Enmet SPECTRUM-RAL Manuel d'utilisateur télécharger pdf (Page 11)

SPECTRUM RAL ENMET Corporation

4.2 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 that a different key is set is given in section 4.6.

4.3 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 section 4.4.

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.

4.4 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 exposed to 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 section 4.3. 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.

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Enmet SPECTRUM-RAL Manuel d'utilisateur Page 11

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