ABB Endura AZ20 series

Combustion Oxygen Monitor
Endura AZ20 Series Probe 4 Troubleshooting – Functional Checks
IM/AZ20M–EN Rev. B 9
4 Troubleshooting – Functional Checks
4.1 Equipment Required
 AZ20 User Guides (transmitter User Guide IM/AZ20E–EN,
and the probe User Guide IM/AZ20P–EN)
 digital multimeter (10 M input impedance on mV
ranges)
 earth continuity tester
 test gas 1 (typically within the range 10 to 21% O2 in N2)
 test gas 2 (not < 1 % O2 in N2)
 reference air supply (refer to the probe User Guide
IM/AZ20P–EN)
4.2 Thermocouple / Electrode Assembly
Functional Checks
Referring to Fig. 4.2:
1. Using either a mercury or digital thermometer, measure
the ambient temperature at the thermocouple terminals
A (TC+ green and TC– white).
2. Measure the voltage across the transmitter’s
thermocouple terminals A (TC+ green and TC– white).
Refer to Table 4.1 for the voltages that should be present
at the thermocouple terminals, according to the
temperature measured at step 1 when the probe
temperature has stabilized.
3. If the thermocouple voltage is correct, remove the probe
from the flue and replace the cell (refer to Section 5.7,
page 16) and / or the thermocouple / electrode assembly
(refer to Section 5.8, page 20).
Warning. Due to the presence of high voltage heater
terminals / wires (85 to 265 V) in the probe head the probe’s
functional checks, must be carried out by suitably trained
personnel only – refer to
A in Fig. 4.1.
Fig. 4.1 Live Heater Terminals in Probe Head
Caution.
 Functional probe checks are made with the probe /
transmitter system powered up.
 Before performing functional checks:
– ensure the process temperature is within the
limits 20 to 800 °C (68 to 1472 °F) and allow a
minimum 30-minute warm-up period for the
probe cell to stabilize at operating temperature
– ensure reference air and test gases are applied
as detailed in the probe User Guide (IM/AZ20P–
EN).
 If precision accuracies are required, allow a 1-hour
stabilization period.
ACJCACJC
A
B
Fig. 4.2 Checking the Thermocouple /
Electrode Assembly
Note.
 For flue temperatures up to 700 °C (1292 °F) the
probe thermocouple is heater-maintained at
700 °C (1292 °F).
 For flue temperatures over 700 °C (1292 °F) the
probe thermocouple and heater are the same as
the flue temperature.
 For process temperatures between 700 and
800 °C, (1292 to 1472 °F) refer to K-type
thermocouple tables for millivolt values.
A