Emerson Rosemount 3900 Quick Start Manual page 23

May 2023
2. Measure and record the pH of the process solution sample
with another temperature compensated and calibrated pH
instrument.
For best results, perform standardization at the process
temperature.
3. Adjust the transmitter to the standardized value.
4.3 Calibrate Rosemount oxidation reduction potential
(ORP) sensor
Calibrate an ORP sensor using an ORP standard solution.
Prerequisites
Saturated quinhydrone ORP standard solution is available from
Emerson (PN R508-8OZ) (460 ± 10 mV). You can also make ORP
standard solution by adding a few crystals of quinhydrone to either a
pH 4 or pH 7 buffer. Quinhydrone is only slightly soluble; therefore,
only a few crystals are required.
WARNING
Corrosive substance
The solution used during calibration is an acid; handle it with care.
Follow the directions of the acid manufacturer.
Wear the proper protective equipment.
Do not let the solution come into contact with skin or clothing.
If contact with skin is made, immediately rinse with clean water.
Procedure
1. Make a temporary electrical connection between the sensor
and the transmitter to dissipate any accumulated electrical
charge.
2. Immerse the sensor in the standard solution. Allow one to two
minutes for the ORP sensor to stabilize.
3. Adjust the ORP value on the transmitter to the solution value
shown in
The resulting potentials, measured with a clean platinum
electrode and saturated KCl/AgCL reference electrode, should
be within ±20 millivolts of the value shown in
Note solution temperature to ensure accurate interpretation
of results. The ORP value of saturated quinhydrone solution is
not stable over long periods of time. Therefore, make these
standards fresh each time they are used.
Quick Start Guide
Table 4-1.
Quick Start Guide
Table 4-1.
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