Abstract: A servo instrument, particularly a servo altimeter, with a minimum of display error. The instrument comprises a capsule assembly, a sector adapted for rotation corresponding to the displacement of the capsule assembly, a photosensor for producing an output showing its angular position relative to the sector, a support for rotating the photosensor while supporting it adjustably in a direction of tracing the sector, a cam adapted to make the amount of the adjustment of the photosensor variable by the position of the support, a motor, means for generating a signal showing the rotating positional angle of the motor, and an amplifier for amplifying the output of the photosensor and driving the motor so as to maintain the output of the photosensor constant.

Abstract: An aircraft instrument with an acceleration compensation device comprises at least a capsule, a rocking axle, a link mechanism to transmit displacements of a free end of the capsule to the rocking axle, a first gear integrally provided with the rocking axle, a second gear meshed with the first gear and being rotatable, and weights. The weights are provided on the first gear and the second gear each correspondingly, and rotative force of the weights caused by an acceleration force works on the rocking axle so as to cancel the rotative force of the rocking axle by the displacements, due to the acceleration, of the free end of the capsule.