6 Operating Instructions
17
If the actual temperature display 18) shows
, press
in the control
field 21) during 2 sec to switch on the temperature controller.
Press
and then
and/or
to change the temperature setpoint. If the desired
value is indicated by the setpoint display 19), safe by pushing
again.
Switch on the evaporation tube heating with toggle switch 17) to connect the controller
power output to the heater.
The green heating current OK LED 15) indicates that supply voltage (24 VDC) is applied
to the heating and the current is within its tolerance.
If one of the red heating current LED's 14) or 16) lights, the current is too low or too high,
probably caused by a defective heating element or an interrupt in the electric circuit. The
evaporation tube should be switched off immediately and the device has to be checked
and repaired by the manufacturer or a local service provider.
Wait until the measured gas temperature 18) agrees with the set value 19) /-
2
°C.
During the heating up phase the heating current OK LED 15) lights continuously green.
The LED starts blinking in intervals of a few seconds when the measured gas
temperature approaches the set value. When the set value is reached the heating
on/off-duty cycle stabilizes on a ratio depending on the adjusted temperature.
Heating up times are approximately 2.5
min from ambient to 200
°C and 4
min to 300
°C.
Due to attachment of low volatile substances on its inner surface, the evaporation
tube may produce particles itself if operated at temperatures above the previous
operation point. In this case, the attached volatile material evaporates, and may
re-nucleate being measured by the connected instrumentation. When the
evaporation tube temperature is increased, it is recommended to run the testo
ASET15-1 with stopped rotating diluter disk but active testo MD19-3E dilution air
supply to rinse the tube with filtered air until no undesired particles are detected
anymore. This process may last up to 20 minutes.
6.3.
Flows and Control LED's in Air Supply Part
Note: All flows mentioned in this manual are standard volume flows in [l/min] which means liters
per minute at standard conditions: 1013,25 hPa / 0°C.
testo ASET15-1 in its pneumatic function is an adjustable diluter where two calibrated flows Q
MD
and Q
AS
are mixed in the secondary dilution mixing chamber 37). Fig. 6.2 shall help to
understand the setting of the secondary dilution air in the air supply part of testo ASET15-1.
Fig.6.2: secondary dilution flows
Measuring gas flow Q
MD
(standard 1.5
l/min) from the testo MD19-3E Rotating Disk Diluter enters
the secondary dilution mixing chamber. Secondary diluted measuring gas flow Q
MG
is drawn from
the instrumentation connected on the measuring gas output 13).
It is evident that Q
AS
must be adjusted to a value where Q
MD
+
Q
AS
>
Q
MG
and therewith Q
EX
>
0 to
ensure no gas is sucked backwards through the excess gas tube and added to the measuring
gas.
