THERMOANALYTICAL INSTRUMENT
A thermoanalytical instrument, and especially a differential scanning calorimeter, has first and second measurement positions, a heater and a temperature sensor associated with each of the measurement positions, and a controller. The controller, which has an associated means for setting a predetermined temperature program, controls a heating power of the first heater to cause the temperature measured at the first position to follow the temperature program. The controller also controls both heaters to eliminate any temperature difference between the measured first and second temperatures. The controller also provides a means for determining the lower of the measured first and second measured temperatures and applies additional power to the heater associated with that lower measured temperature.
1 . A method for controlling a thermoanalytical instrument that comprises a first and a second measurement position, a first and a second heater and a first and second temperature sensor, the heaters and sensors associated with the respective measurement positions, and a controller operatively arranged to control heating power to the first heater to cause the measured first temperature to essentially follow a predetermined temperature program of temperature target values versus time, and to control the respective heaters to minimize any difference between the measured temperatures, the method comprising the steps of:
applying, from the controller, the predetermined temperature program of temperature target values versus time directly to the first and second measurement positions;
determining, in the controller, the lower measured temperature in the first and second measurement positions; and
applying, as needed and from the controller, additional power to the heater associated with the measurement position having the lower measured temperature.
2 . The method of claim 1 , wherein the thermoanalytical instrument further comprises first and second compensation heaters, associated with the respective measurement positions, comprising the further step of:
applying, as needed and from the controller, additional power to the compensation heater associated with the measurement position having the lower measured temperature.
3 . The method of claim 2 , further comprising the step of:
applying an individual offset voltage to each compensation heater.
4 . The method of claim 1 , wherein:
a first control loop of the controller operates in the step of applying the temperature program; and
a second control loop of the controller operates in the step of applying the additional power.
5 . The method of claim 2 , wherein:
a first control loop of the controller operates in the step of applying the temperature program; and
a second control loop of the controller operates in the step of applying the additional power.
6 . The method of claim 4 , wherein:
a means for restricting the additional power applied to only one of the heaters or compensation heaters at any moment in time, operates in the step of applying additional power, the means for restricting being located in the second control loop.
7 . The method of claim 5 , wherein:
a means for restricting the additional power applied to only one of the heaters or compensation heaters at any moment in time, operates in the step of applying additional power, the means for restricting being located in the second control loop.
8 . A computer program for performing the control method of claim 1 on a thermoanalytical instrument, wherein:
the computer program is stored in a memory device of the controller.