Optical dissolved oxygen sensors rely on an oxygen sensitive luminescent coating to perform the measurement. Over time, this coating may experience build-up from the process that can slow the response of the sensor.
The black coating on the tip of the cap contains oxygen sensitive dyes. Care in installation and handling should be used to ensure that the coating is not damaged
General Cleaning Procedure
Once removed from the process, visually inspect the black circular tip of the DO sensor. There should be no scratches or flaking of the black coating. If particulate build-up is present then simple soap and water (Alconox) can be used to clean the sensor tip. Alcohol is also a suitable cleaner if oils or fats are present.
Avoid chlorine-based cleaners. Strong oxidizers such as chlorine can bleach the luminescent coating causing a loss of intensity and shortened sensor life. Also, avoid abrasive scrubbing of the black sensing surface. A simple cotton cloth works well for this…
After cleaning, perform a calibration to determine if the sensor is functioning properly. If further problems persist then a cap replacement may be needed.