38
65-2661RK-XX-04 M2A Transmitter Operator’s Manual
highest response to the calibration gas. The calibration gas can then be removed and the M2A will continue to
display this reading and retain it in its memory until the span adjustment procedure is completed.
Adjusting the Fresh Air Reading
Since there is a background of CO
2
in air of typically 300 - 600 ppm (0.03 - 0.06 %volume), it is necessary to use
a calibration kit with a 100% nitrogen cylinder to set the zero signal of an M2A with a low range detector (0 -
5000 ppm or 0 - 5.00% volume). Fresh air can be used to zero an M2A with a high range detector (0 - 50%
volume or 0 - 100% volume).
1. While in normal operation, press and hold the UP/YES button for 5 seconds to enter Calibration Mode.
Release the button when the following screen appears.
2. If you want to continue with calibration, press and release the UP/YES button. The display will indicate the
target gas and
CAL Mode
for a few seconds before showing
FreshAir Adjust?
.
If you want to exit Calibration Mode, press and release the DOWN/NO button. The M2A will indicate
Leaving CAL Mode
and the M2A will return to normal operation.
3. To continue with adjusting the fresh air reading, press and release the UP/YES button.
ENTER
will
alternate with
FreshAir
on the top display line and the current gas reading will be on the bottom display
line.
To skip adjusting the fresh air reading, press and release the DOWN/NO button. The display will indicate
SPAN w/Cal Gas?
. Skip to the next section, “Adjusting the Span Setting”.
4. Screw the zero air cylinder into the fixed flow regulator.
5. Use the flexible tubing coming from the calibration adapter/splash guard to connect the regulator to the
calibration adapter.
6. Turn the regulator knob counterclockwise to open the regulator.
7. Allow zero air to flow for the length of time determined in “Determining Response Time” on page 36.
8. Turn the regulator knob clockwise to close the regulator.
9. Unscrew the zero air cylinder from the fixed flow regulator. Leave the calibration adapter/splash guard’s
flexible tubing connected to the regulator. The M2A will continue to display the minimum gas response on
the display and retain the response level in its memory.
10. Press and release the ENTER button. The M2A will perform a fresh air adjustment and the display will
indicate
SPAN w/Cal Gas?
.
NOTE:
If the fresh air adjustment fails, see “Troubleshooting” on page 34 for recommended actions.
Adjusting the Span Setting
RKI Instruments, Inc. recommends using a calibration cylinder that is approximately 50% of the full scale value
of your detector (for example, a calibration cylinder for the 0 - 5000 ppm range should have a concentration of
approximately 2,500 ppm).
1. If you want to continue with adjusting the span setting, press and release the UP/YES button.
APPLY
will
alternate with
SPAN Gas
on the top display line and the current gas reading will be on the bottom display
line.
If you want to skip adjusting the span reading, press and release the DOWN/NO button. The display will
indicate
Leaving Cal Mode
and the M2A will return to normal operation.
2. Screw the calibration gas cylinder into the fixed flow regulator.
Calib?
YES/NO
