Global Water's (Redox) ORP sensor is a rugged reliable ORP/Redox measuring device. The ORP sensor is molded to 25 ft of marine
grade cable, with lengths up to 500 ft available upon request. The ORP sensor's output is 4-20 mA with a three wire
configuration. The ORP sensor's electronics are completely encapsulated in marine grade epoxy within a stainless steel housing
(online version has 1-¼ inch PVC x 12 inch pipe nipple, threaded both ends with cap)
Global Water's PC320 ORP Controller to use the ORP sensor's output to control pumps or
alarms. In addition Global Water offers GL500 ORP recorder adds recording capabilities
to the ORP sensor. The GL500 ORP recorder connects to the ORP sensor's 4-20mA output to record data.
Measuring ORP
ORP stands for oxidation-reduction potential, which is the measurement (in millivolts, or mV) of the oxidizing or reducing tendency
of a solution. Oxidation is the loss of electrons from an atom, molecule, or ion, which may or may not be accompanied by the
addition of oxygen. When a substance is oxidized, its oxidation state increases. Reduction is the net gain of
electrons. When a substance is reduced, its oxidation state is lowered. Oxidation and reduction reactions always
accompany each other. Every oxidation and reduction reaction can be characterized by a halfreaction, which provides all of the
chemical substances participating in the reaction (many half-reactions are identified in standard chemistry handbooks or other
reference materials). The ORP of the solution depends on the concentrations of the substances participating in the
half-reaction. In order to calculate ORP when concentrations vary, you must use the Nernst equation. Due to its
logarithmic dependence on concentration and its dependence on multiple solution components, ORP is typically not a good method for
measuring concentration. The best use of an ORP is in monitoring and controlling oxidation-reduction reactions. When an
oxidation-reduction reaction occurs, there is usually a large change in the ORP, which overwhelms the factors that make concentration
measurements an issue. This allows you to ensure that an ORP reaction has gone into completion, and thereby control your
application appropriately.
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