1. Field of the Invention
The invention relates to a low pressure dew and frost point indicator and more particularly to the cooling module of such an indicator.
2. Description of the Prior Art
The prior art known to the applicants is best represented by the prior Sheldon U.S. Pat. Nos. 3,874,220 and 3,886,784, Ford U.S. Pat. Nos. 3,374,658, 3,152,475 and 3,460,373 and Hankison U.S. Pat. No. 3,589,165.
In prior devices, there has been no positive and simple way of positioning the frost point indicating mirror correctly with respect to the cold air stream which is directed against it.
Prior mirrors have also been subject to temperature gradients and undesirable changes of temperature caused by contact with adjacent module components and/or subjection to atmospheric or high pressure gases entering from the surrounding area.
Ejectors of the type used in the prior art have not had the capability of being adjusted for optimum operation of the cold air generation system and then being pre-set in optimum setting.
In case a new reading is required, necessitating raising the temperature in the sampling chamber, the prior art has utilized purge or blow down valves to clear the sample chamber or has cut off air controlled by the input to the sample chamber with relatively large valves in order to allow the sample chamber to become warmer.