J-KEM Scientific Gemini-230, Руководство пользователя

Страница: 14 / 46

14
Autotune Errors. The autotune routine can fail for several reasons. If it fails, the controller displays
the error message “
tunE
” “
FAiL
”. To remove this message turn the controller off for 10 seconds. Try
the procedure titled “Autotuning the Controller for Very Fine Control” above. If autotune fails again,
call and discuss your application with one of our engineers. A common problem when tuning at high
temperatures or with large volumes is for the heater to be underpowered. A more powerful heater may
be needed (contact J-KEM for assistance).
2.3 Tuning for Heating Mantles: A Special Case. This section gives special consideration to heating
mantles, since they’re the most commonly used heaters in research. Every heating mantle size has its own
optimum set of tuning parameters and if you wanted, the controller could be tuned (or autotuned) every time
a different size was used. However, this is cumbersome and is also unnecessary. Factory tests show that
there’s one set of tuning parameters that delivers good performance for all heating mantle sizes. These
tuning parameters were loaded into the controller at the factory prior to your receiving it. If you’re using a
heating mantle and none of the parameters have been changed or the controller hasn’t been autotuned since
you’ve received it, you’re ready to go. If the tuning parameters have been changed or the controller has been
autotuned and you want to go back to using heating mantles, J-KEM recommends that the tuning parameters
for heating mantles be loaded manually (i.e., don’t autotune to the heating mantle) by following the step-by-
step instructions given in Procedure 4 of Section 3.10.
2.4 Sensor Placement. Placement of the sensor is basically common sense. The sensor should be
positioned to sense the average temperature of the medium being heated. That means the thermocouple
should be shielded from direct exposure to the heater but not so distant that a rise in temperature isn’t sensed
by the controller within a reasonable period of time. Several examples follow that show the type of
consideration that should be given to sensor placement.
Use With:
Solutions Place the sensor in the solution. Stir vigorously so that heat is homogeneously mixed
throughout the solution.
HPLC column heated
with a heating tape Tape a thin wire thermocouple directly to the HPLC column. Place several layers of
paper over the thermocouple to insulate it from the heating tape (the thermocouple
should sense the column temperature, not the heater temperature). Wrap the HPLC
column completely with heating tape.
Oven The thermocouple needs to be shielded from transient hot and cold air currents. Don’t
place the thermocouple near the heating coil or an air vent. A small thermocouple
(1/16” or 1/8” thermocouple) that responds rapidly to changes in air temperature is
better than a larger one.