NOTE: The controller must be recalibrated after cleaning the probe.
Frequency
The probe should be cleaned periodically. The frequency required will vary by installation. In a new installation, it is recommended that the probe be cleaned after two weeks of service. To determine how often the probe must be cleaned, follow the procedure below.
1. Read and record the conductivity.
2. Remove, clean and replace the conductivity probe.
3. Read conductivity and compare with the reading in step 1 above.
If the variance in readings is greater than 5%, increase the frequency of probe cleaning. If there is less than 5% change in the reading, the probe was not dirty and can be cleaned less often.
Cleaning procedure
The probe can normally be cleaned using a cloth or paper towel and a mild detergent. If coated with scale, clean with a dilute (5%) hydrochloric acid solution. Occasionally a probe may become coated with various substances which require a more vigorous cleaning procedure. Usually the coating will be visible, but not always. To clean a coated probe, use a fine grit abrasive, such as emery paper. Lay the paper on a flat surface and move the probe in a back and forth motion. The probe should be cleaned parallel to the carbon electrodes, not perpendicular.
Procedure for evaluation of conductivity probe
Can be used for troubleshooting low conductivity, high conductivity, conductivity stuck at 0, and/or conductivity stuck at a number other than 0. Try cleaning the probe first. To find out if the probe or the Walchem controller is faulty, step through the self-test menu. The display should read 1000 ±20. This indicates that the controller is OK and the problem is in the probe, or its connections. If the conductivity reading is not 1000 ±20, return the control module for repair. To check the probe, check the probe connections to the terminal strip (refer to manual). Make sure that the correct colours go to the correct terminals, and that the connections are tight. Restore power and see if the conductivity is back to normal. If not, replace the probe.