What is ORP?
In the oxidation reduction process one molecule loses electrons, while another gain them. We could also say that one molecule reduces while the other oxidases. The potential included in this process is called ORP – redox potential.
ORP is a very important parameter, which we have to control, for example in the water treatment, in swimming pools, in which one oxidant, like chlorine, which we add to the water in order to remove the impurities. The higher the ORP value, the higher is then the power of the disinfectant.
ORP Electrodes
The ORP measurements are based on the difference between the gold and platinum electrode and the reference electrode. The same reference electrode as it is used with pH electrode (Ag/AgCl), is also used with the redox potential.
Do ORP electrodes need to be calibrated?
No. ORP electrodes do not need calibration with the meter such as pH. Still, ORP electrodes need to be conditioned prior to use. When the electrode is new, soak the tip in warm tap water. This will enhance the flow of the reference junction. To check function of the electrode, immerse the tip in ORP solution HI 7021L or HI 7022L. The reading should be +/- 50mV from the value indicated on the bottle. If the reading is not within the +/-50mV, oxidizing or reduction treatment with HI 7092 or HI 7091 is required. It will also prepare the electrode’s surface and speed initial response time. Since in-line process electrodes are already in a solution, a simple test with either HI 7021L or HI 7022L will show you the electrode’s condition. Should your probe not be accurate enough after conditioning & testing, follow the cleaning procedure.
What ORP sensor should I use platinum or gold?
Platinum sensor: use in oxidizing reaction (above 500mV) such as pools & spas, municipal drinking water. Gold sensor: use in reducing environment (below 500mV) such as galvanic applications, mining industry (Cyanide).
Hanna Instruments offers a variety of instrumentation for measuring Oxidation Reduction Potential (ORP). From research grade bench, top meters to titration systems and controllers, Hanna has an accurate, affordable solution for nearly any ORP testing application.
