Brief Guide to Troubleshooting Common

Measurement Problems with Simple Causes

READINGS ARE NOT REPRODUCIBLE

·         Is there sample carryover?

·         Are there sample interferences or complexing agents present?

·         Is the reference electrode junction contaminated?

SLOW RESPONSE (READINGS SLOWLY CHANGING)

·         Was the electrode stored in the wrong solution?

·         Was the electrode poisoned by the sample?

OUT OF RANGE READING

·         Is the electrode plugged into the controller properly?

·         Is there a reference electrode present?

·         Is there enough fill solution left in the reference electrode?

·         Is the electrode placed in the sample solution?

LOW SLOPE OR NO SLOPE

·         Are the standards too old, contaminated, or made wrong?

·         Has the sample pH been adjusted properly to the operating range of the electrode?

·         Is there an air bubble on electrode surface?

·         Is the controller okay?

·         Is there enough fill solution left in the reference electrode?

NOISY RESPONSE (READINGS RANDOMLY CHANGING)

·         Is the controller grounded?

·         Is there an air bubble on electrode surface?

·         Is the controller operating properly?

·         Is there enough fill solution left in the reference electrode?

DRIFTY RESPONSE (READINGS CONTINUOUSLY CHANGING)

·         Is there excessive leaking at the reference electrode junction?

·         Is the reference electrode junction clogged?

·         Was the sensing membrane poisoned by the sample?

·         Are there temperature problems?

·         Is the sample too concentrated?

·         Does the sensing membrane need conditioning?

INACCURATE (BUT CALIBRATION IS OK)

·         Are the standards incorrect?

·         Was the sample pH adjusted properly?

·         Is there sample carryover?

·         Are there sample interferences or complexing agents present?