To control the rate of temperature increase, (for example, 10° c. Per 1 minute), heat tray, two positioned separately with the rate of increase at equal heat throughout the trial.
To control heating rate constant (such as 10 degrees Celsius for one minute) will control both heating tray placed separately. With increased heat evenly throughout the trial.
To control the rate of temperature increase to a fixed (such as 10 degrees Celsius per 1 mins.) to control the heating tray, both of which placed separately. With the increasing rate of heat rate throughout the experiment.