Filter
Top Products
74
9.5.3 Procedure
1. Place the transmitter in ORP mode. See Section 10.6.3, steps 1 - 3. After
selecting and saving OrP, press EXIT twice to return to the main display.
2. Enter the CALIBRATE menu by pressing CAL on the IRC. The Std sub-
menu appears.
3. Rinse the sensor with deionized water and place it in the ORP standard along
with a thermometer. Submerge the sensor tip at least three inches below the
surface of the liquid. Swirl the sensor to dislodge trapped air bubbles. The
main display will show the measured ORP based on the previous calibration.
4. Once the temperature and ORP readings are stable, press ENTER . The
screen changes to look like the figure to the left.
5. Use the editing keys to change the flashing display to the desired ORP read-
ing. Press ENTER to save.
6. Press EXIT to return to the main display.
NOTE
A transmitter adjacent to the one being calibrated may pick up
signals from the IRC. To avoid accidentally changing settings,
use a different security code for each nearby transmitter. See
Section 5.7, Security.
NOTE
During calibration, the sensor may be exposed to solutions hav-
ing ORP outside the normal range of the process. To prevent
false alarms and possible undesired operation of chemical dos-
ing pumps, place the analyzer in hold during calibration. See
Section 9.3, Using the Hold Function, for details.
CALIBRATE
Std
EXIT NEXT ENTER
CALIBRATE
Std
EXIT NEXT ENTER
0 2 5.0
1400
mV
Std
9.5 Standardization
9.5.1 Purpose
This section describes how to prepare ORP standard solutions and how to make the transmitter reading match the ORP
of the standard. Procedures for making ORP standards are taken from ASTM Method D1498-93.
9.5.2 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 about one year. In contrast, quinhydrone stan-
dards contain toxic quinhydrone and have only an 8-hour shelf life.
Iron (II) - iron (III) standard is available from Rosemount Analytical 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.
MODEL 3081 pH/ORP SECTION 9.0
CALIBRATION OF ORP MEASUREMENTS