Servomex SERVOTOUGH LaserExact 2950, Руководство оператора

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SERVOTOUGH LaserExact Monitor, Operator Manual 02950001A_1
48 C
HAPTER
5
5.3.1 PROPORTIONAL versus GLOBAL calibration
Line broadening compensation requires a large number of parameters to be
measured. These parameters are critical for accuracy, but only when line broadening
compensation is used. Most of the parameters seldom or never need to be adjusted.
PROPORTIONAL calibration:
This calibrates the span of the gas concentration by adjusting the proportionality
between the peak amplitude of the absorption line and the gas concentration. Only
the
proportional calibration constant is affected by PROPORTIONAL calibration.
GLOBAL calibration:
Calibrates both the gas concentration span and line width parameters. It is important
to follow the calibration procedure carefully and specify to the instrument the exact
pressure and temperature of the calibration cell. The P, and T values can be set fixed
with the service program, or use 4-20 mA inputs if such probes are connected to the
calibration cell. One can also use the internal sensors if these are close to the values
for the calibration cell. It is also important to use dry gas mixed with nitrogen. For O
2
,
dry air can be used.
USE GLOBAL calibration:
•
If spectral properties of laser is believed to have drifted. This can be evaluated by
qualified service personnel from dump-files recorded with the instrument when it
is measuring on a calibration gas.
•
After major instrument services such as replacement of laser module, main board
or receiver board. (Qualified service personnel only!)
•
After adjustment of laser parameters (modulation amplitude or phase, or other
laser currents). (Qualified service personnel only!)
DO NOT
use GLOBAL calibration when:
•
the instrument is measuring on the process (with process gas).
•
the concentration of the calibration is low such that the signal-to-noise ratio is not
good.
•
the conditions for GLOBAL calibration described above are not satisfied. If
recalibration is required in such cases, use PROPORTIONAL calibration instead.
5.4 Troubleshooting the instrument
During operation essential status information about the instrument is displayed on the
LCD. The instrument messages and their possible explanations and actions to be
taken are given in the table below. If there is no output to the display, please refer
section 6.7.