| http://www.w3.org/ns/prov#value | - Alternatively, known oxygen sensors may incorporate such materials as charcoal filters or metallic barriers, such as silver, for controlling cell permeability to a desired gas as disclosed respectively in US. Pat. No. 2,278; 248 issued to W. A. Darrah on Mar. 31, 1942, and US. Pat. No. 2,787,903 issued to R. B. Beard on Apr. 9, 1957.
|
