") of the probe in
electrolyte (HI 7041S)
for 5 minutes.
• Rinse the new mem-
brane cap (HI 76407A)
supplied with the meter
with electrolyte solution
while shaking it gen-
tly. Refill with clean
electrolyte solution.
• Gently tap the sides of
the membrane cap with
your finger tip to en-
sure that no air bubbles
remain trapped. Do no
directly tap the bottom
with your finger as this
TWIST
AND
PULL
fig. 1
UNSCREW
fig. 2
Untitled-22
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will damage the membrane.
• Make sure that the rubber O-ring sits
properly inside the membrane cap.
• With the sensor facing down, slowly
screw the membrane cap clockwise.
Some electrolyte will overflow.
The Platinum cathode (#8 in the Functional
Description at page 3) 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. You can use a clean
lint-free cardboard or cloth. Rub the cath-
ode 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 deion-
ized or distilled water and install a new
membrane cap using fresh electrolyte and
follow the steps above. Re-calibrate 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 semipermeable membrane
isolates the sensor elements from the envi-
ronment but allows oxygen to enter. If any
dirt is observed on the membrane, rinse
carefully with distilled or deionized water. If
any imperfections still exist, or any dam-
age is evident (such as wrinkles or tears-
holes), the membrane should be replaced.
Make sure that the O-Ring sits properly in
the membrane cap.