Orp Standardization - Emerson Rosemount 398R Reference Manual

Reference Manual
00809-0100-3098
5.5

ORP Standardization

There are relatively few ORP calibration standards available. The most popular one is a solution
containing 0.1 M iron (II) and 0.1 M iron (III) in 1 M sulfuric acid. The standard is available from
Rosemount as PN R508- 16OZ. The poten-tial of the solution measured against a silver-silver
chloride reference electrode is 475 ±20 mV at 25 °C.
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Calibration
Rinse the sensor with deionized water and place it in the ORP standard along with a reliable
thermometer. Submerge the sensor tip at least three inches below the surface of the liquid.
Swirl the sensor to dislodge trapped bubbles. Adjust the temperature of the standard
to 25 ±5 °C.
Wait until temperature and ORP readings are stable.
Following the instructions in the instrument analyzer, store ORP value (475 mV) in
memory.
Remove the sensor from the ORP standard, rinse it, and return it to the process fluid.
Calibration
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