The electrode itself is comprised of a measuring electrode, a reference electrode, and, often, a temperature sensor. Electrode components are usually combined into one device called a combination pH electrode. The reference electrode is filled with an electrolyte of a known value which reacts with the medium being tested. That reaction is what determines the potential of hydrogen. Since pH is sensitive to temperature fluctuations, a temperature sensor is included so readings can be properly compensated. Temperature compensation can be achieved manually or automatically. Manual temperature compensation is usually achieved by entering the temperature of the fluid being measured into the instruments menu. Automatic temperature compensation requires input from a temperature sensor and constantly sends a compensated pH signal to the display. All pH meters require calibration from time to time. They should be calibrated at a minimum of two points. Most manufacturers offer buffer solution at specific pH levels for calibration. For most applications, pH 7.00 and 4.00 (or 7.01 and 10.01 for alkaline values) are suitable for calibration. The ORP meters are the devices designed for the measurement of the oxidation-reduction potential of water. ORP meters are also industrially known as a redox probe. These chemical or microbial species form redox couple, which results in electron loss. The ORP meters measure the number of electrons lost as a merit of the redox potential of the water. The redox probe is able to measure this electromotive force for electrons to pass from the reduced species to the oxidized species. In our vitamin C example, if the concentration of the oxidized and reduced forms of ascorbic acid are the same, then we will measure an ORP voltage of -570 mV. This is according to the standard redox half-reaction:

You can make the ORP negative by decreasing the H +concentration (raising the pH) and/or increasing the dissolved molecular hydrogen concentration. Conversely, you can make the ORP positive by increasing the H +concentration (lowering the pH) and/or decreasing the dissolved molecular hydrogen concentration. Important Considerations The platinum sensor is often preferred because it is mechanically simpler and safer to produce. Platinum can be welded to glass and has the same thermal coefficient. Sensors made of gold cannot be welded to the glass and are often placed in plastic supports applied to the glass or plastic tube by means of tiny elastomeric bungs. The gold or platinum sensor signal is carried through the electrode body, and together with the reference signal is conducted to the measurement meter via a coaxial cable with BNC connector. Therefore, the answer to when to use ORP meters becomes a little complex. Although, a simplified answer to this question can be to use when the water is being treated or processed. The following are a few examples of applications where ORP meters can be used to identify water quality. ORP electrode acts as an electron donor or acceptor. If the contaminants in water are reductant, then the ORP electrode acts as an acceptor. If the contaminants are being oxidized then the ORP electrode acts as a donor. During this electron transfer, the potential difference is generated owing to the electromotive force. This potential difference is measured by the Aqua-logger or Aqua-meter to give a reading according to the ORP scale. Therefore, ORP meters are also known as differential ORP probes.

Measuring electrodes are made of platinum or gold, which due to their low resistance, will lose electrons to an oxidant or accept electrons from a reductant. Voltage is produced as electrons are added or subtracted. The reference electrode, usually made of silver, is surrounded by an electrolyte solution that produces another tiny voltage. But the voltage produced by the reference electrode is constant and stable, so it forms a reference against which the voltage generated by the measuring electrode may be compared. The more oxidizer or reductant available, the greater the voltage difference between the solutions. AA batteries: 800 hrs. battery life (included) or optional universal, 100–240 VAC (sold separately) Tyler LeBaron. (2013 ) “Changes in Oxidation-Reduction Potential of Aqueous Solutions as a Function of pH and Hydrogen Gas Concentration” The Journal of Kitchen Chemistry 2013. 1. P.12 These important points underscore the importance of actually measuring the molecular hydrogen concentration and making comparisons between hydrogen-water devices based off H 2concentrations, as opposed to pH and ORP alone. ORP Misconceptions

Alternatively, a consultation visit from one of our highly experienced product specialists is available for this range. Typically our specialist will be able to go through the following aspects with you to help you make the right choices and be able to deliver them on time and and on budget.When you add chlorine to a pool, the chlorine gives up its own electron surplus to neutralize or oxidize potentially harmful bacteria. Active chlorine electrons increase the ORP level of the water, thus neutralizing contaminants. For chlorinated pools and spas, a safe ORP reading is usually between 650 millivolts (mV) and 750 mV. As time passes and chlorine breaks down and loses its oxidation potential, the overall ORP reading for the water gradually decreases. Although ORP levels typically correlate with the ratio of sanitizer in the water, ORP does not measure sanitizer levels; rather, it measures the net oxidation and reduction properties of all agents present.

On the other hand, electrons that have a surplus of ions can afford to lose ions to oxidizing agents without becoming destabilized themselves. For this reason, they are referred to as antioxidizing agents, or reducing agents. The higher or lower an ORP reading (positive or negative), the more oxidizing or antioxidizing a substance is, respectively. Accuracy of pH measurements is dependent upon well maintained and properly calibrated instruments. The main factors that degrade the performance of an electrode are coating, contamination and aging. Necessary maintenance and calibration depends on these factors and, of course, of the accuracy required from measurements.

The HI-98190 combines all of the features of a benchtop into a portable IP67 rated waterproof enclosure making them one of the most versatile meters on the market. OSTOJI?, S. M., STOJANOVI?, M. D., CALLEJA-GONZALEZ, J., OBRENOVI?, M. D., VELJOVI?, D., ME?EDOVI?, B., KANOSTREVAC, K., STOJANOVI?, M. & VUKOMANOVI?, B. (2011). Drinks with alkaline negative oxidative reduction potential improve exercise performance in physically active men and women: Double-blind, randomized, placebo-controlled, cross-over trial of efficacy and safety. Serbian journal of sports sciences 5, 83-89.

ORP is unaffected by temperature but readings will vary as the pH fluctuates. As the pH goes up, the millivolt reading on an ORP meter will go down. This can greatly affect the effectiveness of sanitizers such as chlorine, which is by far the most commonly used chemical for water sanitation. For example, at a pH 6.0, 96.5% of the Free Available Chlorine in the water is in the active killing form, while at pH 8.5, only 10% is in that form. Bringing the pH down or adding more sanitizer will raise the millivolt reading. For more information about how to interpret ORP readings and use ORP meters, research your chosen ORP meters and its unique features. ORP is the acronym for "Oxidizing-Reduction Potential" which is the activity of oxidizers and reducers in relation to their concentration. Oxidizers are chemicals and chemical compounds that accept electrons from other substances while reducers donate electrons. ORP is especially important when discussing water quality as it's most notable feature is its ability to measure the oxidation of contaminants. SHIRAHATA, S. A. N. E. T. A. K. A. (2002). Reduced water for prevention of diseases. Animal Cell Technology: Basic and Applied Aspects 12, 25-30.

When an oxidizing and/or reducing agent is dissolved into an aqueous sample, they may react with materials present and produce a voltage, or electromotive force (EMF), that is related to the ratio of oxidized to reduce species in the sample. An electron exchange can develop between this solution and an inert metal sensor immersed in the solution, and the voltage can be measured (when compared to a reference electrode) with a pH/mV meter. This type of measurement is known as redox or ORP. The units of measurement are in mV.