Summary #
pH, Redox, Conductance, and Oxygen sensors require regular calibration to stay accurate, and some sensor types offer additional maintenance actions for troubleshooting or fine-tuning readings. This article covers the calibration process for each sensor type and the available maintenance actions, including Oxygen sensor electrode care.
Applies to #
- ProfiLux 4 Series (incl. Industrial Line / IL)
- ProfiLux 3 Series
- ProfiLux Mini Series
- Software:
- GHL Connect (App, Webinterface, myGHL)
- GHL Control Center
Calibration #
For general sensor settings such as regulation, alarms, and virtual sensors, see Sensors – Configuration Guide. For Flow sensor calibration, see Flow Sensors – Setup Guide.
Calibrating pH, Redox & Conductance Sensors #
- Available via the Calibrate Electrode button. Follow the on-screen wizard, which guides you through each calibration point with the required calibration liquids.
- At the start of calibration, select a Calibration Tolerance (2–5). Use the smallest value (2) whenever possible for the highest accuracy — for older, aging sensors that no longer stabilize enough to complete calibration, a higher tolerance (4–5) is recommended.
- Redox: The wizard additionally requires the supplied Null-plug for the first calibration point, before switching to the sensor itself for the second point.
- Conductance (Freshwater / Seawater / Brackish): The wizard also asks whether temperature compensation should use a fixed manual temperature or a live Temperature sensor reading (recommended for the most accurate results).
Calibrating the Oxygen Sensor #
- The Oxygen sensor must be calibrated directly at the ProfiLux display — it cannot be calibrated via software.
- Start the calibration from the sensor’s menu on the display: Sensor settings -> Oxygen X (X being the sensor’s index) -> Calibration. Follow the on-screen instructions.
- Calibration consists of two separate steps, a Null-calibration and an Air-calibration, which must be performed at least 30 minutes apart.
Maintenance #
Some actions below are only visible in Expert view.
Adjust Temperature #
(Physical Temperature sensors only; not available on ProfiLux Mini)
- Fine-tunes a reading that deviates from a known reference temperature.
Fix Dig. Temperature Sensor Issue #
(Not available on ProfiLux Mini)
- Resets the sensor’s calibration values — useful if they were accidentally changed and are now causing implausible readings.
Oxygen Sensor Electrode Maintenance #
- Becomes necessary once the sensor can no longer be calibrated, the membrane is damaged, or the response time has increased significantly.
- Covers cleaning the membrane, replacing the electrolyte solution and membrane head, and regenerating the anode and cathode.
- For the full step-by-step procedure, see the Oxygen Sensor Maintenance guide in the Downloads section below.
Notes #
- As a general recommendation, pH, Redox, Conductance, and Oxygen sensors should be recalibrated every 2–4 weeks due to natural sensor aging, and sooner if a reading no longer looks plausible.
Common Issues #
Cause
The sensor’s reading doesn’t stabilize within the allowed time, which is common with aging or worn sensors.
Solution
Try fresh calibration liquid first, since old or contaminated liquid can cause the same symptom. If the issue persists, increase the Calibration Tolerance (up to 4–5 for older sensors) and retry. If calibration still fails, the sensor has likely reached the end of its service life and should be replaced.
Cause
If ADC 1 and ADC 2 end up nearly or exactly the same after calibrating, the sensor isn’t producing a meaningful signal difference between the two calibration points.
Solution
Repeat the calibration with fresh calibration liquid. If the values remain nearly identical afterward, the sensor is likely defective — replace it, or contact GHL support with the recorded values.
Cause
The sensor’s stored calibration values were accidentally changed.
Solution
Use Fix Dig. Temperature Sensor Issue to reset the calibration values.
Cause
The membrane, electrolyte, or electrodes have degraded over time.
Solution
Perform the Oxygen Sensor Electrode Maintenance procedure described above.