MODEL 54eA | SECTION 16.0 |
| TROUBLESHOOTING |
16.8 TROUBLESHOOTING WHEN NO FAULT MESSAGE IS SHOWING - OZONE
| Problem | See Section | |
| Zero current was accepted, but the current is outside the range | 16.8.1 |
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| Error or warning message appears while zeroing the sensor (zero current is too high) | 16.8.1 |
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| Zero current is unstable | 16.8.2 |
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| Sensor can be calibrated, but the current is less than about 350 nA/ppm at 25°C | 16.8.3 |
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| Process readings are erratic | 16.8.4 |
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| Readings drift | 16.8.5 |
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| Sensor does not respond to changes in ozone level | 16.8.6 |
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| Ozone readings are too low | 16.8.7 |
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16.8.1 Zero current is too high
A.Is the sensor properly wired to the controller. See Section 3.3.
B.Is the zero solution ozone free? Test the zero solution for ozone 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.
16.8.2 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 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.
16.8.3 Sensor can be calibrated, but the current is too low
A.Sensor current is a strong function of temperature. The sensor current decreases about 3% for every °C drop in temperature.
B.Sensor current depends on the rate of sample flow past the sensor tip. If the flow is too low, ozone readings will be low. Refer to the sensor instruction sheet for recommended sample flows.
C.Low current can be caused by lack of electrolyte flow to the cathode and membrane. See step C in Section 16.8.2.
D.Is the membrane fouled or coated? A dirty membrane inhibits diffusion of ozone through the membrane, reduc- ing the sensor current and increasing the response time. Clean the membrane by rinsing it with a stream of water from a wash bottle or gently wipe the membrane with a soft tissue.
If cleaning the membrane does not improve the sensor response, replace the membrane and electrolyte solu- tion. If necessary, polish the cathode. See the sensor instruction sheet for details.
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