Improvements relating to radiation thermometers.

摘要

A purge assembly for mounting to a radiation thermometer, comprises a purge tube (4) for mounting in front of the radiation thermometer. At least two axially spaced chambers (6,9) are positioned about the purge tube (4), each pair of chambers being linked by a respective restrictive opening (8) such that a difference in pressure exists between adjacent chambers in use. An upstream chamber (6) with respect to the flow of purge fluid is connected to source of purge fluid such as air in use and a downstream chamber (9) with respect to the flow of purge fluid opens into the purge tube (4) via a swirl reducing system (13) whereby purge fluid is emitted into the purge tube in use. The chambers are positioned such that fluid flows through the chambers generally towards the lens and then through the downstream chamber opening towards an outer end of the purge tube away from the lens.