Thermoanalytical instrument

Abstract

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.

What is claimed is: 
     
         1 . A method for operating a thermoanalytical instrument as a differential scanning calorimeter in a dynamic power compensation mode, the thermoanalytical instrument comprising a first and a second measurement position, each of the measurement positions having a primary heater, a compensation heater and a temperature sensor associated therewith, and a controller, provided with a predetermined temperature program of temperature target values versus time and operatively arranged to control heating power provided to the primary and compensation heater at each measurement position, the method comprising the steps of:
 applying, from the controller, a heating power signal to the respective primary heaters to cause the temperatures at the respective measurement positions to follow the predetermined temperature program; and   while the predetermined temperature program is being applied, using the controller to iteratively perform the steps of:
 receiving a series of time-based temperature signals from the respective temperature sensors; 
 determining the measurement position having the lower measured temperature, based on the time-based temperature signals; and 
 providing, as needed, an additional heating power signal to only the compensation heater associated with the measurement position having the lower measured temperature. 
   
     
     
         2 . The method of  claim 1 , further comprising the step of:
 applying an individual offset voltage to each compensation heater.   
     
     
         3 . The method of  claim 1 , wherein:
 a first control loop of the controller operates in the step of applying the heating power signal; and   a second control loop of the controller operates in the step of applying the additional power.   
     
     
         4 . The method of  claim 3 , 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.   
     
     
         5 . 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. 
 
     
     
         6 . A method for controlling a thermoanalytical instrument that comprises a first and a second measurement position, a first and a second heater, a first and a second compensation 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 first and second heaters and the first and second compensation 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 through the respective first and second heaters;   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 compensation heater associated with the measurement position having the lower measured temperature.   
     
     
         7 . The method of  claim 6 , further comprising the step of:
 applying an individual offset voltage to each compensation heater.   
     
     
         8 . The method of  claim 6 , 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.   
     
     
         9 . The method of  claim 6 , 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.