The higher temperature Isotech Black Body fixed point cells consist of very pure metals within a graphite. Graphite reacts with air to form carbon dioxide. The height of the reaction is temperature dependent. The effect is small at low temperatures, but increases at higher temperatures. For Indium, Tin and Zinc cells in general no attention needs to be paid. However, for aluminium, silver and copper cells oxygen should be excluded, as others can damage the cells quickly. With the Isotech Model 984 Gas Flow System there is a reliable instrument on the market.

The Isotech 984 Gas Flow System connects an inert gas, such as argon or nitrogen, to the cell in its unit. The instrument has a regulator and flow meter, optimized to set the flow to 0.2 l/min and has an alarm if the gas flow is interrupted.


A Black Body is defined as either a source with zero reflectivity or a source that emits as much radiation as possible (at all wavelengths) for its temperature.


Emissivity is the ratio of radiation emitted by a surface to that emitted by a Black Body at the same temperature. Isotech has a range of high emissivity sources. This in combination with thermal uniformity for use as primary standard sources for low uncertainty wavelength independent calibration.

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