Servomex SERVOTOUGH LaserExact 2950, Руководство оператора

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SERVOTOUGH LaserExact Monitor, Operator Manual 02950001A_1
46 C
HAPTER
5
If only a gas mixture with higher gas concentration is available, dilute the gas mixture
with nitrogen using a calibrated gas mixing system to the specified values above.
Significantly lower concentrations should not be used because the measurements
might be influenced by noise as well as by adsorption and desorption processes in
the cell and the tubes.
WARNING
If using toxic, asphyxiant or flammable sample or calibration gases,
open cabinet or alignment chamber enclosures in a force ventilated
open area, or in another appropriate environment in which any
hazardous gases are directed away from the user.
Follow the steps described below to perform verification and calibration.
1.
Let the instrument operate for at least 1 hour before performing the verification
and/or calibration.
2. Run the service program (ref. Section 4.1 for start-up).
3. Check that the fixed temperature and pressure settings are correct, or that the
PLC inputs for the gas temperature and pressure are correct (i.e. set to
calibration conditions).
4. Introduce the calibration gas into the cell. Wait until the system reaches stable
levels.
5. Check if the reading is in agreement with the concentration of the certified gas.
If required, perform calibration (PROPORTIONAL or GLOBAL) as described in
Section 4.3.7.
6. Save the instrument settings to a file as described in Section 4.3.9.
7. If applicable re-set the pressure and temperature parameters to process
conditions (ref. Section 4.3.5).
8. The calibration is completed and the monitor can be used for measurement.
Note that when gas is flushed through the cell, the cell pressure is higher than the
ambient pressure. The pressure difference depends on the flow rate and the
diameter and length of the outlet tubes. It is therefore highly recommended to
measure the gas pressure close to the cell, using an absolute pressure sensor in
order to provide the instrument with correct gas pressure during the verification and
calibration procedure. If only the ambient pressure is known or the pressure sensor is
located far away from the cell, one can switch off the gas flow before calibration, wait
1 minute for the readings to stabilise and subsequently perform calibration. In this
case the gas pressure is equal to the ambient pressure.
Special care should be taken for reactive and “sticky” gases such as HF, NH
3
, HCl
and H
2
S. Because of the nature of these gases, it is difficult to obtain the required
concentration in the cell due to adsorption and desorption in the connection tubes.
The following recommendations should then be followed: