Hanna Instruments HI 4010 - Manual (Page 11)

11
stabilized. This value should be less than the previ-
ous noted (more negative).
•
Determine the difference between the two-mV values.
An acceptable value for this slope is -56 ± 4 mV.
X. X. X. X. X. Corrective action Corrective action Corrective action Corrective action Corrective action
•
Verify protective cap has been removed (HI 4010).
•
Verify plastic film has been removed from inner stem
(HI 4110 or HI 5315 electrode).
•
Verify electrodes are connected properly to meter and
meter is powered. For HI 4110 verify sensor is screwed
into the inner stem.
•
Verify dilute standards are freshly made and stored.
Remake solutions if appropriate.
•
If the sensor slope just misses the suggested slope
window, soaking the sensor in a standard may solve
the problem. (Choose 10
-2 M fluoride or 1000 ppm
standard).
•
A scratched sensing surface can be polished with fluo-
ride toothpaste (without baking soda). Use a small
drop of the paste and a soft wipe. Using a circular
motion, and gentle pressure, rub the surface of the
electrode with this micro abrasive material. Rinse
with water. Check to see if small scratches have been
eliminated. Rinse in deionized water and blot dry.
Soak in a fluoride standard for 1 hour. Repeat section
IX.
•
If the reading is jumpy or unstable, shake sensor
down (see section VIII).
•
If the membrane is damaged, the response becomes
extremely sluggish, or the slope of the electrode has
decreased significantly, and procedures above have
not helped, the sensor (or module) should be re-
placed.