7
Gain Adjustment (Including Cleaning Procedure)
The gain is set at the factory and will likely not require adjustment during initial startup. However, it doesn’t hurt to inject a
raw water sample (as detailed in step 4 below) and make sure reading is in the “ballpark” of -200 (+/- 20 units). If it is much
higher or lower, then perform below procedure starting with step 1.
1. Disable power to the sensor and stop sample flow.
2. Unscrew by hand the Probe Retaining Nut, remove probe, & allow water to drain.
3. Clean the probe using a squeeze bottle filled with DI or tap water, a cleaning agent
(comet or dish soap), and the provided cleaning brush (located inside the door of the
sensor enclosure). Fill the probe’s bore with water and add a small amount of
cleaning agent. Scrub the bore and top of probe with the brush and then rinse
thoroughly. Next, unscrew the piston (located inside the probe block) and
thoroughly clean and rinse in the same fashion. Final step is to clean up inside the
probe block area using the brush and then rinse thoroughly with the squeeze bottle.
Reinstall sensor parts and then return power back to the sensor.
4. Introduce a sample (at least 100 mL) of raw water with no coagulant into the sensor,
either through the 1” openings on the sides of the probe block or into the sample
injection port located on the front side of the probe block. Reading should be
negative and appear fairly stable 30 seconds after raw water is introduced. If the
reading is drifting negative, allow more time for reading to stabilize. If reading drifts
positive, it is an indication that residual coagulant may still be inside the probe block
or on the probe / piston surfaces. Try cleaning again and be sure to use the cleaning
agent on all surfaces. Once reading appears to have stabilized, add more raw water
until the reading stops going any more negative.
5. Press the Menu button, then navigate to the SCM Overview Screen and press the
Gain button, this will take you to the Automatic Gain Adjust screen. Press the Select
button and the up and down arrow buttons to edit the Target SC True Value. Change
the value to be -200 or whatever value is preferred. Set for a value of -300 if more
sensitivity to chemical feed changes is desired. Set for a value of -100 if less
sensitivity is desired. Make sure to enter a negative value!
6. Press the Select button again after editing the value (text will turn from purple to
blue). Press the Start button, and the gain will take less than one minute to set.
Note: It is a recommended to clean the sensor and check the raw water reading (after
cleaning) at least once per month to ensure the value remains within 15% of the value
used in step 5. Routinely performing the gain adjustment as detailed above will
compensate for probe and piston wear.
Sensor Cleaning Frequency
Typical cleaning frequency might be once per week to once per month and is largely determined by water quality and user
experience. The basic cleaning procedure is outlined in steps 1 to 4 of the above Gain Adjustment procedure.
It is recommended to clean the sensor on a routine basis (at least monthly) and whenever any of the following occur:
Signal Health drops below 95% (Note: Low Signal Health readings can also occur due to worn mechanics)
Reading appears suddenly unstable, or appears to be drifting due to possible fouling (e.g. manganese fouling)
Reading appears unresponsive to changes in coagulant dosage or water quality
