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MODEL 54eA SECTION 15.0
TROUBLESHOOTING
15.7 TROUBLESHOOTING WHEN NO ERROR MESSAGE IS SHOWING —
MONOCHLORAMINE
15.7.1 Zero current is too high
A. Is the sensor properly wired to the analyzer? See Section 3.3.
B. Is the zero solution monochloramine-free? Take a sample of the solution and test it for monochloramine level.
The concentration 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. Be careful not to touch the membrane or cath-
ode. Touching the cathode mesh may damage it.
15.7.2 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 uS/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 mesh filled with electrolyte solution? Often the flow of elec-
trolyte and be started by simply holding the sensor with the membrane end pointing down and sharply shak-
ing the sensor a few times as though shaking down a clinical thermometer.
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 50 nA 15.7.1
Error or warning message appears while zeroing the sensor (zero current is too high) 15.7.1
Zero current is unstable 15.7.2
Sensor can be calibrated, but the current is less than about 350 nA/ppm at 25°C 15.7.3
Process readings are erratic 15.7.4
Readings drift 15.7.5
Sensor does not respond to changes in monochloramine level 15.7.6
Readings are too low 15.7.7
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