TC M Temperature Controller User Manual V1.08
Electron Dynamics Ltd page
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6.6
Relay Feedback – Autotuning
The TC M features an auto tuning function as standard using the relay feedback method, this makes this
tuning very much easier. The user is able to select the setpoint around which the auto tuning should occur
and how long for the unit to make measurements. The unit then sets up the relay feedback conditions
under which oscillation occurs, these peaks are analysed and from these the PID parameters are
calculated. The test aborts at the end and uses the new PID parameters for temperature control.
6.7
Ziegler - Nichols open loop – step response
This is open loop so there is no the control function is off, it involves making a step change at the
output The input / thermal response should be noted, then using graphical means should be
analysed, to give the initial process dead time and the process time constant. From these the
respective terms can be calculated -
Td is Process time constant t is pseudo dead time and Kp the process gain
From this the PID terms are calculated
P term is 1.2 ( t/ ( Td * Kp) ) I term is Td / 0.5 and D term is Td * 0.5
6.8
Ziegler - Nichols closed loop – ultimate gain method
This is a closed loop so the control function in on. With the P term set low and the I term and D
term off. Monitoring the temperature the gain or P term is increased until there is sustained and
continuous oscillation of the temperature. The Gain ( P term ) required and the period of the
oscillation should be noted. From these the PID terms can be calculated.
Where
Gu is the gain and Tu is the period
From this the PID terms can be calculated
Where
P term = 0.6 Gu I term = 0.5* Tu D term = 0.125 Tu
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Graphical User Interface
The TCM series Temperature Controller can be operated via the
Graphical User Interfaces,
one written in
Java and the other in C++. They are very similar with minor differences.
The GUI will be broken down into eight functional categories, each will be explained in the remainder of this
section of the manual:
I. Pull Down Menus
II. Control
III. Set Point
IV. Sensor
