ENMET SPECTRUM-RAL-DC - Manual (Page 13)

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3.1.3 Calibration
NOTE: Calibration should be performed at normal room temperature (20-25°C) for optimal
performance. If the instrument is exposed to temperature extremes just prior to calibration, it should be
allowed to stabilize to room temperature. The internal temperature of the instrument can be verified by
cycling through the "see DATA" menu.
In order to calibrate the instrument, it is first zeroed as described above. Then the sensor is presented
with a known concentration of the target gas, in air or an inert gas such as nitrogen, called the "span
gas". After an appropriate interval, which is timed, the new span setting is examined for validity.
A valid key entry sets the instrument at the "run ZERO" location of the maintenance menu. Press the
OPTION pushbutton once to access the "run CAL" display, then press the SELECT pushbutton; "AIR
SET" is displayed. Zero the instrument as described in paragraph 3.1.2 above. When the zero timer is
complete, the display indicates "SPAN=XXX", where the numbers indicate the correct span gas
concentration for the instrument. The span gas value for this instrument is 20 ppm CO.
Assure that the correct span gas is available, connect the calibration adapter to the cylinder, then press
the SELECT button; "GAS SET" is displayed. Unplug the regulator-flowmeter assembly from the
airline, connect it to the calibration adapter and set the flow at 1.0 SCFH. Then press the SELECT
button; "XXX:0.Yv" is displayed. The XXX is a counter which counts down in seconds to zero from
120 to provide the proper time interval for calibration. The 0.Yv indicates a sensor signal which is used
during the sensor replacement procedure. When the timer reaches zero, the new calibration and zero
gas settings are examined for validity. If the values are reasonable, the display is transferred to the gas
concentration numerical display in the operations menu. Return the regulator-flowmeter assembly to the
airline.
If the new zero and calibration settings are not reasonable, "C-FAULT" is displayed. Turn the
instrument OFF, then ON again. This re-boots the system with the most recent valid zero and
calibration settings.
3.1.4 Changing the Alarm Level
A valid key entry sets the instrument at the "run ZERO" location of the maintenance menu. Press the
OPTION push button twice to access the "set ALM" display, then press the SELECT button;
ALM=0000" is displayed. This is called the alarm update window, and the value displayed is the
present alarm setpoint. The underscore cursor is under the far left digit. Press the OPTION button to
index the underscored digit; press the SELECT button to index the underscore cursor one position to
the right. When the desired new alarm point is set, press either the OPTION or SELECT button to
return to the alarm update window. If the new alarm setting is valid, "set ALM" is again displayed.
Press the OPTION button four times to return to the operations menu.