Abstract: Weighing apparatus of the electromagnetic load compensation type is disclosed including zero-position detector means for generating a position signal that is a function of the extent to which a loaded weighing pan or the like is displaced from its no-load position, and regulating means responsive to said position signal for generating a compensating current for displacing the weighing pan toward its no-load position, characterized by the provision of filter means connected between the zero-position detector and the regulating means for suppressing the undesired extraneous interference acceleration signals produced, for example, by external shock or vibration forces imparted to the weighing apparatus. In one embodiment, the filter electrical components are constant, and in a second embodiment, means are provided for varying the electrical characteristics of at least some of the filter components as a function of the load applied to the weighing pan.

Abstract: A level detection system and a servo system employing the level detection system are disclosed. The level detection and servo system employs the use of a reasonably broad band-pass characteristic to avoid criticality in narrow band-pass systems. The level detection system includes an input level comparison circuit responsive to an input signal having a recurrent frequency and a reference signal. A filter having a band-pass characteristic which will pass the recurrent frequency of the input signal and its side-bands is responsive to the input level comparison circuit. The output of the filter is coupled to a second comparison circuit. The second comparison circuit is employed as a control means to drive the servo motor in the servo system.

Abstract: An adaptive filter circuit using a time modulated dead band for suppressing the effects of spurious noise associated with an error signal used in controlling a position drive motor associated with process controlling elements. The circuit includes means for restricting all signals, including both control signals and spurious noise, to a positioning motor during those periods of operation when little positioning is required. However, in those instances where a relatively large amount of repositioning is required, the system provides means for switching to a nonrestrictive mode of filtering which thereby permits maximum control over motor operation.

Abstract: An electric impedance network for AC carrier frequency control systems which provides optimal arithmetical symmetry in frequency response with respect to the carrier frequency, characterized by having a symmetrical even amplitude response and a symmetrical odd phase response for a substantial frequency band around the carrier frequency.