Summary #

To ensure long-term measurement accuracy and reliability, the KH Director and its components require regular basic maintenance. This guide covers proper pH sensor care, calibration intervals, and routine hardware maintenance for the measurement cell, tubing, and connected dosing pumps.

Applies to #

• KH Director

Sensor & Measurement Cell Maintenance #

The pH sensor is a precision instrument with a delicate sensor tip. Proper handling and periodic cleaning of both the sensor and the measurement cell are essential for accurate titration.

• No Mechanical Cleaning: Never wipe, scrub, or brush the sensor tip. Mechanical contact can permanently damage the sensor.
• Combined Cleaning Process: Over time, calcium deposits can build up on the sensor and inside the measurement cell. Since the internal fill level is not visible from the outside, use the built-in software functions for a safe cleaning process:
  1. Prepare a mild cleaning solution (e.g., a 10% citric acid solution or a 50/50 mix of water and citric acid).
  2. Connect the Sample water tube to the container with the cleaning solution.
  3. Run the “Flush measurement cell” function in the software. Repeat this process 2–3 times to ensure the cell is thoroughly rinsed with the cleaning solution.
  4. To achieve a deep clean, let the solution sit inside the cell for 15–20 minutes after the last flush to dissolve stubborn deposits.
  5. After the soaking period, reconnect the sample tube to your aquarium water and run the “Flush measurement cell” function again to rinse out the acid.

pH Sensor Calibration & Replacement #

The KH Director calculates the KH value by precisely detecting the pH drop during titration. A well-calibrated sensor is essential.

• Calibration Interval: Perform a 2-point calibration using fresh pH 4 and pH 7 buffer solutions approximately every 2 to 4 weeks, or whenever you notice unexplained measurement drifts. Always wipe the sensor dry before moving it between fluids to prevent cross-contamination.
• When to Replace: The sensor must be replaced if a calibration fails, if it responds very slowly to pH changes, or if the difference (delta) between the ADC values for pH 4 and pH 7 in the software drops significantly.

Sensor & KH Director Storage #

If the KH Director is taken offline, the pH sensor must be protected from drying out.

• Keep it Hydrated: A pH sensor must never dry out. If removed from the device, store it in its original protective cap. Use the original storage fluid that came with the sensor or a KCl storage solution.
• Device Shutdown: If the device will be inactive for a long time, run the “Empty measurement cell completely” function and flush the internal lines with RO water to prevent salt crystals from forming.

Hardware Maintenance #

Sample Water Inline Filter #

The inline filter protects the internal components and the pH sensor from detritus and suspended particles.

• Inspection: Check the filter regularly for visible dirt, discoloration, or a restricted flow rate. The replacement frequency depends entirely on your aquarium’s bioload and suspended particles.
• Placement: To extend the life of the filter and prevent it from clogging too quickly, ensure the sample water intake tube is placed in a clean, calm area of your sump, away from detritus accumulation or macroalgae.

Tubing and Seals #

Airtightness is the most critical factor for the KH Director’s accuracy.

• Inspection: Periodically check all Flex-PVC line (Reagent) for kinks or visible air pockets. Ensure all connections are seated firmly.
• Sensor Seal: Whenever the sensor is removed, inspect the rubber seal for cracks or hardening. A damaged seal allows air into the cell, leading to failed titrations.
• Vent Line:
  The clear vent tube on top of the KH Director must remain unobstructed and its end never submerged in water.
  • Water in Vent Line: If you notice water inside the vent tube, it indicates that the measurement cell has overfilled or failed to drain correctly. Immediately verify the calibration of your Sample and Waste pumps. After checking the pumps, run the “Empty measurement cell completely” function to ensure the cell is clear.

Dosing Pump Maintenance #

The KH Director relies on the mechanical precision of the connected GHL Doser to deliver consistent fluid volumes.

• Inspection and Cleaning: Regularly check the dosing pump heads for signs of wear or plastic abrasion (dust) inside the housing. Dirty or worn-out rollers can cause inconsistent rotation.
• Maintenance Schedule: Clean the pump rollers and the internal housing if you notice any debris. If a pump head shows significant mechanical play or fails to rotate smoothly, it should be replaced.
• Internal Tubing: Check the internal bridge tubes of the pumps for flattening or leaks and replace them if necessary to maintain dosing precision.