Emerson Clarity II Instruction Manual page 60

MODEL CLARITY II
8.2.2 Sensor Fail
Sensor Fail means the photodiode measuring the scattered light from the sample has probably failed. The ana-
lyzer calculates turbidity from the difference between the scattered light signal and the dark current. Dark current
is the signal generated by the photodiode when no light is falling on it. If the difference between the scattered light
signal and the dark current is equivalent to less than 0.005 NTU, the analyzer displays the Sensor Fail fault. The
0.005 NTU limit was selected because the intrinsic turbidity of perfectly filtered water is 0.010 - 0.015 NTU.
A. Are the lamp and detector windows clean? A dirty lamp or detector window can reduce the intensity of light
reaching the sample photodiode leading to low results. Clean the sensor (see Section 7.2.1) and check the
turbidity.
B. Repeat sensor calibration. See Sections 6.2, 6.3, or 6.4.
C. If after cleaning and recalibrating, the Sensor Fail fault persists, replace the sensor.
8.2.3 EEPROM Failure
EEPROM failure means the analyzer is unable to store data in the non-volatile memory. Thus, if power is lost then
restored, all configurations and calibrations will be lost. Call the factory for assistance. The analyzer will probably
need to be replaced.
8.2.4 Factory Failure
Factory failure means the factory calibrations have been corrupted. Call the factory for assistance. The analyzer
will probably need to be replaced.
8.2.5 Need Cal
The Clarity II sensor contains two photodiodes. One measures the intensity of the light scattered by the sample.
The other measures the intensity of the lamp. Because turbidity is proportional to the intensity of light falling on the
sample photodiode, any reduction of the lamp intensity will be measured as a decrease in turbidity even though
the true turbidity remained constant. The analyzer uses the lamp intensity measurement to correct for changes in
apparent turbidity caused by reduction of lamp intensity. However, if the lamp intensity gets too low, the correction
may not be valid. At this point the analyzer displays the Need Cal warning. Calibrating will cause the analyzer to
increase the current supplied to the lamp, thus increasing the lamp intensity.
A. Calibrate the sensor using slope (Section 6.2), standard (Section 6.3), or lamp calibration (Section 6.5). Using
slope or standard calibration is strongly recommended. Use lamp calibration ONLY if a turbidity standard is not
available.
B. If a replacement lamp board is not available, order one as soon as possible.
8.2.6 Weak Lamp
The Weak Lamp warning appears when lamp intensity is low and the current being supplied to the lamp (see
Section 8.2.5) has been increased above a level likely to significantly reduce lamp life.
Replace the lamp board as soon as possible. After you replace the lamp, recalibrate the sensor using either slope
or standard calibration. See Section 6.2 or 6.3. Recalibration is necessary to reset the lamp power supply. Grab
calibration will not resent the power supply. Failure to recalibrate using slope or standard calibration may signifi-
cantly reduce lamp life.
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SECTION 8.0
TROUBLESHOOTING