Emerson Rosemount5081 - Glasswarn

- If cleaning the sensor lowers the impedance below 800 megohms...
a. The sensor is in good condition.
b. Return the calibrated sensor to service.
- If cleaning does not lower the glass impedance and the sensor can be
calibrated...
a. The sensor is probably in good condition; however, it may be nearing
the end of its life. The electrode slope is a good indicator of remaining
life.
Slope Condition of sensor
54-60 mV/unit pH Sensor is in good condition.
48-50 mV/unit pH Sensor is nearing the end of its life. Once the slope
drops below 48 mV/unit pH, the sensor can no longer
be calibrated.
b. The Glass Fail High (GFH) limit is probably set too low for the sensor.
Set the GFH limit to about 150 megohms greater than the measured
glass impedance.
c. If the GLASSWArn message was also flashing, raise the GWH limit from
its former value by the same amount the GFH was raised from its
former value.
• If cleaning does not lower the glass impedance and the sensor cannot be
calibrated, the sensor has failed and should be replaced.
GLASSWArn
GLASSWArn is an electrode fault message. It means the glass impedance is outside the
programmed Glas Warning High (GWH) or Glass Warning Low (GWL) limit. Ideally, when
the measurement system exceeds the glass warning limits, you will have adequate time to
diagnose and correct problems before a failure occurs. High impedance implies the
electrode is aging or the sensor is not completely submerged in the process liquid. Low
impedance suggests the pH sensitive glass is cracked. The message also appears if
inappropriate limits have been entered into the transmitter.
If the measurement system was previoulsy commissioned and operating correctly,
GLASSWArn likely means a real problem exists. However, if the system is being started up
or if the advanced diagnostic feature is being used for the first time, GLASSWArn could be
caused by a miswired sensor or by programmed limits that are not correct for the sensor.
NOTICE
GLASSWArn is a sensor diagnostic message. All sensor diagnostic messages are optional. They
can be turned off.
Troubleshooting GLASSWArn problems is exactly the same procedure as troubleshooting
GLASSFAIL problems. Refer to GLASSFAIL.
Diagnostics and troubleshooting
58 Rosemount 5081