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7.6.3 Procedure
1. Before starting, refer to Section 8.7, Buffer Calibration Parameters, to deactivate auto cali-
bration.
2. Enter the CALIBRATE menu by pressing CAL on the IRC. The CALIbrAtE sub-menu
appears (pictured above left).
3. At the CALIbrAtE sub-menu, press ENTER . The CAL bF1 prompt appears.
4. Rinse the sensor with deionized water and place it in the first buffer along with a calibrated
thermometer. Submerge the sensor tip at least three inches below the liquid level. Do not let
the weight of the sensor rest on the glass bulb. Swirl the sensor to dislodge trapped bubbles.
The main display will show the measured pH based on the previous calibration.
5. Once the pH reading and temperature are stable, press ENTER . The display changes to the
screen shown at the left. Use the editing keys to change the flashing display to the pH value
of the buffer at the measurement temperature. Press ENTER to save the value as buffer
bF1. The transmitter expects a reading to be entered within 20 minutes after the CAL bF1
prompt appears. If ENTER is not pressed, the transmitter leaves the CALIBRATE menu and
returns to the process mode.
6. At the CAL bF2 prompt, remove the sensor from the first buffer. Rinse the sensor and ther-
mometer with deionized water and place them in the second buffer. Submerge the sensor tip
at least three inches below the liquid level. Do not let the weight of the sensor rest on the
glass bulb. Swirl the sensor to dislodge trapped bubbles. The main display will show the
measured pH based on the previous calibration.
7. Once the pH reading and temperature are stable, press ENTER . The display changes to the
screen shown at the left. Use the editing keys to change the flashing display to the pH value
of the buffer at the measurement temperature. Press ENTER to save the value as buffer bF
2. The transmitter expects a reading to be entered within 20 minutes after the CAL bF2
prompt appears. If ENTER is not pressed, the transmitter leaves the CALIBRATE menu and
returns to the process mode.
8. The calibration is complete, but the transmitter remains in the CALibrATE sub-menu for two
minutes after ENTER is pressed.
9. Remove the sensor from the buffer and return it to the process. If the transmitter was in hold
during calibration, wait until readings have stabilized before taking the transmitter out of hold.
10. The transmitter uses the calibration data to calculate a new slope. Refer to Section 13.7,
Buffers and Calibration, for more details. If the slope is unacceptable, the calibration will not
be updated, and the transmitter will display a SLOPE Err HI or SLOPE Err LO error mes-
sage. Refer to Sections 12.5 and 12.5, Troubleshooting, for assistance.
11. To leave the CALIBRATE menu, press EXIT .
12. For quality control and troubleshooting, it is helpful to know the electrode slope. To display the
slope, press CAL on the IRC. The CALIbrAtE sub-menu will appear. Press NEXT . The Std
sub-menu appears. Press ENTER . The Std prompt appears. Press ENTER again and
SLOPE xx.xx will appear in the display. The four digit number is the electrode slope. For a
good sensor, the slope is between 50 and 60.
MODEL 3081 pH/ORP SECTION 7.0
CALIBRATION OF pH MEASUREMENTS
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 having pH outside
the normal range of the process. To prevent false alarms and possible unde-
sired operation of chemical dosing pumps, place the analyzer in hold during
calibration. See Section 7.3, Using the Hold Function, for details.
CALIBRATE
CAL bbF 11
EXIT NEXT ENTER
CALIBRATE
CAL bbF 22
EXIT NEXT ENTER
CALIBRATE
CAL bbF 22
EXIT ENTER
CALIBRATE
CAL bbF 11
EXIT ENTER
4.00
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