Combustion Calorimeters measure the heat released from a combustible solid-liquid substance. This is done by weighing a precise measure of the sample substance into a crucible, placing the crucible inside a "bomb" (a sealed metal cylinder called a vessel), filling the vessel with oxygen and igniting the substance. The sample burns and the resulting temperature increase of the vessel is measured and from it the calorific value (CV) is calculated by comparing it to a previous combustion of a known substance.

Simple Actually!

The process gets complicated if a high accuracy is required. Then it is important to harness the environmental influences during the measuring cycle. That is to say that the vessel should not gain or lose any energy to the environment.

The energy released during the combustion results in a temperature increase of the vessel. This energy must be removed after the measuring cycle is complete. This is done via a "Cooling Apparatus" of some kind.

Each manufacturer has a different system, but all measure the same. Of importance is accuracy, which is governed by international standards like DIN, ASTM, CEN and ISO. The standards are very much the same if not copies of each other. All calorimeter systems must conform to these standards, and they do.

These are the features which separate calorimeter models from different manufacturers:

• Speed of operation
• Convenience of operation
• Interfacing to the real world (visible, transparent data and parameters)
• Relying on resources (water, electricity, air-conditioning)
• Floor Space
• Cost to purchase, operate and maintain
• Ease of maintenance
• Robustness in the field
• Exceeding the international standards

The last item is controversial - Does it matter if the instrument exceeds the sample preparation accuracy in regards to moisture, consistency and repeatability? Sometimes the sample is very "precise" and an instrument with higher precision makes a difference.

The above information applies to all calorimeters in the DDS Oxygen Bomb Calorimeters Range.