Michell Instruments XTC501, User Manual, Page: 37 / 56

XTP501 & XTC501 User’s Manual
Michell Instruments 29
CALIBRATION
3.2 2-Point Calibration
This is a 2-point adjustment that is overlaid on top of the factory calibration. It is
designed to correct minor drift and minor changes during transit. This calibration makes
the unit more accurate throughout the range than the single point calibration.
1. Apply the lower calibration gas and purge the unit for at least 5 minutes.
View the chart until a flat line shows for 1–2 minutes.
t
t-2
21
6
%
t
t-2
7
6
%
Figure 28 2-Point Calibration Page
2. Press
ENTER
to highlight CAL TYPE and set to 2 POINTS. Press
ENTER
to de-select.
3. Press
ENTER
to highlight REF GAS 1 and use the
Up
(

) and
Down (

)
buttons to match the value of the concentration of the lower calibration
gas.
NOTE: This value only needs to be set when using a new
gas cylinder.
Press
ENTER
to de-select.
4. Ensure the Adjusted value at the bottom of the page has stabilized.
NOTE: There will be a ~ symbol next to 'Adjusted' while the
reading is stabilizing. When the ~ symbol disappears, the
reading will be stable and the next change can be made.
5. Press
ENTER
to highlight ACTUAL 1 value and press the
Up
(

) button
3 times. Ensure that the Adjusted value equals the REF Gas 1 value
(±0.01%). Press
ENTER
to de-select.
6. Apply the upper calibration gas and purge the unit for at least 5 minutes.
View the chart until a flat line shows for 1–2 minutes (see above).
7. Press
ENTER
to highlight REF GAS 2 and use the
Up
(

) and
Down ( 
)
buttons to match the value of the concentration of the upper calibration
gas. NOTE: This value only needs to be set when using a new
gas cylinder. Press
ENTER
to de-select.
8. Ensure that the Adjusted value at the bottom of the page has stabilized.
9. Press
ENTER
to highlight ACTUAL 2 value and press the
Up
(

) button
3 times. Ensure that the Adjusted value now equals REF Gas 2 value
(±0.01%). Press
ENTER
to de-select. Press
ESC
to return to the Main
Menu.
10. The Adjusted reading will now be the same as that displayed on the
Main Page and be equal to the upper calibration gas.
11. The calibration process is complete. Return to sampling the process gas.