XZR250 User’s Manual
Michell Instruments
23
MAINTENANCE
!
CAUTION: ALWAYS use silicone-free gas. Silicone vapors will
damage the zirconia sensor; refer to section 5.1.3 Using the
Sensor with Silicones.
3. Replace the sensor head: refer to Section 9 Replacing Parts.
6.2
Calibrating
Due to the zirconia technology used in this device, no “zero” calibration is required and only
a “span” calibration needs to be performed.
Calibration is achieved by initiating a calibration routine via the digital display, and
monitoring the status of the output. The fixed reference is factory set to 20.7% O
2
for calibration with air however this value may be altered via the digital display for
calibration with a reference gas of any known oxygen concentration 1-21%. Any new
calibration value will be stored on power loss.
For optimum performance it is recommended that the sensor is calibrated close to the
oxygen concentration expected during normal operation.
A software delay prevents calibration from being completed before the zirconia sensor
has been powered ON for 5 minutes. If a calibration is initialised during this delay the
unit will calibrate after the 5 minutes have elapsed.
NOTE:
The sensor has a finite life span ranging from 1-7 years depended on the fuel type used
in the boiler. Michell Instruments operates a service exchange program, for more details
please contact your local Michell office or representative.
NOTE:
If you notice during routine calibration that you require a higher pressure then previously
to achieve a specified flow rate, the sampling tubes may have become clogged and should
be cleaned thoroughly. Refer to section 6.1.2.
