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..
Sensor current too low
The sensor current during calibration is substantially less than 250 nA/ppm at 25 °C (77 °F).
1.
Is the temperature low, or is the pH high? Sensor current is a strong function of pH
and temperature. The sensor current decreases about 3% for every °C drop in
temperature. Sensor current also decreases as pH increases. Above pH 7, a 0.1 unit
increase in pH lowers the current about 5%.
2.
Sensor current depends on the rate of sample flow past the sensor tip. If the flow is
too low, chlorine readings will be low. Refer to the sensor instruction sheet for
recommended sample flows.
3.
Low current can be caused by lack of electrolyte flow to the cathode and membrane.
See step 4 in
Chlorine zero reading unstable
4.
Is the membrane fouled or coated? A dirty membrane inhibits diffusion of free
chlorine through the membrane, reducing the sensor current and increasing the
response time. Clean the membrane by rinsing it with a stream of water from a wash
bottle.
Do not
use a tissue to wipe the membrane.
5.
If cleaning the membane does not improve the sensor response, replace the
membrane and electrolyte solution. If necessary, polish the cathode. See the sensor
instruction sheet for details.
Chlorine process readings erratic
1.
Readings are often erratic when a new sensor or a rebuilt sensor is first placed in
service. The current usually stabilizes after a few hours.
2.
Is the sample flow within the recommended range? High sample flow may cause
erratic readings. Refer to the sensor instruction sheet for recommended flow rates.
3.
Are the holes between the membrane and the electrolyte reservoir open? Refer to
Chlorine zero reading unstable
.
4.
Verify that wiring is correct. Pay particular attention to shield and ground
connections.
5.
If automatic pH correction is being used, check the pH reading. If the pH reading is
noisy, the chlorine reading will also be noisy. If the pH sensor is the cause of the
noise, use manual pH correction until the problem with the pH sensor can be
corrected.
6.
Is the membrane in good condition, and is the sensor filled with electrolyte solution?
Replace the fill solution and electrolyte. Refer to the sensor instruction manual for
details.
Diagnostics and troubleshooting
104
Rosemount 5081
Summary of Contents for Rosemount5081
Page 4: ......
Page 10: ...Contents vi Rosemount 5081 ...
Page 12: ...Startup procedure 2 Rosemount 5081 ...
Page 23: ...Mounting 5081 on a pipe Figure 3 2 Installation Instruction Manual 13 ...
Page 24: ...Installation 14 Rosemount 5081 ...
Page 28: ...Wiring 18 Rosemount 5081 ...
Page 50: ...Programming basics 40 Rosemount 5081 ...
Page 130: ...Diagnostics and troubleshooting 120 Rosemount 5081 ...
Page 136: ...Digital communications 126 Rosemount 5081 ...
Page 140: ...Engineering drawings 130 Rosemount 5081 ...
Page 141: ...Engineering drawings Instruction Manual 131 ...
Page 142: ...Engineering drawings 132 Rosemount 5081 ...
Page 143: ...Engineering drawings Instruction Manual 133 ...
Page 144: ...Engineering drawings 134 Rosemount 5081 ...
Page 145: ...Engineering drawings Instruction Manual 135 ...
Page 146: ...Engineering drawings 136 Rosemount 5081 ...
Page 151: ...EU Declarations of Conformity 138 Rosemount 5081 ...