Errors resulting from cracked glass electrodes.

A tiny crack in the membrane of a glass electrode is not always visible to the naked eye. Frequent shocks may create cracks in the glass that cause measurment errors. These cracks will cause the analyzer to read 0 mV and the analyzer interprets that to a reading near pH 7. in many process the setpoint is near pH 7. This means a cracked pH sensor can cause an inaccurate reading that is near the setpoint, and it may not be noticed quickly. This can be a critical and dangerous situation.   Without additional diagnostic, the error will not be detected until the process is out of control.

Yokogawa's Transmitters have an impedeance check function. The analyzer checks the impedance of pH (and reference) sensors via the solution ground. The Transmitter can be set to generate an alarm if the impedance limits are exceeded.