Accurate measurement, control, and repeatability of pH/ORP sensors is an essential trait for the proper treatment of process water. pH/ORP sensors, even in processes that do not cause abrasion, coating, plugging, or any other problems, still require calibration to account for aging and other changes. While calibration will be required occasionally, a properly working pH sensor will not need to be adjusted often in general-purpose applications. In this article, we’ll dive into some of the problems faced in pH/ORP sensor applications!


Cleaning pH/ORP Sensors

One of the most common causes of inaccurate measurement problems with pH sensors comes from their lack of proper cleaning. Improper cleaning of pH sensors can lead to slow response, incorrect readings, and more. Cleaning the pH/ORP sensor can reverse these problems and should be part of your regular maintenance routine. The frequency of your maintenance routine will depend on the application. 


Common Problems With pH/ORP Sensors

Even if a pH/ORP sensor is calibrated correctly and working properly, problems can begin to arise during use. Below are some of the most common problems that are faced when using pH sensors, and some fixes for these issues!



Drifting happens when a pH sensor’s readings shift up or down over time. Drifting happens when the asymmetry potential, or mV offset, becomes greater. When this happens, the pH sensor will require more frequent calibration. This is commonly caused by the depletion of KCl from the reference electrolyte, which can happen when the reference electrode is used in the wrong process solution.


Improper Cable Preparation

Improper cable preparation happens when a cable is not the correct length. To prevent this problem, you should always use a cable that is the correct length for the application, rather than trying to cut a longer cable down to size.


Slow Response Time

Slow response time from a pH/ORP sensor is typically caused by a coating or plugging of the junction. This usually occurs when a thin film builds up on the glass sensor. The most common remedy for this problem is cleaning the sensor with a 5% – 10% solution of HCl.


Cracks In The Membrane

One more common problem with pH sensors is an invisible crack in the membrane of a glass electrode. These cracks are typically invisible to the naked eye and are caused by frequent temperature shocks. These cracks can be extremely dangerous because they are undetectable without additional diagnostic testing.

To learn more about pH sensor troubleshooting, visit this article from the Yokogawa website!


Contact Sentrol Inc To Learn More!

If you have additional questions about pH/ORP sensor performance, please don’t hesitate to contact us! Our service engineers provide facilities in New England, the Mid-Atlantic, and Eastern Canada with instrument repair, calibration, and much more! Call us today at (888) 877-1778 or fill out the contact form on our website, and we’ll get back to you as soon as possible! Looking to purchase pH/ORP instruments from industry leading manufacturers? Shop our online store!