Electric pH and ORP meters — useful or not?
Many customers ask us whether purchasing an electrical measuring device is worthwhile. PH value and ORP measurement (redox potential) Is it worth it? The answer: It depends on what you want to measure.
Video: Measuring pH and ORP with Hanna Instruments
Key takeaways from the video
- Electrical measuring devices can be used at highly antioxidant water “blinds”
- ORP values below -200 mV are problematic for standard measuring electrodes.
- Measuring electrodes must be calibrated regularly and replaced if necessary.
The problem: "Blindness" at extreme redox values
Electrical measuring devices show a redox potential of alkaline ionized activated water. Below -200 mV, no reliable values are available. more. The measuring electrodes can essentially "go blind" in extremely antioxidant, hydrogen-rich water.
Why is this happening?
The platinum measuring electrode reacts to the dissolved molecular hydrogen (H2) in water. At high H2 concentrations, a thin layer of hydrogen forms on the electrode, which distorts the measurement. The device then displays either:
- Fluctuating, unstable values
- Values that do not go lower than approximately -400 mV (even though the water is more heavily reduced)
- Extremely long measurement times until stabilization
Which measurement method is suitable for which purpose?
| Measurement method | Suitable for | Restriction |
|---|---|---|
| Indicator drops (pH) | Rapid pH test (range 4–10) | Not exact, but reliable |
| Electric pH meter | Accurate pH measurement | Regular calibration is required. |
| Electrical ORP meter | Redox potential up to approx. -200 mV | "Blinded" by strongly negative values |
| H2 measuring device (e.g. Trustlex) | Dissolved hydrogen in ppb/ppm | Most precise method for H2 content |
our recommendation
For the everyday use are the included pH indicator drops (Reagents) sufficient and more reliable than many inexpensive electrical devices.
If you still wish to use an electrical measuring device:
- Calibrate Replace it regularly (at least monthly) with buffer solutions
- Trade Shows Dispose of the water immediately after ionization (hydrogen escapes quickly).
- Expect the following from ORP measurements no exact absolute values — the trend is more meaningful
Further FAQs:
- pH measurement with indicator solution
- pH-redox combination meter — useful?
- Redox potential — detailed explanation
- Hydrogen measurement
- Redox values of activated water
- Conductivity and PPM measurement
Measuring device in the shop: Digital TDS meter for water quality
