Is a plastic or rubber ring under the pyro case necessary?
Plastic stand off may be necessary to achieve the right height position, since the Fresnel lens has a focus point. It may also be necessary to isolate the detector from pcb tracks underneath it. It is not, however, a necessity. Rubber around the detector protects the device against thermal drafts within the case and is a recommended feature. There is no recommendation on which supplier to use for the plastic or rubber.
