The CV2256 is a filament bolometer. The cold resistance is 55 Ω and the maximum operating resistance is 110 Ω.
When placed in a source of RF energy, usually microwaves, the filament absorbs energy and heats-up, thus the maximum operating resistance indicates the upper end of the power it can usefully measure.
The filament is held in the folds of the two supports. This is open circuit and no filament can be seen.
The concentric connections.
The ring connects to one end of the filament with the other connection passing through the hole in the centre.
The thin glass tube envelope is 9 mm in diameter and, including the base pins, is 21 mm tall.
Reference: Data-sheet. Type CV2256 was first introduced in 1955. See also1955 adverts.
