Problems may arise due to errors with electrode function, standards, or due to the limitations of ORP measurements.  Follow the steps below to isolate the source of the problem:

Cleaning and Reconditioning

As the WQ-ORP sensor ages, it may exhibit sluggish or noisy readings. Symptoms that signal the need for cleaning/reconditioning include:

  • Slow response ORP readings in standard solutions
  • Erroneous ORP readings in Zobell solution (outside the range 231 +/- 40 mV at 25° C)

Reference Electrode Problems:

A blocked reference junction may be a cause of slow response, off-scale and noisy readings.

Soak the WQ-ORP sensor in a beaker of warm water (50°C) for 15 minutes to remove dried gel or salts from the junction. Then place in a beaker of warm 4M KCl solution. Set aside until it returns to room temperature. The gel should be moist and the junction flow should be restored.

Glass Bulb Problems:

The glass bulb of the ORP probe will get dirty over time.  We suggest the following solutions for cleaning:

  • Inorganic Deposits: Immerse electrode tip in 0.1 M HCl for 10 minutes. Wash the tip with distilled water.
  • Organic Oil and Grease Films: Wash electrode tip in a liquid detergent and water.

Replacing the sensing module for a WQ-ORP sensor isn’t possible, as the sensor is one continuous piece – if necessary, the entire unit should be replaced.


Short Term

Between measurements, store the ORP electrode in a beaker containing a solution with a similar ionic composition to the samples.

Long Term

When storing for longer periods, store the ORP electrode in the storage bottle that came with the electrode. The storage bottle should contain either commercially prepared storage solution, or a 1:1 solution of pH 4 buffer and 4M KCl. Ensure that the foam or cotton ball in the storage bottle is thoroughly wetted with storage solution to maintain a moist environment around the ORP bulb and junction.

Do not store the electrode in distilled or deionized water – this will cause ions to leach out of the glass bulb and render the sensor useless. After storage, there may be white KCl crystals deposited on the electrode. Such salt formation will not interfere with measurements. Simply rinse the electrode with distilled water to remove the crystals and blot dry before use.


 REV: 13H24


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