Fault Finding Guides · Free PDF
pH and Conductivity Analyser Fault Finding Guide
A one page guide to pH and conductivity analyser problems: electrode condition, reference faults, coating, grounding and temperature compensation.
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A one page A4 guide to print for the workshop or keep on your phone in the field. The full content is also shown below.
Download PDF A4 · 52 KBBefore you start
- Permit, isolation and control room informed.
- Put the loop in manual or inhibit trips as authorised.
- Use certified test equipment in hazardous areas.
- Record as found readings before changing anything.
Quick checks
- Slope and offset from last calibration?
- Sensor clean and wet?
- Temperature reading correct?
- Analyser and lab agree?
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Symptoms, causes and fixes
| Symptom | Likely causes | Checks and fixes |
|---|---|---|
| Low slope | Aged or coated glass, old buffers | Clean; fresh buffers; replace if below limit |
| Large offset | Reference poisoned or junction blocked | Clean junction; replace sensor |
| Slow response | Coating, dry glass, cold sample | Clean and rehydrate; check temperature |
| Drifting | Reference problem, ground loop, flow effects | Check solution ground; isolate; stable flow |
| Conductivity reads low | Coating, air in cell, wrong cell constant | Clean; remove air; calibrate |
| Temperature wrong | Faulty temperature sensor or wiring | Compare with thermometer; fix wiring |
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Limits often used
- pH slope about 90 to 105 % of Nernst.
- pH offset within about ± 30 mV.
- Conductivity standard within ± 2 % after calibration.
Related Tools, Procedures and Calculators
Frequently Asked Questions
Why is my pH slope low?
The glass is ageing or coated; clean, use fresh buffers, and replace if it stays low.
What causes pH drift?
Reference junction problems or ground loops.
Why calibrate with fresh buffers?
Old or contaminated buffers give wrong calibration values.
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