How to Calibrate an Online pH Analyzer and Troubleshoot Common Issues
Author: Zhejiang Weilan Technology Co., Ltd.Source: Official sitePublished: Category: Technical Articles
Summary: Why regular calibration matters for online pH meters, the standard two-point calibration procedure, and fixes for drifting or slow readings.
Electrodes age and drift over time. Regular calibration is essential for accurate online pH measurement.
Calibration Frequency
- Normal water treatment duty: every 2–4 weeks
- Hot or heavily fouling media: weekly or shorter
- Always calibrate a new electrode before use
Two-Point Calibration Procedure
- Rinse the electrode with deionized water and blot dry (do not wipe).
- Immerse in pH 6.86 buffer, wait for a stable reading, confirm point 1.
- Rinse, then immerse in pH 4.00 (acidic range) or pH 9.18 (alkaline range) buffer, confirm point 2.
- Record the slope. A slope below 90% indicates electrode aging — replace it.
Troubleshooting
| Symptom | Likely cause | Fix | |---------|-------------|-----| | Continuous drift | Fouled electrode, reference leak | Clean or replace | | Slow response | Aged glass membrane | Activate with dilute HCl or replace | | Frozen reading | Open circuit, broken cable | Check wiring | | Wrong temperature | Faulty compensation probe | Replace probe |
Maintenance Tips
Check weekly for oil or scale on the electrode. For long-term storage, keep it in 3 mol/L KCl solution — never dry.
See our online pH analyzer for replacement instruments.