7.2.3 Standardization
Preparation of ORP standard solutions
ASTM d 1498-93 gives procedures for making iron (ii) - iron (iii) and quinhydrone ORP
standards. The iron (ii) - iron (iii) standard is recommended. It is fairly easy to make and has
a shelf life of approximately one year; in contrast, quinhydrone standards contain toxic
quinhydrone and have only an eight hour shelf life. Iron (ii) - iron (iii) standard is available
from Rosemount as PN R508-16OZ. The ORP of the standard solution measured against a
silver-silver chloride reference electrode is 476 ± 20 mV at 25 °C (77 °F).
Standardizing with an ORP sensor
1. Press CAL on the IRC to enter the CALIBRATE menu.
The STD submenu appears.
2. Rinse the sensor with DI water and place it in the ORP standard with a reference
thermometer. Ensure that the ORP sensor is submerged at least 3 in. below the
water level.
3. Once the temperature and ORP readings are stable, press ENTER.
4. Use the editing keys to change the flashing display to the desired ORP reading. Press
ENTER to save.
5. Press EXIT to return to the main display.
7.2.4 Matching transmitter to ORP sensor's temperature
element
1. Press PROG on the IRC.
2. Press NEXT until the TEMP submenu appears in the display. Press ENTER.
3. Press EXIT to return to the main display.
7.3 Calibrating contacting and toroidal
conductivity sensors
7.3.1 Overview of calibrating contacting conductivity sensors
Contacting conductivity sensors do not require frequent calibrations. The sensors are
ready to be installed right out of the box.
7.3.2 Calibrating with contacting and conductivity sensors
1. Pres CAL on the IRC. Press ENTER.
Measurements
46 Rosemount 5081
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