ABB Endura AZ20 series

Combustion Oxygen Monitor
Endura AZ20 Series Probe 4 Troubleshooting – Functional Checks
12 IM/AZ20M–EN Rev. B
The following examples show calculations for process
temperatures <700 °C and >700 °C:
Example 1 – Process Temp. <700 °C
For test gas of 20.95 % 02 (air):
EmV = 0.0496 x (700 + 273.16) (log
10 20.95/20.95)
±CmV
EmV = 48.2608 (log
10 1)
EmV = CmV (cell constant)
Example 2 – Process Temp. <700 °C
For a certified test gas of 1 % 0
2:
EmV = 0.0496 x (700 + 273.16) (log
10 20.95/1) ±CmV
EmV = 48.2608 (log
10 20.95) ±CmV
EmV = 63.76 mV ±CmV
Example 3 – Process Temp. of 800 °C
For a certified test gas of 1 % 02:
EmV = 0.0496 x (800 + 273.16) (log
10 20.95/1) ±CmV
EmV = 48.2608 (log
10 20.95/1) ±CmV
EmV = 63.76 mV ±CmV
4.4 System Functional Check
This section checks the AZ20 probe and associated transmitter
for system functionality and accuracy.
1. Perform a manual 2-point calibration using the 2 test
gases selected – refer to the probe User Guide
(IM/AZ20P–EN).
2. If this fails, check the transmitter calibration – refer to the
transmitter User Guide (IM/AZ20E–EN).
Note. Pure N2 or any other inert gas cannot be used to
calibrate a zirconia system ’gas zero’ as this equates to an
infinite cell output voltage. A gas with a known value close
to zero (for example 1 % 0
2 in N2) must be used for this
purpose.