Abstract: In the present invention the cell of the electrolytic hygrometer is fabricated with a helical pair of different wires which may be either two precious metals or one of these with one non-precious metal. Appropriate polarities are included.

Abstract: A simple and economical means for assuring the removal of electrical power from the equipment in an enclosure when in a hazardous environment, and from the enclosure itself, before the enclosure is opened to that environment, by including an arm which in the "On" position of the equipment switch, extends immediately over the head of a bolt whose removal is necessary for opening of the enclosure, and in the "Off" position of the equipment switch is no longer over the head of that bolt.

Abstract: The invention comprises an improved electrolytic cell of the Keidel type, U.S. Pat. No. 2,830,945, in which the original set of electrodes is replaced by two sets having a ratio of length of not less than 3 to 1 and having independent terminals and independent bodies coupled together. The invention also may comprise potting the element including the longer set of electrodes and leaving the element including the shorter set of electrodes unpotted.