Abstract: A membrane-enclosed amperometric cell (MEAC) for use in determining the concentration of an electroactive species of interest (EASI) in an ambient medium comprises: a working electrode defined by a periphery; a liquid electrolyte covering the sensing area in a film of uniform thickness and being in electrolytic contact with a counter eletrode; a flexible polymer membrane of generally uniform thickness that is substantially impermeable to the electrolyte but permeable to the EASI; the membrane extends in a substantially conforming manner over the sensing area and the electrolyte film thereon; the cell of the invention has a physical permeation barrier that (1) consists of a layer of a substantially inert solid material which is substantially impermeable to the electrolyte and to the EASI; (2) extends between the ambient medium and the sensing area; (3) is disposed in a parallel configuration and in physical contact with the membrane; (4) has at least one opening permitting access of the EASI through the membra

Abstract: A sealed adjusting device for mounting in the wall of a sealed instrument housing that includes at least one adjustable element, such as a potentiometer. The adjusting device comprises an elongated sleeve-like mounting hub capable of being sealingly secured in the housing wall, and a normally freely rotatable or freely turnable knob structured as a hollow capsule rotatably inserted onto one end of the mounting hub. The other end of the mounting hub receives or is connected with a portion of the adjustable element. A spring is provided within the mounting hub to hold the knob in its freely turnable or rotatable position. The knob is operatively connected with a clutch-sleeve for temporary engagement with the rotatable operating end of the adjustable element when the knob is pushed against the spring.