Emerson Rosemount5081, Instruction Manual, Page: 53 / 152

7.1.4 Manual calibration
Prerequisites
Ensure that auto-calibration is OFF and the appropriate buffers are used.
Procedure
1. Enter the CALIBRATE menu by pressing CAL on IRC.
The CALIBRATE sub-menu appears.
2. At the CALIBRATE sub-menu, press ENTER .
The CAL BF1 prompt appears.
3. Rinse the sensor with DI water and place it in the first buffer along with a calibrated
thermometer. Submerge the sensor tip at least 3 in. below the liquid level. Do not
rest the sensor on the glass bulb. Dislodge any trapped bubbles by swirling the
sensor body.
4. Once the pH reading and temperature are relatively stable, press ENTER . Use the
editing keys to change the flashing display to the appropriate pH of the buffer
solution. 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. If you do not press
ENTER , the transmitter exits the CALIBRATE menu and
returns to the process mode.
5. At the CALBF2 prompt, remove the sensor from the first buffer. Repeat steps 3 and
4.
The calibration is now complete, but the transmitter remains in the CALIBRATE sub-
menu for two minutes after you press
ENTER .
6. Remove the sensor from the buffer and reinstall it into the process stream. If the
HOLD feature was turned on, be sure to turn off HOLD.
The sensor will not calibrate if the electrode slope (calculated by the transmitter
during calibration) is unacceptable. The transmitter displays a SLOPE ERR HI or
SLOPE ERR LO error message. Refer to
Chapter 8 for assistance.
NOTICE
To display the electrode slope, press CAL on the IRC. The CALIBRATE sub-menu appears.
Press NEXT . The STD sub-menu appears. Press ENTER . The STD prompt appears. Press
ENTER again, and the slope appears on the display. For a good sensor, the slope is
generally 50 to 60 mV.
Measurements
Instruction Manual 43