MODEL 54eA SECTION 15.0
TROUBLESHOOTING
15.5 TROUBLESHOOTING WHEN NO FAULT MESSAGE IS SHOWING - FREE CHLORINE
15.5.1 Zero current is too high
A. Is the sensor properly wired to the controller. See Section 3.3.
B. Is the zero solution chlorine-free? Take a sample of the solution and test it for free chlorine level. The con-
centration should be less than 0.02 ppm.
C. Has adequate time been allowed for the sensor to reach a minimum stable residual current? It may take sev-
eral hours, sometimes as long as overnight, for a new sensor to stabilize.
D. Check the membrane for damage and replace it if necessary.
15.5.2 Zero current is unstable
A. Is the sensor properly wired to the analyzer? See Section 3.3. Verify that all wiring connections are tight.
B. Readings are often erratic when a new or rebuilt sensor is first placed in service. Readings usually stabilize
after about an hour.
C. Is the conductivity of the zero solution greater than 50 μS/cm? DO NOT USE DEIONIZED OR DISTILLED
WATER TO ZERO THE SENSOR. The zero solution should contain at least 0.5 grams of sodium chloride per
liter.
D. Is the space between the membrane and cathode filled with electrolyte solution and is the flow path between
the electrolyte reservoir and membrane clear? Often the flow of electrolyte and be started by simply holding
the sensor with the membrane end pointing down and sharply shaking the sensor a few times as though shak-
ing down a clinical thermometer.
If shaking does not work, try clearing the holes around the cathode stem. Hold the sensor with the membrane
end pointing up. Unscrew the membrane retainer and remove the membrane assembly. Be sure the wood ring
remains with the membrane assembly. Use the end of a straightened paper clip to clear the holes at the base
of the cathode stem. Replace the membrane.
Verify that the sensor is filled with electrolyte solution. Refer to the sensor instruction manual for details.
Problem See Section
Zero current was accepted, but the current is outside the range -10 to 10 nA 15.5.1
Error or warning message appears while zeroing the sensor (zero current is too high) 15.5.1
Zero current is unstable 15.5.2
Sensor can be calibrated, but the current is less than about 250 nA/ppm at 25°C and pH 7 15.5.3
Process readings are erratic 15.5.4
Readings drift 15.5.5
Sensor does not respond to changes in chlorine level 15.5.6
Chlorine reading spikes following rapid change in pH 15.5.7
Chlorine readings are too low 15.5.8
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