ELTRA CS-800 User Manual

47
Fig. 25: Analysis time
The analysis respectively the combustion, takes normally a maximum of 100
seconds. At the beginning of combustion, the IR-cells signals start going up on the
computer screen, reaching a peak maximum depending on the C resp. S
concentrations in the sample. When the signal comes down, the analysis will be
terminated when the signal has reached a comparator level. The value of this
comparator level is entered in the configuration window of the software.
If, for some reason, the signal may not come down to the comparator level, the
analysis is terminated when the maximum analysis time expires. This time is also
entered in the configuration window.
The analysis stops also when the maximum analysis time expires before the signal
comes down to the comparator level.
The meaning of setting a maximum analysis time is to protect the induction
generator from overheating, in case the signal may not come down to the
comparator level. One reason why the signal not to come down to the comparator
level is that Hydrocarbons from the oxygen burn on the hot crucible, preventing the
IR-signal from coming down to zero resp. down to the comparator level. One more
reason is a too low comparator level, so that a small positive drift of the base line
during analysis makes the base line higher than the comparator level at the end of
the combustion. In such cases, the comparator level should be set higher.
The comparator level value entered into the configuration window is a minimum
value which increases according to the peak maximum of each analysis. During
combustion, the software takes the peak maximum to add to the entered
comparator value an additional amount depending on the actual peak maximum.
3.8.1
91BAdditional reasons for excessive analysis duration could be:
– Dirty dust trap,
– Saturated chemicals
– Cotton, glass or quartz wool is pressed too tightly
– The oxygen is not pure, or the catalyst furnace is faulty or is cold, or the
copper oxide is used up
– The temperature of the infrared cell is not yet stable. Either it is not yet
operational for at least 1 to 2 hours, or the oxygen flow has not yet been
running for 10 to 15 minutes ( power switch on setting 2 ),
– The thermostatic control of the infrared cell is defective
– Excessive combustion temperature, causing the crucible to emit CO
2
.
3.8.1.1 One of the IR-sources is unstable:
Small resistance changes of one or more IR-sources can cause the current to vary,
thus affecting the intensity of the IR-radiation.
This problem will effect all IR-cells, due to the fact that the IR-sources are all
connected in series.
In order to establish whether this problem is present or not, an analysis cycle
should be run without a sample or a crucible. The baselines of the IR-cells can
then be monitored on the PC screen.
The baselines should be quite stable and should run between 0.100 V and - 0.100
V on the screen.
It would be very difficult, in case of a problem, to establish which IR-source is faulty
and it is therefore easier to replace them all.
A window of an IR-path is not gastight. The measuring gases pass through the
leakage, either into the chopper housing or to the IR-sensor.
Perform a leakage test of the IR-paths. Replace the faulty IR-path.
Check the base line on the PC screen, by starting analysis without sample. Zoom
to get the scale of 10mV steps.

ELTRA CS-800 Specifications

General

Brand	ELTRA
Model	CS-800
Category	Measuring Instruments
Language	English