A new mercury rheostatic element for regulation and control

Introduction IN many regulating and control systems, the primary or actuating stimulus is available only at a low power level and must be amplified to obtain sufficient power output for the various control functions. This requirement, along with the increased use of automatic controls during the past few years has resulted in many industrial applications which require a simple, reliable power amplifier. Electronic tubes and special designs of rotating machines have been used for amplification where a continuous type of control is required, but in most applications it is difficult to justify the use of tubes or rotating amplifiers. Summary The principal design features, along with several typical applications, were described for a new form of mercury rheostatic element which has been designated as the “Mercurystat”. The unique features of the Mercurystat are its large number of hermetically sealed mercury contacts and the small force and travel required for their operation. It was shown that relatively large amounts of power can be controlled by the Mercurystat and because of the small input power required for its operation, power amplification in the order of 100,000 can be obtained. The performance of this new device along with its simplicity and absence of wearing moving parts should find many applications for it in automatic control systems.