ENMET SPECTRUM-RAL-DC - Manual (Page 12)

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3.0 Maintenance
3.1 Maintenance Menu
From the gas operational display, push the OPTION button four times; "go SETUP" is displayed. This
is the entrance to the maintenance menu. The maintenance menu diagram is shown in Figure 3.
3.1.1 Key
Entrance to the maintenance menu is guarded with a four digit numerical key. The factory default setting
of the key is 1270. When the valid numerical key is inserted, the user is allowed to enter the
maintenance menu.
When in the "go SETUP" location, press the SELECT pushbutton; "Key=0000" is displayed. The
underscore cursor is under the left hand digit. To insert the key, press the OPTION pushbutton to
index the left hand digit, and choose the correct digit; then press the SELECT pushbutton, which locks
in the chosen left hand digit and moves the underscore cursor one space to the right. Continue this
process until the four digit key is complete. When the valid key is inserted in this manner, the display is
transferred to the "run ZERO" portion of the maintenance menu. When an invalid key is inserted,
"INVALID" is briefly displayed, and the instrument returns to the operations menu.
The process by which means a different key is set is given in paragraph 3.1.6, below.
3.1.2 Zero
A valid key entry sets the instrument at the "run ZERO" location, of the maintenance menu, which
enables the setting of the zero gas concentration point. This is desirable if the zero reference of the gas
sensor has drifted over a period of time, indicated by a persistent gas concentration reading in a clean
environment. Note that the calibration sequence given below also includes setting the zero point. If a
full calibration is required, instead of setting just the zero point, push the OPTION button once; "run
CAL" is displayed. See paragraph 3.1.3, below.
To set the zero point without performing full calibration, from the "run ZERO" location press the
SELECT button; "AIR SET?" is displayed. Be certain that the instrument is supplied with clean air,
uncontaminated by carbon monoxide. If uncertain of the environment, use pure compressed air from a
pressurized cylinder, and flow it over the sensor at a flow rate of 1 SCFH.
With the instrument in zero air, press the SELECT button again. "ZERO=30" is displayed; this is a
counter that counts down in seconds from 30 to 0. The validity of the new zero setting is then
examined; if it is reasonable, the display is transferred to the concentration numerical display in the
operations menu.
If the new zero setting is not between reasonable parameters, "C-FAULT" is displayed. Turn the
instrument OFF, the ON again. This re-boots the system with the most recent valid zero setting.