Abstract: An oxygen concentration measuring device having a very small size detecting portion formed of unitary lamination of plate shaped members of an oxygen sensing element, a heater member and/or a temperature detecting member. The element comprises an oxygen concentration cell and a temperature compensation means for compensating a setting voltage to which an EMF generated by the concentration cell is compared. The detecting portion is provided with a printed contact terminal and housed in a probe equipped with a protecting tube. The printed contact terminal of the detecting portion is arranged to mate with a connecting element housed in a funnel-shaped contact member so as to allow easy mounting and detaching.

Abstract: An oxygen analyzer using an oxygen sensor by which the oxygen concentration of a measuring gas can be detected. The oxygen sensor includes an oxygen pump and an oxygen concentration cell. The detecting principle is to vary the reference voltage to be compared with an output electromotive force of the oxygen concentration cell by using a predetermined relationship between the electromotive force and the pumping current, thus eliminating the need of using a reference air of which oxygen concentration is compared as a reference.

Abstract: A moisture (H.sub.2 O) measuring device for high temperature gas deriving the moisture content by taking a difference between measured values of oxygen concentration by an operational process. The one value of the an oxygen concentration is for oxygen content originally included in the measuring gas and the other value of the oxygen concentration is one additionally including oxygen content obtained by electrolysis of the moisture in the measuring gas. The two measured values are controlled by applying voltage for the oxygen pump.