Thermo-analytical instrument
View Patent ↗A thermo-analytical instrument, especially a differential scanning calorimeter has a sample position ( 201, 401 ) for receiving a sample ( 206 ), a reference position ( 202, 402 ), a heating means associated with the sample position and the reference position, a means for setting a predetermined temperature program of nominal values of temperature versus time, a first sensor ( 407 ) for measuring a sample temperature (T S ) at the sample position, and a controller. The controller controls the heating power of the heating means so that measured sample temperature essentially follows the predetermined temperature program.
1. A method for operating a thermo-analytical instrument in an enhanced heat flux mode, the thermo-analytical instrument comprising a sample position and a reference position, means for heating each of the sample position and the reference position, sample temperature sensing means for sensing a temperature of a sample placed at the sample position, reference temperature sensing means for sensing a temperature at the reference position, and means for controlling the power supplied by the means for heating to the respective sample and reference positions, the method comprising the steps of:
placing a sample on the sample position;
measuring sample temperature using the sample temperature sensing means;
applying heating power over time to each of the sample position and the reference position, the means for controlling solely using measured sample temperature as the basis for determining an amount of the heating power being applied, so as to cause the measured sample temperature to follow a predetermined program of sample temperatures versus time that is configured in the means for controlling; and
during the step of applying heating power, determining a temperature differential arising between the respective temperature sensing means and deriving a net heat flow into the sample from the temperature differential determined.
2. The method of claim 1 , wherein:
the step of applying heating power is achieved by a PID control loop.
3. A thermo-analytical instrument, comprising:
a sample position;
a reference position;
means for heating each of the sample position and the reference position,
sample temperature sensing means for sensing a temperature of a sample placed at the sample position;
reference temperature sensing means for sensing a temperature at the reference position, and
means for controlling the heating power supplied by the means for heating, the means for controlling comprising:
a predetermined program of sample temperatures versus time;
a control loop arranged to apply the predetermined program, by controlling the amount of heating power supplied by the means for heating based exclusively on sample temperature as sensed by the sample temperature sensing means; and
means for deriving a net heat flow into the sample, based upon a temperature differential arising between the respective temperature sensing means.
4. The instrument of claim 3 , wherein:
the control loop comprises a PID controller.
5. The instrument of claim 3 , wherein:
the sample position and reference position are selected to minimize an imbalance in thermal mass therebetween, when no sample is on the sample position.
6. The instrument of claim 3 , wherein:
the sample position and reference position are selected such that substantially all of a temperature differential arising between the respective temperature sensing means during the predetermined program is due to a sample on the sample position.
7. The instrument of claim 3 , wherein:
the sample position and reference position are thermally separated from each other.