ROTARY APPARATUS

A rotary apparatus is disclosed. The rotary apparatus comprises a housing, a rotor mounted in the housing and at least one intrinsically safe monitoring circuit for detecting rotor/housing contact or a monitoring circuit fault condition, the monitoring circuit including intrinsically safe amplifier barrier means having a maximum voltage and substantially fixed constant current output, the barrier being electrically connected to both the rotor, by rotary contact means, and the housing, the circuit including first resistor means arranged in parallel with the rotary contact means and second resistor means electrically connected in series between the housing and the rotary contact means and the first resistor means, wherein the impedance of the first resistor is such that in a normal operative non-contact state current substantially flows through the rotary contact means to the second resistor, in a contact fault state flows through the rotary contact means the rotor and the housing and in a circuit fault condition through the first and second resistors with the rotary contact being shorted such that the state of the apparatus is determined by the resistance of the circuit. Energy limitation is provided by the adaption of an alternative barrier, which uses an active output that delivers a fixed constant current to the valve. An upper limit exists on the voltage that can be output to generate the constant current in order to maintain intrinsic safety levels. This approach provides for the current to be very tightly controlled and thus it is possible to achieve highly accurate low level sensing. It also makes the measurement of resistance directly proportional to voltage, which provides for accurate sensing. L'invention concerne un appareil rotatif. L'appareil rotatif comprend un logement, un rotor monté dans le logement et au moins un circuit de surveillance à sécurité intrinsèque permettant de détecter un contact rotor/logement ou un état défectueux du circuit de surveillance, le circuit de surveillance comprenant un moyen de barrière d'amplificateur à sécurité intrinsèque ayant une tension maximale et une sortie de courant constant sensiblement fixe, la barrière étant électriquement connectée à la fois au rotor, par un moyen de contact rotatif, et au logement, le circuit comprenant un premier moyen de résistance disposé parallèlement au moyen de contact rotatif et un second moyen de résistance électriquement connecté en série entre le logement et le moyen de