Emerson Process Management IM-106-910Xi Calibration PASSES, but Still Reads Incorrectly

Xi Advanced Electronics

Instruction Manual

IM-106-910Xi, Original Issue November 2010

Table 5-1. Diagnostic/Unit Alarm Fault Definitions

Message		Status	Self Clearing
NV Mem Fail		A checksum error was detected in the nonvolatile memory configuration data when the unit was	No
		turned on.
Factory Mode		On Xi box I/O board, SW4, position 1 is set on "ON". On transmitter electronics board, SW1,	No
		position 1 is set to "ON". This setting should only be used in the factory.
Board Temp Hi		The transmitter electronic board temperature reading is above 126° C or the	No
		Xi unit I/O board temperature reading is above 86° C.
O2	Htr Ramp Rate	The O2 sensor heater ramp rate is greater than max allowed ramp rate indicating a run away	No
		heater condition.
O2	Sensor Open	The cell impedance voltage is reading less than -1.1 VDC indicating the O2 sensor wires may be	Yes
		disconnected or the O2 sensor junction may be open.
O2	TC Open	The O2 cell heater thermocouple voltage is reading more than the hardware configured threshold	Yes
		voltage. This indicates the thermocouple wires may be disconnected or the thermocouple junction
		may be open.
O2	Temp Low	The heater temperature is below the minimum temperature. The predefined low temperature	Yes
		threshold is the 726° C.
O2	Temp High	The heater temperature is above the defined temperature threshold. The high temperature	Yes
		threshold is the defined by the "High Temp Alm SP" parameter. The default value is 750° C.
O2	T/C Shorted	The O2 sensor heater temperature thermocouple voltage is shorted.	Yes
O2	T/C Reversed	The O2 sensor heater temperature thermocouple voltage is reading a negative voltage indicating	Yes
		the thermocouple wire connections may be reversed.
O2	Htr Failure	The O2 sensor heater temperature is not responding to the controller and can't reach final	Yes
		temperature set by the device, indicating the O2 heater may have failed.
No Flame		The Flame Status Relay Input is set to the OFF state indicating it is not safe to operate the O2	Yes
		heater and the heater should be turned off.
Xmtr Disconnect		Communication failures detected between transmitter and the I/O board indicating the transmitter	Yes
		has been disconnected from the I/O board.
Cal Recommended		Probe calibration is recommended. The cell impedance is above 100 ohms and has shifted 50	Yes
		ohms since the last calibration; the accuracy of the O2 reading may be compromised.
Cal Failed		A calibration error occurred during the last calibration. The measured slope or constant is outside	Yes
		the acceptable range. (Slope: 34.5 to 57.5 mv/decade) (Constant: ±20 mv)
Cell Imp High		The O2 sensor impedance/cell resistance value measurement is greater than 2000 Ohms	Yes
		indicates the cell may be beyond its useful life.
CPU Voltage Low		The CPU voltage is less than 2.7 V indicating the CPU voltage is too low.	Yes
CPU Voltage High		The CPU voltage is more than 3.3 V indicating the CPU voltage is too high.	Yes
Htr Voltage Low		The heater voltage for the O2 cell heater is below 35 volts.	Yes
Htr Voltage High		The heater voltage for the O2 cell heater is above 264 volts.	Yes
Low O2		The O2 reading is below the "Low O2 Alm SP".	Yes

CALIBRATION PASSES, BUT STILL READS INCORRECTLY

There are a few fault conditions where no alarm indication is present and the probe passes calibration, but the O2 reading may still be incorrect:

An incorrect flow rate of calibration gases can cause a shifted calibration. If the flow rate of calibration gases is too low, process gases can mix in with the calibration gases causing a mixture at the cell that is different than what is noted on the calibration gas bottles. Always set the calibration flow rate when a new diffuser is installed, and never readjust this flow rate until another new diffuser is installed. For applications with heavy particulate loading, see "Probe Passes Calibration, But O2 Still Appears To Read Low".

No or improper reference air supplied.

5-4