In short, a small amount of the sample material is combusted in a closed container (The Bomb Vessel) which is filled with oxygen. The heat released by the sample is compared to a calibration (with a known calorific value) and the CV of the sample is calculated. The sample material must be combustible. It can be solid or liquid, but not a gas.
Then the vessel is filled with 30bar (435psi) oxygen and the vessel is placed in the calorimeter and the lid is closed.
Then the calorimeter takes over and after a while ignites the sample (inside the vessel) by sending a high current through the firing wire, which in turn ignites the sample.
Then the vessel temperature rises which is monitored by the unit every 6 seconds with a resolution of 0.000’001C. After 2-6 minutes a temperature equilibrium is obtained and the temperature rise is compared to a calibration temperature rise and the result is calculated.
Once the vessel is cooled it can be used again. Different CAL3K units have different timing procedures and different number of vessels, which influence the samples per hour determinations.