Walchem WDS100, Instruction Manual

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18
Calibration Failure
For WebMaster
The controller will display a calibration failure if the offset calculated in the
Zero Calibration is outside of the range –20 to 40 mV or the slope
(mV/ppm) calculated in the One Point Process Calibration is outside of the
range of the nominal mV per 0.1 to 2.0 ppm.
For WDIS:
The acceptable range for the slope (mV/ppm) is the nominal mV per 0.5 to
2.0 ppm. The range of mV for a Zero Calibration is –100 mV to 100 mV.
For W100 or W600 or 900:
The acceptable range for the slope (mV/ppm) is the nominal mV per 0.2 to
10.0 ppm. The range of mV for a Zero Calibration is –100 mV to 100 mV.
To calculate the nominal slope for your sensor, divide the high end of the
nominal range by -2000. For example, for a 0-20 ppm sensor, the nominal
slope is -2000/20 = -100 mV/ppm.
Possible Causes Corrective Actions
Insufficient conditioning Wait for between 1 hour and 48 hours before
attempting a calibration.
Insufficient sample flow Increase flow rate to between 20 and 100 liters
per hour
Air bubbles in sample Dislodge bubbles
Adjust flow rate higher if necessary
Allow sample to outgas
Loose electrolyte housing Tighten electrolyte housing
Protection cap not removed Remove protection cap
Dirty electrodes Clean electrodes with Emory paper
Replace balls in cleaning attachment
No electrolyte fill solution in
electrolyte housing
Fill electrolyte housing with electrolyte
Air bubbles in electrolyte Empty electrolyte housing and refill it
Faulty sensor Replace sensor
Faulty analysis equipment or
reagents
Consult test equipment instructions
Sample contaminated with
interfering molecule (refer to
Sensitivity specification in
section 6.0)
Remove source of contamination
Faulty wiring Check wiring
Faulty controller sensor input WebMaster, WDIS4
Go to the Sensor Input menu and perform a
self-test. If this passes, then the problem is with
the sensor or its wiring. If it fails, then
disconnect the sensor from the circuit board and
try the self-test again. If it still fails, replace the
circuit board.