Hach-Lange PHC745 - Manual (Page 11)

6. Select Acceptance Criteria and update the settings:
Option Description
Acceptance Limits Sets the tolerance limits for check standard—0.005 pH (default) to
1.000 pH.
Cal Expires on Failure Recalibration is necessary if check standard fails—Yes or No.
7. If prompted, enter a name for the new method settings. Other changes made to the
settings of an existing method are automatically saved with the same method name.
8. Push EXIT until the meter goes back to the measurement mode.
Maintenance
Clean the probe
Clean the probe when there is contamination on the sensor. Symptoms of contamination
are:
• Readings are not accurate or consistent.
• The stabilization time is slow.
• A calibration error occurs.
• Contamination is visible on the probe (e.g., dirt).
1. Rinse the probe with deionized water. Blot dry with a no-lint cloth.
2. Soak the glass bulb of the probe in the applicable cleaning agent. Refer to
Table 4 .
Note: Remove KCl salt build-up from the probe with warm deionized water.
3. Rinse or soak the probe for 1 minute in deionized water.
4. Soak the probe in pH 4 buffer for 20 minutes.
5. Rinse the probe with deionized water.
6. Blot dry with a no-lint cloth.
Table 4 Cleaning agent
Contaminant Cleaning agent Soak time
General contaminants Electrode cleaning solution 12–16 hours
Mineral deposits 0.1 N HCl solution 10–15 minutes
Fats, grease and oils Warm, mild detergent solution 2 hours (maximum)
Protein deposits Pepsin cleaning solution 3 hours (maximum)
Inorganic buildup EDTA solution 3 hours (maximum)
Clean the sleeve junction
Clean the sleeve junction when particles prevent from open or close the sleeve junction
correctly.
1. Make sure that the fill hole is closed and invert the probe. This prevents electrolyte
flow from the probe.
2. Slowly move the sleeve junction away from the glass bulb to open it.
Note: If the sleeve will not open, soak the electrode in warm water until the salt crystals
dissolve.
3. Rinse the area under the sleeve junction with deionized water to remove all particles
or salt crystallization.
4. Slowly move the sleeve junction to the glass bulb to close it.
5. Dry with a no-lint cloth.
11