Emerson Rosemount5081, Инструкция по эксплуатации, Страница: 116 / 152

Chlorine readings too low
1. Was the sample tested as soon as it was taken? Chlorine solutions are unstable. Test
the sample immediately after collecting it. Avoid exposing the sample to sunlight.
2. Low readings can be caused by zeroing the sensor before the residual current has
reached a stable minimum value. Residual current is the current the sensor
generates even when no chlorine is in the sample. Because the residual current is
subtracted from subsequent measured currents, zeroing before the current is a
minimum can lead to low results. See
Oxygen readings too low for more information.
3. Sensor response depends on flow. If the flow is too low, readings will be low and flow
sensitive. Verify that the flow past the sensor equals or exceeds the minimum value.
See the sensor instruction manual for recommended flows.Verify that the chlorine
sensor is installed in the correct flow cell. See Figure and Figure. Verify that the liquid
level in the constant head sampler is level with the central overflow tube and that
excess sample is flowing down the tube. If necessary, disassemble and clean the
overflow sampler. See
Section .
8.4.6 Total chlorine measurement and calibration problems
Refer to the instruction manual for the SCS921 for a complete troubleshooting guide.
8.4.7 Ozone measurement and calibration problems
Problem See Section
Zero current is substantially outside the
range -10 to 10 nA. Ozone zero current outside range
Zero reading is unstable. Ozone zero reading unstable
Sensor current during calibration is sub-
stantially less than about 350 nA/ppm at
25 °C (77 °F). Sensor current less than 350 nA/ppm
Process readings are erratic. Ozone process readings erratic
Readings drift. Ozone readings drift
Sensor does not respond to changes in
ozone level. Sensor not responding to ozone changes
Ozone readings are too low. Ozone readings too low
Ozone zero current outside range
The ozone zero current is substantially outside the range -10 to 10 nA.
1. Is the sensor properly wired to the transmitter?
2. Is the zero solution ozone free? Test the zero solution for ozone level. The
concentration should be less than 0.02 ppm.
Diagnostics and troubleshooting
106 Rosemount 5081