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.
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.