J-KEM Scientific Gemini-230, Руководство пользователя

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3.12 Changing Between PID and ON/OFF Operating Modes. The controller can heat in either of 2
operating modes, PID (Proportional, Integral, Derivative) or ON/OFF mode. The difference between them
is the way they supply power to the heater.
In ON/OFF mode (the simplest heating mode), the
controller is ON when it’s below the set point and
OFF when above. The disadvantage of this mode
is a large over shoot of the set point (5 - 30
o
) on
initial warm up and oscillation of temperature
around the set point thereafter. The reason for
the overshoot is because the heater turns off only
after crossing the set point and until the heater
cools down the temperature continues to rise.
This method works well for heaters that transfer
heat rapidly (such as heat
lamps), it’s acceptable for heaters such as heating mantles (≈ 5
o
overshoot), but it’s terrible for heaters that
transfer heat slowly (vacuum ovens, heating blocks, etc.).
In PID mode the controller monitors the shape of
the heating curve during initial warm up and
decreases power to the heater before the set point
is reached so that the solution reaches the set
point with minimal over shoot. [Notice that the
heater turns off for varying periods of time before
the set point temperature is reached]. The
second feature of PID mode is that it adjusts the
percent of time the heater is on so that the set
point is maintained precisely. The advantage of
PID mode is that it delivers stable temperature
control with any heater
from heat lamps to vacuum ovens. The disadvantage is that the controller must be properly tuned to the
heater being used, whereas ON/OFF mode requires no tuning. Since both heating modes have their
advantages (simplicity vs. accuracy), instructions to change the controller to ON/OFF mode are given below
(though PID mode will probably give better results 95% of the time). The controller can be set back to PID
mode by following Procedure 4 in Section 3.10.
1. Press and hold in both the  or  keys on the front of the temperature meter for the
channel you want to change until the word “
tunE
” appears in the display, then let go
of the buttons.
2. Press  until the word “
CyC.t
” appears in the display.
3. While holding in the * key, press the

key until the word “
on.of
” appears in the
display. NOTE: if the display shows the letter “ A” when the * key is held in, press
the

key until “
on.of
” is in the display, then let go of all the keys.
4. Press the  key until the word “
bAnd
” appears in the display. While holding in
the * key, press the

key until the value “
0.1
” appears in the display, then let go of
all the keys.
5. Press and hold in both the

or

keys on the front of the controller until the
temperature is displayed, then release both keys.
Procedure to change
controller to ON/OFF mode
The controller can be set
back to PID control by
following Procedure 4 in
Section 3.10. To completely
reset the controller to
original factory settings,
follow the procedure in the
Appendix, Section II.