Abstract: A balance beam has a fulcrum, at least one bellows (connected to a source of pressure or vacuum) acting on the beam and a connection to the armature of a differential transformer at one end. A poise is mounted for movement along the beam by rollers riding on shoulders formed on the beam. A carriage having a connection to the poise at the elevation of the axes of the rollers moves the poise and is, in turn, driven by a screw turned by a servomotor controlled by the differential transformer. Provision is made for minimizing temperature error both longitudinally and transversely of the beam. The fulcrum and bellows may be moved to different locations relative to the beam, using spaced drilled holes in the beam and the base plate. Various readouts may be connected to the screw, and recorders and control devices may also be driven by the screw.

Abstract: A circuit for a servo-amplifier saves power when the position servo has reached balance. The servo input is a high frequency differential transformer having its armature positioned by mechanical means driven by a servo motor controlled through amplifier circuitry. The power to the amplifier is turned off in the vicinity of the servo null point.

Abstract: A balance beam has a fulcrum, at least one bellows (connected to the source of pressure or vacuum) acting on the beam at a point along its length and a connection to the armature of a differential transformer at one end. A poise is mounted for movement along the beam by rollers riding on shoulders formed on the beam in a unique arrangement. A carriage having a connection to the poise at the elevation of the axes of the rollers moves the poise and is, in turn, driven by an expansible belt, chain or cable extending around two sprockets, one of which is driven by a servo-motor controlled by a circuit including the differential transformer. Careful provision is made for temperature compensation both longitudinally and transversely of the beam yet the drive elements are elastic. The bellows may be moved to different locations relative to the beam by use of pre-drilled holes in the beam and base plate. Two bellows, on opposite sides of the fulcrum, may be used to gauge pressure differences.