Emerson ROSEMOUNT 5081-A Instruction Manual page 105

MODEL 5081-A
15.2.1 RTD OPEn, bAd RTd, tEMP HI, tEMP LO, and SenSE OPEn
these messages usually mean that the Rtd (or thermistor in the case of the HX438 and GX448 sensors) is open or short-
ed or there is an open or short in the connecting wiring.
1. Verify all wiring connections, including wiring in a junction box, if one is being used.
2. disconnect the Rtd IN, Rtd SENSE, and Rtd REtuRN leads or the thermistor leads at the transmitter. Be sure to
note the color of the wire and where it was attached. Measure the resistance between the Rtd IN and REtuRN leads.
For a thermistor, measure the resistance between the two leads. the resistance should be close to the value in the
table in Section 15.14.2. If the temperature element is open (infinite resistance) or shorted (very low resistance),
replace the sensor. In the meantime, use manual temperature compensation.
3. For oxygen measurements using the HX438 and GX448 sensors, or other steam-sterilizable sensor using a 22kNtC,
the temperature High error will appear if the transmitter was not properly configured. See Section 7.4.
15.2.2 pHgLASS HI and pHgLASS LO
these messages mean that the pH sensor glass impedence is outside the programmed limits. to read the glass imped-
ance, go to the main display and press dIAG. Scroll to the PH prompt and press ENtER. Press NEXt until GIMP (glass
impedance) is showing. the default lower limit is 10 MW. the default upper limit is 1000 MW. Low glass impedance means
the glass membrane is broken or cracked. High glass impedance means the membrane is aging and nearing the end of
its useful life. High impedance can also mean the pH sensor is not completely submerged in the process liquid.
1. Check sensor wiring, including connections in a junction box.
2. Verify that the sensor is completely submerged in the process liquid.
3. Verify that the software switch identifying the position of the preamplifier is properly set. See Section 7.8.3.
4. Check the sensor response in buffers. If the sensor can be calibrated, it is in satisfactory condition. to disable the
GLASS FAIL message reprogram the glass impedance limits to include the measured impedance. If the sensor can-
not be calibrated, it has failed and must be replaced.
15.2.3 AdC FAIL
the analog to digital converter has probably failed.
1. Verify that sensor wiring is correct and connections are tight. Be sure to check connections at the junction box if one
is being used. See Section 3.1 for wiring information.
2. disconnect the sensor(s) and simulate temperature and sensor input.
To simulate
dissolved oxygen
ozone, monochloramine, chlorine
pH
temperature
3. If the transmitter does not respond to simulate signals, call the factory for assistance.
See Section
15.11
15.12
15.13
15.14
SECTION 15.0
TROUBLESHOOTING
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