Is the low conductivity of my process water causing issues with my pH probe?

Document ID

Document ID TE12898

Published Date

Published Date 05/06/2021
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Question
Is the low conductivity of my process water causing issues with my pH probe?
Summary
pH probe function and low conductivity water
Answer
Measuring pH in low-ionic strength water is a challenge. See the following article for details on why measuring pH is challenging in low conductivity water.
Is there information on pH measurement in high purity or low-ionic strength water?

If you notice standard pH probe values drifting or bouncing around and suspect the issue may be because of low conductivity water, follow the below steps.
  • Collect a grab sample of the process water in a bucket or beaker and place the pH sensor into that sample. 
    • This will isolate the sample from the process to ensure nothing from the process is interfering with the readings.
  • Do the sensor readings continue to drift or bounce around? 
    • If yes, add some salt (standard table salt will work just fine) and mix.  Proceed to the next step
    • If no, see the following article for how to test for ground loops  What is a ground loop?  
  • After adding salt, do your pH readings settle out and start to read as expected? 
    • If yes, the low conductivity of your water is causing issues with the pH measurement. 
    • If no, there is something else causing issues with the measurements.  Please check your sensor manual for information on sensor maintenance and troubleshooting.
 

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