Emerson Rosemount5081 Instruction Manual page 66

Diagnostics and troubleshooting
NOTICE
GLASSFAIL is a sensor diagnostic message. Sensor diagnostic messages are optional. They can
be turned off.
Troubleshooting flowchart - GLASSFAIL
1.
2.
56
Be sure the sensor is completely immersed in the process liquid.
If the diagnostic message disappears, the sensor is in good condition.
If the diagnostic message remains, go to Step 2.
Measure the glass impedance. See
• If the glass impedance is low (< 40 megohms)...
a. Check preamp location in program menus (PAMP = _____).
- If the location is incorrect, go to Step b.
- If after selecting the correct location of Preamp in the Program menu, the
glass impedance is still low, go to Step b.
b. Calibrate the sensor.
- If the sensor calibrates properly...
a. The sensor is in good condition, but the Glass Fail Low (GFL) limit is set
too high.
b. Lower the GFL limit to about 10 megohms below the glass impedance
value (GIMP) measured in Step 2.
c. If the Glass Warning Low (GWL) message was also flashing, lower the
limit from its former value by the same amount the GFL was lowered
from its former value.
- If the sensor cannot be calibrated, the pH glass membrane is likely cracked
and the sensor must be replaced. The crack in the glass may not be visible
or may be difficult to see.
• If the glass impedance is high (> 800 megohms)...
a. Check that the sensor is correctly wired to the transmitter. Pay particular
attention to the following:
a. For Rosemount PLUS (+) and TUpH sensors with integral preamplifiers, the
blue solution ground wire must be attached to TB-8 (SOL GND), and the
gray reference in wire must be attached to TB-7 (REF IN).
NOTICE
TB-8 means terminal 8 on the terminal board.
b. If the sensor was wired with the blue solution ground wire unattached and
a jumper between the terminals TB-8 and TB-7, remove the jumper and
reattach the blue solution ground wire to TB-8. Keep the gray reference in
wire attached to TB-7.
Section 8.1.7 for the procedure. Note the reading.
Rosemount 5081