Calvet-type Calorimeters
The detection is based on a three-dimensional fluxmeter sensor. The fluxmeter element consists of a ring of several thermocouples in series. The corresponding thermopile of high thermal conductivity surrounds the experimental space within the calorimetric block. The radial arrangement of the thermopiles guarantees an almost complete integration of the heat. This is verified by the calculation of the efficiency ratio that indicates that an average value of 94% +/- 1% of heat is transmitted through the sensor on the full range of temperature of the Calvet-type calorimeter. In this setup, the sensitivity of the calorimeter is not affected by the crucible, the type of purgegas, or the flow rate. The main advantage of the setup is the increase of the experimental vessel's size and consequently the size of the sample, without affecting the accuracy of the calorimetric measurement.
The calibration of the calorimetric detectors is a key parameter and has to be performed very carefully. For Calvet-type calorimeters, a specific calibration, so called Joule effect or electrical calibration, has been developed to overcome all the problems encountered by a calibration done with standard materials. The main advantages of this type of calibration are as follows:
- It is an absolute calibration.
- The use of standard materials for calibration is not necessary. The calibration can be performed at a constant temperature, in the heating mode and in the cooling mode.
- It can be applied to any experimental vessel volume.
- It is a very accurate calibration.
An example of Calvet-type calorimeter is the C80 Calorimeter (reaction, isothermal and scanning calorimeter).
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