11
stabilized. This value should be less than the
previous value noted (more negative).
• Determine the difference between the two mV values.
An acceptable value for this slope is
56 ± 4 mV (20-25°C)
X. X.
X. X.
X.
Corrective actionCorrective action
Corrective actionCorrective action
Corrective action
• Verify module has been screwed into sensor handle or
inner stem.
• Verify Parafilm® seal has been removed from ce-
ramic junction (HI 4113 or HI 5315 reference).
• Verify fill solution has been added to reference cham-
ber.
• Verify electrodes are connected properly to meter and
meter is powered.
• Verify dilute standards are freshly made and stored.
Remake solutions if appropriate. Store in plastic
bottles.
• If the reading is jumpy or unstable, shake sensor
down (see section VII).
• If the sensor slope just misses the suggested slope
window, soaking the sensor in a standard solution
without ISA may solve the problem.
• 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 module should be replaced.
For HI 4013
1. Dry off module and sensor handle.
2. Unscrew sensing module and replace with a new one.
(HI 4013-51).
3. Soak new module in nitrate solution to condition it
before calibration.
For HI 4113
1. Drain the fill solution by depressing cap. Rinse elec-
trode with distilled or deionized water. Drain.
