Temperature Measurement And Calibration Problems; Temperature Different From Transmitter; Oxygen Measurement And Calibration Problems; Zero Current Too High - Emerson Rosemount5081 Instruction Manual

8.4.3

Temperature measurement and calibration problems

Temperature different from transmitter

1.
2.
3.
8.4.4

Oxygen measurement and calibration problems

Problem
Zero current is too high.
Zero reading is unstable.
Sensor current during air calibration is sub-
stantially different from expected.
Process and standard instrument readings
during in-process calibration are substantial-
ly different.
Process readings are erratic.
Readings drift.
Sensor does not respond to changes in oxy-
gen level.
Readings are too low.

Zero current too high

The zero current is substantially greater than the values in the table below.
Sensor
499ADO
499ATrDO
Hx438 and Gx448
1.
2.
Instruction Manual
Is the standard thermometer, RTD, or thermistor accurate? General purpose liquid-
in glass thermometers, particularly ones that have been mistreated, can have
suprisingly large errors.
Is the temperature element in the sensor completely submerged in the liquid?
Is the standard temperature sensor submerged to the correct level?
Is the sensor properly wired to the transmitter?
Is the membrane completely covered with zero solution, and are air bubbles not
trapped against the membrane? Swirl and tap the sensor to release air bubbles.
Diagnostics and troubleshooting
See Section
Zero current too high
Zero reading unstable
Sensor current different from below
Process and standard readings different
Process readings erratic
Sensor not responding to oxygen changes
Oxygen readings too low
Zero current
< 50 nA
< 5 nA
< 1 nA
99