Brief Guide to Troubleshooting Common Measurement Problems with Simple Causes - Van London

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 READINGS (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?