Abstract: A protective coating for an electronic assembly on a circuit board is made from a pre-fabricated, roll-flattened plastic ribbon having desired pre-determined thickness. From the ribbon, a suitably shaped membrane piece is produced, e.g., by stamping or by water-jet cutting, with openings as may be desired for circuit components to be left uncovered. The membrane is placed onto the circuit board, softened by heating, and pressed on by means of a silicone stamp, for close contact with electronic modules to be protected. The membrane is then adhered to the circuit board by further heating. The starting material for the membrane is a mixture of a thermoplastic material and of a wax including a significant amount of branched-chain and cycloaliphatic hydrocarbons.

Abstract: For testing or/and adjusting a scattered-light smoke detector as to sensitivity to smoke, a transparent body with included scattering centers is introduced into the measurement volume of the detector. Aluminum oxide powder particles can serve as scattering centers. The distribution of light scattering centers is preferably uniform, and their concentration chosen to simulate a smoke density corresponding to the alarm threshold of the smoke detector. Thus, scattered-light smoke detectors are readily calibrated to a desired output signal as a function of smoke density. With a different density of scattering centers, the technique can be used for testing scattered-light smoke detectors in the field. If the scattering centers are distributed outside a measurement volume of an uncontaminated detector, the technique can be used for testing as to contamination.