Chemglass CG-1972-65 - Manual (Page 6)

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It’s important to understand that this controller isn’t a simple ON/OFF type controller (i.e. ON when
below the set point, OFF when above [though it can be made to work this way, see Section 3.13]). Rather
it’s a predictive controller. Based on the shape (slope) of the heating curve, the controller predicts
(calculates) the percent of power to apply to the heater now to control the shape of the heating curve
minutes in advance. The importance of the tuning parameters is that they are constants in the equation the
temperature meter uses to perform its predictive calculations. If the temperature meter is programmed
with tuning parameters that incorrectly describe the heater being used, poor temperature control will
result. But, when the correct values are loaded, temperature regulation of ± 0.1
o is typically achieved.
Manual Tuning. Manual tuning is when the values of the 5 tuning parameters are determined
manually then entered into the temperature meter via the push buttons on the front of the controller.
Experienced users might prefer to manually tune the controller since this allows customization of the
heating process.
Autotune. Autotune is a feature built into the temperature meter that automatically calculates the
tuning parameters (i.e. delay times, heating efficiency, etc.) for any type of heater. After the autotune
procedure is complete and the tuning parameters are determined, the controller loads them into its
memory for current and future use. Heating mantles are a special case and are covered in a separate
paragraph (Section 2.3).
2.2 Autotuning Procedure.
This procedure is not recommended for heating mantles (see Section 2.3). Only the setpoint
controller (the meter on the far left) should be autotuned, never tune the Limit Controller.
1. Set the equipment up in the exact configuration it will be used. For example, to tune a vacuum
oven, place the thermocouple in the room temperature oven then plug the oven into the
controller. If the oven has its own thermostat or power control, turn both as high as they’ll go.
2. Set the controller to the appropriate power level (see Section 3.7). Turn the controller and
heater on, and enter the desired set point temperature. If the set point isn’t at least 30
o C above
ambient, skip this procedure and go to the next procedure, “Autotuning the Controller for Very
Fine Control”
3. Enter a temperature into the limit controller about 25 o C higher than the set point entered
into the setpoint controller.
4. Press and hold in both the ▲ and ▼ buttons (for 3 seconds) on the front of the setpoint
controller until the word “tunE” appears in the display then release both buttons.
5. Press the ▲ button (5 times) until “CyC.t” appears in the display (if you go past this setting,
press the ▼ button until you get back to it).
6. First, hold in the ‘*’ button, while holding in the ‘*’ button press the ▼ button. Continue to
hold both buttons in until the display reads “A --”, or “A ##” where “##” is some number.
7. Release the ‘*’ button and press the ▼ button until “tunE” once again appears in the display.
8. Press and hold the ‘*’ button and “tunE” will change to “off” indicating that autotune is off.
9. While holding in the ‘*’ button, press the ▲ button to change the display to “on”, then release
both buttons.
10. Press and hold both the ▲ and ▼ buttons (for 3 seconds) until the temperature appears in the
display. The controller is now in its autotune mode. While in autotune the display alternates
between “tunE” (for autotune) and the process temperature. When the autotune sequence is
done (this may take in excess of an hour) the controller stops displaying “tunE” and only
displays the process temperature. [To abort autotune manually, repeat steps 4, 9 and 10 except
in step 9, press the ▼ button until “off” is displayed].