In our analysis of the relationship between H2 concentration, pH and ORP, we used the results from predictions of the Nernst equation based on fixed values for both pH and H2 concentrations. When comparing real ORP measurements with predicted results, actual ORP measurements may differ significantly for various reasons.
Although we have not discussed pH meters, their design is very similar to the ORP meter and therefore suffers from the same limitations.
The reasons are not only related to the water being tested, but also to the ORP meter itself. Keep in mind that ORP meters cannot be used to measure H2. At the same time, they have a number of inherent shortcomings that limit their usefulness even for their primary purpose of measuring ORP.
Organic substances/minerals collect on ORP sensors and this contamination can lead to inaccurate readings.
- Ions or other chemical species in water contribute to the overall redox potential and may cause actual ORP readings to differ from predicted results.
- Although temperature affects ORP, most consumer ORP meters do not compensate for this influence of temperature.
- Redox measurements are time-dependent, but there is no time standardization for reading the measurement result.
- Stirring may be necessary to stabilize the reading, but there is no standard for how much the sample needs to be stirred.
- ORP probes have a lifespan of several years, but over that time the accuracy of the readings may decrease.
- As pH increases, the concentration of H+ ions can become so low that the ORP electrode has difficulty detecting them, potentially giving false ORP values.
Therefore, any “hydrogen meter” based on ORP measurement will have these additional inherent weaknesses in addition to its inability to directly measure dissolved H2.
Excerpt from the book by Randy Sharpe: “The relationship between dissolved H2, pH and redox potential”
